[D041987]

So been collecting parts for FBO and got a Catless Downpipe.

My Issue: My car rattles in the am from the wastegate, BMW says it is normal as the flap is partly opened to allow gasses to heat up the cat and does rattle until the car is fully warmed up. But it is excessively loud and sounds like crap and I know that when I install my downpipe it will be even louder so I want to get this answered before I make my decision to install or sell the downpipe.

My Question: I have seen people disable the cat warming function and the noise goes away. Does this full close the wastegate shut so no flutter happens or does it only control the rear exhaust flap by the muffler?

[mike@x-ph.com]

Not sure about rattle but car will sound loud on cold start, adding downpipes will make it sound even louder.

[enemigo13]

yes, it's easy to do with the flash tune, jb4 and other piggybacks aren't able to do it, that why guys selling them tell nothing about it

Originally Posted by D041987

My Question: I have seen people disable the cat warming function and the noise goes away. Does this full close the wastegate shut so no flutter happens or does it only control the rear exhaust flap by the muffler?

[mike@x-ph.com]

Originally Posted by enemigo13

yes, it's easy to do with the flash tune, jb4 and other piggybacks aren't able to do it, that why guys selling them tell nothing about it

We do offer flash

[enemigo13]

Originally Posted by mike@x-ph.com

We do offer flash

[D041987]

What does the Cat Warming function actual do with engine and the exhaust flaps? I read somewhere that timing and or valves are open differently for cold start to allow gasses to pass by which in turn creates the louder engine noise. Is this true?

[D041987]

Anyone have an answer on this?

[STR8-6IX]

Originally Posted by D041987

What does the Cat Warming function actual do with engine and the exhaust flaps? I read somewhere that timing and or valves are open differently for cold start to allow gasses to pass by which in turn creates the louder engine noise. Is this true?

engines run rich on cold starts because the engine is not as efficient when cold, meaning the ECU must dump extra fuel into the engine to keep it running. this is why it is best to drive off as soon as you start your engine.

Im sure that the valves are partially blocked for cold starts as this creates backpressure important for cold starts.

if your wastegate does not make any sound when warmed up, I wouldnt worry about it.