How much power and I getting by this setup (regarding exhaust)

Seraphitia102 · Dec 9, 2004

Yesterday, I got my 2 mid-pipes and 2 tail-pipes changed from the stock 2.25in to the new 2.5in pipes. I have 2 Flowmaster 40's that used to be weld-ins with the stock H-pipe.

I noticed yesterday that after changing my mid/tail pipes from 2.25in to a new custom 2.5in pipe that I got increased power in acceleration.

Approximately how much horsepower did I gain from 2 new mid-pipes and 2 new tail-pipes (2.5 in) with 2 Flowmaster 40's mufflers?

zcs626 · Dec 9, 2004

you mean a new H pipe (which is the equivalent to your 2 mid pipes)?

Seraphitia102 · Dec 9, 2004

well the person who installed my piping and my mufflers didn't replace the actual "H" of the H-pipe. He just cut 2 mid-pipes and 2 tail-pipes and replaced them with 2.5in stainless steel pipes

mustang70 · Dec 9, 2004

Aren't those called the flow tubes?

Seraphitia102 · Dec 9, 2004

I have no clue

Fast02 · Dec 9, 2004

Ive heard people say zero hp gains but two thumbs up on sound. The claims are like 7-10hp per section.....so I dunno

Gearbanger 101 · Dec 9, 2004

If I understand this right and you don't have some sort of crossover section between the exhaust pipes, you may actually loose a little torque while gaining minimal horsepower. Most of the power than people gain from exhaust mods is in their head, because their cars new healthier exhaust note gives them the impression that if it's louder, it must be making more power as well....., which is not always the case.

Seraphitia102 · Dec 9, 2004

so even if Flowmaster and Magnaflow promise horsepower gain (and they said "dyno proven"), it's all just a lie?

JonJon · Dec 9, 2004

I am very confused about how this setup works... there is no crossover? i thought 4.6's don't work so great with no crossover since the engine firing order is like left left left right (or something)...

I do have to say i -DEFINATELY- gained some power with my mid pipe swap. i never believed SOTP readings but it was definately noticable. Probably ~10rwhp.

Gearbanger 101 · Dec 9, 2004

Yeah, but dyno proven in most cases is just a lot of double talk. Yeah, a high flow exhaust is a necessity when you've got ported heads/intake or some sort of power adder. But on a stock car...not even worth doing a dyno run.

The 2-3hp that you might see on the dyno means Jack $hit on the street. You wouldn't even feel it.

Gearbanger 101 · Dec 9, 2004

JonJon said:
I do have to say i -DEFINATELY- gained some power with my mid pipe swap. i never believed SOTP readings but it was definately noticable. Probably ~10rwhp.

two times on you today sir.

Seraphitia102 · Dec 10, 2004

basically, this sums up my setup, I have a stock h-pipe still in.

the only thing changed was the 2 midpipes (the pipes coming out from the cats to the mufflers), and the 2 tailpipes (the 2 pipes coming out of the mufflers)

both the midpipes and tailpipes are changed to 2.5in size, instead of the stock 2.25in. The stock "H" of the pipe is still there. It wasn't a complete exhaust overall, it was just cutting the 2.25 existing midpipes and tailpipes and replacing them with 2.5in piping.

ScottLuscombe · Dec 10, 2004

I gained 18 rwhp with my Magnaflow Cat Back as opposed to my stock system.

It was attached to an already existing Flowtech O/R X Pipe.

This is on a Blower car though.

Cheers,

S

matrixpuba · Dec 10, 2004

it might not add much but u gotta start somewhere right

40th GT · Dec 10, 2004

It probably gave you something like 1-2hp and took away some torque. You pretty much got a custom catback since it appears that you got each part separately. If you don't have/aren't getting significant intake mods, it's pointless to get 2.5" piping.

Seraphitia102 · Dec 10, 2004

40th GT said:
It probably gave you something like 1-2hp and took away some torque. You pretty much got a custom catback since it appears that you got each part separately. If you don't have/aren't getting significant intake mods, it's pointless to get 2.5" piping.

I'm planning to get a cold air intake later (K&N Filtercharger setup maybe?)

Though the 2.5in piping does make me sound like a truck now.

mustang70 · Dec 10, 2004

Mind if I ask how much all this ran you?

hotmustang331 · Dec 10, 2004

Gearbanger 101 said:
Yeah, but dyno proven in most cases is just a lot of double talk. Yeah, a high flow exhaust is a necessity when you've got ported heads/intake or some sort of power adder. But on a stock car...not even worth doing a dyno run.

The 2-3hp that you might see on the dyno means Jack $hit on the street. You wouldn't even feel it.

And your supposed to know everything??? What your saying is the . I have read a dyno comparison of a stock 03 GT I believe it was, and they first swapped the stock catted H with a SLP catted X...they gained 10 +/- 1 peak to peak and up to 15 in other areas of the powerband...next they added a SLP catback to that and gained another 9HP for a total peak to peak of 19.XX RWHP. I believe they said they took 3 runs with each mod and took the highes of each to compare evenly.Could have been the averages of 3 runs on each mod...but either way its a true gain. Remember the factory NEVER sets up a car perfectly, especially on a $25K car...there is always room for improvement.Heads/cams wont help you enough to tell a difference in how much power a mod gives you, the results of power difference added by an exhaust to a stock 4.6 as compared to a head/cam 4.6 would be pretty small...probably that 2-3 HP and since "You wouldnt even feel it" it doesnt even matter. BTW if that 2.5 ich exhaust is mandrel (sp) bent, then I would say you gained around 8-10 RWHP...dont know how much the 2.5 inch pipe helped on the mid pipe...and I believe you have the stock cats right? Should have went with an aftermarket X, would get you real gains, as I have stated above.

Seraphitia102 · Dec 10, 2004

mustang70 said:
Mind if I ask how much all this ran you?

It was pretty expensive actually since I did it seperate.

The first mod to the exhaust was 2 weld-in Flowmaster 40's mufflers at $240.

The second mod was to add custom 2.5 midpipes and tailpipes at another $200.

Seraphitia102 · Dec 10, 2004

hotmustang331 said:
And your supposed to know everything??? What your saying is the . I have read a dyno comparison of a stock 03 GT I believe it was, and they first swapped the stock catted H with a SLP catted X...they gained 10 +/- 1 peak to peak and up to 15 in other areas of the powerband...next they added a SLP catback to that and gained another 9HP for a total peak to peak of 19.XX RWHP. I believe they said they took 3 runs with each mod and took the highes of each to compare evenly.Could have been the averages of 3 runs on each mod...but either way its a true gain. Remember the factory NEVER sets up a car perfectly, especially on a $25K car...there is always room for improvement.Heads/cams wont help you enough to tell a difference in how much power a mod gives you, the results of power difference added by an exhaust to a stock 4.6 as compared to a head/cam 4.6 would be pretty small...probably that 2-3 HP and since "You wouldnt even feel it" it doesnt even matter. BTW if that 2.5 ich exhaust is mandrel (sp) bent, then I would say you gained around 8-10 RWHP...dont know how much the 2.5 inch pipe helped on the mid pipe...and I believe you have the stock cats right? Should have went with an aftermarket X, would get you real gains, as I have stated above.

Thanks for all your info Yes I have the stock cats still. The car is noticeably louder and I did feel acceleration to have been improved. It's nice to gain some power from an exhaust mod but what I really like is that my 4.6 Mustang sounds like a truck now

How much power and I getting by this setup (regarding exhaust)

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