Quote:
Originally Posted by TOPEC
^ just step on the accelerate pedal harder to build boost? once boost target is hit, wastegate opens up. if there was a way to manually open the wastegate on demand, u'll have serious turbo lag when trying to accelerate... which is pretty dumb... and no, cold start does not open up the wastegate to bypass the turbine to warm up the cats quicker. the wastesgate is normally opened until u accelerate, so either way majority of the gas is bypassing the turbine already. the louder exhaust during cold start is due to a) the exhaust flap opening and b) the higher engine idle speed.
|
I'm coming from e90 and I'm well aware of exhaust flap and all the golf tie mods etc. x5 is a bit different man. 35i has exhaust flap, but 50i has no such thing. Yet if you could hear 50i on cold start you won't ever say it's due to "higher engine idle speed". I'm telling you there's something else going on related to "cold start" like I said it's a warming procedure for cats mainly and i suspect wastegte is fully open during that cold start. Growl sound on cold start up (rpms are at about 1500) is like 10 times louder than if I press on accelerate pedal to same 1500 rpms when car is warmed up