TRX250R.ORG
Workshop => The Mad Scientist => Topic started by: DeathPunch88_250R on February 25, 2017, 08:59:33 PM
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Just wondering if a good flowing intake can be built from scratch at a fraction of what a kit costs?
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I used the OEM boot & electrical PVC & made a bracket & clamp to hold it. PM me your number & I can send you a couple pic's
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There is some discussion in another thread http://trx250r.org/threads/6793-New-Project-YFZ-Banshee-Hybrid?p=71802&viewfull=1#post71802 that might keep you from making some of the common mistakes when making home grown intake/air filter engine components. Honda's engineers have already solved the resonance portion of the design by providing a good pattern in the OEM TRX250R boot to follow in the diameter progression vs distance from the carburetor.
Remember an engine that makes good power has an intake that flows well and has the resonance of the system correct. An engine that has a high flowing intake with the resonance wrong will not usually make good power and will have unsolvable jetting issues as well as dips and spikes in the power curve.
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So the pipe on the air intake needs to be the correct Tuned length to reduce resonance issues?
Someone should dyno a Trx250R with different length pipes on the carb and filter to see what it does to the curve. It would be interesting.
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In V8 drag motors a short ram intake usually means shorter intake runners to make more low end torque.A High Ram Intake usually makes More HP in a higher rpm range. Just wondering if the same rule would apply to a tuned intake tube on a Trx250r?
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So the pipe on the air intake needs to be the correct Tuned length to reduce resonance issues?
Someone should dyno a Trx250R with different length pipes on the carb and filter to see what it does to the curve. It would be interesting.
The pipe on the air intake needs to be the correct tuned length to take advantage of resonance. Resonance can our friend or dreaded enemy. Optimizing resonance is the phenomena of pressure waves arriving at the port, reed tip or valve at a time just before intake closing so the trapped air flow into the engine is maximized.
I have done a lot dyno work on the TRX250R intake length. ESR, LED and Honda has obviously also done dyno work on the intake length. The portion of the intake that optimizes resonance on all of the above intakes have tuned lengths that are almost identical. When Troybult finishes his dyno testing on his new intake system, it will also probably have a similar tuned length to the above systems already in the public domain. The engine knows what intake length it wants and has not changed since these engine were designed.........it just takes a few devoted developers doing dyno testing to come up with the same answer. Different cylinders designs, different carburetor sizes, and pipe designs on the TRX does not change the tuned length of the intake very much but it does have a huge effect of the size of the air filter needed. A flow bench or cad package cannot be used to find the optimum tuned length on the intake or exhaust.
Tuning the intake is not a new concept to us old timers, most of the above builders have been doing it on all of their engine packages for over 25 years.
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(http://forums.trx250r.org/vbulletin_imports/1916_8599_2017-04-18_1719.jpg)
(http://forums.trx250r.org/vbulletin_imports/1916_8600_2017-04-18_4988.jpg)
(http://forums.trx250r.org/vbulletin_imports/1916_8601_2017-04-18_3767.jpg)(http://forums.trx250r.org/vbulletin_imports/1916_8602_2017-04-18_7767.jpg)
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(http://forums.trx250r.org/vbulletin_imports/1916_8604_2017-04-18_6470.jpg)
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In V8 drag motors a short ram intake usually means shorter intake runners to make more low end torque.A High Ram Intake usually makes More HP in a higher rpm range. Just wondering if the same rule would apply to a tuned intake tube on a Trx250r?
My v8 testing has showed the opposite to your findings. Short tuned lengths favor higher RPMs where longer tuned lengths move the power to lower RPMs when the cams are optimized for a given tuned length.
The tuned length of a intake tract tunnel in a 4 stroke starts at the valve and ends slightly above the bell mouth of the ram tube. The optimum tunnel shape starts at the valve and ends at the bell mouth of the ram tube. The air flow does not really care if the intake tract tunnel is in the head or built into what we usually call the intake manifold. The engine is just wanting a certain cross-sectional port area vs length from the valve with as few bends as possible.
