YESHONEY

Not sure this question has been answered before because I am not sure exactly what to search for, so if it has been answered I apologize.

I noticed that both my stock exhaust - to a lesser degree and my Milltek - to a greater degree for obvious reasons - has a wonderful exhaust note on cold startup until the idle comes down to 600 RPMs. Is this the secondary air injection doing its job? or is there some other air bypass or valve open to allow a more open exhaust?

I would love nothing more than to make this my standard exhaust note without going to a non resonated version of my current Milltek which has no discernable drone - windows open or closed.

Thanks in advance for any advice or link to a prior thread discussing this. Been active here with S8 since August of last year.

Joe

YESHONEY

Nobody knows??? or has experienced this?


Ok then has anyone removed the SAI and coded out the DTC?

Thanks Joe

Jack88

The car is tuned to run differently when cold, all modern cars are. You don't want it running like that all the time, it wouldn't be good for it, it's only as a way to get everything up to temperature quicker. It isn't because of the SAI that it sounds different.

Greg5OH

it does sound awesome when cold started.
I havent checked the logs to see what it is doing exactly, but typicaly as a cat warmup strategy used pretty much by everyone, you retard the spark, open the throttle and do late fuel injection to get as much heat into the cat as possible. SAI helps with oxidizing the rich fuel mixture that is burnign late in the chamber. Im assuming due to the late ignition timing it allows a large throttle angle opening, allowing more mass flow through the engine. More flow=louder exhaust.

YESHONEY

Thanks both of you for your insights!

I guess the real way to open it up a bit is for cat replacement and ultimately some kind of revamped headers. Both items that would be cost prohibitive and illegal as I wouldn't be able to pass emissions.

So I will enjoy this until I can afford a D4

Joe

Jack88

Enjoy it! Having owned a D4, it is a different beast than the D3 S8. I will say that I test drove a V10 S8 and hopped back in my D4 4.2, and they felt about as quick as each other, but the V10 obviously sounds better. Testing from magazines support that impression, but if you spring for the 4.0t, it's much faster, even in standard form. I just love a car that does a bunch of things well.