im getting a 3" exhaust put on my car soon. is a 2.5" test pipe sufficiant? or do i need to upgrade the test pipes too? if you could explain why that would be awesome. Thanks

 

i would make the test pipes the same size as the exhaust.

 

I just went through this. If your car is turbocharged, the theory is the sooner you can get to the bigger diameter pipe the better. I had LaBree test-pipes and a Stillen dual and hit a plateau where I couldn't make any more power. Installing the APS 3.5" pipes made a difference and installing the APS 3" dual was the icing on the cake. If you're spending the money on the big exhaust, you may as well pop for the big down-pipes:-)

I was going to switch pipes and continue to use my Stillen, but my shop-owner chastised me. "No time to cheap-out" he said.
Regardless, you're going to be loud with big exhaust.
Bruce

 

haha yeah thanks guys how much do the bigger test pipes go for?

 

I just paid $330 for the 3.5" APS, which is less than I paid for my LaBrees last year:-) Prices are coming down!

 

I have 2.5" testpipes with 3" true dual on my car. 2.5" test pipes are fine it seems with my car because I am only running 7.5psi, but as soon as that number gets any higher i'm going to get a set of 3" testpipes made. (Don't see the point of going from 2.5-3.5 esp. when i can get 3" made for cheap)

 

redleader what kind of tt do you have?

 

Got any photos of the exhaust on your car?

 

Has anyone bothered to compare dyno graphs on a 2.5" test pipe to a 3" or 3.5" test pipe? The reason I ask is because I heard a rumor of a shop putting this to the test and the 2.5" test pipes actually help the turbo spool. The backpressure created may be somewhat necessary for the speed of the turbo spooling. I would be interested in seeing the 2 graphs laid on top of each other to see if the peak tq suffers and if the mid range hp suffers for peak hp. Anyone have dyno charts?

 

That would be interesting to see. Use 2.5" testpipes to help turbo spool, but the 3" the rest of the way to get the rest of the gases out as best as possible?

 

the turbocharger itself generates its own velocity to spool the turbo... smaller downpipes are not gonna help!!!

If you have an APS TT kit, those 3.5" downpipes are BADASS.

If I owned the APS TT kit, I would buy those 3.5" downpipes even if I only had a 2.5" exhaust.

 

Here's a thread on the big test pipes with pics from another Z car forum.

http://www.350zmotoring.com/forums/s...53&postcount=1

 

I just put the 3.5" down-pipes on a week ago and they made a big difference!
My torque number is bigger than my horsepower number. The sooner you can get to big-diameter pipe the better.

 

Size matters!!

 

Hey Kevin, since you are running a built motor with high boost, the larger downpipes will definately help you. These HUGE downpipes will result in reduced back pressure (reduced thermal load on the motor) on high boost cars, and more power.