Quote:
Originally Posted by Hotrodz
The difference is the 2.5" will spool faster and torque will come on strong due to the back pressure in the 2.5" exhaust. With the 3" you will see higher whp numbers and your tuner should be able to control the torque better which allows for the increase in top end. Spool not really a factor unless you are using a large turbo from what I can tell on our cars.
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I disagree with this. There is no benefit to downsizing the exhaust for scavenging on a turbo motor, and it will only harm spool speed. You want to maximize the pressure differential across the the turbo to speed up the spool.. back pressure behind the turbo will only reduce spool, flow, and require more boost to make power.
For the 2.5" vs 3" exhaust question, its really just a question of diminishing returns.... It doesn't appear to me (and I haven't really looked at it with much scrutiny so I could certainly be wrong) that the 3" is going to do a whole lot more for you in a modest 500whp type of build.