muffler dyno tests
Team Owner
Joined: Aug 2004
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From: Park City Utah
I respectfully disagree. A proper muffler, with a significant interior volume compared to the exhaust pipe feeding it, appears as a low pressure "dump" for the exhaust flow. The abrupt area/volume increase of the muffler causes a reflected low pressure wave to go back to the header and the exhaust valve.
EITHER WAY...the muffler isn't what is causing the power increase. As you stated it is the volume change that affects the exhaust tuning. Same effect would occur w/an open pipe at the same spot in the exhaust, so the muffler is not a power building device.
Last edited by Tom400CFI; Jan 31, 2014 at 10:03 PM.
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Tom is right. He was merely clarifying you can't "gain" power with the addition of a muffler over straight pipe (or header dumps). You can't increase power over open headers (which I don't even recall Tom mentioning), but you can improve the power over just having straight pipes running all the way back.
Vizzard had pointed out the effects of cams and scavenging and the ability to increase VE above 100% with proper exhaust design. It's not that a muffler adds power...as Tom indicates. You can create the affect Vizzard talks about with the use of a pulse termination box...which doesn't have to be a muffer. I'm aware of that. But we're talking large volume mufflers here which can emulate a termination box if placed properly. I understood the box to be a method for extending exhaust pipe BEYOND the "ideal termination length" that would create best scavenging/horsepower. Those are two different things. A termination box at the correct place to promote scavenging, and then a good flowing rear system to minimize the system backpressure. You could, just as easily/effectively, terminate your exhaust at the ideal length. It would end up under the car and you'd smell the fumes. We're not talking about "undercar dumped" exhaust systems in this thread. We're talking about full length systems. Vizzard also addresses the use of mufflers as many racing venues require "something" anyway.
I'm with Tom. Mufflers will never "create" horsepower. Properly placed and designed, they will minimize loss.
Vizzard had pointed out the effects of cams and scavenging and the ability to increase VE above 100% with proper exhaust design. It's not that a muffler adds power...as Tom indicates. You can create the affect Vizzard talks about with the use of a pulse termination box...which doesn't have to be a muffer. I'm aware of that. But we're talking large volume mufflers here which can emulate a termination box if placed properly. I understood the box to be a method for extending exhaust pipe BEYOND the "ideal termination length" that would create best scavenging/horsepower. Those are two different things. A termination box at the correct place to promote scavenging, and then a good flowing rear system to minimize the system backpressure. You could, just as easily/effectively, terminate your exhaust at the ideal length. It would end up under the car and you'd smell the fumes. We're not talking about "undercar dumped" exhaust systems in this thread. We're talking about full length systems. Vizzard also addresses the use of mufflers as many racing venues require "something" anyway.
I'm with Tom. Mufflers will never "create" horsepower. Properly placed and designed, they will minimize loss.
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Right....on a custom exhaust, built and tuned specifically to accomplish this. We're in agreement. 
Most guys won't go to the effort to do that. I'm just one of the odd types who enjoyed the physics of building one of these systems. But MAKE NO MISTAKE; that ain't gonna happen on a stock or stockish exhaust system on a 'Vette. Oh, I agree. Especially where the mufflers are way back at the rear of the car. After the cats..there isn't any "tuning" going on. This has been covered in the past.
EITHER WAY...the muffler isn't what is causing the power increase. As you stated it is the volume change that affects the exhaust tuning. And sometimes that volume change is a large well flowing muffler. Same effect would occur w/an open pipe at the same spot in the exhaust, so the muffler is not a power building device.
Most guys won't go to the effort to do that. I'm just one of the odd types who enjoyed the physics of building one of these systems. But MAKE NO MISTAKE; that ain't gonna happen on a stock or stockish exhaust system on a 'Vette. Oh, I agree. Especially where the mufflers are way back at the rear of the car. After the cats..there isn't any "tuning" going on. This has been covered in the past.EITHER WAY...the muffler isn't what is causing the power increase. As you stated it is the volume change that affects the exhaust tuning. And sometimes that volume change is a large well flowing muffler. Same effect would occur w/an open pipe at the same spot in the exhaust, so the muffler is not a power building device.
