Why do we need a muffler?
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Junior User
Joined: Aug 2004
Posts: 72
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From: JBER, AK
Why do we need a muffler?
Okay, I know I remember seeing back pressure mentioned several times on this forum, but it always had to do with cats. I have a friend who recently got an '89 EFI 5.8 L 351w auto, it's pretty much like mine except a year newer, and he wants to take off the mufflers and just put a 3" pipe all the way back. It had already had the cats removed. I told him that i thought that was a bad idea, but he said ididn't know what i was talking about and that his Dad said he'd get better power and sound. So can anyone help me out, and give me some info before he pulls off some relatively new mufflers?
Lead Driver
Joined: Sep 2002
Posts: 9,182
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From: Gateway to the West
Well, without the cat he's already screwing himself because the emission's ****'s will eventually catch up with him unless he lives in a location that doesn't yet have tests.
And yes, the loss of backpressure from the muffler will hinder his fuel mileage. Reducing backpressure is helpful only to a point. If the exhaust scavenges too efficiently, the engine will struggle to develope torque. Which will in turn cause it to rev harder and consume more fuel to achieve the same power that a properly equipped engine would.
Oh and yeah it'll sound great (and deafening from inside the cabin) til he passes a cop under full acceleration and gets ticketed for "excessive vehicular noise".
Lemme guess, he wants straight pipes out the REAR of a Bronco I bet too.
And yes, the loss of backpressure from the muffler will hinder his fuel mileage. Reducing backpressure is helpful only to a point. If the exhaust scavenges too efficiently, the engine will struggle to develope torque. Which will in turn cause it to rev harder and consume more fuel to achieve the same power that a properly equipped engine would.
Oh and yeah it'll sound great (and deafening from inside the cabin) til he passes a cop under full acceleration and gets ticketed for "excessive vehicular noise".
Lemme guess, he wants straight pipes out the REAR of a Bronco I bet too.
Last edited by greystreak92; Sep 29, 2004 at 12:11 PM.
More Turbo
Joined: May 2003
Posts: 513
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High end, full rip you would see an increase in power. BUT how many of us spin our motors to the 5-6 grand mark? AND how many of us have motors that eaven will under load?. Just a bad idea. Plus WAY to load for normal use. Keep some of that low end power, and at least put a muffler on it. It will be loud enough with no cats.
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Senior User
Joined: Apr 2003
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mufflers
cats? ha who needs them, but keep the muffler i agree with the back pressure thing, especially if the motor is old!
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Senior User
Joined: Oct 2001
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From: North Texas
Originally Posted by greystreak92
<snip>
And yes, the loss of backpressure from the muffler will hinder his fuel mileage. Reducing backpressure is helpful only to a point. If the exhaust scavenges too efficiently, the engine will struggle to develope torque. Which will in turn cause it to rev harder and consume more fuel to achieve the same power that a properly equipped engine would.
And yes, the loss of backpressure from the muffler will hinder his fuel mileage. Reducing backpressure is helpful only to a point. If the exhaust scavenges too efficiently, the engine will struggle to develope torque. Which will in turn cause it to rev harder and consume more fuel to achieve the same power that a properly equipped engine would.
But he wouldn't find any performance benefit either, except perhaps a few hundredths of a second in the quarter mile.
I think you ought to tell him to go ahead and put straight pipes on his Bronco. If he lives near a cemetery, it would be entertaining the see the dead awaken.
For noise level, think NASCAR stocker, and if he thinks that much noise would be "cool," well, wait until he's old enough to actually get a license...
- R
Senior User
Joined: Sep 2003
Posts: 436
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From: North Carolina
the better you can get the exhaust flowing, say by removing cats or the muffler, will reduce the pressure of the gases that the pistons are pushing out and therefore the engine performs better by not having to work as hard to push out the exhaust.
