Quote:
Originally Posted by XutvJet
Beyond the obvious CELs that will now be thrown even with the defoulers, the engineer in me thinks that exhaust flow going from 4" opening tumbling into a ~5" pipe and then out through a 3" pipe is going to impact the exhaust pulses in a negative way. This can impact power delivery, low rpm driveability, and wonky and tinny/farty sounding exhaust noise created within the larger portion of the DP can. With some sort of cats in place, the pressure differential (i.e., backpressure) helps align the exhaust pulses has they go through the varying shaped pipes with little reverberation. The ideal setup would be a graduated straight pipe design like the aftermarket uses.
At least it looks stock and there should still be some power gained assuming the DME doesn't go into some sort of power protective mode when getting odd O2 sensor readings.
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I'm an automation engineer, I design control for large turbines and pump VFDs. I think the turbulent flow is not a big deal compare to the reduction in restrictive flow, the burble/farty sound is a feature I would want. Our BMWs run rich on cold starts, any excess unburnt fuel can ignite in a 6" empty can now, which I prefer, think about it, do you want an explosion in a 6" can or 3" pipe? Which is less harmful to the resonator and muffler? Also, I've driven the car now, not only does it not go in limp mode, the CEL didn't even trip. Its driving like nothing happen, except the quicker acceleration I can feel under my ass, and a louder blow off valve, nothings else changed.