cut-out @ track, uncapped or capped?
Registered User
Joined: May 2001
Posts: 97
From: Reno, NV
Originally posted by WS Sick
3/4 inch SLPs and their Y into a SINGLE 3 inch pipe is restrictive on a 350 that sees over 5800 rpm.
Let me put it this way, with a pressure gauge hooked to the pipe before the cut-out with the cut-out closed we had 11 psi (5 is border good). with the cut-out open we had 2 PSI.
There is a book out there by a well known and well respected individual named David Vizzard "How to build Horsepower" volume 1. He put a set of headers and pipes on an 80 Z with a pellet type converter and the 70 hp 350 stocker. He reduced the backpressure by I think it says 6 psi and he gained 27 hp with that crappy motor.
3/4 inch SLPs and their Y into a SINGLE 3 inch pipe is restrictive on a 350 that sees over 5800 rpm.
Let me put it this way, with a pressure gauge hooked to the pipe before the cut-out with the cut-out closed we had 11 psi (5 is border good). with the cut-out open we had 2 PSI.
There is a book out there by a well known and well respected individual named David Vizzard "How to build Horsepower" volume 1. He put a set of headers and pipes on an 80 Z with a pellet type converter and the 70 hp 350 stocker. He reduced the backpressure by I think it says 6 psi and he gained 27 hp with that crappy motor.
Wow! So how much would my car gain with cut outs placed just after the light off cats? Full off road exhaust makes about 22 rwhp on my car.
Registered User
Joined: Dec 2003
Posts: 2,724
From: Oklahoma where trees are made of wood.
Over a full offroad exhaust like the mustangs use youwouldnt see the gain an F-body sees with a cut-out.youre brobably only gaining 2 or 3 psi with a cutout so maybe youd see 10 at the wheels.
Registered User
Joined: May 2001
Posts: 97
From: Reno, NV
Originally posted by WS Sick
Over a full offroad exhaust like the mustangs use youwouldnt see the gain an F-body sees with a cut-out.youre brobably only gaining 2 or 3 psi with a cutout so maybe youd see 10 at the wheels.
Over a full offroad exhaust like the mustangs use youwouldnt see the gain an F-body sees with a cut-out.youre brobably only gaining 2 or 3 psi with a cutout so maybe youd see 10 at the wheels.
Registered User
Joined: Jun 2001
Posts: 378
From: San Jose
I gained 1.5 MPH with my cutouts open at the track on my mustang. My friend has cutouts on his 96 Cobra, traps 106's with them open (gears being his only other mod). Also have a friend with a 99 Cobra with cut outs but no track times.
any ways, heres a dyno I found in a book of mustang dynos i have, not sure if it helps any:
-Off Road H Pipe----Open Headers-
RPM......HP.....TQ............HP.....TQ
2400....199...436...........202...441
2800....243...455...........247...464
3200....282...463...........286...470
3600....323...472...........322...470
4000....345...453...........342...449
4400....356...425...........351...420
4800....357...391...........351...384
5200....354...357...........343...346
5600....349...327...........337...316
Basically a mild 302 with an 8# Kenne Bell
it goes on to say they showed gains of up to 20lbs/ft with an 18in section added to the headers. the open headers were shorties. looking at it again though, looks like it doesnt help much in this discussion. either way, I gained some MPH with my cutouts open though it does feel like I lost some lowend below 2200 or so and I did lose some MPG's too.
any ways, heres a dyno I found in a book of mustang dynos i have, not sure if it helps any:
-Off Road H Pipe----Open Headers-
RPM......HP.....TQ............HP.....TQ
2400....199...436...........202...441
2800....243...455...........247...464
3200....282...463...........286...470
3600....323...472...........322...470
4000....345...453...........342...449
4400....356...425...........351...420
4800....357...391...........351...384
5200....354...357...........343...346
5600....349...327...........337...316
Basically a mild 302 with an 8# Kenne Bell
it goes on to say they showed gains of up to 20lbs/ft with an 18in section added to the headers. the open headers were shorties. looking at it again though, looks like it doesnt help much in this discussion. either way, I gained some MPH with my cutouts open though it does feel like I lost some lowend below 2200 or so and I did lose some MPG's too.
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