2.5" will be fine. You will get some good gains, will probably make plenty of power for you.
This was more of a thread to highlight the benefits of a larger 2.75-3" system.
I have had the debate many a time with many of rally heads, ford/vauxhall tuners. They all say the same over and over again, "anything over 2.5" is pointless on an N/A all you jap cannon idiots are dumb"
. But In reality they are used to basic engines not Vtec's. When you compare a like for like 90's N/A European engine to a Jap engine of same age and they are miles more advanced and superior in design and efficiency.
Has been proven many times that bigger/Better flow is better for power/torque throughout. The biggest question is, is it worth it over the extra noise and weight. I will have to dig out a load of back to back dyno graphs to show. But would only take a few minutes on Google and you will find yourself on one of the Many honda-tech threads that all end the same. Have never seen anyone lose power from having an exhaust system to large.
From what I have gathered its all in the wide open throttle range. Light throttle response may suffer a bit but not massively. As you have to get a larger amount of air moving and build velocity to start with in a 3", where as a 2.5" system will have less volume of air in it to get moving and build velocity on light throttle. Everything is relivent to engine setup, tune and aplication as to what you want from your engine.
Im not trying to say that 3" is the future, as for cost, space to fit, weight and I cant stand rediculus noise. Just trying to get rid of the myth that 2.5" is the max for N/A, as many people have found plenty of gains with an 3" system on their higher tuned b18's, b20's, K20's etc.
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