Cold start exhaust sound
Thread Starter
Instructor
Joined: Jan 2018
Posts: 152
Likes: 65
Cold start exhaust sound
Apologies to all if this question has been asked and answered many times before. Tonight I started my 2018 z06 A8 on my outside driveway and this is different than usual way inside the garage. So i noticed something in the sound that quizzes me. First a little background, mostly stock excepted I added borla axel back with installed npp, but with stock xpipe and stock exhaust manifold. So I have the settings in the on screen engine setting to track and the consol control **** is set to track also. So it was cool enough outside that the 3500 yellow tack ring came up when it fired. It was loud as usual and I put the car in reverse after a few seconds and I think the sound muffled down half the decibel level compared to initial start up, but still at idle, I never touched the accelerator. It almost sounded like the npp valves had partly closed up, I first thought this, but then I remembered I had pulled #42 fuse earlier today as I was curious if it would make it louder by doing this. Well so I believe that muffle valve sound I am trying to describe could not have come from the npp valves closing. ( don’t get me wrong the sound is still way more louder than if it was in weather, eco, tour mode) but not as loud as soon as the car fired. Could there be another opening and closing valve in the exhaust system or in the engine that is not the npp valve? Thank you in advance .
Last edited by Tray333; Apr 22, 2018 at 10:44 PM.
Burning Brakes
Joined: Mar 2013
Posts: 1,187
Likes: 237
From: Colorado
Cold start is always louder. Probably simply because the mixture is richer. Have NPP exhausts and definitely notice it. Love the sound, and a good excuse to use the remote start to hear it from behind the car.
Safety Car
Joined: Mar 2004
Posts: 4,048
Likes: 1,476
From: South Florida
It is normal. Cold starts, in the OEM tune, start at higher RPM, and are a little richer to warm up the cats. A timer starts in the ECU based on coolant temp and slowly drops the RPMs down in about 10-12 seconds.
Tech Contributor
Joined: Oct 1999
Posts: 41,058
Likes: 9,817
From: Charlotte, NC (formerly Endicott, NY)
Cold Start will be louder but with the Engine Sound Management set in track the exhaust will be very loud any time you are on the accelerator. A side benefit of tracking the car is the more I track my car using lots of wide open throttle over many 20 minute sessions the louder the exhaust seems to get over time. After two days of wide open fun when I took my car off the trailer and drove into the garage yesterday the garage was shaking. Not as loud as a cat less exhaust on a car with a wild cam but it was damned loud.
Bill
Bill
