: Question about exhaust systems' performance

05-05-09, 05:56 PM
I need help understanding something, so I thought I would throw a thought out there, and those with more knowledge can show me my error...

I assume the following about exhaust systems (headers, catback, mufflers, whatever)
1. They work primarily by decreasing resistance to flow.
2. Flow of gases through the engine is proportional to RPM.
3. Resistance to gas flowing through a pipe increases as flow increases. Eventually, as flow increases enough, resistance goes up quite a bit (I remember something about Reynold's number/turbulant flow from way, way back)

My conclusion is that any of the above exhaust systems should show gains primarily at higher RPMS, since even the stock exhaust probably doesn't restrict flow much at lower flow rates.

I figure I must be overlooking something pretty major, because some of the before and after TQ and HP curves seen here show drastic gains in both right from the start (2K RPM), which is not at all what I would expect.

Thanks in advance.

05-05-09, 06:19 PM
i think that applies differently to fi motors