Back pressure
Drifting
Joined: May 2002
Posts: 1,479
Likes: 42
From: Dallas / Ft. Worth The Republic of TEXAS
There is zero chance that this is possible and your dealer is a moron. Seriously even if you have LT's with no cats and a loudmouth it would still be impossible. No need to do experiments - as already stated find another dealer.
Burning Brakes
Joined: May 2008
Posts: 752
Likes: 28
From: Ottawa, Ontario
OK, but lets take the LS3 as an example. If it was just "bigger is better", then Chevy would have just put the Z06 exhaust system on it and gotten more power from it, but they didn't. The reason is that a bigger exhaust system would have lost them some low end power and made the engine less driveable at lower rpm. The LS7 is a bigger air pump, needing bigger tubes. This is also the reason that they have the NPP mufflers open at 3,500 rpm, to allow for a bit more backpressure at low rpm (better driveability) and then less at higher rpm (more peak horsepower). We have all been in a car where the owner has put in a cam that was way too big...I saw lots of these when I was a kid. The thing would scream at 6,000 rpm but when you were at 1,500, it had far less power than it did when it had its' original cam from the factory. It's a compromise that must be made...bigger ports, cam, exhaust etc for top end power, against smaller for low end driveability. If not, then everyone would be making headers with three inch tubes...after all, less backpressure. Header tube sizing is very important for just this reason.
The reason the NPP only opens at 3,500 RPM is so the car/exhaust can pass the drive by noise requiements that manufacturers must meet. It has nothing to do with more back pressure equals more performance.
Burning Brakes
Joined: Oct 2010
Posts: 763
Likes: 2
Others have already commented on pipe sizes, flow velocity and scavenging so I won't say anthing moe on that.
The reason the NPP only opens at 3,500 RPM is so the car/exhaust can pass the drive by noise requiements that manufacturers must meet. It has nothing to do with more back pressure equals more performance.
The reason the NPP only opens at 3,500 RPM is so the car/exhaust can pass the drive by noise requiements that manufacturers must meet. It has nothing to do with more back pressure equals more performance.
Thread Starter
Heel & Toe
Joined: Oct 2001
Posts: 20
Likes: 0
From: lawton ok
Thing's like that and the OPs problem are a pain in the *** to diagnose, and the dealer is probably only paid an hour or two by chevy for it, so they try to make it a pain for you to change the exhaust out and come back because it just doesn't pay.
It's also a pain in the *** for independents as well, you come in with misfires not caused by one of the usual suspects. After being billed a few hours running through the usual suspects like plugs and coils, being told you are looking at an even bigger bill to go through other possible causes, you're probably already pissed and direct that anger at the shop and their reputation. Now if after 10 hours some vague crappy cause is found and fixed and you pay your $1k bill, you will curse the shops reputation every chance you get.
So you really need to go a mile in a shops shoes before you bitch and moan over what they do.
It's also a pain in the *** for independents as well, you come in with misfires not caused by one of the usual suspects. After being billed a few hours running through the usual suspects like plugs and coils, being told you are looking at an even bigger bill to go through other possible causes, you're probably already pissed and direct that anger at the shop and their reputation. Now if after 10 hours some vague crappy cause is found and fixed and you pay your $1k bill, you will curse the shops reputation every chance you get.
So you really need to go a mile in a shops shoes before you bitch and moan over what they do.
