Backpressure....I might need to change some things.
03-25-2008, 12:24 AM
#11
4th Gear Member
Join Date: Nov 2006
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RE: Backpressure....I might need to change some things.
ORIGINAL: 67mustang302
it's about running the exhaust system size that yields the best power(which is usually much smaller than most people think).
it's about running the exhaust system size that yields the best power(which is usually much smaller than most people think).
The Borla catback designed for the 93 Cobra was made of 2.5" tubing.
I suppose this has to do with the mufflers themselves being of a straight through design.
http://www.allfordmustangs.com/Detailed/70.shtml
03-25-2008, 01:07 AM
#12
6th Gear Member
Join Date: Apr 2007
Location: California
Posts: 10,468
RE: Backpressure....I might need to change some things.
I have a good book on 4 stroke engine performance tuning, and the exhaust section has info on the approx hp ranges supported by pipe sizes, and a well built dual 2.5" setup is capable of supporting up to around 475hp before it becomes restrictive. Dual 3" is good for up to around 650hp. That's straight through design though, so add a restrictive muffler or cat and the power drops. I see plenty of people putting 3" setups on mostly stock cars, sounds good, kills power.
03-25-2008, 12:02 PM
#14
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Join Date: Oct 2005
Location: Ohio USA
Posts: 4,616
RE: Backpressure....I might need to change some things.
Alot of cars out there with 240-270 Hp ready to challenge the stang.
You did the right thing with the exhaust, now you need to focus on the engine.
HCI, NOS ,BLOWER.
You did the right thing with the exhaust, now you need to focus on the engine.
HCI, NOS ,BLOWER.
03-25-2008, 05:25 PM
#15
Thread Starter
Join Date: Dec 2007
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Posts: 44
RE: Backpressure....I might need to change some things.
well i called the local speed shop and they said having no muffs, and no cats is making my car run like crap also, everyone here says i dont need backpressure, ok to smplify it, do i need mufflers..
03-25-2008, 07:05 PM
#16
Join Date: Feb 2007
Posts: 37
RE: Backpressure....I might need to change some things.
ORIGINAL: cleanfitty
This is why almost everyone who runs dumps says they felt a loss in torque when they took the tails off, and most people who add tailpipes feel an increase.
This is why almost everyone who runs dumps says they felt a loss in torque when they took the tails off, and most people who add tailpipes feel an increase.
03-25-2008, 09:35 PM
#17
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RE: Backpressure....I might need to change some things.
ORIGINAL: mr_spider3
well i dont agree with that. i have a stock 5.0 mustang. and i know my car very well, i got to know mine from driving in the winter and when you dont want the tires to spin you find the best throttle spot, i guess you would say. well im out of the winter now and putting the throttle to the same spot after taking off my mufflers, i have noticed an increase in torque, and i have no tail pipes.
ORIGINAL: cleanfitty
This is why almost everyone who runs dumps says they felt a loss in torque when they took the tails off, and most people who add tailpipes feel an increase.
This is why almost everyone who runs dumps says they felt a loss in torque when they took the tails off, and most people who add tailpipes feel an increase.
ORIGINAL: 1990lxhatch
pull your headers and run open ports sometime.
pull your headers and run open ports sometime.
If you've ever done that, you must havebigger juevos than I do...
03-25-2008, 10:13 PM
#18
3rd Gear Member
Join Date: Nov 2007
Location: Washington, Seattle
Posts: 551
RE: Backpressure....I might need to change some things.
ORIGINAL: cleanfitty
I said "some backpressure" in other words "some restriction"
I don't give a rats **** if you call it 'pipe length tuning'
I said "some backpressure" in other words "some restriction"
I don't give a rats **** if you call it 'pipe length tuning'
Resonant tuning is what you are talking about, but you keep calling it back pressure.
If backpressure were the only thing that mattered, then we would all be crimping our exhuast down from the factory size.
WTF?
That would increase backpressure right? And by your theory, increase performance?
ORIGINAL: cleanfitty
Upgrading exhaust on a stock motor yeilds some very small results and most people upgrade their exhaust for primairly fora louder more aggressiveexhaust note(and looks).