The old 4 barrel intake manifolds had intake tunnel lengths/tuned lengths that were way too short. These short tuned lengths were at an RPM that was out of reach of the breathing and mechanical limits of most engines. Then came the tunnel ram type of intake manifolds in the 1970s that had tuned tunnel lengths that were 6" or more longer than the 4 barrel manifolds. The tunnel ram manifolds typically made more power everywhere in the RPM range. Engineers found that making the runners real long could make a small block Chevy make big block type power in the mid range but there was not enough space under the hood for these carburetor type manifolds.
20 to 25 years later when fuel injection became the norm we could make the runners as long as we needed and feed the runners from a large plenum with the throttle body mounted at one end. Engine power started to escalate without the need for wild cam timings because the tuned length of the intakes were optimized for the cam and RPM range where the engine needed to operate. This group of intake systems were known as tuned port manifolds.
Engineers are often handcuffed and cannot do what they know will work well because of space confines or marketing will not allow them to introduce certain technologies because of the prejudices of the consumer.
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Someone gave a tip to use Zip Ties in the Chat Box so I used some with good results. I plan to get a Red Filter in place of the blue one.
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(http://forums.trx250r.org/vbulletin_imports/1916_8605_2017-04-18_2510.jpg)
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Okay thanks Jerry I ended up Using the stock boot
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Better to go with Whats proven!
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(http://forums.trx250r.org/vbulletin_imports/1916_8599_2017-04-18_2430.jpg)
(http://forums.trx250r.org/vbulletin_imports/1916_8600_2017-04-18_2157.jpg)
(http://forums.trx250r.org/vbulletin_imports/1916_8601_2017-04-18_3413.jpg)(http://forums.trx250r.org/vbulletin_imports/1916_8602_2017-04-18_4787.jpg)
My testing has shown that the intake pictured is a very good intake for engines with 39mm or smaller carbs and engines that make under 45 hp. As the power goes above 45 hp, the surface area of the filter needs to increase as well as the inside diameter of the small portion of the intake boot. The length of the small diameter portion of the intake boot is the portion of the system that should not be changed much. This is the tuned length portion of the intake NOT THE DISTANCE FROM THE CARB TO THE AIR FILTER!!!!
On the big bore engines that are making over 60 hp the air filter needs twice as much filter surface area as the one pictured above. Air filters with a lot of surface area helps prevent the engine from sucking dirt through the filter. Air filters with excess surface area allows the filter to be oiled slightly heavier without hurting the air flow through the air filter. Excess surface area also reduces the amount of suction the engines places on the particles of dirt that are trying to sucked through the filter.
If you have room, install an air filter with as large of a diameter and length as possible. There have been a few rare occasions when a very large filter will cause a drop in power even after re-jetting the carburetor. When this occurs I usually find when I get the tuned length correct the power is restored and or better.
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Cool Jerry! Thanks for the reply on my Intake.
I will take my old filter to the parts store when I go get the new one and see if they can get Me a longer filter.
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So basically...
higher HP engine w/ smaller filter = higher intake velocity = increased suction = decreased air filter effectiveness
higher HP engine w/ larger filter = lower intake velocity = increased intake volume = increased air filter effectiveness
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In my honest opinion an air intake with a "bell type" velocity stack would be the best design to go with as opposed to a straight pipe leading into the carb.. Such as this, I know BDT and LED have a velocity stack design in their intakes..
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So basically...
higher HP engine w/ smaller filter = higher intake velocity = increased suction = decreased air filter effectiveness
higher HP engine w/ larger filter = lower intake velocity = increased intake volume = increased air filter effectiveness
Yes your right.
Foam filters, K&N filters and paper filters work on entirely different principles
Dry paper filters have extremely small air passageways (pores) for the air to flow through. There are not many dust particles that are smaller than the pores in a paper filter so the particles are prevented from passing through and stay on the outside of the filter.
The K&N filtering medium is an oiled cotton gauze that is comprised of small fuzzy cotton strings that are woven into a mesh. Dirt particles larger than the string mesh will not pass through the gauze. Smaller dust particles are suppose to stick to the oil impregnated fuzz that is suppose to overlap the cotton string mesh. A brand new K&N properly oil filter will do a pretty good job of catching almost anything but most guys ruin a K&N the first time they clean and oil the filter. A slightly dirt K&N will usually provide better filtering than a freshly serviced filter.
