LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Cutout HP Gains??

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Old Nov 25, 2008 | 03:01 PM
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Default Cutout HP Gains??

On a car making over 400hp, what is the typical HP gain using a cutout on a car already equipped with an aftermarket catback?
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Old Nov 25, 2008 | 03:04 PM
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look at the end of achotrd's thread about gettin ready to deal wit speed inc he has a dyno chart on this
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Old Nov 25, 2008 | 03:05 PM
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Right on, let me check it out.
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Old Nov 25, 2008 | 03:08 PM
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Do you know what kind of catback he is running?
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Old Nov 25, 2008 | 03:09 PM
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Yeah, it's pretty significant looking at AC's thread.
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Old Nov 25, 2008 | 03:11 PM
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im not sure i think it says magnaflow somewhere i can tell u that on my car in the 1/4 i gain 2 tenths with the cut out open and im nowhere close to 400hp
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Old Nov 25, 2008 | 03:11 PM
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3" B&B triflow
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Old Nov 25, 2008 | 03:12 PM
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Yeah, I found on a different thread he was running a B&B catback. I am running a Magnaflow and I have a cutout. I forgot to uncap last week at test and tune. Car went 12.05 but, I am looking for that 11 sec pass before the track shuts down for the winter. I didn't have time the put on the x-pipe and bullets I have. I was wondering what to expect.
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Old Nov 25, 2008 | 03:17 PM
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Originally Posted by SpeedDensityZ
Yeah, I found on a different thread he was running a B&B catback. I am running a Magnaflow and I have a cutout. I forgot to uncap last week at test and tune. Car went 12.05 but, I am looking for that 11 sec pass before the track shuts down for the winter. I didn't have time the put on the x-pipe and bullets I have. I was wondering what to expect.
From what AC and z28rob are showin, seems like if you did uncap the cutout you'd get into the 11's.
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Old Nov 25, 2008 | 03:18 PM
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Originally Posted by lt1z28camaro
From what AC and z28rob are showin, seems like if you did uncap the cutout you'd get into the 11's.
i agree u hav 11s with the cutout open
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Old Nov 25, 2008 | 03:20 PM
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I picked up 17rwhp with a cut out! If you went 12.05 yu definitly would be in the 11.s with a good 60ft!! and Yes Its a B&B catback!
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Old Nov 25, 2008 | 03:21 PM
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Saweet!! I think I have a better 60' time in it also. I only ran it a couple times last week and I haven't driven the car since Feburary and it had a TH350 then. I have the T-56 now and I'm trying to remember what it's like.
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Old Nov 25, 2008 | 07:09 PM
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I put down 412 RWHP open and 409 RWHP closed. Guess my borla and LPP headers flow pretty damn sweet.
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Old Nov 25, 2008 | 07:14 PM
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I gain 1rwhp with my cutout open with a 4" catback into a Magnaflow. The gains all depend on the catback/muffler.
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Old Nov 25, 2008 | 07:17 PM
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Borla does flow great!!!!!!! And sounds awesome also!! If I didnt already have a B&B that is prob what I would have gone with!!! With my S60 and LPPs & cut out open I got 413.6/366
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Old Nov 25, 2008 | 07:24 PM
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As per the above threads it is going to depend on how much backpressure your current system has. One more thing if you could place the cutout at the proper distance from the end of your primary tubes you could pick up power from wave tuning.

David Vizard did a test on a dyno motor and he kept shortening the dyno collector pipe and gained 18 horsepower from the wave tuning alone. The sweet spot on that particular setup was like 14 inches from the end of the primary tubes. I suspect yours would be like 16 to 18 inches from the end of the primary tubes.

So proper placement of the cutout can provide some additional free horsepower aside from the backpressure.
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Old Nov 25, 2008 | 08:35 PM
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Originally Posted by LS1 SPEED
The gains all depend on the catback/muffler.
Yup,
I lost 7rwhp with a closed cutout (vs no cutout)
I gained 3rwhp with an open cutout (vs no cutout)

That was with a 3" Hooker on my ~390rwhp LE1HL/LE2 setup.
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Old Nov 25, 2008 | 11:37 PM
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What do you think track times would show? i'm gonna be running a small hot cam, longtubes and hooker catback with no cats anywhere, would i gain anything at the track with an open cut-out or should i not worry about it? I want the sound but dont want to hurt my times....
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Old Nov 25, 2008 | 11:48 PM
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I haven't Dyno'd mine yet to see.. I have a 3.5" Cut-out, I wonder how much it would gain..
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Old Nov 26, 2008 | 09:40 AM
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When I had my old A4 TA I had no cats and a dynomax cat-back. The car had a 3" exhaust and a 2.5 inch cutout. With bolt-ons I gained 5 rwhp and 4 rwtq. After a cam I gained 13 rwhp and 10 rwtq.
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