Originally Posted by alpinelegacy
so what happens when you increase the piping size? lets say 3" (hypothetically of course)
You say EJ25...I thought the Legacy sedan had an EJ253?
My '00 Legacy Sedan has EJ251.
If you were to go to 3", you would get really high flow, but since you're NA, you will have almost no torque at all.
NA engines get torque from backpressure in the exhaust system. 2.25" would be about the largest you would want to go, which also happens to be about the smallest you would want on a FI setup.