Using a water hose or compressed air hose on a K&N while cleaning will crowd some of the cotton strings closer together. When some strings are crowded together this will increase the mesh size between parallel strings. When the mesh size is increased large particles can now pass through the larger mesh holes. When the mesh size is increased on a properly cleaned filter, the fuzz that surrounds each string will not overlap enough between strings to catch the small stuff.
A K&N filter must be 100% oil free after it is cleaned for the fuzz that is suppose to surround each string to be present when it dries. If there is some oily residue remaining in the gauze after cleaning and not 100% dry, the fuzz that normally surrounds each string will stick to the string. A K&N filter that does not have fuzzy strings, will allow the medium to small particles to pass through the filter.
The oiling technique on a K&N is critical. If using the K&N spray oil , spray only the outside of the filter and wait a few minutes for the oil to wick all the way through to the inside. If the oil has not wicked through to the inside after a few minutes, spray the outside again. Repeat the process until the inside of the fabric has the same color as the inside. Using this process guarantees the cotton gauze is thoroughly saturated. Use the K&N oil and do not use ATF of some other imitation air filter oil. K&N oil is not a petroleum oil but I have heard that it is a vegetable based oil so that it has some very very slight tackiness when exposed to air for a while.
I like to use the K&N oil that comes in a squeeze bottle. Use the squeeze bottle to place a bead of oil down the outside edge of each pleat. Wait a few minutes and look at the inside of the filter to see if the oil has wicked through to the inside. If it has not wicked through after a few minutes, make another pass down the outside of each pleat. Repeat the process until the gauze is thoroughly saturated. It is better to slightly over oil the filter than to under oil it. Excess oil will eventually drip off the bottom of the filter or the engine will run lousy for a while if the filter is undersized.
Foam filters have many large interconnected air flow passageways that have the inside walls of the passageways coated with a very tacky substance. The filtering process occurs occurs on the inside surface of the interconnected air flow passageways through the filter. Very large particles will stick to the outside of the filter and or get wedged into the entrance of the airflow passageways. The small particles move through the passageways until they encounter and adhere to a sticky surface. Once all of the sticky surfaces in the interconnected passageways have particles stuck to them,the filter will allow the small particles to pass through the filter unless all of the entrances of the passageways are plugged with large particles.
Mesh type filters filter better as they get dirty until enough vacuum is present to distort the mesh so that particles wiggle through the mesh. Foam filters will pass dirt once the tacky surfaces have dirt stuck to them. With any type of air filter that is not substitute for having as much filter surface area as space will allow.
Each type of filter has their advantages and disadvantages, you have to decide which filter fits your situation best.
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Good Info Everybody! Thanks
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In my honest opinion an air intake with a "bell type" velocity stack would be the best design to go with as opposed to a straight pipe leading into the carb.. Such as this, I know BDT and LED have a velocity stack design in their intakes..
You are correct as long as the straight portion of the velocity stack has the correct tuned length.
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(http://i67.tinypic.com/2ngzia0.jpg)
I made this one then powdered it black. Nothing fancy or much thought into it. Just bored and figured it could suck more being an open filter instead of in the box. My 250r will spend 99% of it's running life in the sand so mud/water shouldn't be much if an issue.
I made it for stock intake tube and filter. Have a uni on it and welded a nut to hold the brake RESI. Essentially just made the front of the stock airbox out of steel
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:redbull:That's a nice job on the fabrication Goose!
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It was a pain in the ass, atleast the circle was. The rest wasn't too bad.
Made it all by hand out of a 2x2 sheet I had laying around, was bored one day and decided to do it. I'm happy with how it turned out.
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Looks good that's for sure
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(http://forums.trx250r.org/vbulletin_imports/1441_8618_2017-04-18_896.jpg)(http://forums.trx250r.org/vbulletin_imports/1441_8615_2017-04-18_8477.jpg)
(http://forums.trx250r.org/vbulletin_imports/1441_8616_2017-04-18_3664.jpg)
I made mine from a aluminum conduit bushing and an ESR center mount hanger.
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Looks good! Wish I had welding machines.Lol