Wrapped/Cooled exhausts?

So ive read some things saying that you can wrap an expansion exhaust to keep it hotter, or inject a water-alcohol max into the pipe to cool the pipe. In doing this, you can supposedly minipulate the powerband of the pipe, allowing the engine to stay in the powerband over a wider RPM range. Anyone tried this? how'd it work out for you?

Re: Wrapped/Cooled exhausts?

This is a prickly one. The basic idea is that the pipe's temperature is a key variable in the way the air pressure responds to the exhaust impulse. HRC (honda) did a lot of research on this, and quite a bit of that is available, though I don't have it myself. Personally I like the idea of maintaining a cooler exhaust, but as far as managing variable exhaust temp, seems like the difficulty would outweigh the benefit. Good Luck, though:)

Re: Wrapped/Cooled exhausts?

i dont really plan on doing it. i just thought it was an interesting theory and i was wondering if anyone has done it. I thought about wrapping my pipe to raise the powerband, but i figured it would just kill the lowend, which i kinda need on a 1 speed lol.

but then i was thinking. if you cool the exhaust, you could lower the powerband and maybe make a real torque monster.

but now im thinking more, and yeah. this is pretty impractical. interesting though.

Re: Wrapped/Cooled exhausts?

if u want a torque monster put a dirt bike pipe (from the right cc) if u can get some one who is upgrading from stock it should be pretty cheap. to raise the power band slightly (and make it slightly quieter) repack your silencer tighter. i did this and it raised my high power band 5 mph (i can still hit the power band wahoo).

Re: Wrapped/Cooled exhausts?

i already have a torque monster, 80metra smallport. i was just talking kinda hypothetically.

Re: Wrapped/Cooled exhausts?

freakbeat phantom /

Shaun from myrons did this and came to the conclusion that it deadened the sound and slowed the bike down...un modded bike though...goped dudes inject water in the pipe they say it yields

Re: Wrapped/Cooled exhausts?

Sorry, did he wrap the exhaust in heat wrap/tape? Or try a water injection thing?

Re: Wrapped/Cooled exhausts?

yeah, what did he do?

Re: Wrapped/Cooled exhausts?

freakbeat phantom /

he wrapped the pipe with that header wrap for cars and it slowed down

Re: Wrapped/Cooled exhausts?

thats interesting. i guess it mustve absorbed part of the sound wave.

Re: Wrapped/Cooled exhausts?

some Ducatis i see have them but 4 strokes are way different than 2

Re: Wrapped/Cooled exhausts?

Well yeah. Ive seen that too, but on a 4 stroke, the main goal is just to evacuate the exhaust gasses as fast as possible, since the sound characteristics don't really matter. Thats why i'm asking if it would have any effect on the powerband of an expansion pipe. Sounds like an interesting idea. I beleive Shaun, but id still like to try this myself.

Re: Wrapped/Cooled exhausts?

The wrap is useful for a stock pipe that isn't performing as it supposed to do. If the exhaust is not getting to the expected top rpm it might help to use the header wrap. It increases the exhaust temperature so the pulse can travel faster en could keep up with the higher rpm.

Cooling ore heating a homemade and calculated exhaust just means the design isn't good.

Not getting maximum rpm? Shorten the header. Etc etc.

Re: Wrapped/Cooled exhausts?

Ahh i see. Thank you.

Re: Wrapped/Cooled exhausts?

thermodynamically, as the pipe is an energy-recovery device, using exhaust gas heat to supercharge the intake, you could see some improvement in efficiency from wrapping the pipe. on the other hand, you would be increasing the temp of the cylinder gasses in the compression stroke, thereby increasing your chance for pre-ignition, which would lower your power output. The heat wrap should slow down the sonic waves in an incompressable exhaust gas medium, by increasing temp the sound waves slow, but the pressure inside the pipe would increase from the temp increase, making the exhaust gasses denser and therfore acting as a tighter 'spring', decreasing response time and raising your powerband. Usually pipes are calculated as adiabatic, as in, no heat transfer through the walls of the pipe, so heat wrap might get a pipe closer to its intended design, but the level of modeling complexity makes this very difficult to do. I would say it is certainly worth experimenting with, but it could go either way depending on the exact pipe itself, even something as insignificant as the thickness of the metal the pipe is made out of, could cause it to switch directions in terms of which way the powerband shifts.

also, on daily driven bikes, heat wrap holds moisture against the bare metal of the pipe and will rust pipes out in a couple weeks, no shit, i've seen it happen with RD yammies.

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