Print Page - Everything you ever wanted to know about racing fuel

FAQ's & Technical Articles => Techincal Section => Fuel/Oil/Coolant => Topic started by: rsss396 on December 09, 2013, 01:23:58 PM

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:23:58 PM

Everything you ever wanted to know about

Racing Fuel

[/HR][/COLOR][/SIZE][/FONT]

By Peter Billllinton , Rex Heatley and JohnStorm

SOME BASIC FACTS

WELCOME to the world of racing fuels. Within the pages of this book we will bediscussing such exotic and volatile fuels and fuel additives as Methanol,Nitromethane, Dinitropropane, Acetone, Propylene Oxide, Nitrobenzene andothers.

However, in order to evaluate the advantages and disadvantages of these specialfuels for use in high performance engines it is necessary to have a clearunderstanding of the laws of thermodynamics as applied to the internalcombustion engine.

HOT AIR ENGINE

For our purpose it is sufficient to state that such an engine is in simpleterms a hot air engine depending on the expansion of a quantity of air, heatedby the combustion of fuel, in a confined space, thus providing the drivingforce on the piston the reciprocating motion of which is converted by thecrankshaft into a rotary motion, so driving the flywheel and thus the source ofpower.

It follows, therefore, the more air, by weight, we can ignite in a givencombustion space and the greater we can increase the temperature, the greaterwill be the expansion and the force applied to the piston.

COMPRESSION

This at once highlights a term used by many without quite understanding itsimplications, the term being Compression Ratio.

This is the ratio between the piston at the top of its stroke leaving a spacein the combustion head and this volume added to that swept by the piston, thatis the bore and stroke volume. If, for example, this works out at ten to one itmeans the mixture is compressed to one tenth of its normal volume and thenignited.

If we assume the engine is not supercharged and at normal atmospheric pressure14.7 Ibs. per sq. in. approximately, and 100 per cent volumetrically efficient,the force on the piston would be 147 Ibs. per sq. in.

This, however, will not be the case in practice as the engine will not take ina charge of mixture equal to the space left by the piston at bottom deadcenter, in some cases the exhaust gases are not completely evacuated and theheat of the cylinder walls, head and valves, all have their effect on heatingup the incoming charge, reaching, with petrol, some 700°F.

Thus it is obvious, owing to the heat conditions existing in the engine, thatthere are definite limitations to the power output which can be maintained, andthese conditions, so far as petrol is concerned, are reached much

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:24:52 PM

earlier than with alcohol.

LESS POWER

There is a common mistake in thinking that so called racing fuels contain in themselves, quantity for quantity, more energy than petrol. This is not so, and in fact alcohol's have considerably less internal energy than petrol, their respective calorific values being 19,000 British Thermal Units per-pound weigh tfor petrol and some 8100BTU's for alcohols.

This means that, gallon for gallon, less power can be obtained from the alcohol's, but the limiting conditions mentioned above eliminate this particular drawback.

The amount of air required by petrol to burn correctly is several times more than that required by alcohol, so that in effect the advantage of alcohol is that the amount of heat liberated per pound weight of air used is greater.

Since the engine is an air engine where air is the working medium, heated by the ignition of the mixture, causing expansion, the fact that we can get a cooler and therefore heavier charge into the engine means a higher power output to be attained, fuel for fuel and weight for weight.

In other words the advantage of alcohol is its high latent heat evaporation figure as compared with petrol, allowing it to act as a refrigerant.

You may have at some time or other noticed inlet pipes tending to show frost when using alcohol.

The difference, for those interested in the heat values, is some 135 BTU for petrol and 472 BTU for alcohol, and just to clear all that up, it might be worth while saying that one British Thermal Unit is defined as the amount of heat required to raise the temperature of one pound of pure water one degree F.

OPTIMUM ON PETROL

Over the years the motor engine has been developed and adjusted by design features to operate at its optimum on petrol, this being available in bulk at a reasonable cost.

This fuel is a natural product of the earth, but, as we know, it has undergone a number of changes and has had certain additives incorporated to produce the required results when used with the modern combustion engine. Here then is our reference level or datum line.

If you have an engine, in good condition and tune, running, shall we assume, on top grade petrol and providing a known power output, it is possible by change of fuel to obtain a higher output, and to do this you can go to an alcohol based fuel.

To get maximum benefit from the new fuel you will have to adapt the engine to run under the new conditions being applied, and you will at once find there are advantages and disadvantages.

As we now have some understanding of the nature of the work the fuel is expected to carry out, they can be considered, and the new fuel used to its maximum.
ALCOHOL FUELS

RIGHT at this point it might be as well to point out to readers that the handling of alcohol fuel, even in small quantities, is dangerous since poisonous Methyl Alcohol is the basis of most of these fuels.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:25:22 PM

In some cases toprevent it being used for drinking an additive is used, called Pyridine, aboutone half per cent being the amount.

This gives it a nasty smell and a vile taste, but pure fuel is, of course,without this deterrent.

The problem still remains, however, since it can get into the system byabsorption through the skin or cuts, and can be inhaled from exhaust gases.

The effects are cumulative and if enough build up is allowed it oxidizesforming Formaldehyde causing blindness and insanity.

The use of rubber gloves, avoiding splashing and handling in confined space andin general treating with commonsense, however, reduces the risks to acceptableproportions.

Should, however, any get in the eyes immediate medical attention is necessary.

For those who have not handled alcohol fuel it might be as well to say it is aclear, colorless liquid, cool in touch, with an odor different from petrol, andhas an attraction to moisture in the atmosphere.

ADVANTAGES AND DISADVANTAGES

Let us now investigate the advantages and disadvantages of going over to thisfuel, and at all times taking petrol as our reference level, having in mind thebasic requirements of fuel in the heat engine.

The first question must be is it easy to obtain and the answer is there are anumber of garages retailing the fuel, in certain cases with other fuels addedin specified quantities.

Having obtained the fuel, as already explained, it must be handled with careand commonsense.

There is no real problem in keeping in store any quantity left over from onemeeting to another, provided it is kept in a can, or tank for that matter, withthe cap kept on during the store period, which can extend into years, contraryto popular belief.

COST

Cost of the alcohol depends on what other fuels have been incorporated, but asguide pure alcohol is, in small quantities, about just over half as much againas the cost of top grade petrol. You must bear in mind at this point, however,you will require double the amount of alcohol as compared to petrol for reasonswhich will be explained later.

Another point to consider is that alcohol is a solvent and so far as certainpaints are concerned it acts as a perfect paint stripper. Alcohol also has avery thorough scouring effect on tanks, pipe lines and so on, not forgetting itcan on certain

types of fiberglass tanks cause them to disintegrate into a rather nasty stickymess.

CONSUMPTION

Consumption of alcohol will be, in rough figures, double that of petrol, due tothe calorific value being about half that of petrol.

The correct air-fuel ratio for petrol is 14.1 to 15.1, but for alcohol it is7.1 to 9.1 so that means we must pass at least twice the weight of fuel, in thecase of alcohol, to heat the same amount of air to the same temperature as weneed for petrol.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:25:54 PM

Since the specificgravity of the two fuels is near enough the same it means in effect we have topass through the jets double the quantity of the fuel.

Apart from doubling up the flow capacity of the jets, and we would add herethat this does not mean doubling up the diameter of
the jet hole as many people think, but, in fact, increasing the diameter by 1.4times or if you like by 40 per cent since a little thought will remind you ofthe fact you are dealing with the area of the hole in the jet and not thediameter.

It is of little use increasing the capacity of the jet to pass double theamount of fuel unless steps have been taken to establish that the fuel lines,taps, float chambers and so on are also capable of passing double the fuel andthe actual flow should be measured.

RICH SIDE

Now unlike petrol you will find alcohol fuel will continue to provide increasedpower for a mixture well above the ideal mixture strength and you can alwaystend, therefore, to jet up on the rich side, and so avoid any possible chanceof running into troubles through weak mixture causing burnt valves and holedpistons.

This larger amount of fuel compared to petrol and especially as it is a fuelwith much higher latent heat value tends to do two things. The density of thecharge entering the engine is higher than petrol and a greater weight ofmixture is therefore being exploded.

This is a fuel with a large cooling effect provided by part of it evaporatingafter it has reached the combustion chamber and so tending to cool the valves,piston and so on.

Some may well get into the combustion chamber as liquid, due to the reductionin temperature of the induction system, pipes, carburetor, etc., and soextending the cooling effect, in the process counteracting the effect of thehigh internal temperature.

In view of this amount of fuel entering the chamber, with possibly some of itin liquid form, the ignition system must be beyond reproach since if the sparkis weak the mass of fuel will just soak the plug and then at once ignitiontroubles arise affecting starting in particular.

Owing to the use of alcohol a higher compression ratio can be used with thisfuel as compared with petrol, another consideration is the type of plug usedwhich will be a hotter type than used before with petrol.

NINETEEN TO ONE

We have just mentioned the higher possible compression ratio used with alcoholand the limit that can be used with any particular fuel depends on the tendencyof the fuel to detonate.

As a rough guide the ratio for petrol is limited to about ten to one, or withcertain additives to as much as 12 to one. With alcohol, however, you can go upto 19 to one or higher in certain cases. (For all practical purposes however,14 to one should be considered the maximum usable ratio in modern short strokeautomotive engines.)

The possible use of a much higher ratio, of course, means we get a higher poweroutput from the engine, and this, in fact, is almost the main advantage ofalcohol fuel.

DETONATION

Detonation with alcohol fuel is really not a problem, but pre-ignition is, orcould be unless the mixture is kept

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:26:21 PM

well on the richside.

