[Papa]

What is the loudest setting for the NPP exhaust.
Do you turn it to track mode? I though therenweremstill other options in track mode.
Whatcha think?
Papa

 

[Dasyatis]

What is the loudest setting for the NPP exhaust.
Do you turn it to track mode? I though therenweremstill other options in track mode.
Whatcha think?
Papa

Sport & Track modes or all modes with it inactive

 

[jsvette]

Sport & Track modes or all modes with it inactive

By inactive it means to take the NPP off of automatic setting. This leaves it open all the time. It will be 'loud' anytime you are feeding it gas, however regardless of setting once you are cruising and not stepping on the gas, the exhaust gets quite.

 

[booie]

By inactive it means to take the NPP off of automatic setting. This leaves it open all the time. It will be 'loud' anytime you are feeding it gas, however regardless of setting once you are cruising and not stepping on the gas, the exhaust gets quite.

What happens when you put it in econ mode? I've heard the back pressure is increased substantially to run V4 mode?

 

[mjw930]

What happens when you put it in econ mode? I've heard the back pressure is increased substantially to run V4 mode?

With an NPP equipped car there are 2 sets of valves. All cars have 1 set of valves. In econ mode the first set of valves before the exhaust close to dampen the unbalanced exhaust pulses and provide additional back pressure to optimize the operation in 4 cylinder mode. There are both sound and performance reasons for these valves.

If you put the NPP in open all the time mode the car will still close the first set of valves in V4 mode. If you have it in sport or track mode it never goes into V4 mode so the first set of valves are always open.

 

[Pete]

I don't know if this has already been posted but I found in the C7 manual (10-39) fuses 32 and 41 control exhaust valves 1 and 2. I just pulled the fuses and my car stays loud even cruising under 1700rpms and decelerating it sounds great all the way back to idle. And no more valve squeaking. I didn't get any check engine lights for my 20 min test drive.

 

[JCobalt]

I don't know if this has already been posted but I found in the C7 manual (10-39) fuses 32 and 41 control exhaust valves 1 and 2. I just pulled the fuses and my car stays loud even cruising under 1700rpms and decelerating it sounds great all the way back to idle. And no more valve squeaking. I didn't get any check engine lights for my 20 min test drive.

That's great news! Let us know if anything strange happens down the road

 

[Lipstic]

I don't know if this has already been posted but I found in the C7 manual (10-39) fuses 32 and 41 control exhaust valves 1 and 2. I just pulled the fuses and my car stays loud even cruising under 1700rpms and decelerating it sounds great all the way back to idle. And no more valve squeaking. I didn't get any check engine lights for my 20 min test drive.

Please keep us updated. If you have no problems, I'm doing the same for sure!





Sent from my iPhone using Corvette Stingray Forum

 

[petemoss]

Sounds like there could be a Mild to Wild box coming in the future if that is true. On the C6 the box just turned off and on the fuses, via the garage door opening buttons on the visor. Like that idea more than messing with the modes. I have he box from my C6, but it only controls one fuse.

 

[Pete]

I think pulling the fuses only leaves the front valves open. People with A6 trans would still have to leave their cars in track mode for the exhaust to stay loud? I'm driving it to the corvette expo tomorrow so I'll let you know if all goes well.

 

[Xp800]

I tried the fuse pull. I have an M7 with NPP.

Observations:

1. Engine Sound Management selections have no effect, as expected.
2. V4 mode sounds crappy. Forced it to V4 in Eco mode. It is very coarse sounding - a bit like a tractor. Sound seemed to noticeably increase interior vibration and seat resonance at highway speed. Added unpleasant booming.
3. The behavior on low RPM throttle tip-in (on upshifts especially) where the sound is quiet and then NPP valves open at about 1700 RPM is gone. Again, as expected.
4. There was no CEL thrown in my drive to work (~35 minutes).
5. Got a CEL on the way home from work.
6. CEL cleared when fuses replaced and restarted about 5 times.

