marcouvo

After reviewing the previous posts, can anyone confirm for a 2015 C7 A8 with NPP that setting ESM to Track keeps the NPP valves open at all times?

That's how I read it, just wanted to make sure.

I have the Trifecta tune on the way with the AFM de-activated. Trifecta can also de-activate the NPP.

rettop

It sure seems to me that ESM in Track keeps NPP open. I'm basing this on the sound only. As an aside, can you tell me what Trifecta is please?

marcouvo

Thank you. I can now also confirm. I asked Trifecta to dis-able the AFM, so with the ESM in track mode, I can always hear the exhaust open.

Trifecta is an after market company providing tuning for the C7 and other cars.

Trifecta also improved throttle response and shifting. Trifecta claims 30 ft-lbs torque increase at 3550 rpm. Sure feels like it. Have not had the car on a dyno.

xp800

I can guarantee you the only way to keep the NPP valves 100% open 100% of the time is to pull the NPP fuse. Even in ESM Track mode and even with AFM disabled, the NPP valves will close as intended under certain conditions. The A8 is worse than the M7 in this regard. And before you ask, I've owned both and have spent extensive time playing with them (since October 2013).

The NPP logic is not in a module that a tune controls (no matter what the vendor).

I guarantee you (in an A8 especially) that with AFM disabled and in Track ESM, you will be missing some V8 goodness if your NPP fuse is in place (from personal experience and experimentation). The experiment is easy enough, just pull the fuse (41 or 42) to see what you notice. However, with the A8, you will enter V4 mode a LOT no matter what driving mode dial setting, and even with the NPP fuse pulled the exhaust will go quiet in V4 mode.

Big thread here:

https://www.corvetteforum.com/forums...ck-result.html

rettop

Thanks for the Trifecta info. Pretty amazing what they do. The question about the NPP staying open may have to be the elimination of the V4 mode according to what the preceding (to this) poster has to say. However driving the A8 in manual mode does preclude the use of V4 I think and pulling the 42 fuse should then for sure give the LS1 full throat.

xp800

The NPP valve function is not related to AFM in cars with two sets of vlaves. There are some Z06 which appear to only have NPP valves that serve a dual purpose, but that's a different subject.

So unless Trifecta has truly accessed the module that controls this function (maybe they have), your NPP control is different from AFM.

How do I know?

Here are the tests I have run on my 2015 Z51 A8:

1. ESM set to Off/Track, Auto (AFM active)
2. ESM set to Off/Track, Paddle Shift (AFM inactive by default)
3. ESM set to Off/Track, Auto, AFM disabled
4. NPP fuse pulled, Auto (AFM active)
5. NPP fuse pulled, Paddle Shift (AFM inactive by default)
6. NPP fuse pulled, Auto, AFM disabled

And #6 is a night and day difference to live with if you like V8 sounds all the time while in Drive. #5 if you paddle shift, pull the NPP fuse and you'll get the same results, but the consequence of AFM active with NPP fuse pull is more noticeable V4/V8 transitions (so when in Drive). So this becomes a potential downside for some when in Drive.

The ONLY condition in which the NPP valves NEVER actuate is with the fuse pulled, and the ONLY way to avoid V4 AFM is by paddle shifting or disabling AFM through a tune/Range Technology plug.

*** The A8 closes the NPP valves a LOT more even in ESM Off/Track than the M7, but with AFM active it's quiet anyway. Even with AFM disabled on an A8 the NPP valves close. Once both AFM is gone and the NPP fuse is pulled, you can finally hear everything - even the downshifting the trans does by itself. MUCH better this way.

My conclusions after owning the 2014 M7 and then moving to the 2015 A8: AFM really sucks to live with in all modes (should be relegated to Eco like the M7) and the ONLY way to avoid NPP actuation is with the fuse gone (or one of Theta's solutions). Otherwise you're missing some good sounds.

My 2014 Z51 M7 was easier as AFM only intrudes in Eco mode. But while the NPP actuation profile is different in ESM Off/Track, it's STILL THERE. Conclusion: only the NPP fuse pull keeps the NPP valves always open.

rettop

I totally agree with you. Congrat's on some really good research and testing.
Theta's switch solution for NPP is good. Perhaps a Range Tech device can also be switched? I'd be surprised if it couldn't. So two side by side switches could give total (well kind of) control.

meyerweb

In track mode, the NPP valves close in 4th and 5th gear at speeds below 36-37 mph in order to pass federal sound tests. That's 1700 rpm in 4th gear, and 1200 rpm in 5th.

Edit: The above is true for a 2015 M7. Not sure about an automatic.

See posts 248 and 252 here: https://www.corvetteforum.com/forums...post1589742949

As others have indicated, the only way to prevent the AFM valves from closing (without throwing a CEL) on an automatic equipped C7 is with a tune.

marcouvo

Thanx for the info.

My original post is incorrect: the ECM does not control NPP functions.