The reason for this is that if the mixture is on the weak side it burns slowlyand can still be so doing when the exhaust valve has opened which then becomesoverheated. This in turn ignites the next charge before the correct time, thewhole process becoming a chain reaction causing even more rise in temperatureand so it goes on until the piston holes and other damage then follows.

The first signs of this process taking place are a loss of power, a generalrise quite quickly of overall temperature, the head in particular.

To avoid this, run on the rich side always and use plugs with a good heatcapacity.

It might be worth mentioning at this point that an engine set up correctly forrunning on alcohol, even though on a rich mixture, will be found to be(compared to petrol), a much cleaner running engine inside the cylinder head,and provided the ignition side is up to its job there will be less fouling ofplugs than on petrol.

IGNITION SETTING

Due to the different rate of burning of alcohol compared to petrol the ignitionsetting will have to be changed.

It will have to be advanced and the amount necessary will depend on the shapeof the cylinder head and general design.

For example, on a well designed hemi-head an extra five to six degrees mightwell be enough, whereas on a poor designed head it might be something like 15degrees.

Optimum ignition setting is tied up with the air-fuel ratio and it will befound that with alcohol it is not so critical as with petrol, that is to saythe drop off of power is not so progressive as will be seen later.

STARTING

Provided the engine is set up for running on alcohol correctly there should belittle trouble in starting except perhaps on a very cold day and it should bepossible to start up on the fuel mix used for the actual racing.

The main problem, due to the cooling effect of the fuel, is to get the engineto operating temperature in the short time available from fire-up to staging.

For this reason so far as motor cycle type engines are concerned, you willnote,

in many cases, the finning on the cylinder barrels and heads is almosteliminated. This, by the way, also helps to increase the power to weight ratio,or if you like tends to counteract the weight of the extra amount of fuelcarried as compared to petrol.

LIMIT

From reading this far, you should have come to the conclusion that if yourengine is now on its limit running on petrol, while large increases of powerare obtainable by the use of higher compression ratios it is possible to get areasonable increase in power output, ten per cent or so, with the existingratio, provided you make quite certain you get enough fuel through to theengine and, in fact, that you tend to run on the rich side.

Once you have gone over to alcohol and obtained satisfactory running, you havecommenced an extension of your power output by anything up to 25 per cent asyou adapt the engine to run with the new fuel.

The rather attractive feature that you tend, even with the increase of power tostand less chance of doing

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:26:45 PM

damage to the engine than when on petrolshould also be considered.

FINAL POINT

One final point to consider. If you change over to

alcohol from petrol where you were using a mineral oil, it is not necessary tochange over to a castor based oil. For modern engines, the present typeadditive mineral oils offer a higher performance level than the additive castorbased oils, and under controlled conditions the light viscosity oils have anadvantage where the warm up time is limited.

FUEL FLOW AND CAPACITY

Now that the decision to change to fuel other than petrol has been made, thefirst thing to look at is the fuel tank. If of fiberglass, bear in mind the newfuels act as solvents and most petrol resisting paints, shellac, varnish, ethylcellulose, cellulose nitrate and soft Bakelite suffer in contact, notforgetting sealing compounds such as Bostic, Hermatite, Osotite and similarleak stoppers.

If the tank resists on test, do bear in mind that if, at a later date, youpropose using Nitro Methane you will have to test still further as this acts asa solvent on many resins, polyvinyl acetate, acetylchloride, chlorinated rubberand low boiling hydrocarbons.

The obvious way to test is to deposit a little of the fuel on the tank surfaceand see if it reacts, bearing in mind it may attack the paintwork and not theactual material of the tank itself, so do not get misleading results.

If the tank is of metal construction, particularly of aluminum, it should beanodised, thus stopping chemical reaction causing a white deposit to formtending to clog fuel lines and carburetor parts that come in contact.

If of steel and tin plated, the fuel will tend to take off the tinplate andform a deposit on other metal parts in the fuel system.

Washing out the entire system is sometimes carried out with petrol to stop thisdeposit building up too much.

Bear in mind alcohol will descale material unaffected by petrol and it isadvisable to wash out and clean the whole tank first with a small amount offuel, to make sure you start clean, and to frequently inspect it to keep insuch condition.

In passing it might also be worth consideration that at least one well knowncarburetor uses a plastic float that gets more than a little upset with fueland another uses plastic cut-off valves in the float chamber which also object.

FUEL CAPACITY

At this stage it is necessary to work out how much fuel you need to carry andat what flow rate it will have to leave the tank.

There is no point in carrying more fuel than required, since, apart from theweight, you are just increasing the fire risk.

The rate of flow will establish the diameter of the outlet pipe or pipes, and apoint often missed, the diameter of the breather hole, usually incorporated inthe cap. This last point does not apply if the tank is pressurised.

Having decided on the amount and the rate of flow, you have to consider thecut-off valve and the fuel lines

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:27:10 PM

themselves.

in the case of a small engine the minimum bore diameter anywhere in the systemshould be 6mm., and for the rest 13mm. and the fuel lines should have, atworst, that diameter, preferably up to twice the diameter to reduce friction,and be made of Polythene, Neoprene or other alcohol resisting material.

Do not fall into the trap of using fuel lines of these diameters and use, attheir termination's, unions which restrict the actual effective diameters tomuch less. The ideal set-up is where the internal diameter right throughout thewhole system to the carburetors is of the same diameter, providing thatdiameter is large enough to reduce friction to a sensible minimum.

FUEL FLOW

Now check the actual flow right down to the fuel line that supplies thecarburetor or fuel block.

If gravity feed is used this is simple to do, but remember to check with thetank at the same height as used, and time the flow and quantity.

If the tank is pressurized, for your own interest, check with the cap open,then under pressure and the difference will surprise you, also how quickly theair pressure drops, more so if the air space over the fuel be smaller.

If the tank supplies some form of fuel pump, remember the pump diaphragm willhave to be of Neoprene or it will dissolve.

Electrically driven pumps are easy to check, but those driven by the engineitself present a problem.

If the makers' figures are available all is well, but if not you will have toestablish the actual quantity of fuel pumped per stroke, then from the rate atwhich the pump is operated, calculate the actual flow rate.

In all cases the rate should be at least twice the estimated maximum demand ofthe engine at peak requirement.

The major obstruction will usually be found in the cutoff valve of thecarburetor float chamber and although some manufacturers can supply valvesmodified to increase the flow at this point, they usually do not allow enoughand you will have to fabricate your own.

Remember here by increasing the diameter of the orifice by 40 per cent you willdouble the flow of fuel.

Do check however the flow rate through the valve and make certain it is enough. . . so many fall into this simple trap.

The figure of twice the required maximum demand rate may sound excessive, butbear in mind apart from the sudden demand, you have to force the fuel againstthe actual acceleration of the car or bike.

One final comment before leaving the fuel lines and means of getting the fuelto the engine itself.

Do check that the fuel cut-off valve, when in the open position, is in factfully open, and having done that check, if the tank has a breather, that fuelcannot spill out and possibly be blown back onto or into the engine, or forthat matter the driver.

TWICE AS MUCH

The actual amount of fuel required by the engine will be double the amount itconsumed when on petrol, but if you are starting from scratch so to speak, thea mount is determined by the amount of air consumed by the engine, which ineffect is directly related to its capacity at full throttle.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:27:35 PM

With regard to a supercharged engine the amount requiredwill be dependent on the boost pressure, so that for every 15 lb. approximatelyof boost, that is the amount over atmospheric pressure, as would be indicatedon the gauge, you will have to consider the actual effective capacity increasedby the same amount as the basic engine capacity.

For example a 1000 cc. engine running at a boost pressure of 15 lb. would beregarded as of 2000 cc. and the same engine running at some 30 lb. pressurewould work out at 3000 cc. and proportionally for other boost pressures.
FUEL-AIR RATIOS

SINCE fuel-air ratios are quoted by weight of both parts it will be necessaryto establish the actual weight of each component before we can determine thecorrect ratio we require.

To put this into practice you must take the cubic capacity of one cylinder ininches, since we are considering weight in pounds, multiplied by the number ofcylinders that are fired per revolution, times the total revolutions per minutefor a normally aspirated engine, but for a supercharged engine this figure willbe increased as indicated previously.

This total figure will be the volume of air consumed per minute, which must nowbe converted to weight of air in order to find the amount of fuel necessary tomix with it at the nominated ratio.

In order to carry out this calculation it is necessary to know that you convertcubic centimeters to cubic inches by dividing the total figure by 16.4, whichmust be converted yet again to cubic feet by dividing by 1728.

Since one cubic foot of air weighs 0.081 pounds at a temperature of 32 degreesF, or alternatively one pound of air equals 12.4 cu. ft., it is now possible todetermine the weight of air in pounds involved per minute.

The next step is that of ascertaining, from the previous calculation, theactual amount of fuel involved by considering the fuel-air ratio.

SIX PARTS TO ONE

In the case of pure methanol a ratio of approximately six to one, that is tosay six parts of air to one part of fuel by weight.

This means a total of seven parts, one will be that of the fuel itself, that isto say a seventh, but since the actual weight of the fuel is eight pounds pergallon of methanol, we will have to divide that figure by eight to convert togallons.

The final figure so obtained is the fuel required at full throttle in gallonsper minute.

Since this is assuming 100 per cent efficiency it means in effect this will bea mixture on the rich side, but as methanol is insensitive to small ratiochanges this is unimportant and in fact a built-in safety factor, avoiding leanmixture troubles such as burnt pistons.

