Exhaust Not Worth It

[JCviggen]

How did this turn into an argument about the O2 sensor? Its pretty pointless from what I can see. Even if the pipe diameter would change the accuracy very slightly, it still has no trouble finding 14.7 AFR idle and cruise even with a 4 inch DP so its well within spec. Density of the exhaust changes constantly at all rpms and loads because the pressure varies wildly anyway depending on how much exhaust gas needs to pass through. At full throttle the sensor is ignored altogether for fuel mix purposes (aside from its findings during the learning fase that are applied to the fuel table)

There is no good argument for smaller piping on turbo cars aside from (in)convenience.

Back in the old days when my car was stock-ish I added a 3in DP to the stock exhaust and there was a good performance gain without remapping. Later on I changed the exhaust itself and that didnt really give anything extra anymore, but we were talking about an asthmatic 15G car.

[Reximus]

well to be honest, we don't live in a perfect world... there is not one thing that's good for everything. stock exhaust gives you more driveablility at low rpm range like what most people are doing on the streets. a wide open race exhaust helps the high end but loose some low end performance... it's all matter of what kind of purpose you're aiming at... one thing could be right for one while horrible for another. personally, i like high rpm fun, so i would definitely go for near straight pipe (since where i live there is smog test involved every two year). but i will go with a well built one from now on, since the first one i got wasn't fit for my purpose :lol:

[ozzimark]

well to be honest, we don't live in a perfect world... there is not one thing that's good for everything. stock exhaust gives you more driveablility at low rpm range like what most people are doing on the streets. a wide open race exhaust helps the high end but loose some low end performance...

Well, sure, for an NA engine. The turbine already adds plenty of backpressure, so that's not really a concern. If it does move the powerband too much for your liking, just adjust the cam timing to move it back, and you'll still end up with a net gain in power. ;)