davepl

As you may know, particularly in a convertible inside a garage, the initial cold start "bark" you get on startup when left in Sport is awesome.

I am wondering if anyone know exactly why, and if we can cause it to do that every time by changing the calibration.

If it's because it cold-starts very rich, I suppose in theory we could increase the cranking fuel (at the cost of emissions) to replicate it every time.

Normal cold fuel pressure is 350kPa, cold is 400. But hot starts use an even higher pressure (up to 525) so it's not just the pressure.

Cranking pressure is 425 across the whole range, so it's not that.

So, the question is, why does that first fireup sound so much better?. Is it specific to the LT4? Or just to direct injection?

Please don't say "because the engine is cold" or "it's the first time it's been started"... It's the why that we'd need to know to replicate it! And yes I realize it might void a warranty, but I'm not coming to do it your car, so that's OK.

Snorman

It's pretty cool when I start it up in the trailer when I get to the track on Friday evenings, and especially the next mornings after it's been sitting all night.
S.

Rguy271

The ECM's have specific "cold" maps for startup, to try and get the engine/cats up to temp as rapidly as possible. More fuel, higher RPMs.

RajeeK

Want the best exhaust sound all the time.

2015-2016 - Pull fuse 41

davepl

Pulling fuse 41 and 42 makes no difference over Track mode on my car, so far as I can tell.

jaden61

I have not looked under the hood or in the car, because I am not a fuse puller, but this manual says fuses 32 and 42. I know sometimes things change.

http://www.chevrolet.com/content/dam...ers-manual.pdf

tome

Another reason is that the car is programmed to start with open baffles regardless of any settings, then after a few seconds baffles close. I am quoting a GM Engineer who said they wanted it to sound like a sports car when it started regardless of mode setting.

ramyk

I'm sorry but I doubt that's true. Cold starts with exhaust left in stealth vs sport is night & day. The exhaust definitely does not open itself up on every start.

davepl

Indeed. If left in Track it will start in Tour. If left in Sport it will start in Sport, which is the loudest cold start.

That presumes engine sound management is set to Link to Drive Mode, of course.

tome

Im quoting an engineer from the 2013 reveal so its very possible they made operational changes since then. I should have qualified my source and timing of the information. Beside according to my gf i am ALWAYS wrong.... so might as well be wrong here also.

RajeeK

Mind it significantly different with the fuse pulled even when compared to track mode.

ktoonsez

I also love that sound and you are right it sounds much better after a long rest like early in the morning. I believe it is the result of the throttle opening more during "cold crank" vs. starting with a warm/hot engine. So to produce the same effect you would have to adjust the airflow table to be equal for all ECT's.

vipervetteguy

This same argument has gone on in so many threads regarding the pulled fuse. Here's how I KNOW that I have the real answer: I have run a switch to the fuse that allows me to essentially "pull" or "replace" the fuse any time I choose. As soon as I move the switch the change in sound is apparent. Admittedly, if I hit the switch when under a very light throttle, the volume difference is smaller, but still there.

K B Vettin

emissions require cars to pass smog within mins of starting so they idle high at cold start to warm the cats up faster.

DFW_Z06

Pulling fuse 42 makes a difference on the A8s. I pulled mine and noticed a significant difference (note: my exhaust has always been set to track.)

The drone was annoying on the highway, so I replaced the fuse.

brahmabull1126

So which fuse to pull then for a manual C7 ZO6??

keagan

That makes both of us, that's why I'm vetteless!