From this calculation it will be possible to determine the total amount of fuelrequired to carry in the tank, plus the rate of flow to the carburetors orinjectors, single or multiple as the case might be.

Providing the actual fuel flow can be allowed to take place as it would undernormal operating conditions, it will be possible to check the jet sizes relatedto the actual amount of fuel they will pass per minute.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:28:24 PM

If this is not possible, for example in the case of anengine driven pump system, either the maker's figures will have to be used, orthe displacement per revolution or stroke established, times the number ofthese per minute, giving the estimated flow.

These figures are empirical but will at least provide a basis on which to startand experiment, and will prove whether the pump has sufficient capacity or not,and for the particular application in mind, this figure should be at leasttwice the estimated flow rate.

READY TO START

At this stage we are ready to start up and from the actual running of theengine, commence to see if the mixture is about right by the normal methods,but -it must be appreciated our estimated requirements have been taken at fullthrottle or maximum fuel demand.

Tuning, insofar as intermediate settings of the throttle, follows normalpractice, but for starting conditions, it may be slightly different, as in mostcases of fuel other than petrol, it is unnecessary to provide an excessivelyrich mixture for starting as this will only cause plug wetting, making itdifficult or even impossible to start.

As previously stated when the engine is set up, which is often not the case,and in tune, it will be possible to start up and run right away. However forthose that may find starting a problem, especially in cold weather conditions,it may be advisable to add some volatile component to the fuel, or even startup by the simple means of introducing another fuel, such as lighter fuel, bythe simple means of squirting a small amount into the air intake of the engine.

FIRE DANGER

A warning at this stage would not be out of place in the use of Ether orcompounds containing a high proportion of Ether, such as Easistart, . orsimilar aerosol packs, except those specifically formulated for spark ignitedengines, as opposed to diesel, due to the danger of flash fires, and alsodamage to the engine caused by possible detonation.

The preferred method of obtaining easy starting is that of blending certainother fuels with the methanol in controlled proportions, for example the use ofAcetone up to a maximum of 5 per cent by volume, petrol also up to the samemaximum amount, or Ether, but at a maximum of 3 per cent.

With regard to Ether, the blending of this with the fuel should, for reasons ofsafety, be left to the fuel supplier due to the extremely low flash point ofthis material, in fact, a figure of minus 40 degreesF.

Since as stated before, these fuels, if by any mischance, get into the eyesimmediate medical attention is necessary.

If this is impossible due to circumstances, to obtain, the following actionwill do until professional attention ca n be secured.

The eyes should be continually washed out with clean water for a period of atleast 15 minutes, needless to add, with care.

Clothing contaminated with fuel should be removed to stop the fuel penetratingto the skin, and if it has, the area effected washed thoroughly with soap andwater.

It may seem some stress is made of the dangers of fuel, but it is better toknow the dangers and take the necessary precautions, which after all onlyamount to common sense, rather than go along in total ignorance.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:28:51 PM

COMPRESSION RATIOS

WHEN we were first considering changing over to Methanol it was stated a smallpower gain would be obtained right away with just the change of fuel, but toobtain the full benefit the engine would have to be modified to do so.

Going back to our simple heat engine again as a basis, we can say by the use ofMethanol we are getting twice the weight of fuel to ignite, at the same time wecan increase the compression ratio to a much higher figure thus producing muchgreater power or force on the piston, and so in fact obtaining a more efficientengine.

This extra power will, however, do two things, one being to produce more heatso the engine will run hotter, the other being that it will create much highermechanical stresses.

The extra heat generated we can cope with, for example by using a richermixture so gaining the cooling action of the Methanol itself, but themechanical stresses are another matter.

When the fuel is ignited the resultant force is applied to the piston top, alsoto the cylinder head, but since the head is fixed and the piston movable, thelatter starts on its downward stroke, the closed valves making sure the wholeforce is so applied without possible escape elsewhere.

Now if the studs or bolts, holding the head down, cannot cope with the nowincreased power we are going to be in trouble.

On the other hand if the head is well and truly held down, the force will beapplied to the bolts holding the cylinder barrel to the crankcase.

Provided all these hold, the extra force is applied to the little and big ends,plus the crankshaft itself.

This is why, as a good example, the dirt track JAP engine has the bolts thathold the head on extended right down past the barrel, or in some cases throughthe finning, right into the crankcase itself, making a really solid mechanicalassembly.

HIGHER COMPRESS!ON

There comes to mind as another example a well known twin cylinder machine withthe engine made as an alternative in light alloy, the barrels and heads beinginterchangeable, the makers advising the use of the iron barrels for Methanoldue to the alloy barrels tending to fracture at the base.

We must also, at this point, consider if it is proposed at this stager or at alater point in time, to use Nitro-methane, the question of the actualcompression ratio to be used will be determined by the amount of Nitro-methanein the Methanol and as a guide Chart 1 gives approximate values on theconservative side.

Methods of obtaining higher compression ratios depend on many factors, which ina simple case, may be had by the fitting of high compression pistons, ifavailable.

In some cases a thinner head gasket may be the answer, or total elimination ofthe gasket and face grinding the mating surfaces.

Again it may be possible to have the ratio increased by removal of metal fromthe head, or the block for that matter, but in such cases you must check thatthe valves have enough clearance to miss the piston.
Another method is that of building up the inside of the cylinder head with newmetal and then machining to the required shape.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:29:27 PM

Remember in the case of a V-8 engine if you have the headsskimmed to get higher compression, you will be in trouble with the inlet portsnow being out of line with the manifold, due to the heads sinking lower inrelation to the manifold itself, so give the matter some careful thought beforegoing ahead.

CHART 1

Approximatecompression ratios recommended for use with Nitro-methane / Methanol fuelmixes.

[TABLE=class: MsoNormalTable, width: 144]
[TR]
[TD=width: 80, bgcolor: transparent]

Compression Ratio

[/TD]
[TD=width: 102, bgcolor: transparent]

% Nitro in Methanol per volume

[/TD]
[/TR]
[TR]
[TD=width: 80, bgcolor: transparent]

16 to 1

15 to 1

14 to 1

13 to 1

12 to 1

11 to 1

10 to 1

9 to 1

8 to 1

7 to 1

6.5 to 1

[/TD]
[TD=width: 102, bgcolor: transparent]

10%

18%

28%

38%

46%

56%

66%

75%

85%

94%

100%

[/TD]
[/TR]
[/TABLE]

It must be remembered that for all practical purposes 14 to 1 should beconsidered the maximum usable compression ratio in modern short strokeautomotive type engines.
NITROMETHANE
NOW that we are considering the use ofNitromethane it may be as well to get one well held idea out of the way beforewe go any further . . . that is that more power and therefore more performancecan be obtained by simply adding more Nitromethane to the fuel tank. Nothingcould be further from the truth, friends!

In actual fact this is perhaps one of the quickest ways of running into seriousmechanical trouble.

The actual name Nitro in itself to most people sounds explosive and at once theidea of using this fuel leads the imagination to think of it getting into thecylinder head end then being exploded by the spark, thus producing a violentexplosion in the engine, the extra power then doing more work and so giving theextra performance.
The introduction of more Nitro-methaneto the fuel is not just that of the addition until enough power is obtained,but rather that of well controlled amounts used in relation to the otherfactors.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:30:02 PM

CHART 2

Recommended jet diameter increases(guide only) for Nitro - methane / Methanol fuel mixes over those used forstraight Methanol fuel.

[TABLE=class: MsoNormalTable, width: 146]
[TR]
[TD=width: 94, bgcolor: transparent]

% Nitro in Methanol
per volume

[/TD]
[TD=bgcolor: transparent]

Jet diameter
increase
over Methanol

[/TD]
[/TR]
[TR]
[TD=width: 94, bgcolor: transparent]

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

[/TD]
[TD=bgcolor: transparent]

1.0

1.12

1.22

1.32

1.41

1.5

1.58

1.66

1.73

1.8

1.87

[/TD]
[/TR]
[/TABLE]

Chart 2 indicates the increase in jet size toallow the increased amount of fuel to flow as the ratio of Nitromethane to fuelis increased.

These figures in all cases provide a mixture on the rich side since aspreviously pointed out, these fuels are relatively insensitive to mixture ratiocompared to petrol, and the consequences of running weak mixtures with thesefuels is likely to be more serious than with petrol since the power level willbe so much higher, also the thermal stresses.

Note how with 40 per cent nitromethane mixture the jet size has increased by1.41, or put another way by 40 per cent on the diameter, which as mentionedbefore means an actual fuel flow of twice the original amount, so by comparisonwith petrol we now have four times as much fuel required by the engine.

At 80 per cent mixture the fuel flow rate has be-come three times the rate andtherefore six times greater than petrol, hence the need to check the fuel pumpand fuel lines to make quite certain they can cope with this requirement.

DANGERS

Now, as before, it is necessary to know the dangers involved with the use ofnitromethane mixtures so

that the necessary precautions can be taken and understood, reducing them to adegree that makes the use of

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:30:32 PM

such fuels acceptableunder the circumstances in which we normally operate.

Provided you know the dangers you can work with these fuels and come to noharm, but if you do not, then it is possible through lack of simple precautionsto suffer, so bear them in mind at all times.

After combustion, mixtures containing nitromethane exhaust relatively largeamounts of nitric acid in vapor form, making the use of a proper gas maskessential by the driver, and for those close to the car in the start area.

The reason for this is that nitric acid, when inhaled, causes a muscularreaction making it impossible to breathe.

