link http://www.foxvalleykart.com/print/prt_fuel6.html
THE QUESTION OF FUEL
PART 6 - Additive Performance Testing
By John Copeland
In earlier segments of this series we've talked about fuel additives used to improve engine performance. We've looked at the basic properties of fuels that may impact how much energy they make available upon combustion and how some additives may increase ( or decrease) that available energy. We've also looked at various means of detecting these additives and how the tech man can spot them in the field. Now it's time to take a hard-numbers look at what sort of advantage the fuel cheater can expect to gain from using these materials.
As you may recall from Part Five, (NKN June 1995), we established a threshold of detectability for each of the nine additives that we have been testing, both on the Digatron meter, and with two different water absorption tests. In order to generate meaningful data for this performance testing portion of the project, we ran fuel samples with more than one concentration of the additive in question. For example, earlier testing showed the threshold of detectability for Propylene Oxide to be about 2% by volume, when mixed with otherwise legal race gas. We then ran dyno testing on that fuel with 2% Propylene Oxide added and compared it back-to-back with the same sample with 10% added, also back-to-back against a legal sample. Hopefully this will address the question of "Oh yeah, Well I heard that Johnny Go-fast put some of that stuff in his gas and it gave him more top end between 18,000 and 19,000 RPM!" Let's find out if adding this stuff really works, and(http://www.foxvalleykart.com/images/fuel61.jpg) how.
In order to insure uniformity of results, all samples were based on Phillips B32 race gas. Comparison testing on the dyno has shown that this high-quality race gas will produce consistently higher performance than four other race gasolines generally available, and substantially higher performance than any pump gas or combination of pump gases. As with earlier tests in this series all samples were mixed 20:1 with Burris oil, mixing four ounces of Burns Castor and two ounces of Burris Blend per gallon of fuel. All testing was done on Fox Valley Kart's electronic engine dyno with periodic base-line samples re-run to insure repeatable data. Torque readings, from which horsepower is calculated, are accurate to .001 foot-pounds. All data, torque, RPM, cylinder head and exhaust temp, are collected by the computer 10 times each second, then computer averaged around each plotting point. While the absolute horsepower numbers may vary from one dyno to another, what we're interested in here are comparative figures.(http://www.foxvalleykart.com/images/fuel62.jpg)PROPYLENE OXIDE
Propylene Oxide's primary contribution to the combustion process centers on it's high heat of vaporization. As we discussed in Part Four of this series (NKN June 1995), this high heat of vaporization means that, as it passes from a liquid to a gaseous state in the carburetor, it absorbs a significant amount of heat and, thus, cools the incoming fuel charge significantly, making it denser. While Propylene Oxide brings along some of the oxygen it needs for it's own combustion, it also takes additional oxygen from the carburetor air. It's specific energy is slightly less than that of gasoline, so don't expect any help there. It's combustion products are C02, CO, and water vapor. As you can see from the graph, there is no measurable performance difference between the base-line fuel and the sample containing 2% Propylene Oxide, slightly above the threshold of detectability with the Digatron meter. However, by increasing the concentration to 10% by volume, well above what even the most bumbling tech man should be. able to spot, we begin to see the effect of improving the charge density on the low end. This effect diminishes as RPM increases, probably because this higher air velocity through the carb dramatically improves the atomization of the gasoline and the resulting chilling of the incoming charge.
Conclusion: Yes, using Propylene Oxide may help the low end performance or used in sufficient quantities. But unless there is no fuel tech at all, you can't get away with running enough to get any improvement
ETHYL ETHER(http://www.foxvalleykart.com/images/fuel65.jpg)
Most commonly used, fuel-wise, as the major component in starting fluid for those cold winter mornings, Ethyl Ether has both a very high heat of vaporization and a very low flash point. Those properties make it the perfect cold weather engine starter but, (thank goodness) we don't race in sub-zero conditions. It's specific energy is lower than gasoline and it's very low boiling point (95 degrees) make it difficult to keep around in mixed fuel for very long: it simply evaporates away! Regardless, some folks have insisted that it was the secret key to better lap times, so let's take a look. In the first graph, again using 2% Ethyl Ether, We could find absolutely NO measurable variance in power output over the same fuel without the Ethyl Ether. Tiny variances in the raw data were too small to show up on the graph at all. By increasing the concentration to 10% the effect of the high heat of vaporization begins to show up on the low end. The cooling effect of the vaporization of the Ethyl Ether treated fuel was greatest at the lowest RPM and steadily decreased. Although it is hard to pick up on the graph, the performance actually dipped below that of the undiluted race gas at the highest RPM range, although very slightly. Once again, Ethyl Ether is very easily detectable with the Digatron meter in concentrations as low as 1%.(http://www.foxvalleykart.com/images/fuel66.jpg)
Conclusion: Unless you're racing at the South Pole, there really isn't anything to be gained here. Small concentrations don't do anything at all. And even if you wanted to run enough to get the minor low speed charge cooling effect. the smell is a dead give-away. Spend your time and money elsewhere.
