Stock LS3 Exhaust... how restrictive? - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

DarkObsession · 11-25-2013, 05:18 PM

I tried a search but... yeah

I want to do some really minor, bolts ons to my LS3 in the near future. I'm thinking CAI, maybe catch can, etc. Nothing that requires a tune and stuff that I can easily take back to stock when I want to.

Problem is since I want to be able to go back to stock easily, I really don't want to touch the exhaust. So the question is, is the stock LS3 exhaust that restrictive? I race this car but again, I'm not looking for 11s or anything. I'd like to be able to easily hit 12s in the car (and I'm basically there with a better launch if you look at my sig) so I don't need a ton of power.

Opinions?

Thanks guys!

shibbs · 11-25-2013, 05:30 PM

Stock exhaust isn't restrictive, just ugly and heavy. That being said, I won't be switching mine out from stock anytime soon. Get some high-flow cats and it'll open up the sound a lot.

Iron Lung Jimmy · 11-25-2013, 05:33 PM

From the cats back, not restrictive at all. The cats are most of the restriction.

Go with Solo high flow cats. No tune necessary, sound will improve immensely, and you will notice a performance increase.

Best bang-for-the-buck mod ever.

F-16 Camaro · 11-25-2013, 06:09 PM

What size is the inlet/exhaust of the stock cat?

Will a 3" HF Cat fit without much cutting/reducing?

Dexman1349 · 11-25-2013, 06:11 PM

I believe the stock system is a 2.5"...

VADER SS L99 · 11-25-2013, 06:22 PM

Quote:

Originally Posted by Dexman1349

I believe the stock system is a 2.5"...

No its not. The cat back(after the cats) are 2.5" I believe but the factory cats inlet is tiny. I might have a pic still saved on my computer from when I measured and took pics. Hold on a sec I will try to find them.

VADER SS L99 · 11-25-2013, 06:27 PM

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As you can see its only about 2". You might not be able to tell in the pic but the inside diameter of the pipe actually reduces to about 1.8-1.9" further into the pipe. This is one reason people are able to gain 15RWHP from high flow cats alone without a tune.

VADER SS L99 · 11-25-2013, 06:31 PM

Quote:

Originally Posted by F-16 Camaro

What size is the inlet/exhaust of the stock cat?

Will a 3" HF Cat fit without much cutting/reducing?

If your getting high flow cats only without doing long tube headers your going to want to just get the direct fit SOLO or JBA high flow cats which are 2.5". Your not going to make anymore power with a 3" cat over a 2.5".

GlennP · 11-25-2013, 07:14 PM

More restrictive than straight pipes, I know that much >

Angry Irish · 11-25-2013, 08:11 PM

Quote:

Originally Posted by Iron Lung Jimmy

From the cats back, not restrictive at all. The cats are most of the restriction.

Go with Solo high flow cats. No tune necessary, sound will improve immensely, and you will notice a performance increase.

Best bang-for-the-buck mod ever.

What he said.... Solos all day long. Best mod I've done.

Bo White · 11-25-2013, 08:27 PM

Only once you pass 500rwhp is when the stock cat back becomes a real restriction.

grocerygetter · 11-25-2013, 08:39 PM

what bo said. with a better muffler and x 2.5" will take u to 600...but u will leave a tad on the table, I know I am...but I have zero drone on the interstate, nice trade off.

Joe@CPR.com · 11-25-2013, 08:51 PM

We actually found this out on a members car infernometallicss. He has long tubes, cold air, our cam (big) milled heads, circle d stall and at the time of test that was it. He has the no weeds cutouts w/ stock cat-back including the middle resonator. So we dyno'd it cutouts open and closed and it made roughly 30 more rwhp with them open! Now on a bolt on only car i don't think it's going to be that much at all, but start really moving some air and it does become a restriction for sure!

VADER SS L99 · 11-25-2013, 09:11 PM

Quote:

Originally Posted by Joe@CPR.com

We actually found this out on a members car infernometallicss. He has long tubes, cold air, our cam (big) milled heads, circle d stall and at the time of test that was it. He has the no weeds cutouts w/ stock cat-back including the middle resonator. So we dyno'd it cutouts open and closed and it made roughly 30 more rwhp with them open! Now on a bolt on only car i don't think it's going to be that much at all, but start really moving some air and it does become a restriction for sure!

That is very surprising. Did it have the stock L99 mid section resonator? Did the car ever come off the dyno for the test? As in was it a back to back test? I read about a LOSS in power from cutouts open on a LS3 car that had full bolt ons(and I do mean full bolt ons with aftermarket cat back). Same car got a Magnuson 2300 and showed a 10RWHP/10RWTQ gain with cutouts open at around the 550RWHP point.

30RWHP is huge. Sure would throw a wrench into the debate on weather the stock cat back is holding power back under 500RWHP.

