DP and Powerlog Compatibility

[Bio248]

I would get a 2.5" dp too if I had a gt. No need for a 3". Bigger is not always better.

prove it. i dont see how a 3" can be bad on a GT at all.

[FoSHO99]

prove it. i dont see how a 3" can be bad on a GT at all.

lol whats there to prove? Its a personal preference if anything, if your going to stay n/a a 2.5" dp will suffice. A n/a gt making 200hp at best doesn't need a 3" downpipe that just goes into a 2.25" stock catback. With a 2.5" you still retain some low end torque. This is comparable to putting headers on a s/c car, you notice the lack of low end torque and on a n/a car you could use all the low end torque your car can get. Even on fwd cars where there is a crossover pipe, your exhaust sizes can play a role in your powerband or torque curve.

Generally on v8 n/a setups they try to get the collector size to 20% more than the size of the primaries. This creates a scavenging effect, or create vaccum in the exhaust that ultimately sucks the exhaust from the cylinder when the valve opens. To get any kind of scavenging affect or decent powerband on a n/a car, you need to maintain the velocity in the exhaust and going with a 3" downpipe to a stock 2.25" catback is not going to be your best option. There are plenty of s/c cars that have 2.5" collectors on their headers that run 12 sec 1/4 mile times and have high trap speeds. I also run a 2.5" downpipe on my turbo car. Its a matter of personal preference of what dp to go with, but on a n/a car, the only reason i would get a 3" dp is if I wanted to topswap later.