LS7 exhaust

[cholmes]

Ok guys, I went back through my notes on Engine Masters episodes, I binged watched a BUNCH of them on a "MotorTrend on demand" free trial, and it turns out I remembered wrong......but not too wrong. It was Season 6, Episode 83, "Mandrel- v. Crunch-Bent Exhaust" in case you want to watch it.

Engine details: LS3, 10.7:1, 225/239 113 LSA cam, long tube headers, advertised as 530HP by the builder. All the exhausts except open headers had an "H" pipe.

Tests, all done on an engine dyno at WestTech:
Open headers: 502 Lb-ft @ 5200 rpm, 544 Hp @ 6400 rpm

Crunch bent 2.5" exhaust with Dynomax "Turbo" mufflers: 491 Lb-ft @ 5300 rpm, 534 Hp @ 6300 rpm

Crunch bent 2.5" exhaust with straight through "Magnaflow copy" mufflers: 490 Lb-ft @ 5300 rpm, 535 Hp @ 6300 rpm

Crunch bent 2.5" exhaust with no mufflers: 491 Lb-ft @ 5300 rpm, 537 Hp @ 6400 rpm

Mandrel bent 2.5" exhaust with no mufflers: 494 Lb-ft @ 5300 rpm, 538 Hp @ 6400 rpm

So the 2.5" exhaust does cost power over open headers after all, but worst case is 12 Ft-lb and 9 or 10 Hp, depending on mufflers. Mandrel bent picks up a whole 3 Ft-lb and 1 Hp over crunch bent (ONE horsepower!), and remember, these pipes had bends to get over a stick rear axle.

Put another way, an ugly, muffled, 2.5" crunch bent exhaust lost a maximum of 1.8% from open headers on a 540+ Hp engine. Max torque loss was 2.4%. Not much!

[kinger]

Ok guys, I went back through my notes on Engine Masters episodes, I binged watched a BUNCH of them on a "MotorTrend on demand" free trial, and it turns out I remembered wrong......but not too wrong. It was Season 6, Episode 83, "Mandrel- v. Crunch-Bent Exhaust" in case you want to watch it.

Engine details: LS3, 10.7:1, 225/239 113 LSA cam, long tube headers, advertised as 530HP by the builder. All the exhausts except open headers had an "H" pipe.

Tests, all done on an engine dyno at WestTech:
Open headers: 502 Lb-ft @ 5200 rpm, 544 Hp @ 6400 rpm

Crunch bent 2.5" exhaust with Dynomax "Turbo" mufflers: 491 Lb-ft @ 5300 rpm, 534 Hp @ 6300 rpm

Crunch bent 2.5" exhaust with straight through "Magnaflow copy" mufflers: 490 Lb-ft @ 5300 rpm, 535 Hp @ 6300 rpm

Crunch bent 2.5" exhaust with no mufflers: 491 Lb-ft @ 5300 rpm, 537 Hp @ 6400 rpm

Mandrel bent 2.5" exhaust with no mufflers: 494 Lb-ft @ 5300 rpm, 538 Hp @ 6400 rpm

So the 2.5" exhaust does cost power over open headers after all, but worst case is 12 Ft-lb and 9 or 10 Hp, depending on mufflers. Mandrel bent picks up a whole 3 Ft-lb and 1 Hp over crunch bent (ONE horsepower!), and remember, these pipes had bends to get over a stick rear axle.

Put another way, an ugly, muffled, 2.5" crunch bent exhaust lost a maximum of 1.8% from open headers on a 540+ Hp engine. Max torque loss was 2.4%. Not much!

Where is the post like on this!  Great summery I really appreciate it, I have obsessed getting mandrel bent straight through when in reality I probably wouldn't have noticed a simple Midas muffler swap.  Also makes me feel like my current set up is really optimized and I am not leaving much on the table. 

Great info!

[cholmes]

Glad you like it! It was a real eye opener for me.

I'll admit that even if it won't help, I'll use mandrel bent tubing when I redo my exhaust, just because it looks better. I also won't worry at all about denting it as needed to clear something like a subframe or suspension.

[Tigoldbitties]

Im running dual 3.5” exhaust with x pipe and rarely scrape unless its a huge speedbump or speed table. Alot of people will say you cant run 3.5”, well “they” probably cant fabricate an exhaust themselves either. The only downside is weight. You can always go with 3.5” titanium 

[wtfx100]

Post pics fab master.