CMKworm

iTrader: (2)

Same effect?

txhorns281

iTrader: (12)

well... depends on where you dump... if on the Y pipe, then no, you're releasing much needed backpressure to hold vaccum in the system...

I think on TD setups the X-pipe helps scavenge out exhaust further down the system, which is what you need since you want to retain the pressure of running exhaust all the way back to the axle, but also be as free flowing as possible... On stock cubes dual cutouts on the Y sounds great but probably does less for performance...

Maybe big H/C setups get benefit from dual cutouts on the Y help, but nothing significant over what you'd get running full exhaust... while dumps do help performance-wise, they're mostly for sound IMO...

I'm sure people will disagree but I vote either doing TD setup or aftermarket Y into a 3" catback... That's where you're gonna maximize exhaust scavenging, not from dumping out your backpressure...

Joker # 9

iTrader: (1)

My brothers SS has Dual cut outs, on his custom off-road 3" Y-pipe. On the dyno and at the track it did significantly better with the cut outs open rather than closed. This is a stock motor with stock manifolds too.

5POINT7

Yup, I agree completely.

Dope

iTrader: (2)

Didn't we decide that we don't need backpressure years ago?

Cutouts == gain power, every time. Stock motor or modified. End of story.

Oh, and if you put cutouts on your y-pipe, then sure, you are effectively running dual exhaust. I don't think it'll matter much, it'll be insanely loud no matter what.

Dope

SouthFL.02.SS

Dual cutouts in the Y is closer to running open headers than true duals in my opionion.
In an X-pipe, as mentioned before, the X junction will scavenge. In an H-pipe, there will be an added benefit with the cross member. Straight pipes on an ls1 suck altogether, yet dual cutouts prove some benefit over a catback.

777

iTrader: (21)

i'm not a big fan of cutouts however they do work

LS1LT1

iTrader: (16)

I used to not like cut outs much but now I wouldn't be without one, true duals are great and sound awesome but there almost always seems to be fitment issues. A good header and Y pipe set up (like the QTPs) along with an electric QTP cut out is a great system IMO.

mrr23

iTrader: (3)

people keep confusing backpressure with velocity. damn 60s era way of thinking. one day the world will smarten up and the phrase 'needing backpressure' will go away.

blkZ28spt

mrr23 is onto it. You don't want a single ounce of backpressure. What you want is exhaust gas velocity. And no, dual cutouts will not be like running a dual exhaust, some have already hinted at that. As they said it is becuase of the junction (H or X pipe) that creates a scavenging effect. What that does, as I understand it, is allow the exhaust pulse from a cylinder on one side of the engine to suck/pull an exhaust pulse from the other side.

5POINT7

Why don't we need backpressure? I was always told the opposite.

blkZ28spt

Why would we need backpressure????/ Think about it. Backpressure would be fighting the flow of the exhaust that we want how could that possibly be good? As we stated people confuse exhaust gas velocity with backpressure, for one.

SouthFL.02.SS

Backpressure makes the TQ peak move lower in the rev range. Thus the car feels faster because torque is made available right away. BUT! The amount of PEAK TQ is reduced when compared to a free flowing setup (cutouts).

Running open cutouts raises peak TQ output, but it's available much higher in the rev range (car feels flat at the low/midrange as a result- but will be faster down the strip as revs hold high down the 1/4). TD's X-junction scavenge, therefore that lack of tq down low is lessened, and the car feels stronger in the midrange with TD's as a result.

Cliff Notes:

Backpressure: Feels "Faster," but is not faster.
Cutouts: Free flowing, raise hp and tq peak numbers.
TD's: Scavening helps down low/mid, just as free flowing as cutouts.

5POINT7

Cool, thanks Southie.

MeentSS02

iTrader: (11)

I think what I would take away from the posted information is that for around town driving, you really aren't going to want dual cutouts. It will feel like a slug driving around at normal RPMs, and probably will be one to an extent. If your car lives at the track, then by all means, dual cutouts all the way since your car will be operating at much higher RPMs than it would be on the street.

mrr23

iTrader: (3)

pretty much yes. i posted awhile back my back to back dyno runs with my single 3" cutout.

here's where i put mine on my stock exhaust http://www.stealthram.com/qtpcutout.html

now here's the results gained 11/13 on the dyno.

distance ------- closed ------ open
60ft ----------- 1.987 ------- 2.074
1/8 ------------ 7.902 ------- 7.912
mph ----------- 93.20 ------- 93.97
1/4 ------------ 12.102 ------ 12.080
mph ----------- 117.12 ------ 118.06

no change in ET. lost 60ft to gain mph. you can where until the car reached over 3000 rpms in first gear (60ft) it slowed down. by the 1/8 mile it caught back up. by that time, i was in 2nd gear which has an rpm drop to 4200 rpms. and so does 3rd. even on the dyno the gain was after 3000 rpms. i replaced the single cutout with the bassani dual exhaust i'm testing and picked up 3 mph and almost .3 over the cutout.

bud8fan

iTrader: (9)

what about a 3" cutout on a sts turbo verses a 3" tailpipe exiting at the stock location on a truck.gain or lose power either way...