Theta

Yep - it's the same with several others here. Perhaps older BCM flash? I've not received any updates as of yet, and I had a late-August production car.

cam30era

My car (M7) is open at start up. And with mode set to off, it is louder than "on". But it is louder still above 1700 RPMs. As pointed out previously, something is going on to mitigate resonance or drone below 1700.

B Stead

It's a complicated car so I'll simply the post a little:

If the car goes into V4 mode then the AFM muffler valves might as well work.

So the real goal should be to prevent the car from going into V4 mode. That might be done with the iTune device.

And the V4 mode does shut-down the NPP operation and so preventing the V4 mode might be the goal for the NPP
.

runutzzzzz

I'm VIN 387 so I'm that can't be it!

So I just wanted to see what would happen today with NPP fuse pulled. In ECO when V4 kicks in, the before mufflers still close and it's just as quiet. In other words, even with NPP always open, it was still very quiet

I don't remember what is sounds like on all other modes but IIRC, my valves only close in higher gears and low RPMs


The V4 valves quiets down the exhaust note even with the NPP valves always open.

Theta

I see - I wasn't concerned with V4 because I have it tuned out. However, I could see a need to keep the AFM valves working if V4 really sounds that bad.

We might be on the same page about having them 'always open', but as other have mentioned, there is a 1700rpm tip-in before full actuation.

aedmonster

Hi Guys:
This is absolutely fascinating. Wondering if you guys have come up with anything? I think it would be one of the very best mods for our cars! My M7 has the same issue & it's just would sound so much better with it open at lower rpm's. Please don't give up on this one.

Thanks
John

Theta

Got the relay and parts a few days ago, planning on testing the concept a little bit in the next few days.

I will need to wait until mine can fire back up before really going at it, but it won't be long.

runutzzzzz

So you're thinking 2-6 weeks?

Theta

Awww... You suck... But it's kind of true.

runutzzzzz

Just teasing. I keep waiting for your post where it's done and you started it!

I would be working on it non-stop til it's done! Back when I got my STS kit for my C6, I started the install at 3pm and finished up around 2AM in my garage when it was like 100 degrees in there! I was younger then. LOL

Theta

Totally understand, my friend.

Believe me, it's killing me waiting on things, getting stuff coated, etc. That's why little things like this keep me busy while I wait. I'm dreading the good weather just in case it isn't finished in time.

xp800

Updated the OP as well with this.

Fuse 41 only pulled for a week. 3 trips to and from work and about 8-9 start-stop cycles. NO CEL!!! All this really solves is the 1700RPM NPP issue. What you give up is on-the-fly changes to Engine Sound Management, so 100% open NPP all the time. V4 mode is unaffected.

I have only been operating in Engine Sound Management OFF. Not sure why it would make a difference in CEL if set to AUTO, but I wanted to mention it.

I like it better, but I can understand why the NVH guys may have done this. The bass resonance is noticeable in the upper gear tip-in lugging as described previously. However, I like it better as I can hear what the car is doing all the time.

So it -appears- that the LED fuse may not be necessary to prevent CEL. Theta's control box would be the long term solution.

Theta

Good news about not needing a load fuse! That makes it even easier, to be honest. Now it's just a matter of a remote relay.

It's sitting on the counter here, but it's a few project steps behind the shifter and manifold (and the final SC work).

xp800

I am hoping some others may try and validate this before claiming victory, but the solution absolutely becomes easier if this is the case.

canyon vette

xp800 Thank you for your experimentation & reporting the results.

I'll pull fuse 41 before my next drive and report back.

Again, thanks for your contribution to the loud crowd.

Pat Salerno

I could be wrong, but I believe that the reason you have not seen a CEL is because with the Engine Sound Management disabled, the control module doesn't attempt to activate the exhaust baffles and never sees the open circuit setting therefore not setting an error code. The LED fuse makes the Control Module think there is a load on the circuit and prevents an error code, just like the bypass devices which have an internal resistor to simulate the load..
Perhaps you should activate the ESM and see if you get an error code without the LED fuse before proceeding with a switch option.
Best of Luck, Pat

lBl

Theta

This is a very good point - it won't (shouldn't) receive an error code back from the module until it attempts to activate it.

xp800

Even with engine sound management off the NPP valves will sometimes close, so the NPP circuit is getting hit just much less frequently. It is not driver mode dependent. Below 1700 RPM in fourth and fifth gears at throttle tip in the valves will close and then open abruptly at 1700 RPM. It's a relatively small complaint to be sure, but I think it's much more noticeable with a manual transmission since lugging the engine up from lower RPM is much more common. And the on off nature of the sound gets a little bit annoying after a while when you know how it could sound. An automatic probably moves through it or doesn't stay in the lower RPM.

canyon vette

First day drive report.

Pulled fuse 41 as promised, and drove up the coast about a 150 miles.

Now the car maintains the same growl as when it first fires up from idle trough the 1700 rpm tip in point where it use to be reopened up.

It now sounds like I wanted it to when I turned the "sound Management" off in the first place.

My original expectations of the NPP exhaust option was to control (turn on and off) the sounds & tones of what previous generation C6 aftermarket exhaust system sounded like at a touch of a dial.

With the fuse removed it's more like a sweet aftermarket exhaust system tone all the time.

On the open highway I even experimented with the sound of the car in "Eco" mode. In 7th gear cruising at 70 mph the tachometer was right at 1500 RPM and running in V4 "Eco" mode and didn't sound that bad at all.

I think the reason it didn't negatively effect the sound quality as much as some here had feared is because, just as soon as you gas it just a bit more still cruising in 7th gear to around 1600-1700 or 72 mph it kicks back into V8 mode and the beautiful rumble come right back almost as it did before the fuse pull.

The only time I noticed the exhaust tone in "Eco" mode sound a little funky/raspy was at idle when I got out and walked behind the car.
Not horrendously bad like a riced out Honda with a fart can muffler bad.

I don't normally use "Eco" mode I just tried it today to report back here with my findings.

My Stingray sounds like a real sports car now.

No CEL's so far, and I'm very pleased with the results!

Thanks again xp800, I think from here forward this great zero cost mod. should be named after you the "the xp800 exhaust mod."

Cheers.

$$$frumnuttin'

great stuff, guys....subscribed...I want more bottom notes at start up. Also, wife is complaining she can't hear me coming into the driveway now...