I did try combinations once back in my garage.

Fuse 41 controls the NPP rear valves. With 41 gone and 32 in place, Engine Sound Management has no effect. I will assume for now that 32 is the front V4 valves.

Will try driving without 41 only and see if it throws a CEL. I suspect it will. So the experiment was somewhat of a success, but with a CEL I will not leave it this way. For me personally, the only minor annoyance of the standard NPP "open all the time" setting was #3 above; it is too abrupt and on/off for my tastes. Not that big a deal, since with the fuse pull V4 mode is not nice and there no -option- of going quiet while driving.

I can't see anyone wanting the forward V4 valves disabled (32) unless you tune out V4 mode and remove the valves from the exhaust.

It seems the only elegant solution would be to tune out the CEL sensor for the NPP valve function. But then there's no option of being quiet without a much more elaborate switch/relay/Mild2Wild type system, but the location of the fuse box makes heat and water a problem.

 

[Chip]

A question for those of you that have pulled both fuses: What does the car sound like (at a steady state speed) when the computer kicks it into the V-4 mode? I have heard all along since the launch, that the engine will produce an annoying drone without the inboard set of exhaust valves active. What say you? (XP800 when you say "sounds crappy" do you mean it drones?)

 

[JCobalt]

A question for those of you that have pulled both fuses: What does the car sound like (at a steady state speed) when the computer kicks it into the V-4 mode? I have heard all along since the launch, that the engine will produce an annoying drone without the inboard set of exhaust valves active. What say you? (XP800 when you say "sounds crappy" do you mean it drones?)

I just drove it, and it sounded great. I didn't try Eco mode though. I did get a check eng light.

 

[rdslon01]

I just drove it, and it sounded great. I didn't try Eco mode though. I did get a check eng light.

Your M7 cannot go into V4 unless you are in Eco mode.

 

[JCobalt]

Your M7 cannot go into V4 unless you are in Eco mode.

I know that that is why I said I didn't try it in Eco mode.

 

[JCobalt]

I know my post was kinda confusing. I meant it sounded great through all the gears. I never drive in Eco mode so it doesn't really matter what it would sound like.

 

[Xp800]

A question for those of you that have pulled both fuses: What does the car sound like (at a steady state speed) when the computer kicks it into the V-4 mode? I have heard all along since the launch, that the engine will produce an annoying drone without the inboard set of exhaust valves active. What say you? (XP800 when you say "sounds crappy" do you mean it drones?)

I would say it was beyond drone. Boomy. A tractor was the only thing I could think of. My biggest perception was the way the sound seemed to cause more interior vibration. And there was absolutely nothing sexy about the sound. I would imagine that someone outside the car may think something was broken...

It takes 30 seconds to pull the fuses and try. I'd be interested in how others would describe it.

 

[Chip]

It takes 30 seconds to pull the fuses and try. I'd be interested in how others would describe it.

Any takers?

 

[Pete]

It takes 30 seconds to pull the fuses and try. I'd be interested in how others would describe it.

I pulled both fuses out today and put it in Eco mode at about 40mph in 4th gear...It sounds like a chevy Vega with headers... haha.. It wasn't a smooth drone sound. More like a V8 running on 4 cyls. It wasn't a bad sound, just the wrong sound coming from a vette. As soon as I put it in Eco mode the check engine light came on. I assume it knew the valves didn't close.

 

[Xp800]

I like Vega with headers more than my tractor.

I left only 41 out today. Two start-stop cycles and about 20 mins driving. No CEL, but will give it more time. Eco mode is as it should be. I like that the NPP valves truly never close, so the 1700RPM hitch is gone.

There's another thread on a different board about this as well. A member there has an idea for both a 'spoof' fuse for 41 and possibly a remote box. The spoof fuse uses a small LED to let the circuit see a load, but no current to actuate the valves. So no CEL. But then there is no quiet mode either without a remote box.