Little imagination is required to see the dangers involved with this possibleevent taking place, and in fact there have been cases of drivers becomingalmost unconscious due to the bad fitting of face masks.

FIRESUITS

The mandatory use of fire suits adds to the generally held view that withnitro-methane mixtures the fire risk is increased, but this is not so.

If you care to test this you can do so as follows. Take a small amount ofpetrol, about one teaspoonful say, and place in a small tin lid and thenignite. It will catch fire almost with a bang.

Now take the same amount of methanol and after the tin has cooled down, repeatthe exercise observing the almost lazy manner in which it ignites, burning witha blue colour, the edges of the flame lined in places in yellow and orange.

Now take the same amount of nitro-methane, 98 per cent if you like, and repeatthe experiment and see how difficult it is to ignite, burning with a greentinted flame in a reluctant manner.

This is due of course to the respective flash points of the three fuels, petrolbeing the lowest at between zero and 40 degrees F. approximately, methanol at67 Degrees F., and nitromethane at 110 degrees F.

In other words with petrol you have a major fire risk and far less so withnitromethane mixtures.

The real problem with nitromethane is its ability to release high power,especially when ignited in a confined space.

Associated with this is its liability to be affected by shock.

Dropping a can of nitromethane will not cause an explosion, as the can, due toits construction of light weight material, will not have sufficient rigidity,but an amount in a very solid thick-walled container may.

EXPLOSION

There are three main possible causes of nitromethane becoming shock sensitiveand they are as follows:

The use of hydrazine as an additive, which, be it noted, is barred byregulations in the USA for that very reason.

The use of caustic soda or any other alkaline, used for cleaning out a tank orfuel lines.

Alloy tanks, which before anodizing, have been cleaned with such a substanceand have retained a small deposit.

To avoid any such possible troubles the tank must be filled with water and 10per cent vinegar, plus a little ordinary household washing-up liquid, and leftto soak for several days.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:31:01 PM

One final note of warning concerning burning nitromethaneand methanol is that they can burn almost unseen in daylight, and you may wellhave a carburetor or injector ignited by a backfire without appreciating thedanger.
RUN IT RICH!

We are now in a position to consider the use of Nitromethane blends inpractice.

Like methanol, nitromethane has a strong tendency to pre-ignition, but unlikemethanol it has a much lower knock rating, that is to say it will detonate.

Both these conditions will be fully explained at a later stage, but in themeantime by making sure the mixture ratios are well on the rich side, these twoconditions should be reduced to manageable proportions.

In addition to rich mixtures it is highly desirable to have a very cleancombustion chamber, giving both freedom from Carbon deposits and a smoothflowing surface with no sharp edges that can get too hot.

While polished combustion chambers are the subject of much debate inconventional high performance engines, they have a real use when usingnitromethane fuels.

Since, as has been stated, the figures quoted tend to provide a rich mixture soas to be on the safe side, it will be as well to know the signs of an over richmixture.

Difficulty in starting coupled with mix-firing during the early part of therun, cleaning out at a later stage, or large quantities of liquid fuel comingout of the exhaust system are the two major signs.

PLUG READINGS

Plug readings are another method and can be taken without the usual method ofcutting the engine at full power.

An examination when the engine has completed a run will prove quitesatisfactory, provided new plugs are used.

Signs to look for are as follows whenever the amount of nitromethane is 25 percent or over, starting with a weak mixture, as this is the most dangerouscondition and to be avoided at all cost.

WEAK. The center insulator rather white looking in color and may wellhave the surface rough or blistered, even in some cases with the insulationchipped, a fairly sure sign of pre-ignition.

One or both electrodes on careful examination may show very small beads ofmetal attached to them evident to the naked eye, and almost always considerableblueing of one or both electrodes.

CORRECT. The porcelain center electrode insulator light grey brown incolor, often with the earthed electrode just showing signs of heat.

RICH. Sometimes difficult to distinguish from a weak mixture as in bothcases the center insulator will be rather white looking, but in this case thesurface will be smooth and both electrodes will be almost as the originalmetal.

Another check as a rough indication is that with the engine being turned overwith the ignition off, signs of vapor should be seen at the exhaust, and ifnot, a weak mixture could well be suspected.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:31:25 PM

Fuel pump pressure is of importance since with Nitromethane(as already mentioned) we are dealing with a fuel that is liable to becomeunstable when confined and subjected to shock.

If you now consider a high pressure pump forcing the fuel under pressure alongthe line, it is quite possible for an air bubble to form, which can then beregarded as a slug of air, which by the pressure behind it, will be forced alongthe line in a series of pulses hitting the fuel in front of it, now compressedin a narrow space, thus providing the ideal conditions for an explosion, hencethe limit of 100 Ibs. per square inch mentioned.

In view of this you must consider placing the fuel cut-off valve after thepressure pump, provided the re-lief valve is set well below the 100 lb. persquare inch point, the advantages of so doing being evident on a littlethought.

PUMP PRESSURE

While on pump pressures there is also the question to be considered when usingcarburetors fed from float chambers, of the actual fuel cutoff valve liftingunder pressure.

In some cases some four pounds pressure will do just that and cause flooding,so a check will have to be made to establish just what line pressure can beutilized without this taking place.

OIL CONTAMINATION

It is most important to check the oil at frequent intervals and if the amounthas increased, as a result of the fuel getting down the bores past the rings,essential to change when the increase is 25 per cent or more for two reasons.

In the first place such a mixture of fuel and oil is no longer a goodlubricant, and in the second place there will now exist a danger of sump firesand even explosions, since the oil mist plus the oxygen-rich atmosphere is veryliable to catch fire or explode.

The only way to overcome such a fire is by the use of C02 type or"OnBoard" Freon type fire fighting equipment, the nozzles directedinto the sump itself.

The first signs of such a fire are lazy, yellowish flames, seen possibly at oneor more of the sump breathers or rocker cover outlets.

It is important when using over 20 per cent nitromethane mixtures to check theengine over after shut off for at least two minutes by visual examination forsuch possible fires.
BLENDING NlTROMETHANE

BLENDING various proportions of fuels to provide our "experimental"batches of Nitro laced fuels means that at some time or other we will be leftwith quantities of unused fuel of a known percentage mixture strength. Becauseof its high cost, leftover fuel is remixed with more fuel to provide a newbatch of greater or lesser Nitro strength as required. To accomplish this, aspecial mixing chart below indicates how this can easily be done.

NITRO PERCENTAGE

Provided you know the exact mixture you have in use and the amount, it ispossible to get your supplier to provide additional fuel to bring the totalquantity up to the new required percentage mixture.

On the other hand you can do this yourself by using a hydrometer which isavailable specially calibrated for just

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:31:55 PM

this use, indicating by percentage the amount ofNitromethane in the fuel, checked by volume and not weight.

For those unfamiliar with the hydrometer, it is a simple device which uses acalibrated weight to float in the fluid to be checked, the level at which thefloat sits in the fuel indicating the specific gravity of the fuel. As we knowwater is 1, Methanol coming out at 0.79 and Nitromethane at 1.13, it is easy toestablish the fuel mixture.

To avoid having to consult tables or graphs the special hydrometer mentioned isdirectly calibrated, so you just read off the actual content of Nitromethane inpercent.

FUEL TEMPERATURE

It must be mentioned here that the average fuel test hydrometer is calibratedto give a completely accurate reading at one specific temperature, usually 68degrees Fahrenheit. Thus if you check 100 percent Nitromethane solution whichis at 68 degrees Fahrenheit, the hydrometer will give you a reading of 100.

If you mix one gallon each of 100 percent nitro and methanol and thetemperature of this solution remains at 68 degrees your reading will be 50 onthe hydrometer scale indicating that you have a 50-50 mix or 50 percent nitrocontent. Mix any ratio of nitro and methanol with the temperature at 68° F andthe hydrometer will accurately indicate the percentage, be it 10 percent, 40percent, 80 percent or any other ratio.

EXAMPLE: Our tank contains a 55% nitromethane mix and wewish to reduce it to 20% by the addition of straight methanol. On the graphdraw a connecting line between the two percentages to be mixed with the lowestpercentage (in this case 0%) on the left. Where this line intersects therequired percentage line (20%), draw another vertically down to the base line.The number of pints to the left of this line (in this case just under 3) is theamount of the high percentage (55% in our example) required, and the number ofpints to the right of the line is the amount of the lowest percentage (0% orstraight methanol in our case) required. The two amounts will total one gallon.

Changes away from the baseline temperature of the fuel (68° F) will have aneffect on the hydrometer reading. Changes in fuel temperature affect thespecific gravity of the nitro and therefore give you a false reading.

If the temperature drops the reading will be high, giving the impression thatthe nitro content of the mix is higher than it really is. If the temperaturegoes up the reading will drop, causing you to assume that there is less nitroin the mixture than there really is.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:50:49 PM

Here lies. the danger - the natural mistake in thisinstance would be to compensate for the false reading by adding more nitro,with the possibility that your engine may run lean with damaging results.

If you run strictly according to volume (for example mix three gallons of nitroto one of methanol for a 75 percent mix) you'll always be on the safe side.However, unless you want to keep running that same mix, you will either have todump what is left in the tank when you want to change percentage or use ahydrometer.

With the hydrometer however, you can run into trouble, as you will NEVER find alocation where you can guarantee the ambient temperature will be 68°F, and youwill need to measure the temperature of the fuel before attempting to determinethe percentage of nitro it contains.

