ATS-V exhaust dump valve operating modes
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Don't forget about the info this thread doesn't have... since this thread was been posted you can now program the exhaust valve behavior in the CCM via HP tuners-- startup rumble by drive mode, valve open/close points by RPM/gear/drive mode, etc. Back when this thread was posted, HP tuners didn't allow tuning of the CCM so you were stuck with the factory programmed valve behavior unless you pulled the fuse to leave them open all the time. If you have HP tuners and don't mind paying the CCM licensing fee, IMO it's a much more versatile option to tune the valves to do exactly what you want rather than just pulling a fuse and leaving them open at all times.
2020 XT5, 2017 ATS-V M6,1968 Corvair, 1974 Corvette, 2003 HD Road King
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Another option is to use a wireless relay and program to the homelink. I like utilizing both options although I normally just leave them closed.
When you use the "mild to wild" wireless relay setup, can the CCM still open the valves automatically above 3500 rpm, or are they fixed closed or open based on your wireless relay setting? Because based on a cutaway of the factory muffler I'm guessing GM's programming of having the valves open above 3500rpm regardless of drive mode is because there may be too much backpressure with the valves closed at WOT at high RPM-- the path the exhaust has to take with the valves closed goes through a much longer length of small diameter tubing, while with the valves open the path is straight through at the full exhaust diameter. Just something to think about.
2020 XT5, 2017 ATS-V M6,1968 Corvair, 1974 Corvette, 2003 HD Road King
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Put the relay across the fuse location in the trunk. And when I say I leave them closed, that means normal operation except start rumble off in touring mode.
That’s what I did. PM me if you want to know how easy it is.
I think the car is too quiet so I just removed the relay all together but I believe you can actually tune them now if you pay for the credits for the CCM
Resurrecting an old thread, Recently purchased a 2016 ATSV. Have done a host of mods and tune. Wondering as the settings in HPT seem to be very similar to that of a 2016 Camaro SS I owned. The Camaro guys figured out how to personalize the NPP valve settings to adjust per mode selection. Anyone made any progress on this?
Tuners can set up the valves to be open or closed depending on what mode you're in. The bottom line is no matter how you have it set you don't want the valves closed above 3500 RPM. The engine needs that flow. Having the valves closed at high RPM can cause back pressure, which causes misfires
2020 XT5, 2017 ATS-V M6,1968 Corvair, 1974 Corvette, 2003 HD Road King
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You will need to purchase the credits to enable programming of the CCM.
Yes. I understand that. And have already done so. That is how I found the tables that looked very familiar to those in the camaro tune that I had adjusted with help of others.
In sport and track mode the exhaust valves are open at all RPMs in gears 1-3 but closed in gears 4-6 below 3500rpm on the M6 cars. You can't really tell the valve open and close points in the higher gears with the stock exhaust over the road and tire noise, but you can easily tell when the valves open and close with a louder aftermarket exhaust and downpipes.
If you want the valves opened all the time in every gear in sport and track modes regardless of RPM, you either have to reflash the CCM or pull the fuse and leave them open all the time.
I'm not sure what gear the 3500rpm open/closed gear split comes into play in sport and track mode on the A8 cars as I've never worked on one.
On my car I reprogrammed the CCM for sport and track mode to have the valves always open regardless of RPM in gears 1-4 but closed below 3000rpm in gears 5 and 6. This way you get a little more exhaust noise accelerating through the gears, but the valves still close for quiet cruising at freeway speeds in 5th and 6th gear if you want to drive the car full time in sport or track mode.
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I paid for 2 credits in HPT to access the CCM so that I can enable the "Stealth Start" feature for when I am in Tour and Snow modes. I think it was option 1.... But, for those with exhaust modifications, especially catless downpipes, this really quietens the startup bark when stealthiness is required.
I did the same thing, I disabled startup rumble in tour mode and also in snow mode. No need for a loud "valves open" startup if I already want the exhaust in a quiet mode...
Also, if you have open downpipes or loud exhaust and want to tone down the "blat" sound a bit on a cold start you can disable catalyst rapid lightoff/warmup in the ECM. This disables both retarded ignition timing and split pulse injection which are used on cold starts and for a short time after a cold start start to rapidly warm up the cats, but they also result in an extra "blat" tone out the exhaust on a cold start.
It doesn't totally eliminate the "blat" sound on startup, but it does help. If you let the car sit more than 8 hours or so the cam phasers will bleed down and then the cam timing is a bit off on cold start and that also contributes to the "blat" sound on startup, which goes away as soon as pressurized oil reaches the cam phasers and they move to the correct position.
You have to have hptuners and pay a couple credits to license and tune the CCM (chassis control module) to fiddle with the exhaust valve open/close points by gear and rpm by drive mode and also to enable or disable startup rumble by drive mode.
Catalyst warmup/lightoff is in the ECM via HPtuners.
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