Upgrading exhaust on a stock motor yeilds some very small results and most people upgrade their exhaust for primairly fora louder more aggressiveexhaust note(and looks).
I noticed the difference...
ORIGINAL: cleanfitty
This is why every exhaust manufacturer suggests that going too big will actually hurt performance.
This is why every exhaust manufacturer suggests that going too big will actually hurt performance.
These guys sell mass produced parts to cookie cutter cars... not a good example to use for discussing design principles...
ORIGINAL: cleanfitty
This is why no one runs a dual 3" exhaust system (unless you have a massive build).
This is why no one runs a dual 3" exhaust system (unless you have a massive build).
And, again, I think you are talking mass produced exhaust components?
Designed to 'work' on cars built to a wide variety of specs.......
ORIGINAL: cleanfitty
This is why you don't get headers with real huge primaries (unless you have a massive build).
This is why you don't get headers with real huge primaries (unless you have a massive build).
Regardless of the primary diameter, it isn't backpressure that is working here...
ORIGINAL: cleanfitty
This is why almost everyone who runs dumps says they felt a loss in torque when they took the tails off, and most people who add tailpipes feel an increase.
This is why almost everyone who runs dumps says they felt a loss in torque when they took the tails off, and most people who add tailpipes feel an increase.
My cousin had no cats and dumps on his Mustang when he purchased it. A couple months later, when he had to go through emissions he added cats and dump mufflers.
The care sure felt slower to me.... each scenario will play out differently.
It depends on the rest of the build!!!!!
My point is...
It ain't 'backpressure'!!!!!!!!!!
Once you accept that there is something else at work, you can begin to understand it....
good luck,
jason
03-25-2008, 10:13 PM
#19
2nd Gear Member
Join Date: Mar 2008
Location:
Posts: 153
RE: Backpressure....I might need to change some things.
ORIGINAL: 1990lxhatch
pull your headers and run open ports sometime.
pull your headers and run open ports sometime.
If you've ever done that, you must havebigger juevos than I do...
[/quote]
Haha. Not on my rig brother! I've run bikes, quads and four cylinder cars without manifolds but never a 5.0. That would be like the voice of God. It'd be like Dogma and my head would explode[8D]
If you ever get the chance, Ihighly recommend feeding a GM 2.5 "Iron Duke" some BB's some time. Spits 'em right out. Rather hot and fast I might add. Had a few too many and decided to show my buddies AFTER I removed the manifold[:@]
She'll take more than you feel comfortable feeding her though!!!
03-25-2008, 10:48 PM
#20
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Join Date: Jan 2006
Location: Puerto Rico
Posts: 3,926
RE: Backpressure....I might need to change some things.
ORIGINAL: 1990lxhatch
Haha. Not on my rig brother! I've run bikes, quads and four cylinder cars without manifolds but never a 5.0. That would be like the voice of God. It'd be like Dogma and my head would explode[8D]
If you ever get the chance, Ihighly recommend feeding a GM 2.5 "Iron Duke" some BB's some time. Spits 'em right out. Rather hot and fast I might add. Had a few too many and decided to show my buddies AFTER I removed the manifold[:@]
She'll take more than you feel comfortable feeding her though!!!
ORIGINAL: cleanfitty
pull your headers and run open ports sometime.
If you've ever done that, you must havebigger juevos than I do...
pull your headers and run open ports sometime.
If you've ever done that, you must havebigger juevos than I do...
If you ever get the chance, Ihighly recommend feeding a GM 2.5 "Iron Duke" some BB's some time. Spits 'em right out. Rather hot and fast I might add. Had a few too many and decided to show my buddies AFTER I removed the manifold[:@]
She'll take more than you feel comfortable feeding her though!!!
Guys..... anytime I read about the backpressure BS, is like saying........ the tire is flat, you don't need to fix....all you need is a jack and raise the car frame, so it will be round again. Exhaust tuning, as "dude" mentioned is what is really important, but limiting exhaust flow IS NOT tuning..... tell a 100m sprinter athlete that he needs to plug one of his nostrils to be faster....... and LUK the response you get in return.