Whatever the true percentage of nitro in your tank is, it will always returnaccurate hydrometer reading when checked at 68° F. Let the temperature drop to60°F and you'll get a higher reading (82 percent for an actual 80 percent mix;let it climb to 80°F and your reading will drop to 77 percent for the actual 80percent mix.

To combat this problem refer to the accompanying chart which lists actualpercentages of nitro at various temperatures and hydrometer readings. As can beseen the variations in the true percentage are quite significant.

FUEL TEST CHART
Test hydrometer reads 100% at 68° in known pure nitro.
TEMPERATURE OF FUEL- (°F)

[TABLE=class: MsoNormalTable, width: 297]
[TR]
[TD=width: 50, bgcolor: transparent]

True % Nitro

[/TD]
[TD=width: 334, bgcolor: transparent] 40° 50° 60° 68° 70° 80° 90° 100° 110° 120
[/TD]
[/TR]
[TR]
[TD=width: 50, bgcolor: transparent]

100

[/TD]
[TD=width: 334, bgcolor: transparent] 106 104 102 100 99 97 94 92 90 87

104 102 100 98 97 95 93 90 88 86

97 94 92 90 89 87 85 83 80 78

86 83 82 80 80 77 75 73 70 68

75 73 71 70 70 68 65 63 61 59

66 63 61 60 60 58 56 54 52 50

55 53 51 50 49 48 46 44 42 40

45 43 41 40 39 37 35 33 31 30

35 33 31 30 29 27 25 23 22 20

27 25 22 20 20 18 17 15 13 11

20 16 13 10 10 9 7 5 3 1
[/TD]
[/TR]
[/TABLE]

ACTUALPERCENTAGES OF NITRO

EXTREMES of temperature can play havoc withnitromethane power output and provide for false hydrometer test readings. Graphabove shows the effects of temperature changes on nitro-completely accuratereadings can only be obtained with fuel at 68 degrees Fahrenheit.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:51:26 PM

KEEP IT RICH

Once again we stress as you increase the use of Nitromethane you must run wellon the rich side, even up to the point of the engine starting to misfire on therun, regarding the cost of the fuel as an insurance against engine failurecaused by the increased power developed as the percentage is increased.

A constant check should be kept on the valve clearances as this will at onceindicate if by any chance a valve is stretching at the neck, both inlet andexhaust being suspect when running at high power levels.
TIPPING THE CAN

AS with the introduction of Methanol, the introduction of Nitromethane fuelmeans that ignition settings will have to be adjusted to take full advantage ofthis volatile fuel.

Starting from the position found most satisfactory for Methanol it will befound that as the amount of Nitromethane is increased so will the ignitionpoint have to be advanced, due to the slower burning of the fuel.

The actual amount will depend on the engine design and will vary from engine toengine, but as a guide could be as much as 60 degrees, and since in fact theamount is not too critical some 40 degrees would be a good starting point.

Insufficient advance is usually made obvious by misfiring under load and athigh engine speed, plus a general feeling of lack of power.

It is almost impossible to state a limit of advance as it varies so much engineto engine, but here again a falling off in power would indicate the limit pointhas been passed.

With very high Nitromethane content fuel the ignition point may well come backto a lower reading since owing to the large amount of oxygen being released themixture becomes more sensitive, the flame pattern changing and the lowersetting more effective.

SAFETY FIRST

Since we are talking about using Nitromethane in fair quantity, once again awarning to use a face mask for the driver when he is situated behind theexhausts and therefore in the fume area.

In certain cases it will be possible to extend the use of Nitromethane untilthe absolute figure of 98 percent is attained, usually regarded as 100 percent,at which stage you really have to pour it in to keep the mixture rich enough asthe fuel itself generates its own supply of oxygen, also at a very high rate.

At 80 percent and above, the optimum air fuel ratio no longer exists and thepower output becomes well related to the actual amount of fuel fed into theengine by weight.

In all the information given the engine has so far been regarded as a normallyaspirated engine, that is unsupercharged, but in fact the use of Nitromethaneis providing chemically similar results to the mechanically superchargedengine, but of course advantage can be taken of both methods together, providedcertain precautions are taken, in particular that of using a suitablecompression ratio.

SUPERCHARGING

If for example the normal compression ratio is 10 to 1, then if we nowsupercharge at some 15 pounds boost or approximately one atmosphere, the totalcompression ratio in effect is now doubled, or at 20 to 1 so far as the fuel isconcerned, but in practice it would not be quite so high as this due to losses,but could well be some 16 or 17 to 1.

We are now at a stage where having started on Methanol and then progressed tothe introduction of Nitromethane, we are starting to consider other possibleadditives to obtain high power at perhaps a lower cost since as yet pureNitromethane is relatively expensive in this country.

OTHER ADDITIVES

Tetranitromethane which is very expensive and almost unobtainable can be used,but requires great care in handling as it has an explosive characteristiccoupled with instability.

Dinitropropane which is solid at room temperature and again normally almostunobtainable, could be however a fairly safe additive and effective.

Isopropylnitrate is yet another very reactive substance, inclined to beunstable and unsafe in unskilled hands, and of course one may add, expensive.

Propylene Oxide has some handling problems in pure state but is quite safe whenblended in other fuels.

Used in conjunction with Nitromethane it helps to increase power as it acts asan ignition accelerator, increasing the flame speed and up to 20 percent may beused.

When used with other fuels up to 5 percent, better starting and smootherrunning are the result.

In practice the usual amount used is some 10 percent as with more than thislevel it is necessary to introduce other components, such as for example, wateror benzole to reduce detonation possibilities.

It is only fair to say that when you get to this stage of mixing up your ownblends of fuel you are, to a great extent, more or less on your own and youbecome part chemist plus mechanical engineer.

Due to the high power levels involved great care must be taken and extremecleanliness is essential.

Yet again do check that at all times your fuel lines

and pump capacity is more than adequate to cope with the heavy extra demand asyou tend to get increased power output from these exciting fuels now available,and once again always tend to run on the rich side, the extra cost of the fuelbeing cheaper than a wrecked engine due to a weak mixture.

CHECK YOUR PLUGS

The only sensible way of increasing the amount of Nitromethane is in smallprogressive steps, and at each step checking the plugs which will indicate whenthe limit for that particular engine is being reached by the following signs:-

1 Chipping of bode insulator, similar to weak mixture.

2. Overheating of all metal parts of the plug, in extreme cases to the externaland exposed body of the plug.

3. The center insulator ashen in color with grey streaks, not to be confusedwith the white grey color of weak mixture.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:52:02 PM

It being assumed at all times there is no question of theengine being on weak mixture and here again we repeat at all times work on therich side.
PRE-IGNITION AND DETONATION

BEFORE we consider the use of other additives to the fuel we must get a clearunderstanding of the problem introduced by two well known conditions thatoccur, especially when you are seeking high performance from the engine, and inparticular using fuel of the type we have been discussing.

We have in mind of course Pre-ignition and Detonation and we did state we wouldexplain these two conditions in detail. Let us therefore look at, perhaps, theeasier one of the two to explain and understand, that of Pre-ignition.

The name itself is self explanatory. The fuel is being ignited before it shouldbe, causing all sorts of trouble. To understand we must go back to our simpleheat engine and once again consider just what takes place, taking thecompression stroke as our starting point, assuming that up to that moment oftime the engine has been running satisfactorily.

That being so, we have the piston commencing to travel up the cylinder bore,starting to compress the fuel ready for ignition by the spark at the plug.

IGNITION SETTING

Depending on the ignition setting, the spark should occur at just the righttime to allow the mixture to ignite, the resultant explosion being so timedthat its force is applied to the piston just as it is ready to commence itsdownward stroke.

As we have explained with Methanol for example, as compared to Petrol, theignition setting point has to be advanced since this fuel is slower inigniting, taking longer to burn, hence the need to commence the operation justthat bit sooner so as to get the force of the explosion at the right momentlooking at it from the piston point of view.

If the explosion takes place too late, then the piston has already started todescend, so the force of the explosion is reduced since there is now so muchmore room so to speak in the chamber.

On the other hand if it occurs too soon, the force of the explosion meets thepiston on its way up the bore, trying to force it down, so power is lost and agenera! state of opposing forces exists.

It is just this that makes it necessary to time the ignition setting to agreewith the type of fuel in use so as to get the maximum effect, also to have anignition system that will ignite as much of the mixture as possible in the veryshort time it has to do so.

DETONATION

Having we hope established a reasonable understanding of Pre-ignition we mustnow turn to the other troublesome condition known as Detonation, which again asits name implies, is an explosive force and as such destructive.

Detonation is caused by the actual compression of the mixture to a level whereit reaches the Auto-ignition point, becoming an uncontrollable explosion, thepoint at which this takes place varying from fuel to fuel, hence the use ofadditives to vary this point.

The explosion takes place without the aid of any local hot spots, including theplug itself, and again is out of time with piston movement.

A further cause and a frequent one at that is a small pocket of fuel, afternormal ignition has taken place, getting further compressed by the explosion inthe cylinder head in addition to that of the mechanical compression, thenigniting, after the normal ignition point, so out of time, causing the wellknown "pinking" effect and in a severe case mechanical destruction ofthe engine.

The amount of destruction is to some extent dependent on the actual shape ofthe cylinder head and the space available for the pocket of fuel to collect.

If the pocket that is formed is relatively large, then the force of this veryhighly compressed fuel exploding can do mechanical damage, but if on the otherhand it is small it may not do so, but it can, and will, form a local heatspot, which in turn will cause pre-ignition.

SPARK PLUGS

Right away the first item that leaps to mind is the plug itself, which afterall has just the essential job to do of igniting the mixture.