TOLUENE AND XYLENE
We've chosen to lump Toluene and Xylene together for several reasons. If you read the previous article (NKN July 1995), you probably noticed that we poured substantial quantities of Toluene and Xylene into the base fuel samples trying to get the Digatron meter to react. The best we could do was to push it down to ?8, and that with over 50% of each additive! The reason is simple: both Toluene and Xylene are major components of normal gasoline! They're already in there in substantial quantities.(http://www.foxvalleykart.com/images/fuel67.jpg) Increasing the concentration does nothing but raise the octane rating of the fuel, and, if you've kept up with your reading, you already know that raising the octane, in and of itself, is of no benefit to almost all karting engines. Again, in keeping with our goal of maintaining consistency in our testing routine, we dynoed samples with 2% and 10% of each, both Toluene and Xylene. As expected the 2% graphs show only the most minor variation, with some gain in the low RPM range. This is most likely due to the increased octane rating from adding these materials helping to suppress some high load, low RPM detonation.
(http://www.foxvalleykart.com/images/fuel68.jpg)Conclusion: This one's a red herring. If you must pour something in your fuel to feel like you're getting some sort of special advantage, add Toluene and/or Xylene. The won't do you any good, but they won't do you any harm either, and you most likely won't get caught. One note of caution: if the tech man is using either of the water tests we outlined earlier in this series, a 10% or greater addition of Toluene or Xylene may show up.
1,4 DIOXANE
Of the additives we tested, this one has caused the greatest concern amongst the karting public, and with good reason. It is a skin- absorbable poison and a Class-A carcinogen. While it does not show up on the Digatron meter, it is easily detectable with either of the two water absorption tests outlined in Part Four. Again we ran dyno tests at two concentrations. However, because of 1,4 Dioxane's much higher threshold of detectability, we chose to test at 10% and 20% by volume. The results on the two graphs point out what the effects of this material are, both good and bad, as well as it's ***ulative effect. It is generally thought that 1,4 Dioxane's benefit lies in it's improved oxygenation of the combustion reaction. That appears to actually reduce power output in lower RPMs by, in effect, leaning out the mixture. In this RPM range the carb settings are often too lean already and this additional leaning may result in failure. However, as RPMs increase and the Walbro carb translates into an over-rich condition, the oxygenation effect begins to pay off. Higher combustion temperatures will likely accompany this change. Comparison between the 10% graph and the 20% graph indicate that the addition of more 1,4 Dioxane increases both the negative low RPM effect and the positive high RPM effect.
Conclusion: This is a tough one. Here we have an additive that actually does something; part good, part bad. But more importantly, this stuff is VERY VERY BAD FOR YOU!! Some of you other old-timers will remember when some folks ran Hydrazine (that's liquid rocket fuel, really) back in the 60s. Like 1,4 Dioxane, it was very dangerous to mess with. The sanctioning bodies made it illegal and threatened lifetime suspensions for anyone caught using it. Now there is considerable pressure coming from several sanctioning bodies and clubs to suspend anyone caught using 1,4 Dioxane for life. I totally support this position. Any competitor who exhibits so little regard for themselves or their fellow competitors as to expose them to this material has no business in karting. Let me repeat, 1,4 Dioxane is VERY DANGEROUS, both to use and to be around. If you see anyone using this material, notify the officials IMMEDIATELY! In liquid form it is highly absorbable through the skin and HIGHLY TOXIC. It is also listed as a LETHAL CARCINOGEN. This is not anything that you want being used around you or your family, it has major health risks!. DON'T STAND FOR IT!