dual 3" or single 4"
04-29-2007, 05:04 PM
#1
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Car: Resto-Mod 1987 IROC-Z Clone
Engine: Alky fed L92 Vortec Twin-Turbo 6.8L
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dual 3" or single 4"
I have a 350 that is making 390 HP at the wheels.
I have headman long tubes and duel 3 inch pipes straight back to 2 40 series flowmasters cut before the rear.
i have the stock iroc springs in the car, they are a few years old, but the fenderwell is three inches higher than the tire.
i would like to lower the car and to do so, the duel exhaust i have would need to go.
how would going to the single 4" system effect my power HP and Torque?
does the mufflex Y-pipe kill my ground clearance as badly as my duel pipes?
i also plan on going back to two 3" pipes and mufflers after the rear end.
and explanations or pics would be much apreciated.
I have headman long tubes and duel 3 inch pipes straight back to 2 40 series flowmasters cut before the rear.
i have the stock iroc springs in the car, they are a few years old, but the fenderwell is three inches higher than the tire.
i would like to lower the car and to do so, the duel exhaust i have would need to go.
how would going to the single 4" system effect my power HP and Torque?
does the mufflex Y-pipe kill my ground clearance as badly as my duel pipes?
i also plan on going back to two 3" pipes and mufflers after the rear end.
and explanations or pics would be much apreciated.
04-30-2007, 12:02 AM
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Car: '82 Z28
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Re: dual 3" or single 4"
“Dual” is an adjective describing the two-ness of something—dual carburetors, for instance. A “duel” is a formal battle intended to settle a dispute.
I don't know about the affect on the hp and tq but I'm wanting to do something similar. The dual 3 inch on my car right now only gives me 3 inches of clearance, well maybe a 1/4 inch more now since I've been over speedbumps. In the planning stages now of doing a dual 3 inch into single 4, running it over the axle.
I don't know about the affect on the hp and tq but I'm wanting to do something similar. The dual 3 inch on my car right now only gives me 3 inches of clearance, well maybe a 1/4 inch more now since I've been over speedbumps. In the planning stages now of doing a dual 3 inch into single 4, running it over the axle.
05-15-2010, 12:56 PM
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Re: dual 3" or single 4"
i did a search and found this thread and wanted to ad. i think that you are loosing power with dual 3 i think you would gain with a single 4. dual 3 i would use for 600+crank hp
05-15-2010, 01:21 PM
#4
Re: dual 3" or single 4"
A single 4" in the stock location with muffler out behind the rear axle will have good ground clearance, but you still will have problems with the Y pipe with the longtubes.
The y pipe going from the long tubes to the stock exhaust path means you will have to go under the frame rails (around the tranny x-member). This will be the lowest point on the car.
HP wont be lost. Single 4 flows more than enough for 390whp. There are LSx guys making well over that on single 3" systems.
Depending on how your current exhaust is and how tucked up the mufflex exhaust will be, you may have good clearance you may not. Any pics of the current exahust and ride height of the car?
I have lowered my car with the eibach prokit and its pretty low in front. Nice stance in the rear. My longtubes with 3" to single 4" ypipe I made did not offer me great clearance. I hit on just about everything. It was frustrating and I wished I went with shorty headers by Dyno Don, or fabbed my own.
The y pipe going from the long tubes to the stock exhaust path means you will have to go under the frame rails (around the tranny x-member). This will be the lowest point on the car.
HP wont be lost. Single 4 flows more than enough for 390whp. There are LSx guys making well over that on single 3" systems.
Depending on how your current exhaust is and how tucked up the mufflex exhaust will be, you may have good clearance you may not. Any pics of the current exahust and ride height of the car?
I have lowered my car with the eibach prokit and its pretty low in front. Nice stance in the rear. My longtubes with 3" to single 4" ypipe I made did not offer me great clearance. I hit on just about everything. It was frustrating and I wished I went with shorty headers by Dyno Don, or fabbed my own.
05-15-2010, 01:26 PM
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Car: 02wrx/88 rs
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Re: dual 3" or single 4"
550hp will need 1210 cfm of flow. Single 4" flows 1440cfm at 28" of H20. I think its a good match. Dual 3's flow more like 1625 cfm total and would be abit large for a 550hp machine but not horrible. Dual 2.5's however flow 1130 cfm and would be a touch small.
Keep in mind with a single exhaust you need one muffler that will also flow as good as the straight pipe. Dynomax ultraflo rounds, bullets, magnaflow straight thru, borla straight thru, and other straight thrus should do it.
My street 383 loved single 4" exhaust. Sounded great too. No lack of power anywhere. I would estimate 500 crank hp based on 400whp thru the automatic trans but it may have been closer to 550. It was a strong motor.
My turbo car now has dual 3" on a 9 to 1 compression 401" motor. Mild hyd roller cam, and it has plenty of low end power when normally driving. Feels fine to me even with 2.73 gears and a loose converter which is close to 4200 stall. I dont think you can go too large on the exhaust that it would kill off a drastic amount of power.
Keep in mind with a single exhaust you need one muffler that will also flow as good as the straight pipe. Dynomax ultraflo rounds, bullets, magnaflow straight thru, borla straight thru, and other straight thrus should do it.
My street 383 loved single 4" exhaust. Sounded great too. No lack of power anywhere. I would estimate 500 crank hp based on 400whp thru the automatic trans but it may have been closer to 550. It was a strong motor.
My turbo car now has dual 3" on a 9 to 1 compression 401" motor. Mild hyd roller cam, and it has plenty of low end power when normally driving. Feels fine to me even with 2.73 gears and a loose converter which is close to 4200 stall. I dont think you can go too large on the exhaust that it would kill off a drastic amount of power.
thats what i was told
05-15-2010, 01:28 PM
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Re: dual 3" or single 4"
ha ha ha i just notice YOU posted that response. ha ha and i quoted you from another thread
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05-15-2010, 02:17 PM
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Re: dual 3" or single 4"
Dual 3" & single 4" are overkill for 390hp. Your long tubes are the reason for your loss of ground clearance. No room on the drivers side for exhaust to come off that side & retain clearance.
Get a street car, get you some shorties or mid-lengths & run it all out the passenger side.
05-15-2010, 03:13 PM
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Car: 1991 Camaro Z28
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Re: dual 3" or single 4"
I think in the last 3 years the OP has figured it out already.
05-15-2010, 03:20 PM
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Car: 1985 IROC-Z Silver
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Re: dual 3" or single 4"
wow this is old
Last edited by z28freak84; 05-15-2010 at 03:38 PM.
05-15-2010, 03:31 PM
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Re: dual 3" or single 4"
There is simply no way to run exhaust on the drivers side, without compromising ground clearance by a great deal. Using oval pipes helps, but still doesn't tuck it up good.
1/4 mile track only? Fine.....On the street? Not possible. Even just putting around the parking lot in a Saturday night gathering, your messing with speed bump issues at 2mph.
We have F-bodies running 10s with the single, stock routing exhaust. There is simply no excuse to run "true duals". The only thing is gives is a different sound, not speed or performance, over a single exhaust that is made good. Duals are just the easy easy out.
Last edited by Stephen; 05-15-2010 at 06:46 PM.
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