not enough back pressure??
04-28-2003, 05:25 PM
#1
1st Gear Member
Thread Starter
Join Date: Jan 2003
Location: United States
Posts: 72
not enough back pressure??
when u put headers on and open up the exaust more, does back pressure become an issue? i had straight pipes and 1 chamber flowmaters but after adding MAC 1 5/8 equal lenth shorties and a 70mm TB, i went to an H pipe and 2 chamber flowmaters b/c of everyone telling me i wouldn't have near enough backpressure. now i miss the way my car used to sound and i wondering if quieting it down was even necessary. thanks.
04-28-2003, 09:00 PM
#2
2nd Gear Member
Join Date: Mar 2003
Location: United States
Posts: 282
not enough back pressure??
You should keep the headers, put the old exhaust back on if you want (straight pipes and 1 chambers are too loud for me on a street car, but that's just me and the cops' opinion), but change the throttle body to either a 65mm or your stock one. Prolly your stock one because a stock engine really won't get any benefit from a bigger MAF until higher RPM's. The stock one should do just fine. If you remember, you prolly lost some lowend power when you put the 70mm on. Put a smaller one on and your powerband should drop some RPM's, i.e. more lowend.
05-09-2003, 06:43 AM
#4
Join Date: May 2003
Location: United States
Posts: 7
not enough back pressure??
hmm back pressure.... well im not 100% on this.. but back pressure only really comes into play at lower rpms.. like from idle to around 1500 rpms.. and if you drive a stang and you race it im sure you dont spend very much time in the 1500 rpm range.. casue if ya do i bet you loose alot of races.. and i asked this from 20 diff mechanics at 3 differant ford delaerships.. and my father is also a ford mechanic.. so im sure he knows a lil about stangs considerign he works on them all day long.. but hey dont take my word for it if you dont want to.. i never said i was 100%sure but hey im going by what i was told
05-09-2003, 05:44 PM
#5
I ♥ Acer
Join Date: Mar 2003
Location: United States
Posts: 2,199
not enough back pressure??
Backpressure is the same on any car.
What it is is "back" "pressure" sound that out. It's backed up by a restriction, the gasses can't flow fast enough. I don't see how that is beneficial to the power making of a motor, ANY motor.
High exhaust velocity with zero backpressure is ideal, and extremely hard to get. However, Very low backpressure and high velocity is awsome.
By jumping to say...a 6" pipe you would literally have no backpressure. BUT, the exhaust VELOCITY would be jack. Therein lies the problem, finding a diameter that offers high velocity and no backpressure for the RPM range the engine is used in the most.
This is the same reason why X pipes can make as much, if not more, power and torque than open headers. Better velocity.
What it is is "back" "pressure" sound that out. It's backed up by a restriction, the gasses can't flow fast enough. I don't see how that is beneficial to the power making of a motor, ANY motor.
High exhaust velocity with zero backpressure is ideal, and extremely hard to get. However, Very low backpressure and high velocity is awsome.
By jumping to say...a 6" pipe you would literally have no backpressure. BUT, the exhaust VELOCITY would be jack. Therein lies the problem, finding a diameter that offers high velocity and no backpressure for the RPM range the engine is used in the most.
This is the same reason why X pipes can make as much, if not more, power and torque than open headers. Better velocity.
05-10-2003, 03:48 AM
#6
Join Date: Apr 2003
Location: United States
Posts: 10
not enough back pressure??
on a 5.0 you definetly need backpressure. on my 88 i ran open headers at the track because it sounded good. however my low end torque suffered greatly. backpressure can mean seconds on an et. my car ran 15.0 at 97. 15.0 is really slow but the fact that it was at 97 meant that it had the horsepower to run a mid-13.I talked to a guy at the track with a 10 second malibu and he told me that with some pipe my car could gain over a second in the quarter. this is just something to think about.
05-10-2003, 04:10 AM
#7
I ♥ Acer
Join Date: Mar 2003
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not enough back pressure??
Blah Blah Blah BLAH.
The open headers increase the flow velocity AT HIGH RPM'S.
Go talk to some guys that build REAL cars and see what they say. I'd LOVE to hear guys from Nascar, F1, IRL, ect., say that.
They know it's all about fluid dynamics. Nascar's are all running X pipes for a reason, they can tune it for the high RPM's and still meet the noise requirements. With very little-no back pressure, but high exhaust velocity.
The open headers increase the flow velocity AT HIGH RPM'S.
Go talk to some guys that build REAL cars and see what they say. I'd LOVE to hear guys from Nascar, F1, IRL, ect., say that.
They know it's all about fluid dynamics. Nascar's are all running X pipes for a reason, they can tune it for the high RPM's and still meet the noise requirements. With very little-no back pressure, but high exhaust velocity.
05-10-2003, 10:18 AM
#8
3rd Gear Member
Join Date: Feb 2003
Location: United States
Posts: 708
not enough back pressure??
This is where my buddy JEEP proves hios mopar-ishness. You DO want backpressure. Dont take advice from a guy who has a 2.5 inch (or whatever stupid thing you came up with) on a saturn. You want youre exhaust to be free-flowing but NOT at the expense of back pressure.
05-10-2003, 09:01 PM
#10
I ♥ Acer
Join Date: Mar 2003
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Posts: 2,199
not enough back pressure??
I've got a stock puny 1 7/8" on the satty, danka-vara-much.
We've dyno'd this stuff on the Chevelle I used to drive. Guess when it made the most power? On 3.5" X back pipes, no mufflers, and equal length long tubes. We had the highest exhaust velocity with that combo from 5000-8000 RPM, where I drove it the most. The car absolutely HATED backpressure, and I've yet to personally see a motor that liked it.
We've dyno'd this stuff on the Chevelle I used to drive. Guess when it made the most power? On 3.5" X back pipes, no mufflers, and equal length long tubes. We had the highest exhaust velocity with that combo from 5000-8000 RPM, where I drove it the most. The car absolutely HATED backpressure, and I've yet to personally see a motor that liked it.