Does anybody have any experience with the APS 3.5" exhaust? I'd like to know if it would be detrimental with the stock turbo.

 

Detrimental? no. Overkill...slightly! On a 600+whp car I moved from a 2.75" downpipe to 3.5" and the gains where negligable. I'd suggest staying with one of the quality 3" exhaust that are out there since they will be less noisy than a 3.5" exh.

 

Thanks...

 

I bet it'd work best with your stock downpipe!

 

The APS 3.5" exhaust is not out yet. Some of the parts on their website have not been constructed yet.

 

It just looks pretty sick.... There are too many options for this car...

 

I just replaced my 2.75 hks downpipe with the RMR 3" and I feel a differance on the top end.

 

There is an almost exponential increase in flow when you go up in size even by relatively small amounts (like half an inch). I don't have the formula for flow in a tube handy, but most of us recall that the area of a circle (the cross sectional area of the exhaust) is determined by:

Area= Pi times R squared (where R is the radius and pi is...well...approximately
...3.141592653589793238462643383279502884197169399 37510582097494459230781640628620899862803481534211 7067982148086513282...rounded .

So to go from a 3" to a 3.5" exhaust gives you an increase in cross-section from about:

28.27 square inches to 38.48 square inches ... that's about a 36% increase in cross-sectional area which should give you about that much more flow.

 

I have a full APS exaust, 3" though. Excellent in every way. Cant imagine 3.5" would make much difference unless I has heavily modified. These guys have it: http://www.turboperformance.net/bsp/

 

Over kill deffinately Its not going to hurt performance but you wouldn't see any diff between that and a 2.75 or 3 inch exhaust... specially on the stock turbo your not pushing enough out to need that diameter

 

Yeah. I was completely talking about the setting of highly modified with aftermarket higher-flow turbos and all. I agree that 3" is plenty big until the really big hp numbers...like 500-600 or so...then the 3.5" might start making a significant difference.

 

We have a 3.5" turbo back on our shop car. It is also my daily driver that takes me everywhere. I did see an improvement in spool and overall power. We offer these custom systems to our customers looking to make real bog power. I was actually surprised because it's not that much louder, but flow so much more. We did use 2 mufflers though.

 

Out of curiousity how did you measure your "improvement" in spool and power? Have you actually measured a noticeable increase in HP when going from a 3" to 3.5" system? You have to assume that both systems are identical in bends and one does not a have a restriction somewhere in it. I have measured the difference from a 3" system to a 3.5" open dump downpipe and it made almost no difference at over 600whp.

 

It was measured by the good ole butt dyno. No hard facts just gave the car a better responce. We just built one and I was real happy with it. I was actually surprised it wasn't louder.



That is actually suprising that there wasn't difference on your car with an open dump. What was the actual difference, 5-15hp?

 

RNR,

Who's 3.5" turbo back do you use? I'm thinking of ditching the 3" in favor of a 3.5".