Exhaust Settings

[Ty88]

Hi. Proud new owner of a 2023 CT5 V Blackwing 6 speed here. I have only had the car for 2 weeks so we are still getting to know each other. Just got out of 4500 rpm jail yesterday.

Are the various exhaust settings purely acoustic changes or is the exhaust system actually less restrictive at the louder settings?

Looking forward to learning all about this car.

Thanks.

 

[shbox]

There are active dampers in the pipes at the rear (you can see them if you bend down and look inside). So, yes, less restrictive when opened up.

 

[Grainofsand]

I would assume less restrictive at louder settings, since the valves are more open.

 

[Ty88]

I was hoping that was the case. Thanks all.

 

[bloominguez]

There are active dampers in the pipes at the rear (you can see them if you bend down and look inside). So, yes, less restrictive when opened up.

FWIW, I asked this question at Spring Mountain. Now, as we know, they don't necessarily have the correct answers. But they said it was "maybe 5 hp less" in the quietest setting. Obviously I don't think they have exact numbers. But they were saying that there wasn't much of a difference in hp at all with the dampers activated, you're doing it more for sound than for power.

 

[Head Hunter]

While we're on the subject, what is it that causes the popping and burble/gurgle on deceleration?

 

[RDATLTE]

While we're on the subject, what is it that causes the popping and burble/gurgle on deceleration?

I believe that @Mirza Grebovic stated that it was programmed in intensionally.

 

[Head Hunter]

I believe that @Mirza Grebovic stated that it was programmed in intensionally.

I understand it was intentional, but are they just pushing more fuel through the exhaust on deceleration to create the sound?

 

[CBH]

I think so. You're off the accelerator, so it could shut down fuel completely, but if that happened, there shouldn't be anything to ignite as it leaves through the exhaust.

My Ducati does it a little, and current Harley does not do it at all. My old bike crackled and popped like crazy, but it was carbureted. An Evo Harley is the only engine that sounds as good as an American V8.

 

[FI Fiend]

While we're on the subject, what is it that causes the popping and burble/gurgle on deceleration?

It has to do with decel fuel cut off (DFCO). When you let off the gas in gear most cars with cut the fuel supply such that you spin the engine using the cars momentum. That's why some people suggest letting off the gas in gear to help slow down (vs say coasting in N). I think in the BW DFCO settings allow some unburnt fuel to ignite in the exhaust. Not sure specifics there though, like whether it just cuts the fuel a little later or if it allows some small amount to consistently pass thru at particular RPM ranges. Likely the latter since it usually only happens when you let off the gas at higher RPMs

 

[Exia]

In Sport and Track mode for the exhaust, valves open in the exhaust and bypass the muffler, essentially making it straight piped. If you left it in quiet mode at full throttle the exhaust would still open at a certain rpm to allow the exhaust to free flow (I think 3-4k) since your asking for immediate power and would then close once you go under this threshold.

Its the same system GM has used for almost 10 years when the C7 came out. Leaving it in track or sport will essentially never shut it up unless you are cruising below a certain rpm which only happens on the highway.

It essentially will always be open unless the rpm is under 1500rpm while cruising. However in the Blackwings all the sound deadening doesn't make this as noticable and the car might still sound quiet even in track mode at 2krpm, but rest assured its loud outside the car.

In Corvettes and Camaro's it basically sounds loud all the time and the only time it shuts up is on the highway if you are under 1500-1600 rpm.