Gains from cutout
Thread Starter
On The Tree
Joined: Nov 2003
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From: SeaCoast NH
Gains from cutout What is the gain from having the cut out open vs. going all the way through the catback system? I guess I'd like to see two dyno runs with cutout open then closed.
Basically I'm trying to decide if the QTP package is worth it to me.
Basically I'm trying to decide if the QTP package is worth it to me.
!LS1 11 Second Club
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From: Miami
http://home.att.net/~carlos.ramirez1...2/site1003.jpg
The gains won't be as dramatic on a near stock or bolt on only setup. This was my full bolted & cammed car.
The peak numbers values are high by about 15 to 18 across the board, but the two pulls are closed vs. open.
Interesting eh? 20+ hp parasitic loss to the bends and muffler.
Next mod: QTP electric. No more getting under the car for me.
The gains won't be as dramatic on a near stock or bolt on only setup. This was my full bolted & cammed car.
The peak numbers values are high by about 15 to 18 across the board, but the two pulls are closed vs. open.
Interesting eh? 20+ hp parasitic loss to the bends and muffler.
Next mod: QTP electric. No more getting under the car for me.
Last edited by SouthFL.02.SS; Nov 18, 2003 at 05:02 PM.
TECH Senior Member
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From: Troy, AL
It depends on what kind of power your engine is capable and how restrictive everything behind the cuttout is. I picked up 28 RWHP with my cuttout open. I made 423 RWHP open and 395 closed.
Thread Starter
On The Tree
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From: SeaCoast NH
Which catback are you running?
I'm using Corsa.
The main reason for the initial post was because I didn't know if I should buy the QTP with duel electrics $600 or their OR pipe of $300. Maybe I'll just add a cutout later.
I'm using Corsa.
The main reason for the initial post was because I didn't know if I should buy the QTP with duel electrics $600 or their OR pipe of $300. Maybe I'll just add a cutout later.
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From: In front of my computer
Thru 3" flowmaster 80 series single outlet catback. No retrictions in the size. 3" all the way back from collector to tailpipe.
Thru muff........11.52@117.1 on a 1.59 60'
Thru cutout.....11.41@119.8 on a 1.58 60'
So a tenth and 2.5 mph. Neither run had wheel spin.
Flowmaster sucks.
Stu
Thru muff........11.52@117.1 on a 1.59 60'
Thru cutout.....11.41@119.8 on a 1.58 60'
So a tenth and 2.5 mph. Neither run had wheel spin.
Flowmaster sucks.
Stu
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Joined: Apr 2003
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From: Miami
Originally Posted by taJon
Which catback are you running?
I'm using Corsa.
The main reason for the initial post was because I didn't know if I should buy the QTP with duel electrics $600 or their OR pipe of $300. Maybe I'll just add a cutout later.
I'm using Corsa.
The main reason for the initial post was because I didn't know if I should buy the QTP with duel electrics $600 or their OR pipe of $300. Maybe I'll just add a cutout later.
I'm really not running a catback. I simply kept the stock I and over the axle pipes and replaced the stock muffler with a single 3" inlet / dual 3" outlet Spintech splitcase. It sounds great, but the reduction from 2.75" to 3" was done by some bonehead down the street who did not use a cone, just a big nasty weld bead. Money's tight right now, so I've gotta drive around with the POS setup for a while. True duals Xpipe planned.
In retrospect , I shoulda just gotten a full 3" catback. Live and learn. If I woulda known then what I know now, a Hooker catback would be hanging back there, with a 3" QTP cutout in the I-pipe.
Here is a problem I have been considering. Everyone that has dynoed with their cut out open and shut haven't dynoed without a cutout installed. How much power is being lost because the cutout messes up the flow of the pipe? Think about the design. When its open there is no problem but when its closed the exhaust gases are bouncing off the closed pipe and coming back to distrupt the flow. This has to be considered. If you have a stock exhaust it should help a lot but if you have a good flowing exhaust like mine I think it may do nothing for you. Also, in both cases it will hurt performance when its closed. What do you think?
My 3" Cut-out picked up 8.3 HP and 18.4 TQ over my 3" single in/out Borla cat-back on the dyno. Bolt-on car with Jet Hot LT's. 
I also pick up 2-3 MPH and 2-3 tenths in the 1/4. 
I also pick up 2-3 MPH and 2-3 tenths in the 1/4. Last edited by BAIN; Nov 19, 2003 at 10:22 AM.
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From: Orlando
FWIW, I did dyno pre-cutout install right at 300 RWHP with a lid and filter swap. After the cutout went in, I redynoed sometime later and did 305 closed. I opened it up and did 322. Your theory sounds like it would be a little bit of a factor, but realistically, I don't think it's interrupting the exhaust flow all that bad. Especially at WOT when the exhaust gases are really screaming out of the tailpipe.
