E31 Poly Bushes and Resonator
Discussion
I’ve had the CSi for exactly a year now and so it was MoT time (no problem there). I’ve had a judder under braking for a while now, getting progressively worse. I took the opportunity for the excellent people at Phoenix Motorsports to have a look.
This can often be caused by front thrust arm bushes, so had them replaced with ploy items. Front disks were running out or true, these replaced with BMW CSi disks and pads. The car has always felt very tight but it’s noticeably sharper with the poly bushes. Brake judder completely eliminated. It’s better handling than such a big car has any right to be!
The last time the car was with Phoenix I had the rear boxes replaced with Magnaflow ones as the original were too corroded to modify. The sound was great at idle but, strangely, attenuated as revs increased (see separate thread). So, against all the advice on here I had the rear resonator box replaced with an X pipe. The result - slightly louder, much better through the rev range, only slight resonance at a trailing throttle at around 70mph.
My recommendation: go for poly bushes, without a doubt. If you have a V8 the consensus would appear to be to leave the resonator box on. But, with a V12 I’d take the resonator off . The natural harmonic balance of the V12 appears to assist in this. Also, the resonator weighs almost 20Kg - well worth saving!
However, the sound is still something of a (mild) disappointment to me. This appears to be a combination of the inherent smoothness of the V12 combined with the long pipe-run. Next thing to is investigate is 100-200 cell race cats - anyone have any experience of these?
This can often be caused by front thrust arm bushes, so had them replaced with ploy items. Front disks were running out or true, these replaced with BMW CSi disks and pads. The car has always felt very tight but it’s noticeably sharper with the poly bushes. Brake judder completely eliminated. It’s better handling than such a big car has any right to be!
The last time the car was with Phoenix I had the rear boxes replaced with Magnaflow ones as the original were too corroded to modify. The sound was great at idle but, strangely, attenuated as revs increased (see separate thread). So, against all the advice on here I had the rear resonator box replaced with an X pipe. The result - slightly louder, much better through the rev range, only slight resonance at a trailing throttle at around 70mph.
My recommendation: go for poly bushes, without a doubt. If you have a V8 the consensus would appear to be to leave the resonator box on. But, with a V12 I’d take the resonator off . The natural harmonic balance of the V12 appears to assist in this. Also, the resonator weighs almost 20Kg - well worth saving!
However, the sound is still something of a (mild) disappointment to me. This appears to be a combination of the inherent smoothness of the V12 combined with the long pipe-run. Next thing to is investigate is 100-200 cell race cats - anyone have any experience of these?
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