Does anyone have a guide that tells what size exhaust pipe will support what HP. I have a flowmaster guide, but the pipe sizes seem very large. Dual and single please.

 

This really won't answer your question, but then again, I don't think the question can be answered with hard and fast numbers.

Every person and/or company you talk to will give you a different answer on this. Company "A" will tell you a single 3" pipe will only support 350 hp and company "B" will tell you it will support 400 hp. Then you'll read a magazine article in which someone with a single 3" pipe is making 450 hp, or someone will tell you about "a friend" who makes 500+ on a 3" pipe.

Personally, I think what is ahead of the intermediate pipe, - headers, y-pipe(or not) ant catalytic - will be more important in determining how much power you can make.

Between the major catback manufacturer's, you're not going to see a lot of variation in design other than the type of muffler. And the quality of materials used. So it'll come down to how much you're comfortable spending. For instance, a full stainless system is going to cost more than one made from mild steel, and some muffler's will cost more than others(depending on design and materials).

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Edelbrock's catalog recommends these diameter cat back systems, depending on HP and cubic inches.

ci HP Tubing Size

300-350 250 2.5"
300 3.0"
350 3.0"

350-400 300 3.0"
350 3.0"
400 3.0"
450 3.0"
450+ 3.5"

These numbers are for edelbrock's cat back, though I assume others are similar. I hope this helps.

 

Sorry those numbers got all mixed up. Here they are again.

for 300-350 cubic inches
250 HP -- 2.5"
300 HP -- 3.0"
350 HP -- 3.0"

for 350-400 cubic inches
300 HP -- 3.0"
350 HP -- 3.0"
400 HP -- 3.0"
450 HP -- 3.0"
450+ HP - 3.5"

Hope these came out readable. Also these are for a single pipe exhaust. Dual exhaust would use different diameters.

 

George Baxter makes 910 HP through a 4" Mufflex cat-back, with a 3" Mufflex Y-Pipe.

Food for thought. The car weighs 4100 pounds and runs 9.7's at 140 MPH.

Steve

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Spohn Performance: F-Body Chassis/Suspension Specialists

 

A good mandrel bent 3" pipe flows to 325hp and then starts becoming a restiction; a 3.5" pipe about 400hp; and a 4" pipe around 500hp. I asked Mufflex the same question when I picked up my 3.5" exhaust. They did George Baxter's exhaust FYI.

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1985 IROC LG4 POS Best: 15.20s at 92.1mph
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From an older SUMMIT magazine tech article..

HP____________Single_____Dual
200-300 --------- 3 ------- 2¼
300-400 --------- 3½ ------ 2½
375-450 --------- 4 ------- 3
450-550 --------- 4½ ------ 3½
550-650 --------- 5 ------- 3½

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[This message has been edited by deadbird (edited November 22, 2000).]

 

If you have the chance, get theoctober 2000 HOT ROD magazine. in there they did dyno tests on the sixe of the headers, and the exhaust pipe. I read that the bestdiameter pipe is 50% larger than your exhaust valve. that is i think for street purposes. that size of pipe will actually suck the gasses out to creat a low pressure region in the cylinder. if it is much larger than that it is like haveing to small of pipe.

anyway, that is just my input. If I were you I would ask a professional engine builder to find teh proper exhaust pipe size to suit your needs.

 

ATR claims their single 3" will go 9's on a TTA. I have personally seen low 10's with their "Single Shot" 3" on Turbo Regals at the GS Nationals. It's basically the same thing with a different muffler, so thats kinda why I use their stuff. That and it tucks up behind the bumper like the factory pipes for the sleeper look.

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According to Flowmaster literature the following are maximum horsepower levels for a given single pipe size (similar to the rest given)
2.00" - 100 HP
2.25" - 150 HP
2.50" - 250 HP
3.00" - 300 HP
3.50" - 400 HP
My personal experience and general mathematics end up with somewhat similar results - for "optimal" power
2.00" - 140 HP
2.25" - 180 HP
2.50" - 225 HP
3.00" - 325 HP
3.50" - 440 HP

This is not saying a smaller pipe than "optimal" can not produce more than the power listed. In fact,,, this IROC I just finished is pushing over 340 horses through a single 2.5" Dynomax!!!! And I'm in no real hurry to change it.

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86 IROC - 9.8:1 - 355, TFS twisted wedge heads, 218/228-110, fully ported GM base and plenum, SLP runners, 52mm BBK, 24# SVO, 1 5/8" Headman headers, 2.5" Dynomax, TH350, 2200 stall, B&M Megashifter, 3.23 peg leg, 245/45ZR17s on 212 Eagles