Exhaust Manifold design

[Parker]

I ran a little search but didnt come up with much; I'm looking for some information about designing a Tri-y style manifold. Right now I have just gotten our exhaust guy in the swing of designing before building something. We have almost all of the Carroll Smith books, but they are in the hands of the freshmen right now so I cant look through them.

Maybe anybody here have some tips? This is our first year designing a manifold, and my second year welding one; we made one to fit in our chassis last year with the remains of two different moto headers.

Thanks,
Parker

[Parker]

I ran a little search but didnt come up with much; I'm looking for some information about designing a Tri-y style manifold. Right now I have just gotten our exhaust guy in the swing of designing before building something. We have almost all of the Carroll Smith books, but they are in the hands of the freshmen right now so I cant look through them.

Maybe anybody here have some tips? This is our first year designing a manifold, and my second year welding one; we made one to fit in our chassis last year with the remains of two different moto headers.

Thanks,
Parker

[Jersey Tom]

Equal length primaries would be the first big thing.

Match the tuning frequencies of your exhaust with your intake. Personally I'm a big fan of impedance transform now. Search it on the forums here.

Group cylinders that are out of phase. For example, 1-4 and 2-3 on an F4i.

[BryanH]

IMHO these engines live & die on the exhaust system. Build 1st set identical diameters and lengths to the original bike system, When the ECU is completely mapped try some small changes one at a time. I have found testing exhaust changes requires you to minimize changes in inlet accoustics throughout the rpm band (short runners <170mm needed).
Have watched as a local exhaust manafacturer borrowed the dyno for testing prototype setups on new 6L Chev/Holden. More than half made less than stock(260kw). 2 were good(303kw), 1 complete system incl headers was very good (344kw) They were checking/changing ecu calibration for each. Seems hard to go forward, easy to go back

[Jersey Tom]

The exhaust is definately key. Dont know why.. but we've tried moving the powerband around by changing intake runner lengths to little avail. Changing exhaust primaries.. big difference.

[Garlic]

Instead of having your powertrain guy design an exhaust on theory, have him design an adjustable system instead, and test it.

While exhaust can be a packaging problem, the nice thing about it is it is straightforward and simple to test on a dyno without packaging constraints.

[golfer17]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Jersey Tom:
Equal length primaries would be the first big thing.

Match the tuning frequencies of your exhaust with your intake. Personally I'm a big fan of impedance transform now. Search it on the forums here.

Group cylinders that are out of phase. For example, 1-4 and 2-3 on an F4i. </div></BLOCKQUOTE>

i would highly recommend testing a scavenging exhaust against one that doesnt when running a 4-2-1 setup and see which one gives a powerband that you like better. if you have the resources and time, i think it is well worth the effort.

[Parker]

Thanks for the replies guys. Our resources are very very low at the moment. We dont quite have the chassis sorted out to dyno test it, and there isnt an engine dyno within a reasonable distance of our school. Otherwise we would already be doing it the trial and error way.

Golfer,
We are trying to use a scavenging system in the end. the bike came with a non-scavenging exhaust on it and I'm pretty sure that the only reason was to increase ground clearance.