what's the deal with backpressure in an exhaust system?
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Honda-Tech Member
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From: Toronto, Canada
what's the deal with backpressure in an exhaust system?
some say backpressure is good.
some say the faster you get out the exhaust gases the more efficient it is for performance.
what's the dillyo?
some say the faster you get out the exhaust gases the more efficient it is for performance.
what's the dillyo?
Joined: Oct 2003
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From: Vancouver, Washington, United States
Re: what's the deal with backpressure in an exhaust system? (frostcivic)
THE MYTH OF BACKPRESSURE"
Backpressure is one of the most common terms used win talking about exhaust systems it is also highly misunderstood.
So what is Backpressure?
Backpressure is the resistance of air flow
So if Backpressure is resistance than why does a loss of Backpressure because a loss in HP, well I will tell you know that is does not.
"THE TRUTH OF BACKPRESSURE"
Backpressure is used on engines to
(1) help with fuel economy
(2) help with meeting emissions laws
On a tuned high performance engine Backpressure is not needed in fact Backpressure will hinder HP gains. There was a test done in SCC car magazine where they did a header comparison on a B18C in a Acura Integra and guess what just for fun they did a dyno run with no header at all. The run with out a header made more gains threw out the full RPM range than any header they tested. Now keep in mind no header no Backpressure.
Now with all that said and done lets move on to what Backpressure and the lack of Backpressure do to the exhaust system.
Reversion this is the start of all exhaust systems.
So at the stat of the intake stroke you have cam over lap and the gasses in you header are under high pressure causing the gasses to be pushed back into the cylinder causing a bad fuel/air mix.
Exhaust with Backpressure
Scavenging
This also starts at the intake stroke win you have cam overlap. The momentum of the exiting exhaust gasses creates a brief vacuum in the header, pulling out the remaining exhaust gases from the combustion chamber, and allowing the new fuel/air charge to be at its best
Exhaust without Backpressure
How to rid Backpressure
Backpressure is resistance in the exhaust so to rid it we have to have bigger piping but at the same time not to big. Why not to big because the exhaust gas moves slower threw larger piping. But also considering that the gasses flow at different rates at different spots in the RPM band you also have to trade off some high or low RPM power with all that said
The magic size for most N/A Honda engines is about 21/4 to 21/2 inch
Thanx to SHO
Backpressure is one of the most common terms used win talking about exhaust systems it is also highly misunderstood.
So what is Backpressure?
Backpressure is the resistance of air flow
So if Backpressure is resistance than why does a loss of Backpressure because a loss in HP, well I will tell you know that is does not.
"THE TRUTH OF BACKPRESSURE"
Backpressure is used on engines to
(1) help with fuel economy
(2) help with meeting emissions laws
On a tuned high performance engine Backpressure is not needed in fact Backpressure will hinder HP gains. There was a test done in SCC car magazine where they did a header comparison on a B18C in a Acura Integra and guess what just for fun they did a dyno run with no header at all. The run with out a header made more gains threw out the full RPM range than any header they tested. Now keep in mind no header no Backpressure.
Now with all that said and done lets move on to what Backpressure and the lack of Backpressure do to the exhaust system.
Reversion this is the start of all exhaust systems.
So at the stat of the intake stroke you have cam over lap and the gasses in you header are under high pressure causing the gasses to be pushed back into the cylinder causing a bad fuel/air mix.
Exhaust with Backpressure
Scavenging
This also starts at the intake stroke win you have cam overlap. The momentum of the exiting exhaust gasses creates a brief vacuum in the header, pulling out the remaining exhaust gases from the combustion chamber, and allowing the new fuel/air charge to be at its best
Exhaust without Backpressure
How to rid Backpressure
Backpressure is resistance in the exhaust so to rid it we have to have bigger piping but at the same time not to big. Why not to big because the exhaust gas moves slower threw larger piping. But also considering that the gasses flow at different rates at different spots in the RPM band you also have to trade off some high or low RPM power with all that said
The magic size for most N/A Honda engines is about 21/4 to 21/2 inch
Thanx to SHO
Thread Starter
Honda-Tech Member
Joined: Nov 2003
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From: Toronto, Canada
Re: what's the deal with backpressure in an exhaust system? (Option)
so if i add a resonator to my current exhaust system will it create backpressure, little or none at all?
Darth ModerVader
Joined: Jan 2001
Posts: 11,539
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From: Mustafar
Re: what's the deal with backpressure in an exhaust system? (frostcivic)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by frostcivic »</TD></TR><TR><TD CLASS="quote">so if i add a resonator to my current exhaust system will it create backpressure, little or none at all?</TD></TR></TABLE>
Just be sure to use a high-quality perforated core resonator, rather than the louvered kind. A louvered resonator will indeed reduce flow and performance, but a straight-through perforated core model shouldn't decrease flow by any noticeable amounts.
Just be sure to use a high-quality perforated core resonator, rather than the louvered kind. A louvered resonator will indeed reduce flow and performance, but a straight-through perforated core model shouldn't decrease flow by any noticeable amounts.
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