If this gets overheated and then retaining the heat, becomes hot enough toignite the fuel itself, without the aid of the spark across the electrodes,then it will do so as soon as the fuel is introduced into the cylinder and isdirected by the upward motion of the piston towards the head and the plug,obviously well before the correct moment of time.

This means that we must be selective in our choice of plug and use the correctgrade, the so-called "hot" type being out, further to that thecondition of the plug must be first class.

It is quite useless and in the long run expensive, to waste time with poorplugs, so just remove the one you pinched from the lawn mower and treatyourself to the correct grade of "cold" plug right away.

ENGINE TEMPERATURE

Let us now assume we can forget the plug situation and say all is well. We nowhave to consider engine temperature as the next possible cause of preignition,or some part of the cylinder head becoming so hot in itself that it acts as theplug, igniting the mixture all out of time with the piston movement.

This means at once forces opposing each other in the engine, producing stillmore heat and so the whole thing getting into a vicious circle.

The obvious possible cause would be weak mixture as a start since this cancause an increase in temperature due to the combustion of the fuel being morecomplete, eliminating the cooling effect of any fuel that may be left over innormal conditions, which in the case of Methanol could well be in liquid form,and sometimes when considerable overlap timing is used, can be seen ejectedfrom the exhaust ports.

VALVES

Remember we did point out that in the case of Methanol you had the advantage ofa lot of fuel being introduced to the cylinder acting as a coolant, to thevalves in particular.

This being so it follows that if you do have a weak mixture, you are almostcertain to have the valves reaching high temperatures, especially the exhaustvalves which in fact can reach a high enough temperature to ignite the fuelthus causing pre-ignition.

Now let us say we have the right plug, correct ignition setting for the fuel inuse and adequate mixture being

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:52:36 PM

introduced to the cylinders.

We can still suffer pre-ignition, however should there be a rough part of thehead, say a small ridge by the plug hole, which, since it is so small in mass,can build up and retain enough heat to become a small red hot mass, againtaking over from the plug and doing its work all at the wrong time.

Yet again another cause could be faulty valve operation or incorrect tappetsettings so that the fuel mixture, although in itself rich enough, is unable tobe placed in the cylinder head at the right time, again causing the effort ofthe eventual explosion, when it does take place, to be out of time with thepiston movement.

AUTO-IGNITION

CERTAIN fuels are more sensitive to pre-ignition than others and this is due toa function known as the Auto-ignition temperature characteristic, which in factmeans that once above the flash point of the fuel under consideration, there isa temperature point at which this fuel will ignite, this being the particulartemperature known as the Auto-ignition temperature of that fuel.

Since this point varies from fuel to fuel, it does mean by the choice of thefuel selected for use, plus if required the use of additives, the optimum fuelmixture can be selected to reduce pre-ignition sensitivity by the act ofraising the Auto-ignition temperature point of the total fuel mixture.

In order therefore to take advantage of this information it is necessary toestablish the actual temperature at which the fuel it is proposed to usesuffers from this Auto-ignition characteristic.

Once this information is obtained it then becomes necessary to make quite surethat the temperature inside the combustion chamber does not under anycircumstances exceed this figure, as otherwise we run straight into trouble.

If for example it does, due to the use of a very high compression ratio, wewill, to avoid trouble, either have to reduce this ratio, or use another typeof fuel, or yet again with the existing fuel, use an additive to increase thetemperature point, bearing in mind that the higher the compression ratio usedthe greater the heat produced in the charge, as previously explained whenlooking at our simple heat engine.

In connection with this statement it must be appreciated that apart from theheat produced by the actual compression of the fuel, there is to this added theresidual heat from the engine internals, which in themselves may be below thecritical point, but when added to, or combined with the other, exceed the vitalfigures

A further point that should be considered is that the temperature of the fuelunder compression is related to the actual time taken to compress it, so thatas an example, a high revving engine may well pre-ignite at a certain point andnot do so at lower revolutions.

This explains why in the Start area, or on the line, all may seem well, butonce the power is turned on and the engine speed increased troubles commence.

OCTANE RATINGS

The Octane rating of the fuel in use indicates the detonation sensitivity ofthe fuel and relates directly to the maximum possible compression ratio thatmay be used with that particular fuel.

Again the use of additives will allow that ratio to be a altered.

Naturally every effort must be made to eliminate detonation and on the smallestindication of it taking place, prompt action taken at once to correct theexisting conditions.

With street vehicles it is possible to get the well known audible indicationsof "pinking", but with the competition engine, due to the high noiselevel this may not be so.

Also on multi-cylinder engines you may well have trouble in one or morecylinders, the rest of the engine then masking the trouble, and in fact runningthe faulty cylinders into destruction, the overall noise quite dominating the"pinking" to the point of it being inaudible.

The only real way to check on detonation taking place is by examination of thecylinder head and piston, or what remains of the latter if the trouble has beensevere, which is often the case.

Yet once again you will appreciate how vital it is to make sure you are gettingenough mixture to the engine, the cost of the fuel, even if most of it is blownout of the exhaust system being just so much less than that of mechanicalfailure and the resultant expense putting it right.

While on the matter of getting fuel to the engine we would say withouthesitation that on competitive engines over three litres in capacity, the useof normal carburetors fed by means of float chambers is suspect when using fuelother than petrol, and if supercharged, the capacity figure will be even lower.

FUEL INJECTION

It is for this reason that fuel injection is so popular on large engines usedon special fuels to produce high power outputs, and in the case of the verylarge engines it becomes the only practical way, the use of carburetors beingabortive.

Since in general for competition work you are not too concerned with fueleconomy, the simpler forms of fuel injection are quite satisfactory,eliminating the expensive and elaborate but effective systems of holding theoptimum fuel to air ratio over the operating range of the engine, and ingeneral we see used continuous feed types, such as for example the Hilborn,Enderle, etc.

Power is always difficult to obtain and you cannot take out more than put in,as many have found out, and in fact you cannot get as much in practice, so ifyou propose the use of certain horsepower, you must provide fuel in quantityenough to release the necessary energy to provide that amount of power, aftertaking into consideration the losses in the system of actually converting theenergy from the input form to the output form.

We are now almost at the end of the road. With the information we now have, itonly remains for us to use certain additives to mix with the fuel in order toobtain a mixture that will enable us to extract more power out of existingengines, without stressing them mechanically to destruction.
POWER FUEL ADDITIVES

WE are now at the stage where you have come to the end of what one might termthe usual fuels and enter the area of the additives, that is to say where yoube come part chemist, part engineer, and full-time optimist.

The main object in the use of an additive is to obtain out of the existing fuela further increase in power output at the engine shaft.

Other uses are to alter the tendency of the fuel to pre-ignite and/or detonate,to obtain easier starting, particularly under cold climatic conditions, toreduce running temperature, or as a means of obtaining better mixing of thefuels, that is to say to act as blending agents, not of course all of theseattributes at the same time.

Before we go any further let it be made quite clear that when you commencehandling chemicals, liquids or fuels, call them what you will, it is essentialto maintain a very high standard of cleanliness personally and with regard tocontainers used in the operation, also to mark the contents of each containerwith its known contents

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:53:10 PM

since you are now inthe realm of chemical mixing, which under certain conditions could becomedangerous.

ACCURACY PARAMOUNT

Accuracy of measurement is paramount and attention to detail essential, and ifyou are not sure of what you are doing then leave it alone, and in nocircumstances experiment with mixtures of fuels unless you really know what youare doing as the result could be poisonous or explosive, and the explosioncould well occur long before the mixture gets placed in the tank.

Any containers used must be clean internally, and made of a suitable materialto resist the fuel chemically (see the Basic Fuel Characteristics (http://www.turbofast.com.au/racefuel15.html)page). They should be marked clearly with the nature of the contents, andre-marked when any changes are made.

Many engines have been wrecked due to not marking containers correctly so makethis one of the essential items to be done without fail.

MARK CLEARLY

In general it is safer to obtain fuel, plus any required additives, alreadypre-mixed by the supplier who will do this and mark the container in such amanner there is no doubt at all of the contents, the proportions of the mixturebeing clearly marked.

It also pays to keep a complete and very accurate record of all fuels andmixtures used, together with carburetor or injector system settings, and theresults obtained for future reference, plus, of course, ignition data and typeof plugs and so on.

Having, we hope, given due warning, let us now consider which additives we canuse, taking in turn the basic fuels we have so far discussed and the use ofadditives with them, with the objective use of the additive stated.

In connection with this we have regarded the use of up to 10 percent as anadditive, and over that amount we consider to be a major component of the fuel.

PETROL ADDITIVES

Since almost our major requirement is that of getting more power out of theengine let us see what can be done taking our basic fuels in turn, startingwith Petrol.

Additives are:-

Nitromethane. This increases power, measured at the engine shaft, inproportion to the percentage used, limited by mechanical considerations such ascompression ratio, rate of fuel flow possible in existing system.

If the engine is on the maximum compression ratio usable with petrol, thisratio will have to be dropped by a figure of one ratio if 10 percent additiveused, and by half a ratio if 5 percent additive is decided upon.

With regard to the fuel flow the jet diameter will have to be increased by afigure of 1.125 for use with 10 percent, and in proportion less for the 5percent.

Methanol. The use of Methanol enables a power increase to be obtained bythe simple act of using a higher compression ratio and in fact with 10 percentthe ratio can be increased by 1.5.

