Trying to understand the cumulative effect of breathing mods

SS_Firehawk

What Jcosta was eluding to was being naturally aspirated, 2.5" is the best size for the car. 3" is best for forced induction applications making 650+ bhp.

Example: Our car's stock exhaust is a coffee straw. 2.5" exhaust is a regular straw, and a 3" exhaust is a water hose. Blow through the coffee straw and sure you get velocity, but there is a lot of back pressure. Blow through the regular straw and we still have very good velocity, but we also have much less back pressure. Blow through a water hose, the size of the hose is so large, there is very little velocity and no back pressure. It's too big to be efficient for the application.

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jcosta79

I'm not sure what diameter piping FI uses for their CBE, but if it's 3" it's likely too large for N/A applications. I had 3" exhaust piping on my 517 RWHP Corvette, so it's a good bet that on a 370Z it's way overkill.

The power gain you are going to get by replacing the stock exhaust is in the muffler section. OE mufflers tend to be very restrictive because they have multiple baffles inside slowing down and quieting the exhaust. Aftermarket mufflers are typically less restrictive and offer a more "straight through" exhaust flow.

Hope that helps.

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