do you lose hp or gain it with a CUTOUT?
02-09-2007, 07:46 PM
#1
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do you lose hp or gain it with a CUTOUT? i have a full exhaust with a cutout..when its open and i floor it, it may just be me, but it feels somewhat slower..Do you lose power or gain it from a cutout..i thought u lose it cuz theres no back pressure..
02-09-2007, 07:50 PM
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definately gain.. it wouldn't make sense why it would feel slower.. a guy with a 99' z28 with similar mods as you and QTP headers gained 8-9hp on a dyno before/after using cutout.
think about what its doing, seems logical it would always make power.
you probably are just used to the pressure feeling the catback made?
I'm no expert tho.
think about what its doing, seems logical it would always make power.
you probably are just used to the pressure feeling the catback made?
I'm no expert tho.
Last edited by Finite1; 02-09-2007 at 07:58 PM.
02-09-2007, 07:52 PM
#3
It's just you. What you're going to gain by bypassing your magnaflow will be on the order of 5-10hp (10 being pretty optimistic). The best of drivers simply are not going to feel a 10hp difference in a 300rwhp+ vehicle.
And you don't need back pressure to make power. Taking advantage of exhaust scavenging can increase hp within a certain RPM band, but that isn't the same as backpressure, and that's dependant on the design of your headers, and will not be affected by a cutout.
And you don't need back pressure to make power. Taking advantage of exhaust scavenging can increase hp within a certain RPM band, but that isn't the same as backpressure, and that's dependant on the design of your headers, and will not be affected by a cutout.
02-09-2007, 08:32 PM
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lol i thought i was the only one that felt that... i have mac mids, ORY, and a hooker catback with a QTP cutout, def. feels a tad slower with it open, but track times are the same... so maybe it just kills torque, yet increasing hp a tad.
BTW, how does it sound like **** above 3k? mine sounds amazing above 3k, its BELOW 3k where it sounds like ***, raspy and everything.
BTW, how does it sound like **** above 3k? mine sounds amazing above 3k, its BELOW 3k where it sounds like ***, raspy and everything.
02-10-2007, 01:26 AM
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Originally Posted by jRaskell
It's just you. What you're going to gain by bypassing your magnaflow will be on the order of 5-10hp (10 being pretty optimistic). The best of drivers simply are not going to feel a 10hp difference in a 300rwhp+ vehicle.
And you don't need back pressure to make power. Taking advantage of exhaust scavenging can increase hp within a certain RPM band, but that isn't the same as backpressure, and that's dependant on the design of your headers, and will not be affected by a cutout.
And you don't need back pressure to make power. Taking advantage of exhaust scavenging can increase hp within a certain RPM band, but that isn't the same as backpressure, and that's dependant on the design of your headers, and will not be affected by a cutout.
but im not NA anymore
02-10-2007, 01:01 PM
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you gain hp buddy, hard to ralize that it would but you dont gain as much as would to get full exhaust. I love the sound of it though. Im just gonna get corsa true dual tips
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02-10-2007, 03:32 PM
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I do notice a bit of a lack of low end torque with it open but it's not enough to bother me.. and I think it sounds amazing at all RPMs. Nice and deep... for those of you that have the cutouts... are you just bypassing the muffler like myself or have you either removed the cat or positioned the cutout to bypass the cat as well? If you have done either of those, I can see how your exhaust would be raspy but that's just the way it's going to be without a cat.
02-10-2007, 05:42 PM
#11
Originally Posted by Finite1
definately gain.. it wouldn't make sense why it would feel slower.. a guy with a 99' z28 with similar mods as you and QTP headers gained 8-9hp on a dyno before/after using cutout.
think about what its doing, seems logical it would always make power.
you probably are just used to the pressure feeling the catback made?
I'm no expert tho.
think about what its doing, seems logical it would always make power.
you probably are just used to the pressure feeling the catback made?
I'm no expert tho.
you sure aren't an expert.
why wouldn't it make sense? torque is seat of the pants feel. the reason your car feels slower is cause your losing low end torque. it makes it faster in the long run but that is not something you will feel.
02-10-2007, 05:46 PM
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My car feels slower with the cutout open, but dyno 3rwhp higher. Here is the dyno sheet, 1st run-cutout closed, 2/3 runs-cutout open: link
Last edited by bastien; 02-10-2007 at 05:54 PM.
02-11-2007, 06:50 AM
#16
Originally Posted by LS1>girlfriend
that whole backpressure myth is a load of ****. how many drag cars do you know of with more than headers?
That is because those cars run more air through them!!!
Less modded motors get the backpressure bump while the more umph motors need less restriction.
Anyway pressure is only for low end torque at lowwwwww RPMs and definately not for quarter mile times. (most definately)
If I can find it there was a VERY comprehensive mod by mod dyno test (put a part on, test it, put another part on test it, take the first part off leave the second part on test it) where the guy was almost stock (I think with something like a filter) he lost 7-9 ft/lbs of torque with the cut-out open.
That was on a LT1 though and their heads don't flow the same numbers as the LS1 (lower obviously)
Afterwards though with more parts on it, it needed less restriction and gained when the cut-out was opened up. It still sounded like **** though at anything other than idle.
I can definately see how a LS1 with higher flowing heads and especially the earlier ones with the bigger cam wouldn't see a loss in torque with the cut-out open.
The later ones also have more incoming air with the higher flowing intake manifold and better flowing headers as well.
The thing about back pressure being important has a lot to do with old school cars (especially). It wasn't about it flowing to much it was about how it sorta dumped it at the end without harmonicly controlling/flowing it. When I get to that part <- I usually quite reading about it and switched to a **** site though.
Last edited by Genesis_26317; 02-11-2007 at 06:55 AM.
02-11-2007, 10:24 AM
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I don't understand why everyone thinks an LS1 with a cutout sounds like ****... I am in love with the way mine sounds. Loud and mean.. that's what I wanted. Stock, they sound stupid. They barely make any noise. Throw on a lid and it's better but still too quiet and tame. With the cutout, it screams. Of course a full exhaust setup would sound better but the cutout is much cheaper than a catback.
Click my sig pic for a sound clip. That's only up to 3k and it sounds even better when it's revved higher.
Click my sig pic for a sound clip. That's only up to 3k and it sounds even better when it's revved higher.
02-11-2007, 08:16 PM
#18
Originally Posted by Kalgorn
I don't understand why everyone thinks an LS1 with a cutout sounds like ****... I am in love with the way mine sounds. Loud and mean.. that's what I wanted. Stock, they sound stupid. They barely make any noise. Throw on a lid and it's better but still too quiet and tame. With the cutout, it screams. Of course a full exhaust setup would sound better but the cutout is much cheaper than a catback.
Click my sig pic for a sound clip. That's only up to 3k and it sounds even better when it's revved higher.
Click my sig pic for a sound clip. That's only up to 3k and it sounds even better when it's revved higher.
02-11-2007, 08:27 PM
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Originally Posted by Kalgorn
I don't understand why everyone thinks an LS1 with a cutout sounds like ****... I am in love with the way mine sounds. Loud and mean.. that's what I wanted. Stock, they sound stupid. They barely make any noise. Throw on a lid and it's better but still too quiet and tame. With the cutout, it screams. Of course a full exhaust setup would sound better but the cutout is much cheaper than a catback.
Click my sig pic for a sound clip. That's only up to 3k and it sounds even better when it's revved higher.
Click my sig pic for a sound clip. That's only up to 3k and it sounds even better when it's revved higher.