That is to say an engine running on 10 to 1 on petrol can now, by the use of 10percent Methanol, run on a ratio of 11.5 to 1 provided, and we stress thispoint, steps are taken to enable the fuel rate of flow to be increased by afigure of 1.125 minimum, or put another way, the jet diameter increased by thatamount on the diameter.

In each case, that is either Nitromethane or Methanol used as an additive, themixture should be premixed and not just supplied to the tank relying on mixingtaking place by accident as it were.

Before we leave petrol it might be pointed out while other additives aresometimes used, they do not as a result of being mixed increase the poweroutput potential of the total fuel.

METHANOL ADDITIVES

We must now consider Methanol as the basic fuel.

To obtain power increase additives are:-

Nitromethane. Bearing in mind we are, as an additive only considering amaximum amount of 10 percent, although we know in fact up to 100 percent can beused as has already been explained, the power increase at the engine shaft willbe in proportion to the amount of additive used, provide' and once again westress this, the fuel flow and jet diameter is increased by 1.125.

The compression ratio will have to be modified, on the maximum for Methanolbefore the additive was introduced and for 10 percent will have to be loweredby a ratio of 1.

Propylene Oxide. This fuel additive in general is safe to handle exceptfor two possible conditions, which under certain circumstances could well bedangerous these are the effects cause by the fuel coming in contact withcopper/alloy containers, fuel tanks, etc., or by rust particles getting in thefuel by accident, for example from a rusty container, or from rust from damagedcan top cap.

To avoid this possibility this fuel is better kept in, and used from, a plasticcontainer of the pure polythene type.

If rust particles are introduced they can do two things. One is to Polymerizeslowly, or put another way, change its chemical state, in this particular caseto form slowly a nasty waxy solid akin to polythene.

The second condition is where the polymerization process takes place quicklydue to external heat on the container, say for example from strong sunlight,which causes the speed up, resulting in a possible explosion.

The remedy is of course obvious so take steps to keep it cool, bearing in mindthe boiling point of this fuel is 93 degrees F. Or as we now tend to regardtemperature, 34 degrees C.

The best increase in power is obtained by some 5 percent as additive, as abovethis figure the gain does not increase in proportion, like the other additives,but in fact tends to decline, so stay at the 5 percent mark.

This fact is known and although reasons can be given for this behavior, at thismoment of time there is a lot of experimental work to be done with thisadditive when used with pure methanol, but anyone carrying out such work mustbe very much out on their own.

NITROMETHANE ADDITIVE

We now come to our last basic fuel, that being Nitromethane, assumed pure, andundiluted, and again our object in using the additive is to obtain a power gainat the engine shaft.

The additive is:-

Propylene Oxide. We have a slight change here in that this can be usedup to a figure of 30 percent rather than our previous 10 percent.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:53:43 PM

Increase in power output will not be proportional to theamount used, but varies from engine to engine, and also with the use of otheradditives with the total fuel, water being a good example.

In general terms one may well expect an increase of some 10 percent at theshaft for the addition of 10 percent additive, but over this figure it isalmost impossible to give an estimate as so many factors will influence theresult.

Due to the oxygen provided by the Nitromethane, the usual air-fuel ratios nolonger hold good and from that fact alone, it is very difficult to state whatthe actual power increase will be.

It has been very clearly stated before that care should be taken when usingNitromethane, but this be-comes even more necessary when dealing with this fuelplus propylene oxide additive.
ANTI PRE-IGNITIONADDITIVES

WE now come to the use of additives for reasons other than power increase. Inthis chapter we will deal only with additives that can be of assistance to usin connection with Pre-ignition and the other problem of Detonation.

We again go through our three basic fuels in the same order.

WHEN USING PETROL . . .

We have three additives in Methanol, Acetone and Benzole (Benzene) and all ofthem are introduced with the main object of reducing Detonation by increasingin effect the Octane rating of the total fuel. Pre-ignition in general shouldnot present a problem when using as basic fuel petrol.

Methanol in Petrol. This is the best from the point of view of reducingDetonation, followed by Acetone and then Benzole in that order.

Methanol can be added in all proportions up to 100 percent, but as an additivelimited to 10 percent will give an Octane increase of about 5 points. Forexample 98 Octane can be increased to 103, or looking at it another way, cheapfuel of say 91 Octane can, by the use of 10 percent Methanol, or approximatelythree quarters of a pint per gallon, will produce fuel of 96 Octane.

Acetone in Petrol. Can be used up to 100 percent but with the nominal 10percent will give an increase of 3 points rather than 5.

The major difference from Methanol being that due to the higher calorific valueof Acetone, the consumption does not increase so much, but still provides ahigher octane rating.

Benzole (Benzene) in Petrol. Again can be used up to 100 percent butwith the 10 percent amount will provide in points a rise of 2.

In many cases this additive is used to counteract detonation since some 10percent will, in certain cases, provide enough rise in octane rating to do justthat.

WHEN USING METHANOL .

Now we come to Methanol as the main fuel, and as additives to reducePreignition and/or Detonation we have two.

Acetone in Methanol. Here we are concerned only with Pre-ignition sinceMethanol has itself a very high octane rating, and is therefore to be regardedas almost free from detonation problems.

Once again our figure of 10 percent is the most advantageous use of theadditive, as over that figure has a declining effect in proportion to theamount used.

The effect of using this additive is to move the auto-ignition point upwards,and this was fully explained as will be remembered.

Water in Methanol. Up to 5 percent or a maximum of 10 percent with theobject of increasing the octane rating even higher, to reduce detonation undervery high supercharge conditions.

WHEN USING NITROMETHANE

Last of all now we have Nitromethane as our main fuel. Here we have threeadditives to help with preignition and or detonation.

Methanol in Nitromethane. Since Nitromethane has itself a tendency topre-ignite and detonate, the sole object of up to 10 percent Methanol as anadditive is to reduce this tendency to detonate while having only a minoreffect on pre-ignition.

Water in Nitromethane. Up to a maximum of 2.5 percent as this is themaximum amount that will mix without separation taking place. It reduces bothpreignition and detonation due to the internal cooling effect alone.

In practice a combination of Methanol and Water is the better use of the twoadditives, the proportions being 2.5 percent water and 7.5 percent Methanolgiving a good safe usable blend of Nitromethane, with almost the full powercapability of undiluted Nitromethane.

Acetone in Nitromethane. Up to a maximum of 5 percent. This reducespreignition by raising the auto-ignition point and any small decrease indetonation is incidental.
EASIER STARTING ADDITIVES

WE now come to the last use of additives and that is to assist with starting,which should not be a problem but nevertheless sometimes is. Again we deal withour three basic fuels as before.

WHEN USING PETROL . . .

Acetone is the only safe additive to use, its function being that itincreases the volatility of the mixture, without reducing the basic fuelproperties too much. Up to 5 percent being quite enough to use.

Ether is the only other additive to use with Petrol and may be used inthe same manner as Acetone and for the same reason, but is in fact notrecommended for use with spark ignition systems, and has obvious handlingproblems.

It can also quite easily produce a wrecked engine, so use it if you must, butyou have been warned

WHEN USING METHANOL .

Acetone is the only additive and up to 10 percent maximum. The action ofthis is to increase the volatility of the total fuel or put another way itreduces the flash point temperature.

Main use is on very cold days, but in fact it even then should not be reallynecessary, however let us say it is convenient.

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:56:20 PM

WHEN USING NITROMETHANE

When our main fuel is Nitromethane, the only additive is again Acetone for thesame reasons as when used with Methanol.

All fuels have one common blending agent, this being Acetone, but in most caseswill mix satisfactorily without, but where found necessary, the amount usedshould be the minimum required to obtain complete mixing without trace ofseparation, visually checked.

In some cases it may be necessary to use quite high percentages, for examplesome 30 percent when blending Benzole and Methanol.

Over recent years the methods used in producing petrol have changed and withthe modern petrol's better blending is obtained with Methanol due to therefining techniques now used without a blending agent being used.

STALE FUELS

Many think that fuels when stored become less effective with age, but in factthis is not so provided the cans or containers are fitted with caps or snap onlids that fit correctly.

Two fuels that are difficult to keep unless great care is taken in sealing thecontainers are Ether and Propylene Oxide, the high rate of evaporation beingthe problem.

In conclusion, may we just repeat three major things to keep in mind.

· First of all apart from Petrol, always tend to keep the mixture on the richside and never on the weak.

· In all cases never rush, take your time and be quite accurate in yourmeasurements.

· Last of all do not experiment unless you know what you are doing as it couldbe both expensive and dangerous.

GOOD RACING!

