Custom Exhaust

[alexander525]

due to the insanly high price of a full front to back system on the 525i i was thinking of getting an after market remus muffler than getting my local exhaust shop to straight piping it to a header. so i would be getting rid of the resonator and cat. aside from failing emission laws would this be a bad move for the car. do you think their would be too little back pressure and in turn hurt my overal HP and TQ. any ideas on this would be great!

[jbraswell]

You may loose a little power down low, but at higher RPMs it may "feel" faster, at least mine did without exhaust. BUT.. it will be very loud, and very raspy. If I were you I would at least keep the resonator.

[Wrighty525isport]

You may loose a little power down low, but at higher RPMs it may "feel" faster, at least mine did without exhaust. BUT.. it will be very loud, and very raspy. If I were you I would at least keep the resonator.

I agree, keep the resonator. By definition it has an effect on exhaust pulses and pressure waves so removing it may cause an imbalance. Exhaust science is more of a specialist subject than alot of people sometimes think. is the cat before or after the resonator? i'd probably get rid of it as it is just a flow restriction at the end of the day.

If after the exhaust change the car runs well, no flat spots or hesitation and your plugs look normal after a good few miles you haven't upset anything to the degree that the ecu can't adjust to compensate, then its smiles all round :D

[alexander525]

yeah thats what some guys at work where telling me when i brought the idea up. they figured i would just be throwing away low end and mid range power. and knowing BMW they made that stock ehaust the way it is for a reason