3" Exhaust, Stock Tunnel Brace and Knock Sensors..... Lesson Learned.

[GTAHVIT]

Originally Posted by f5journal

So...you know the flutter sound??? Does my description sound correct? And what do you think it actually is?

Darryl

I think it is pretty much what you say... then engine thinks there is some detonation so it richens up the mixture to keep it safe... and that flutter is the sound of poor combustion due to too much fuel not enough spark. so there is a little blow by on the valves... That is my total guess.

[f5journal]

Thanks Chris. A couple more tidbit facts. My exhaust at the manifold was running cooler on that side on three cylinders. I have a little infrared Fluke meter I've been watching it with. This make sense. Also, that side has been running richer. The exhaust tip on that side pukes soot on that exhaust bezel and it runs down the back.

All of this is coming together now. Thanks again

d

[GTAHVIT]

Originally Posted by f5journal

Thanks Chris. A couple more tidbit facts. My exhaust at the manifold was running cooler on that side on three cylinders. I have a little infrared Fluke meter I've been watching it with. This make sense. Also, that side has been running richer. The exhaust tip on that side pukes soot on that exhaust bezel and it runs down the back.

All of this is coming together now. Thanks again

d

I'm not entirely sure if it would richen up only one bank. But I can't see why it wouldn't either...

The good news is, you're getting closer.

[GTAHVIT]

Originally Posted by f5journal

Thanks Chris. A couple more tidbit facts. My exhaust at the manifold was running cooler on that side on three cylinders. I have a little infrared Fluke meter I've been watching it with. This make sense. Also, that side has been running richer. The exhaust tip on that side pukes soot on that exhaust bezel and it runs down the back.

All of this is coming together now. Thanks again

d

any changes?

[2SSRSinBama]

i'm going to have to do something, mine is hitting the tunnel brace as well... think i'll just pull that joker off!

[f5journal]

Update: My temp fix dislodged and rattle returned (not unexpected). So, it has gone back to the fluttering and low octane table.

This is actually good as it proves out what is happening

I intend to do a real fix next weekend

[GTAHVIT]

Originally Posted by f5journal

Update: My temp fix dislodged and rattle returned (not unexpected). So, it has gone back to the fluttering and low octane table.

This is actually good as it proves out what is happening

I intend to do a real fix next weekend

Very cool. Glad to hear you've got it figured out.

[f5journal]

I'll update here and say a bit more in Fuse Pull

OK, permanent fix invoked. As you can see, I had to cut alot of exhaust off to fix this problem. Those tips are also double-walled. It took a Lennox Gold bimetal blade in a good Dewalt Sawzall for each one

As it turns out, the slight exhaust rattle was more than that. The car is noticably quieter over all. So, there must have been some hum or droning noise that I did not attribute to the problem.

The good news: It runs way better. KR must been pulling alot. Also did the fuse pull over night and it is even better.

Also, I have assured that I really have 93 octane this time. I posted earlier that my friendly place where I routinely fill up is accused of putting lower grade in the 93 tanks

PS, while the bumper was off, I decided to go charcoal black underneath getting rid of some of the pregnant look to the back of the car. It used to have charcoal bezels with a narrow connecting line of charcoal and then all white underneath

Thanks

[GTAHVIT]

that's great news. Glad to hear you got it sorted out.

[Jay'SS Ride]

Thanks for posting this. I didn't know the tunnel brace could have this impact. I'm about to get my car back from the shop, I just put a 3" exhaust. I better call them up and ask them to put in those washers.

[GTAHVIT]

Originally Posted by Jay'SS Ride

Thanks for posting this. I didn't know the tunnel brace could have this impact. I'm about to get my car back from the shop, I just put a 3" exhaust. I better call them up and ask them to put in those washers.

[CSM088]

I've had my 1SS LS3 for about 2 weeks now and I think it has this problem! Its a 2010 that I bought used.

Anyway, I hear a light fluttering or popping in the exhaust when I downshift and it continues even as the car's speed and engine RPM's gradually fall. At first I thought nothing of it..

Until I heard about the fuse pull and tried it. Mainly just because I have been putting in premium fuel since I bought it but couldn't be sure the previous owner and/or the dealership didn't ever put in 87 octane fuel. So I tried the fuse pull and WOW I awakened the beast within. I noticeably felt the Camaro accelerate much smoother and faster.

That was a couple of days ago, and the car is noticeably slower since. I'm going to do another fuse pull and see if I again notice the difference just to confirm that this is happening. Then I suppose I need to locate this rattle (??).

My main concern here is that have the stock exhaust on the car, and no ground effects... so perhaps there is a different condition that is false triggering the knock sensors?

[PQ]

Originally Posted by CSM088

I've had my 1SS LS3 for about 2 weeks now and I think it has this problem! Its a 2010 that I bought used.

Anyway, I hear a light fluttering or popping in the exhaust when I downshift and it continues even as the car's speed and engine RPM's gradually fall. At first I thought nothing of it..

Until I heard about the fuse pull and tried it. Mainly just because I have been putting in premium fuel since I bought it but couldn't be sure the previous owner and/or the dealership didn't ever put in 87 octane fuel. So I tried the fuse pull and WOW I awakened the beast within. I noticeably felt the Camaro accelerate much smoother and faster.

That was a couple of days ago, and the car is noticeably slower since. I'm going to do another fuse pull and see if I again notice the difference just to confirm that this is happening. Then I suppose I need to locate this rattle (??).

My main concern here is that have the stock exhaust on the car, and no ground effects... so perhaps there is a different condition that is false triggering the knock sensors?

It's possible. My stock trash can mufflers were rattling like crazy. Not bad enough to take it's toll on the performance with KR or anything but yours might.

[brAnd7onX]

I have this same problem with my new borla s type catback which is a 2.5" exhaust I believe? I even added washers (12 total) to the brace and it seems to still hit it at light acceleration from a stop when the car is warmed up... The pipes are tight all the way to the x-pipe so I don't know what else to do except take the brace off completely. It's so damn annoying when I hear it hitting the brace!