BASIC FUEL CHARACTERISTICS

[TABLE=class: MsoNormalTable, width: 5]
[TR]
[TD=width: 229, bgcolor: transparent]

GENERAL DESCRIPTION

METHANOL (Methyl Alcohol) CH30H is a volatile, highly inflammable, water-clear liquid with a mildly spirituous odour. Miscible with water or nitromethane in all proportions and almost all with petrol.
[/TD]
[TD=width: 252, bgcolor: transparent]

BASIC CHARACTERISTICS

[TABLE=class: MsoNormalTable, width: 100%]
[TR]
[TD=width: 20%, bgcolor: transparent]

Flash Point

[/TD]
[TD=width: 21%, bgcolor: transparent]

Boiling Point

[/TD]
[TD=width: 19%, bgcolor: transparent]

Freezing Point

[/TD]
[TD=width: 12%, bgcolor: transparent]

Specific Gravity

[/TD]
[TD=bgcolor: transparent]

Lbs/Gall approx

[/TD]
[/TR]
[TR]
[TD=width: 20%, bgcolor: transparent]

F C

[/TD]
[TD=width: 21%, bgcolor: transparent]

F C

[/TD]
[TD=width: 19%, bgcolor: transparent]

F C

[/TD]
[TD=width: 12%, bgcolor: transparent]
[/TD]
[TD=bgcolor: transparent]
[/TD]
[/TR]
[/TABLE]
61 16 148 64 -144 -97 0.796 8[/TD]
[/TR]
[TR]
[TD=width: 229, bgcolor: transparent] NITROMETHANE CH3NO2
is an inflammable water-clear liquid with a mild odour, containing approximately 53% by weight of oxygen. Water will mix with nitromethane to the extent of 2.5% only, by volume.
[/TD]
[TD=width: 252, bgcolor: transparent] 110 43 214 101 -20 -29 1.13 11.25[/TD]
[/TR]
[TR]
[TD=width: 229, bgcolor: transparent] ACETONE (Dimethyl Ketone) CH3COCH3
is a highly volatile, highly inflammable, water-clear liquid with a strong, sharp, characteristic odour. Miscible with all the chemicals listed here, and water.
[/TD]
[TD=width: 252, bgcolor: transparent] 0 -18 133 56 -138 -94 0.791 8[/TD]
[/TR]
[TR]
[TD=width: 229, bgcolor: transparent] ETHER (Diethyl Ether) C2H5OC2H5
is an extremely volatile, highly inflammable, water clear liquid with a strong, lingering, characteristic odour. Miscible with all the chemicals listed here but not with water.
[/TD]
[TD=width: 252, bgcolor: transparent]-40 -40 95 35 -183 -116 0.714 7[/TD]
[/TR]
[TR]
[TD=width: 229, bgcolor: transparent] BENZOLE, (Benzene) C6H6
is an inflammable water-clear liquid with a dull sweet odour Miscible in most proportions with all the chemicals listed here but not with water.
[/TD]
[TD=width: 252, bgcolor: transparent] 12 -11 176 80 41 5 0.879 8.75[/TD]
[/TR]
[TR]
[TD=width: 229, bgcolor: transparent] NITROBENZENE C6H5NO2
is an inflammable, yellow, oily liquid with a strong odour of almonds. Miscible in most proportions with all the chemicals listed here but nrot with water.
[/TD]
[TD=width: 252, bgcolor: transparent] 190 88 412 211 41 5 1.20 12[/TD]
[/TR]
[TR]
[TD=width: 229, bgcolor: transparent] PROPYLENE OXIDE (1 :2. Epoxypropane) CH3-CH-CH2
is an extremely volatile, very reactive, highly inflammable, water-clear liquid with a light gaseous odour. Miscible with all the chemicals listed here but only partially with water.
[/TD]
[TD=width: 252, bgcolor: transparent] 32 0 93 34 -155 -104 0.83 8.25[/TD]
[/TR]
[TR]
[TD=width: 229, bgcolor: transparent] UCON LB625 (Polyalkalene glycol)
A water-clear synthetic lubricating oil with exceptionally high film strength properties. Miscible with all the chemicals listed here but not with water.
[/TD]
[TD=width: 252, bgcolor: transparent] 430 221 - - -25 - 32 1.0 10[/TD]
[/TR]
[/TABLE]

[/COLOR][/SIZE]

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:57:33 PM

[TABLE=class: MsoNormalTable, width: 461]
[TR]
[TD=width: 10%, bgcolor: transparent]

[/TD]
[TD=width: 48%, bgcolor: transparent] [TABLE=class: MsoNormalTable, width: 100%]
[TR]
[TD=width: 25%, bgcolor: transparent]

Conservative Maxium Compression Ratio

[/TD]
[TD=width: 25%, bgcolor: transparent]

Air/Fuel Ratio for Max Power lbs/lbs

[/TD]
[TD=width: 25%, bgcolor: transparent]

Energy from Combustion B.T.U/lb

[/TD]
[TD=width: 25%, bgcolor: transparent]

Coolling Effect (Latent heat of Vaporisation) B.T.U./lb

[/TD]
[/TR]
[/TABLE]

[/TD]
[TD=width: 42%, bgcolor: transparent]

Use in Internal Combustion Engines

[/TD]
[/TR]
[TR]
[TD=width: 10%, bgcolor: transparent]

Methanol

[/TD]
[TD=width: 48%, bgcolor: transparent]17 : 1 4.5 : 1 9770 472[/TD]
[TD=width: 42%, bgcolor: transparent] Methanol permits the use of very high compression ratios when unsupercharged or high boost pressures when supercharged. The large cooling effect increases volumetric efficiency and is of particular use in the supercharged engine reducing charge temperature after compression. A tendency to pre-ignition is most noticeable at weak mixture levels.
[/TD]
[/TR]
[TR]
[TD=width: 10%, bgcolor: transparent] Nitromethane
[/TD]
[TD=width: 48%, bgcolor: transparent] [TABLE=class: MsoNormalTable, width: 100%]
[TR]
[TD=width: 25%, bgcolor: transparent]

6.5 : 1

(10 : 1 with rich mixtures)

[/TD]
[TD=width: 25%, bgcolor: transparent]

2.5 : 1 to 0.5:1 at least

[/TD]
[TD=width: 25%, bgcolor: transparent]

5000

[/TD]
[TD=width: 25%, bgcolor: transparent]

258

[/TD]
[/TR]
[/TABLE]

[/TD]
[TD=width: 42%, bgcolor: transparent] Nitromethane enables considerable power increases to be obtained (70 percent minimum with proper use). Most often used blended with methanol, in various propor ,tions to provide power increases consistent with engine strength, etc. A tendency to detonation is reduced by an increase in mixture strength, reduction in engine temperature, reduction in compression ratio or the addition of methanol.
[/TD]
[/TR]
[TR]
[TD=width: 10%, bgcolor: transparent]

Acetone

[/TD]
[TD=width: 48%, bgcolor: transparent] 17 : 1 9.4 : 1 12,500 225 approx[/TD]
[TD=width: 42%, bgcolor: transparent] As a basic fuel acetone appears to have all the required characteristics, these in general Iying midway between methanol and petroleum. An exception is its very high anti-knock rating which approaches that of methanol. Other uses are as an additive to other fuels, notably to methanol to reduce pre-ignition sensitivity and promote easier starting under low temperature conditions, up to 10 percent for this purpose.
[/TD]
[/TR]
[TR]
[TD=width: 10%, bgcolor: transparent]

Ether

[/TD]
[TD=width: 48%, bgcolor: transparent] 4 : 1 9.8 : 1 15,000 153[/TD]
[TD=width: 42%, bgcolor: transparent] Not used as a basic fuel in spark ignition engines due to its very low knock-rating, but this characteristic is desirable in the small high-speed diesel engine where it is used in relatively large percentages (approx. 15 percent to 35 percent by volume) as an additive. Its volatile nature and low flash point make it useful as an additive tuP to 5 percent) to improve starting and give a rapid throttle response.
[/TD]
[/TR]
[/TABLE]

Title: Everything you ever wanted to know about racing fuel
Post by: rsss396 on December 09, 2013, 01:58:25 PM

[TABLE=class: MsoNormalTable, width: 461]
[TR]
[TD=width: 10%, bgcolor: transparent]

Benzole

[/TD]
[TD=width: 48%, bgcolor: transparent] 15 : 1 10.8 : 1 17,300 153[/TD]
[TD=width: 42%, bgcolor: transparent] Most often used blended with methanol to give a greater energy per unit volume with reduction in the latent heat vapourisation, this being a compromise often used for long distance racing where fuels other than petrol are allowed.
[/TD]
[/TR]
[TR]
[TD=width: 10%, bgcolor: transparent]

Nitrobenzene

[/TD]
[TD=width: 48%, bgcolor: transparent] not known 8 : 1 10,800 143[/TD]
[TD=width: 42%, bgcolor: transparent] Blended in very small proportions with other fuels it is thought to act as an ignition accelerator. As this material has a strong odour even after combustion it is sometimes used as an additive in other fuels (approx. 0.5 percent) to mask the normal exhaust odour making it difficult to detect the base fuel type.
[/TD]
[/TR]
[TR]
[TD=width: 10%, bgcolor: transparent]

Propylene Oxide

[/TD]
[TD=width: 48%, bgcolor: transparent] not known 9.6 : 1 14,000 220[/TD]
[TD=width: 42%, bgcolor: transparent] Used as an ignition accelerator additive particularly with nitromethane (up to 20 percent by volume with pure nitromethane) where noticeable increases in power are possible. Easier starting and smoother running are other benefits when blended with most other fuels (up to 5 percent)
[/TD]
[/TR]
[TR]
[TD=width: 10%, bgcolor: transparent]

Ucon

[/TD]
[TD=width: 48%, bgcolor: transparent] At 0 F this oil compares to SAE 20 at the same temperature, and at 210 F it compares to SAE 50 at the same temperature
[/TD]
[TD=width: 42%, bgcolor: transparent] Used to advantage in all two stroke engines operating on fuel/oil mixtures. The unusually high him strength properties allowing a reduction in the amount of oil in the fuel by as much as 55 percent. Of particular use in very small high speed two stroke engines where the normal oil content can be up to 30 percent of the total volume, with the attendant restriction on the amount oF fuel that can be burnt.
[/TD]
[/TR]
[/TABLE]

TRX250R.ORG

FAQ's & Technical Articles => Techincal Section => Fuel/Oil/Coolant => Topic started by: rsss396 on December 09, 2013, 01:23:58 PM