[E92_335i_UK]

Hello all,

Quick query:

I have a 2007 335i which has been heavily modified. Key point is that the exhaust comprises 2No. 3-inch straight pipes - these go from the respective turbo straight out the back of the car.

Recently at Brands Hatch it failed the drive-by noise limit (no surprises there), so I purchased one of the over-priced ‘bung’ style exhaust silencers. Wedged it into the left hand pipe (as you look at the back of the car) and proceeded with tearing round. No noise problems but within less than a lap the car went into limp mode.

Come in to pits, switch car off and on again - fault clears and car is good as gold, but half a lap in anger and ping - back to limp mode...

Whip the bung out to drive home, no problems what so ever...

My question is -

A) does the car ECU monitor the difference in back pressure between the two exhausts and therefore by introducing a ‘blockage’ specifically into one exhaust I have created a significant variation in back pressure and caused the car to fault...

B) Or is it simply the quantity of back pressure itself that is likely to be causing the ecu fault?

My thinking is that if A is correct, I could buy another bung style silencer for the right hand exhaust, thereby ‘balancing out’ the back pressure and the car would operate without falling into limp mode.

At £75 a pop i’d Rather ask the question here and gather some expert opinions before spending that cash...again!

If the answer is B - these bungs create too much of a restriction, increasing back pressure significantly and cause the car to fault then I will need to accept defeat and have some in-line non-restrictive silencers welded in.

Thanks