Relationship between backpressure and torque
Relationship between backpressure and torque Can someone help me understand the relationship between backpressure and torque?
Also, I don't understand why a motor under load at the same rpm would generate more exhaust gas than a motor not under load?
Also, I don't understand why a motor under load at the same rpm would generate more exhaust gas than a motor not under load?
Staging Lane
Joined: Apr 2004
Posts: 68
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I'll take a stab, but someone else will have to tell you if I'm right or not.
Very simple example:
Underload: on the highway - floor it.
Not under load: sitting in garage in neutral (being an *** to the neighbors) - floor it.
under load, the motor is working harder, dumping more fuel into the combustion chamber - more exhaust gasses.
Not under load, it doesnt take much fuel at all to turn a free spinning motor - less fuel and gasses.
That has to be a step in the right direction, isnt it?
Very simple example:
Underload: on the highway - floor it.
Not under load: sitting in garage in neutral (being an *** to the neighbors) - floor it.
under load, the motor is working harder, dumping more fuel into the combustion chamber - more exhaust gasses.
Not under load, it doesnt take much fuel at all to turn a free spinning motor - less fuel and gasses.
That has to be a step in the right direction, isnt it?
Originally Posted by term
Can someone help me understand the relationship between backpressure and torque?
Also, I don't understand why a motor under load at the same rpm would generate more exhaust gas than a motor not under load?
Also, I don't understand why a motor under load at the same rpm would generate more exhaust gas than a motor not under load?
Originally Posted by term
Can someone help me understand the relationship between backpressure and torque?
Also, I don't understand why a motor under load at the same rpm would generate more exhaust gas than a motor not under load?
Also, I don't understand why a motor under load at the same rpm would generate more exhaust gas than a motor not under load?
Real page-turner!!
Originally Posted by term
The fuel amount should be based on the air going through the maf I would think, and the intake stroke should suck the same amount of air under load or not
Put a load on the engine, and you have to open the throttle more to maintain the same RPM. More throttle means more air/fuel being allowed into the cylinders, which means a larger quantity of reagents being combusted, which results in more exhaust products.
Seriously, drop the $20 or so and read the book I mentioned previously. It's great stuff.
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TECH Enthusiast
Joined: Mar 2004
Posts: 647
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From: Australia
Backpressure is often a misunderstood term. For high RPM applications you want minimal backpressure. For street applications you want some backpressure.
Backpressure to some is nothing more than a restriction in the exhaust. To me it means increased velocities at lower RPM which aids the extraction of exhaust gases via a vacuum effect. All exhausts flow and all exhausts create a vacuum after the exhaust pulse - its the exhaust design that determines how use of those exhaust pulses are optimised.
A smaller exhaust will provide increased velocities at lower RPM and so will generate more torque in the stock power range. A larger exhaust will favour the upper RPM range at the cost of the lower register.
As a general rule of thumb, the best all-rounder is 2 1/4" on an unopened 5.7l. A stroker will favour 2.5" and turbos/SC 3".
Backpressure to some is nothing more than a restriction in the exhaust. To me it means increased velocities at lower RPM which aids the extraction of exhaust gases via a vacuum effect. All exhausts flow and all exhausts create a vacuum after the exhaust pulse - its the exhaust design that determines how use of those exhaust pulses are optimised.
A smaller exhaust will provide increased velocities at lower RPM and so will generate more torque in the stock power range. A larger exhaust will favour the upper RPM range at the cost of the lower register.
As a general rule of thumb, the best all-rounder is 2 1/4" on an unopened 5.7l. A stroker will favour 2.5" and turbos/SC 3".
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Originally Posted by MNR-0
As a general rule of thumb, the best all-rounder is 2 1/4" on an unopened 5.7l. A stroker will favour 2.5" and turbos/SC 3".
TECH Addict
Joined: Feb 2004
Posts: 2,826
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Originally Posted by MNR-0
Backpressure is often a misunderstood term. For high RPM applications you want minimal backpressure. For street applications you want some backpressure.
Backpressure to some is nothing more than a restriction in the exhaust. To me it means increased velocities at lower RPM which aids the extraction of exhaust gases via a vacuum effect. All exhausts flow and all exhausts create a vacuum after the exhaust pulse - its the exhaust design that determines how use of those exhaust pulses are optimised.
A smaller exhaust will provide increased velocities at lower RPM and so will generate more torque in the stock power range. A larger exhaust will favour the upper RPM range at the cost of the lower register.
As a general rule of thumb, the best all-rounder is 2 1/4" on an unopened 5.7l. A stroker will favour 2.5" and turbos/SC 3".
Backpressure to some is nothing more than a restriction in the exhaust. To me it means increased velocities at lower RPM which aids the extraction of exhaust gases via a vacuum effect. All exhausts flow and all exhausts create a vacuum after the exhaust pulse - its the exhaust design that determines how use of those exhaust pulses are optimised.
A smaller exhaust will provide increased velocities at lower RPM and so will generate more torque in the stock power range. A larger exhaust will favour the upper RPM range at the cost of the lower register.
As a general rule of thumb, the best all-rounder is 2 1/4" on an unopened 5.7l. A stroker will favour 2.5" and turbos/SC 3".
