Triumphrat

jfenton · 06-28-2007

Anyone ever attempt this? Seems lik you could easily make straight pipes out of steel and have them chromed, since they can slip on to the headers. Any more HP gain in making bigger headers?

rodburner · 06-28-2007

Yes,and depending on the design,no.

jfenton · 06-28-2007

I am not a metal worker, but know how to weld, do they use stainless? If so, I don't have a TIG welder. Or can you use something else? Aftermarket pipes are just straight thru pipes too right, so making my own should do the trick?

Bugsy-12GSRC · 06-28-2007

Excuse my ignorance, but what will you do about back pressure

jfenton · 06-28-2007

Do you need backpressure? I don't know, and I though after market exhausts were just open pipes too. Any know?

markbvt · 06-28-2007

There's a big difference between a plain straight pipe and a typical aftermarket exhaust. Those may be straight-through designs, but they all consist of a perforated pipe that goes through a larger chamber. The movement of the exhaust gases within this structure creates back pressure.

My understanding is that plain straight pipes on our parallel twins don't work very well -- they may let the engine rev a little more freely due to the lack of back pressure, but they destroy low-end torque.

Of course, you could slip some baffles into straight pipes to restore some of that back pressure. No idea how well this would work though.

--mark

MadRabbit · 06-28-2007

No engine NEEDS back pressure, but they do respond to changes in exhaust gas velocity.

Most of the aftermarket mufflers are simply straight through glass packs, different inside diameters and lengths will alter exhaust velocity and pressure waves (the velocity has a much broader effect than pressure wave tuning).

sweatmachine · 06-28-2007

common misconceptions, backpressure is always bad.

Pipe length and diameter are what is more important. Our bonnies run poorly with open headers because the headers are too short. It has to do with exhaust pulses and frequency of the pulses.

I made this exhaust system for my ol' XS650:

I researched the XS650 motor and some flat track racers had determined the proper length of exhaust pipe to make the best power, and I figured out how to route the exhaust to both look cool and get the required length.

Straight pipes may not sound the best, but backpressure is never a good thing.

Geoff · 06-28-2007

but, is not the lenght providing the proper amount of back pressure, in this case? else, why would a shorter one not work as well?
I think, for WOT applications only, very little back pressure is wanted, but for normal use, low end torque is needed as well, which does require some back pressure
G

sweatmachine · 06-28-2007

the length of the tubes keeps the exhaust pulses in them, so longer pipes (with no backpressure) are better for low-rpm torque.

Tube diameter is another huge variable.