TURBINE WHEEL
IND 80
EXD 72

The premise that was being put to me elsewhere is to add 15% to the size of the turbine exducer to calculate the downpipe size. I mean, it wasn't an absolute. More a general guide. So that's how I calculated 3.25" d-pipe. As it is, it's a 3" so, not too bad.

 

That's a huge turbine wheel... Do you know its max flow capability?

 

700hp or thereabouts.

http://www.bullseyepower.com/S300.asp

Combo of S366 turbine and S362 compressor. Bit of a hybrid. Doesn't have that BatMo wheel though.

 

With such a large turbine I would certainly build a twin scroll set up using the divided 0.91 A/R housing, as even with the smallest 0.88 A/R single scroll housing apparently available for this turbine, this turbo may show quite a bit of lag, even on a 3.0L.

Would be nice to know the flow capability of the BW turbines, I don't seem to find anything for those Air Werks turbos...

 

This turbo was spec'd quite a few years ago. I'm sure there might be something more contemporary and perhaps a bit smaller. The other side is that we're not looking for street curve. If this thing doesn't hit 1 bar until 4500rpm that may not be suicidal. The head is built to rev to 7500rpm pretty comfortably. The reciprocating mass is significantly lighter than stock. The car will be significantly lighter than stock...so we might get away with it. Worst case scenario, we have to modify this turbo or source something else. One of the new EFR ones do look pretty nice.

 

Follow Porsches recipe on the 944 GTR which looks like the bigger the better!

OT: What the heck did they do with this GTR..?? The engine is flipped 180 degrees? Camhouse and intake flipped...
Or is this a picture bug?

/P

 

Pretty sure the picture has been flipped for some reason lol

 

Lol...yes, unless those were some unique RAEYDOOG tyres too...

Does looke like 4" coming straight off the turbo though.

 

Lol, yes that's a flipped pic.

Limiting flow AFTER the turbo won't do any good. It will just slow down boost build. However if you limit the flow BEFORE the turbo it can help in low/mid range.
Which is basically what you do when you put a smaller turbine housing on. Same goes for smaller diameter header runners.
The best post turbo exhaust is no exhaust. An old truth that still stands. As someone else wrote earlier - that is physics.

But as with most things on a race car you often need to compromise. In your case Pat, if a 3" exhaust will allow you to run a flat floor in the future no need to worry about the few ponies you loose compared to a bigger pipe.

 

Yes but what dia and how long would the downpipe have to be before the turbo effectively saw no exhaust, disregarding space restrictions if you could use a 6" dia downpipe into a twin 3" system would that really lose much ?.

 

keep in mind the previous article is for a normally aspirated engine. the back pressure in a 951 engine is the section between the cylinder head and the turbo(headers/crossover pipe). The exhaust after the turbo should be as large as possible. but as mentioned before there is a point of diminishing returns. 3" and 4" after turbo exhausts, like what is commercially available for our car should be plenty for anyone on this forum. Ask yourself, how would back pressure after the turbo help? All it will do is slow the turbine down. but as we all know you want to keep the turbine rpm has high as possible, when not under load.