My car was fairly new when purchased but already had Milltek DPs and non-res cat back. The general sound is of course great, but cold starts are loud for a while as the revs sit at 1500 and creep down, then right at the end of the process, suddenly, goes to relative silence. No valves on this system, is this just the weird engine mapping at start-up? Please attach a note for my neighbors.

Startup around 1500 loud.

Slowly revs drop down to about 800.

Once it hits about 800 about a second later it gets much quieter.

There's no chance they don't hear me coming :)

that's the engine warming itself up.

as a cold enriched start.
Duh? C'mon Bob! Be nice now...

I do know what you mean on start up, the fast idle loop does come across pretty loud until it steps down. That's still the case with the stocker or res Milltek, just not as pronounced.

cold starts are louder. General sound being warm starts. What's your beef? You just like to stir the pot!

he wasn't complaining about the sound of a warm engine...and my reply had nothing to do with a warm engine. YOU are the one who, for some unknown reason, decided to throw that into the mix and try to correct my already correct statement.

What's the reason?

almost like there is some type of valve in the exhaust manifold.

engine longevity can be optimized by warming up the engine in this manner. my bimmer does the same thing....sounds like it's over-cammed for the first 20 seconds or so after a cold start. it has nothing to do with the exhaust.

Normal for the timing map (in the ECU) to run more retarded timing at startup. In the old days it was called "static timing" and was typically 6-8 degrees BTDC. This makes the engine start easier. It also makes exhaust gas temps go through the roof because the fuel mixture is still "on fire" as it exits into the exhaust headers. Maybe this adds to the volume, I don't know. But the extra noise on startup is common with all the recent hi-perf cars I've owned since the mid-80's when computers started replacing mechanical centrifugal weights, springs, and vacuum timing advance devices.

at startup. I have the non-res. valved catback on the RS, but the valves don't close for the first 2-3 seconds, even with them closed the cold start up is loud. I can't tell a difference. I can hear the mechanical sound of the valves shutting, but no noticeable exhaust difference afterwards on cold start up.

The S has the Milltek downpipes and a resonated catback. These cars are completely different in so many ways.