Turbo exhaust design

[lendaddy]

The way I understand it, the most important thing in a turbo header system is to get the exhaust pressure to the turbo asap. If you look closely at the B&B system it seems to make a fair attempt at this. It would appear that "equal length runners" are of no importance vs a NA motor where they are indeed very important. I believe I am going to fabricate my own set this fall and will concentrate on the quickest route to the turbo possible and use 1.5" runners ala B&B as They certainly did their homework there. Any thoughts? P.S. I manage a S.S. fabrication plant so that is not a problem. Any thoughs ? Am I off on my theory? Thanks

[Oliver911]

You are correct in that equal length runners are not as important on a turbo motor, however if at all possible make them equal length. Also ensure your transitions inside the runners are as smooth as possible. I think you should be able to make a very nice setup. Look into some aftermarket coatings for the exhaust if you want to squeeze every bit of power out of your motor.

Dante Oliverio

[Bill Verburg]

The heat in the exhaust is what drives the turbo impeller as such keep the runs short, double walled ss is better thermally, equal lengths are not an issue, as there is not really any exhaust scavange tuning going on.

[AMCPorsche924Powerhaus!]

I think there is some debate whether to have the headers/manifold really short, or to have some distance for the exhaust to travel, because if you have a longer path for the exhaust to run through on its way to the turbo, the gases have more chance to expand, and therefore more volume of exhaust to ram into the turbine...

[JohnC]

Hi len

I've also been considering building my own turbo headers.A dyno comparison of equal length vs shorty headers would be really helpful, as yet I have'nt seen any such reports.

If you look at early Porsche turbo race headers they use the "shorty" style headers.Later race cars use the equal length primary tubes. If you look at indy cars the engineers seem to go to great lengths (no pun intended) to get equal lengths. See the book Maximum Boost by Corky Bell

Another issue, in my mind anyway,is the shape of the collector. Again, the early cars used the flat collector wheras the newer headers use the triangular shaped collector.

AMC:

As for gas expansion, the highest pressure I would think, would be where the gas has the highest temp.

High Temp =low density = High Pressure

the pressure will only decrease as the gasses begin to cool further down the primary tube.

low temp = high density = low pressure

comments....

[David Griswold]

How's this for short...and equal length...

This is the exhaust that Franz Blam fabricated for my 3.3

David

[AMCPorsche924Powerhaus!]

EDIT:

The only disadvantage to having the turbo closer is heat problems, some **** told me that having the turbo further away allows for more expansion yada but that's bull because the turbo is a restriction so the closer you have it the better, the exhaust flame(s) and all get trapped in that restricting turbo and are forced to blow out, which in turn turns the turbine.
SO how strong are the manifolds on these cars. The 931 manifold is really small and the turbo is close but the manifold always cracks

Do you guys have that problem with 911s.

[This message has been edited by AMCPorsche924Powerhaus! (edited 07-25-2001).]

[erikg]

amg, aren't you in florida ?. If so, give david a call at Prototech, they make their own shorty headers and sell almost everyone that they make direktly to champion motorsports. I have GHL myself, and David hates both my headers and the B&B headers since he's always fixing them for his clients. He gutted my GHL mufler and without adjusting the boost setting on my RUF, the boost pressure went up from 1 bar to 1.2 bar just because the exhaust is more free flowing. I won't tell you what he told me about this mufler, since Wayne would probably delete the language

[Yargk]

I agree that one of the reasons that B & B headers make so much more HP than stock is that they have a shorter path to the turbo. I also think you should try some other tricks in the name of experimentation. If the header tube takes a turn, the most effective shape of the tube isn't a perfect circle. It should be wider perpendicular to the direction of the bend and thinner the other way making it more of an oval in the bend in the pipe. Then it should move to a circular shape again while traveling straight. I heard they tried this with motorcycle headers and produced more than the current race headers available.