11-25-2013, 05:18 PM	#1
DarkObsession Drives: 2011 Camaro SS2/LS3 Join Date: Feb 2011 Location: San Jose Posts: 329	Stock LS3 Exhaust... how restrictive? I tried a search but... yeah I want to do some really minor, bolts ons to my LS3 in the near future. I'm thinking CAI, maybe catch can, etc. Nothing that requires a tune and stuff that I can easily take back to stock when I want to. Problem is since I want to be able to go back to stock easily, I really don't want to touch the exhaust. So the question is, is the stock LS3 exhaust that restrictive? I race this car but again, I'm not looking for 11s or anything. I'd like to be able to easily hit 12s in the car (and I'm basically there with a better launch if you look at my sig) so I don't need a ton of power. Opinions? Thanks guys! __________________ 2011 Chevrolet Camaro SS2/LS3 - Pretty much bone stock (SLP SkipShift Eliminator, GTO clutch fluid reservoir mod) - 13.025 @ 110.492 MPH (12s?? ) 1998 Pontiac Grand Prix GTP (retired) - Cam, exhaust, CAI, 12 PSI, tune - 13.465 @ 101.04 MPH

11-25-2013, 06:11 PM	#5
Dexman1349 2010 2SS/RS M6 Drives: 2010 2SS/RS M6 Join Date: Jun 2010 Location: Auckland, NZ Posts: 1,482	I believe the stock system is a 2.5"... __________________ 2/7/2014: 419 hp, 419 tq Cosmetic: ZL1 front w/mailslot, painted stripes, powdercoated SS rims, tow hook, and full chrome delete Suspension: Pfadt subframe bushings, Pfadt rear UCA bushings, Z28 Upper control arms, Spohn trailing arms with BMR trailing arm & differential bushings, ZL1 Toe Rods and springs, Prothane radius arm inserts & steering rack bushing, Pfadt Sport front sway, FE4 conversion w/ DS rear sway, Pfadt strut brace Drivetrain: RMCR tune, CAI intake, Kooks headers, hi-flo cats & exhaust, VMAX TB, ZL1 fuel pump, LSR Tri-Ax shifter Bumblebee Racecar Build

11-25-2013, 06:27 PM	#7
VADER SS L99 Drives: 2013 A6 GT 5.0 Join Date: Nov 2009 Location: Edmond, OK Posts: 2,909	As you can see its only about 2". You might not be able to tell in the pic but the inside diameter of the pipe actually reduces to about 1.8-1.9" further into the pipe. This is one reason people are able to gain 15RWHP from high flow cats alone without a tune. __________________ BLK/BLK 1SS/RS Ordered 11-01-2009 Took delivery 12-22-2009. Heads/cam/converter/bolt ons. SOLD Feb 2015 to fund 6th gen LT1 SS with 8L90E.

11-25-2013, 07:14 PM	#9
GlennP Drives: 2011 Camaro 2SS Join Date: Oct 2011 Location: Bridgewater, NJ Posts: 373	More restrictive than straight pipes, I know that much > __________________

11-25-2013, 08:27 PM	#11
Bo White Drives: 2015 Summit White 2SS 1LE Join Date: Feb 2012 Location: Vance Alabama Posts: 8,018	Only once you pass 500rwhp is when the stock cat back becomes a real restriction. __________________ Retired wanna be cylinder head porter 2015 2SS 1LE Clutch reservoir, Vararam DRX, ported TB, TSP 2" headers, MGW shifter Totalled: 2010 1SS Wilkes Performance/Eagle 416 shortblock, TSP custom valvetrain, PRC 260 heads, Edelbrock Pro Flo 102, th400 swap, 8" PTC 5500 stall= 535/435 at the wheels tuned Gen 3 Performance and Dyno 10.97 @ 124 full weight in 3100 DA CamaroFest X

11-25-2013, 05:30 PM	#2
shibbs Captain Gingerbeard Drives: 2012 IOM RS/SS 6MT Join Date: Feb 2013 Location: West Twin Cities, MN Posts: 2,489	Stock exhaust isn't restrictive, just ugly and heavy. That being said, I won't be switching mine out from stock anytime soon. Get some high-flow cats and it'll open up the sound a lot.

11-25-2013, 05:33 PM	#3
Iron Lung Jimmy Drives: Iron Lung, Jimmy Join Date: Jun 2009 Location: Louisiana Posts: 1,447	From the cats back, not restrictive at all. The cats are most of the restriction. Go with Solo high flow cats. No tune necessary, sound will improve immensely, and you will notice a performance increase. Best bang-for-the-buck mod ever.

11-25-2013, 06:09 PM	#4
F-16 Camaro Drives: 2010 Camaro 2SS Black Join Date: Jun 2013 Location: Alamogordo, NM Posts: 608 View My Garage	What size is the inlet/exhaust of the stock cat? Will a 3" HF Cat fit without much cutting/reducing?

11-25-2013, 08:39 PM	#12
grocerygetter instigator Drives: 2020 6.2 Trail Boss, 2022 XC90 Join Date: Jan 2010 Location: 72034 Posts: 3,979 View My Garage	what bo said. with a better muffler and x 2.5" will take u to 600...but u will leave a tad on the table, I know I am...but I have zero drone on the interstate, nice trade off. __________________ -John S.

11-25-2013, 08:51 PM	#13
Joe@CPR.com Account Suspended Drives: 03 vette, 94 trans am, 04 gto Join Date: Jul 2012 Location: Mesa, AZ Posts: 995	We actually found this out on a members car infernometallicss. He has long tubes, cold air, our cam (big) milled heads, circle d stall and at the time of test that was it. He has the no weeds cutouts w/ stock cat-back including the middle resonator. So we dyno'd it cutouts open and closed and it made roughly 30 more rwhp with them open! Now on a bolt on only car i don't think it's going to be that much at all, but start really moving some air and it does become a restriction for sure!