Cutouts / Open Exhaust on Boosted Cars - Camaro5 Chevy Camaro Forum / Camaro ZL1, SS and V6 Forums

BaylorCamaro · 08-13-2014, 11:38 AM

Recently installed cutouts on my ZL1, primarily so I could wake the dead

However after talking to some people claiming that cutouts on a boosted car are bad and even some people saying that cutouts can damage valves I started reading up on all of this. It seems like the whole cutouts damage valves is a myth, unless you're running open exhaust right by the headers. However mine is installed right before the mufflers, so way in the back of the car.

Also it seems like on N/A cars the loss of backpressure does not affect performance at all. In fact it helps it, here's a good article. This makes sense since I've seen dyno reports of slight gains with cutouts open. However I have yet to see any dyno reports of cutouts open on boosted cars, in particular supercharged vehicles. So I'm wondering if the cutouts are actually hurting performance on my ZL1?

Thoughts?

Bubble85 · 08-13-2014, 01:18 PM

I love my cut outs but when they are open it is so loud that it shakes the car and gives me false knock so I make signihantly less hp with them open

sprayedv · 08-13-2014, 01:57 PM

On turbos they offer no restrictions and sound great. Since no restriction you can actually gain quite a bit of power.

BaylorCamaro · 08-13-2014, 03:14 PM

Quote:

Originally Posted by Bubble85

I love my cut outs but when they are open it is so loud that it shakes the car and gives me false knock so I make signihantly less hp with them open

hmmm, that thought never crossed my mind. But I could see how that might be an issue.

Quote:

Originally Posted by sprayedv

On turbos they offer no restrictions and sound great. Since no restriction you can actually gain quite a bit of power.

So no issue at all on Turbo builds, is the same true for supercharger builds? Specifically roots style?

I know I must be making some serious back pressure at WOT. Two times now since I have gutted my cats I have blown my mid pipes off my "hollow cats." Both times it happened when I capped off my cutouts, never had the issue when I have them opened up. The first time I attributed it to maybe me not tightening the clamps enough, but then it happened again. I do not think my exhaust is clogged anywhere, I'm assuming it's happening now that that cats are gutted and the exhaust is more free flowing?

TinyToasta · 08-14-2014, 12:50 AM

We have ran my car a couple of times on the dyno with and without diverters open (noweeds). No change in peak torque/hp - but that's with cats... Without cats I would expect gains to be minimal (at best)

BaylorCamaro · 08-14-2014, 09:05 AM

Quote:

Originally Posted by TinyToasta

We have ran my car a couple of times on the dyno with and without diverters open (noweeds). No change in peak torque/hp - but that's with cats... Without cats I would expect gains to be minimal (at best)

I'm not expecting gains, I just want to make sure I'm not losing any power. I'll have to make an appointment sometime on the dyno and check for myself. When you ran it on the dyno do you remember if you lost any low end torque? That seems to be the concern with most people. Saying that with no back pressure you lose low end power / tq.

lbheat · 08-14-2014, 09:15 AM

Yup i get false knock when i have my noweeds fully open and i have them installed right after the headers.

BiggFoot · 08-14-2014, 11:46 PM

Boost with cutouts is no problem . . . I am running 13 psi with meth injection auto start at 9 psi.

LOL, yes my son couldn't keep the note on the road cause I kept throwing him back in the seat.

LuckyZL-1 · 08-15-2014, 12:30 AM

I just dyno'd yesterday and on the 2nd pull forgot to open exhaust controller. Made 720 on all 3 pulls.

08-13-2014, 11:38 AM	#1
BaylorCamaro Track > 1/4 Mile Drives: 2016 C7 Z51 Join Date: Sep 2009 Location: League City, TX Posts: 6,072 View My Garage	Cutouts / Open Exhaust on Boosted Cars Recently installed cutouts on my ZL1, primarily so I could wake the dead However after talking to some people claiming that cutouts on a boosted car are bad and even some people saying that cutouts can damage valves I started reading up on all of this. It seems like the whole cutouts damage valves is a myth, unless you're running open exhaust right by the headers. However mine is installed right before the mufflers, so way in the back of the car. Also it seems like on N/A cars the loss of backpressure does not affect performance at all. In fact it helps it, here's a good article. This makes sense since I've seen dyno reports of slight gains with cutouts open. However I have yet to see any dyno reports of cutouts open on boosted cars, in particular supercharged vehicles. So I'm wondering if the cutouts are actually hurting performance on my ZL1? Thoughts? __________________ Automotive YouTube Channel / Texas World Speedway / MSR Houston

08-13-2014, 01:57 PM	#3
sprayedv Drives: 2012 CTS-V, 2010 Camaro SS Join Date: Sep 2013 Location: Infront of you Posts: 281	On turbos they offer no restrictions and sound great. Since no restriction you can actually gain quite a bit of power. __________________ 2012 CTS-V: Cosmetic Chute.

08-14-2014, 12:50 AM	#5
TinyToasta Drives: way too fast.... Join Date: May 2010 Location: Germany Posts: 297 View My Garage	We have ran my car a couple of times on the dyno with and without diverters open (noweeds). No change in peak torque/hp - but that's with cats... Without cats I would expect gains to be minimal (at best) __________________ custom build forged LSA, 379ci, TVS2300@15psi, 696rwhp/688ft-lbs, built by DH Individual, Customkingz, tuned by Jannetty Racing JRE rough idle cam, JRE ported lower intake manifold, OD cog drive, 6% OD crank pulley, ported ls3 heads, NW102mm TB, 1/2'' RDS spacer, IW 8-rib drive Pfadt Cradle Bushings, Arms & Rods, Pedders Supercar w/FE4 conversion, ZL1 sways, HE Twin Carbon Street Slayer, ZL1 Rear End (3.73) CTS-V Brake upgrade, Street: 22'' Vossen CV1, Strip: 18'' Forgestar F14 on MT Street Radials

08-14-2014, 09:15 AM	#7
lbheat Echale Gas [COTW 3/10/14] Drives: 2010 Camaro SS/RS Supercharged Join Date: Aug 2010 Location: La Puente, Ca Posts: 1,372	Yup i get false knock when i have my noweeds fully open and i have them installed right after the headers. __________________ Kenne Bell 502 rwhp/ 471 rwtq at 9psi (daily driver...for now) Performance: Corsa catback, JRE Super Tensioner, dual pass heat exchanger, R1 slotted & Dimpled rotors cryogenically treated Cosmetic: Giovanna kilis 22", zl1 mailslot bumper, Custom Emblem Pro Badge, painted calipers

08-15-2014, 12:30 AM	#9
LuckyZL-1 Ragtop Rocket!!! Drives: Black on Black Convertible Join Date: Mar 2013 Location: San Antonio Texas Posts: 809	I just dyno'd yesterday and on the 2nd pull forgot to open exhaust controller. Made 720 on all 3 pulls. __________________ ADM built 2013 Triple Black ZL-1 Convertible M6 ADM custom cam, LPE stage 2 heads with dual valve springs, LS-3 ported throttle body, LPE 2 piece pulley, LPE overdrive balancer, 10% overdrive pulley, ported supercharger inlet, ADM race intake system, stainless works 1-7/8 headers, Injector Dynamics injectors, ADM heat exchanger, ADM dual fuel pump system, ADM exhaust switch, ADM 3 tunes tuning package. 744rwhp 727rwtq

08-13-2014, 01:18 PM	#2
Bubble85 Drives: 2012 SS Join Date: Sep 2012 Location: Deale, MD Posts: 261	I love my cut outs but when they are open it is so loud that it shakes the car and gives me false knock so I make signihantly less hp with them open