My Custom High RPM Pipe! Easy to make!

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RCDAD said:
Looks good. Keep us posted on how it holds up.
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Will do. I am hoping it will last. I may build a nerf bar as an extension to the shock mounts to protect the rear of the pipe, just in case the truck flips and lands backend first.
 
Proper header diameter and length are two shot contributing dimensions to high rpm in two strokes. So without the 2" of header you removed high rpm may be limited. Also the sharp design angle of the focused cone of this pipe is another lack of RPM above 17k . It is hard to have the best of all worlds for these variety of motor combinations within the space of fitting under the body . So overall if the mod works for your driving style go for it . Good thinking .
 
Thanks Spint for the heads up. I can add 2" of header and still work like I want it to. Right now I'm just shy of 2" I think. The rounded tip makes sense, I just wanted it to look clean out of the body. Did you watch the second video i did? What did you think, did it sound like it was reving like it should? Any input is great from a guy who has built them before!
 
The second feature that controllers the rpm band is the flat band length between the deflector and the difuser. But to experiment with this requires sheetmetal and some tig welding on the aluminum
 
Changing one can adversely affect the other . They literally have to work in harmony since it is dependant on sound waves to bring a charge of unburned fuel back into the combustion chamber
 
Right now I have 1 3/4 straight pipe from header to the expansion opening. I tried different length hoses from 2" - 3". I found the longer the begining runner was, the more back pressure I gained. The engine sounded like It lost top end at 3" of pipe. The 2" made no difference from my original set up. I suppose a dyno would be the only way to see small differences and fully optimize performance. As for performance I can see, full throttle screams and the truck is alot quicker on the top end, before I would run out of RPM and I thought my gearing was to low, now I can pull the gears alot higher. I am assuming because the engine revs higher, with everything else considered of course. All I did was change my pipe and re tune.
 
What degree of exhaust port timing are you running. Do you have standard crank bearings or are yours fast Eddie ceramic? It sounds like you need to experment with the flat band length between the difuser and the reflector . Maybe Send me your motor specs . Bore stroke . Port timing in degrees and the fuel and oil you run. And I can see what the pipe should be like so you can compare. You mostly run big wide open areas or track type stuff. Mt are a bad compromise anyways because it takes away so much of optimum pipe and tune just to get those heavy tires going.
 
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Stygian said:
I hope this gets worked out, I would love to try this as I have the same pipe.
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It is really close for my engine, I cant say for certain how it will work for smaller unported engines. It is still worth doing, I noticed a big difference over the stock pipe it started as.
 
Sprint 77 said:
What degree of exhaust port timing are you running. Do you have standard crank bearings or are yours fast Eddie ceramic? It sounds like you need to experment with the flat band length between the difuser and the reflector . Maybe Send me your motor specs . Bore stroke . Port timing in degrees and the fuel and oil you run. And I can see what the pipe should be like so you can compare. You mostly run big wide open areas or track type stuff. Mt are a bad compromise anyways because it takes away so much of optimum pipe and tune just to get those heavy tires going.
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Great Questions. I can tell you what I know.

36cc RAMtech-RC engine ported by Flow Systems. 32mm Stroke x 38mm Bore. I am not sure about what degree of porting was done. I did not see anything that suggests that the exhaust port runner was modified other then it was cleaned up a bit. I have no idea what was done to the mixing chamber (lower end).

I also run 40:1 with Redline Racing Synthetic oil only. Also, if I forgot to mention in prior posts, the exhaust header was ported to the same diameter of the tubing heading to the expansion chamber. I have some rounded pipe I can weld on in place of the straight diffuser if needed
 
Did some further testing, it is evident that this pipe will work best on lighter cars or trucks with lower gearing to allow the engine to hit mid and top end quicker. I noticed that I am getting ALOT more top end and top speed from my Mt, however torque is lost down low and the truck is to heavy with stock gearing. I put back my side mount jetpro pipe to compare again, and fur sure, not nearly the top end but better take off. I am going to re gear the mt and see if this helps the motor come to life quicker. Obviously there is more rpm with my pipe, just being able to use it is the tricky part lol
 
for bottom to mid response you need back pressure. you already stated your pipe doesn't have much & i can tell from the vid. for better mid to top response you don't want a lot of back pressure. this is what a lot of racers use. this is why the jet pro & your pipe differ in what they improve. give your pipe a touch more back pressure & you might be happier.
 
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MrMeatHooks said:
Here is the Final product. It looks great, here are some pics to. In the video I did not rev it all the way out, for obvious reasons, but you can tell it has alot left.When my wife has time, I will get a bash vid up.

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after watching this again, maybe experiment w/different i.d. outlets. try a slightly smaller, narrower one but keep it the same length.
 
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Yeah, I was thinking that, a bit smaller would help. It would be easy to put a restrictor in or on to increase BP. It sounds so narly though, I love the sound and performance over my other pipe and want to put it back on.
 
see, good minds think alike but not the same way. i prefer the way a pipe sounds w/back pressure. it has that popping sound. be cool if you could cone the outlet so it narrows at the outlet. that'd prolly give a nice punch & tone.
 
another option would be to gear lower like you said. if you are achieving higher rpm's w/the pipe then you could compensate for the lower gearing top end loss that way.
 
This thing has a loud pop for sure, the video does not do any justice. It sounds like a pumped Motorcycle at idle, under load it is deafening. My jetpro sounds like it has a silencer compared to this thing lol.
 
i would mod exhausts on atv's. just cut the end cap off on a stock pipe then drill holes through the innards (the fewer drill holes the milder which i preferred) & then weld whatever outlet one wanted on the back & drill the hole out in the end cap for it. my rule of thumb was the same size outlet the size of the intake but i would also give & take.
 
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