I know that driving without a muffler (on certain cars) can reduce back pressure enough to actually reduce engine performance, but can driving a car without a muffler cause engine damage? Thanks.
Is no muffler no good?
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Normally, I'd say no ..but I merely did an upgrade on my late mother's 89 Corsica from the L4 muffler to the V6 muffler and I burned out threee mufflers (all replaced free). The only difference in the entire exhaust system was the muffler. The 4 banger had one outlet ..the V6 had two (mounted at the very rear of the car). You would feel, something that could only be described as, "vacuum braking" (as opposed to compression braking) when coasting down hill. Never did figure out the cause ..and the warranty muffler had to be identical to the worn out one ..so it continued until we sold the car after my mother's departure.
There are places where driving with no muffler could indeed cause engine damage. About the 4th unmuffled time past their property, and a .30-06 slug would interrupt the crankcase of said engine.
My $0.02
My $0.02
I have never actually seen it but it has been said that not using a muffler can burn the valves.
i have no muff. on my expedition and lincoln conti the cats cut down the noise..really a big improvement in power in both vehicles
Yeah run with no muffler. Do you care that some people would like some peace and quiet? What about your hearing?
The Iron Duke with a cat is no louder then most sporty exhausts and quite a bit quieter then most aftermarket ones. Similarly most Hondas aren't that loud with no muffler. It's the aftermarket "mufflers" that work as echo chambers that make them loud.
-T
-T
"There are places where driving with no muffler could indeed cause engine damage. About the 4th unmuffled time past their property, and a .30-06 slug would interrupt the crankcase of said engine."
and
"Yeah run with no muffler. Do you care that some people would like some peace and quiet? What about your hearing? "
Most of the time, much to my surprise, this engine (especially at Hwy speed) is no louder without a muffler than with one. The only time it gets a little throuty is under full acceleration. Even at full throttle the car is still quieter than most "tuner cars".
I already have a severe hearing loss, due to a birth defect and don't wish to damage what's left. I can honestly say that I'm not afraid of any further hearing damage from this car and my neighbors don't even notice.
and
"Yeah run with no muffler. Do you care that some people would like some peace and quiet? What about your hearing? "
Most of the time, much to my surprise, this engine (especially at Hwy speed) is no louder without a muffler than with one. The only time it gets a little throuty is under full acceleration. Even at full throttle the car is still quieter than most "tuner cars".
I already have a severe hearing loss, due to a birth defect and don't wish to damage what's left. I can honestly say that I'm not afraid of any further hearing damage from this car and my neighbors don't even notice.
This is a myth. Back pressure is not desirable. If you put a 3" exhaust on a stock Honda Civic the drop in torque is due to improper tuning, not reduced backpressure. If your factory exhaust is 2" and you straight-pipe it (no cat or muffler) with 2" pipe you will see a power and efficiency gain across the entire rpm range. This may be small gain though if the exhaust is designed properly to begin with.
Just don't make it as loud as the jacka#$es with the coffee can mufflers!
[ September 21, 2004, 02:28 PM: Message edited by: rpn453 ]
That's right! And well put.
My impression is that a Magnaflow muffler is basically a straight-pipe, with perforations (in the section of pipe that is encased in the can) that allow sound to be lessened without disrupting flow. Am I correct?
rpn453 - You are right - it's a widespread myth that open exhausts have 'too little' backpressure. The problem is really with a larger diameter aftermarket exhaust, or free flowing muffler, CAUSING restriction by the more rapid cooling and contraction of exhaust gasses downstream. This causes a restriction until the heat/velocity are increased. This is why often there is a loss of low end power when opening up the exhaust. Sort of right for the wrong reason.
Yuk - Magnaflows work well, and are deep sounding.
Yuk - Magnaflows work well, and are deep sounding.
I've heard of that, but I just can't visualize how the slightly cooler and denser exhaust gases cause a restriction. Can you explain that aspect any further?
I always believed the more important factor was the inertia of the mass of exhaust gas moving through the pipe, creating a consistent "pull" at the valve to counteract the negative effects of the pulses. With an overly large exhaust system, the gas would have little velocity and therefore little inertia.
Likely both are factors. I don't actually know who is "more right" here.
Yuk - You are correct on the description of the Magnaflow.
You may notice that some race cars, after they are run, cap the exhaust in some way. Without a muffler in the way, air can enter the system as the engine cools and warp exhaust valves. I would expect that to be a potential problem with a street car with no muffler.
Just to be clear:
that statement should have read:
"I just can't visualize how the slightly cooler and denser exhaust gases cause a restriction in a larger pipe."
Of course there would be some additional pipe friction in a pipe carrying a gas that is cooler and denser than the same pipe transporting the same fluid at a warmer temperature. This would be incorporated into the exhaust tuning.
Couldn't that happen even with a muffler?
I would guess that's necessary because their engines are at higher temperatures when they're shut down than pretty much any street car would ever be.
The exhaust gas cools and slows down. When it cools, it contracts a lot - becoming more dense - harder to push through the pipe. When exhaust pipes are insulated from ambient air [thermal tape, coatings, even thicker wall pipes] they retain heat and velocity, and retain more low end power [everything else being equal].
Old motorcycle racers with straight pipes [esp. of the British persuasion] used to jam rubber balls in the exhaust after a run to prevent exhaust valves from warping from the 'rush' of cold air coming back up the pipe. They would swear up and down that this was saving their exhaust valves, but ignored the fact that on overlap, the valves were open to the atmosphere from the intake side. An old myth that died.
Old motorcycle racers with straight pipes [esp. of the British persuasion] used to jam rubber balls in the exhaust after a run to prevent exhaust valves from warping from the 'rush' of cold air coming back up the pipe. They would swear up and down that this was saving their exhaust valves, but ignored the fact that on overlap, the valves were open to the atmosphere from the intake side. An old myth that died.
Backpressure never helps power. What helps is proper exhaust tuning to help scavenge the cylinder. Higher back pressure hinders cylinder scavenging, but a system with higher overall back pressure may have low pressure later in the exhaust stroke because of proper exhaust tuning and thus perform better than an open header. Properly tuned (which potentially could include cam revisions) an engine should be able to run without even an exhaust manifold--just holes in the block--, but that is undesireable for other obvious reasons (would not be able to take advantage of sylinder scavenging). When it really needs the back pressure, during the power stroke, it has 100% back pressure because the exhaust valve is closed.
Heat = Pressure. Keep velocity up and cylinder scavenging increases, engine heat load decreases, etc. Proper tuning is key, as said above. New oems are tuned rigidly tight for OBD-II.
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