[zugellos]

So I have questions on a specific topic that I've not seen too many posts on

During the first 10-15 seconds immediately after I start my car, the exhaust note that enminates are so so awesome sounding. It has this subtly mean growl to it. This is from a completely stock exhaust system.

Does anyone else with stock exhaust notice this?
Is there any way to maintain that growl throught the powerband without having to change out anything?

Thanks

[zugellos]

It also seems as though this growl subsides once the idle drops below a certain point.

Which kind of gives me the feeling that if I was at rpm's above 1500, this growl would return. Makes sense right?

Any thoughts?

[badblack550xi]

Cold exhaust with higher RPM

[Boss330]

What you are experiencing is "cold start" or "start up" mode.

On cold start the idle rpm is raised and the engine runs at a rich fuel mixture. This is partly to get a cold engine running smoothly and partly to heat up the catalysts more quickly. I believe ignition timing also is different in order to enable the rich fuel mixture to burn in the exhaust manifold/catalyst (thus heating the cat).

When cats are heated (or the software in the DME decides), idle and fuel mixture is gradually returned to normal.

Since cold start/startup mode is a special mode, it can't be replicated just by raising the revs to the same level via the throttle pedal.

[zugellos]

Originally Posted by Boss330

What you are experiencing is "cold start" or "start up" mode.
..................
..................

Since cold start/startup mode is a special mode, it can't be replicated just by raising the revs to the same level via the throttle pedal.

Darn!
Is there any other way of replicating that mode?
I love that growl, it seems there would have to be some way.

No special valves somewhere along the exhaust path that is actuated?

[twelve535i]

The 535i exhaust is not valved. Go for the M performance mufflers. Expensive but gives you great sound with minimal drone