I have the APS TT kit installed with the APS TD 2.5. I am wondering if there is any advantage going to the 3.5 inch test pipes immediately after the turbos and still dumping into the 2.5 system. My guess is the reduction in back pressure and greater surface area for cooling with improve performance but I am looking for answers from someone who has dyno'ed a similar set up.
I dyno'ed the car earlier this week and it was 437 hp.

Thanks.

 

why not APS 3.5 downpipes to APS 3" TD exhaust? If it was my turbo car that is what id run. Prob shouldv posted this in the FI section. More info from turbo guys not exhaust guys

 

I received a response from APS and they said the 2.5 TD is good to around 600 hp without backpressure issues.

 

lol hmmm ok. Again if it was me i would sell the 2.5 to a SC guy or a NA guy apply a few hundred more and get the APS 3" TD exhaust. the Less backpressure the better for turbos

 

You will make more power with less boost with the 3.5" downpipes and 3" dual exhaust, but I've seen dynos to 550 whp with the APS 2.5" true dual all the way. The 3" APS exhaust is obnoxiously loud. If you are expecting the same sound as the 2.5" TD (which to me sounds decent), you're in for a surprise.

FWIW, I have the APS 3.5" downpipes mated to the MD shockwave v2 tdx (the full 3" version of which should be available soon). If you're looking for good power with modest sound levels, that's the combo to choose.