Most, if not all, states in the US require that your vehicle have a properly working muffler. And most of us would surmise that mufflers are required so they can serve their intended purpose: to reduce the amount of noise caused by the engine’s exhaust. So…
Why on earth do states or local municipalities allow the use of these giant “mufflers” that do practically nothing to reduce the noise of the engine? In fact, many of these “mufflers” (I call them “why bother mufflers” or WBMs) seem to actually resonate with the exhaust, accentuating the noise of the vehicle, rather than reducing it. You’ve seen them - they’re usually installed on a car that has aluminum rims that are worth more than the entire car.
To me, if a vehicle is able to create exhaust noise that is louder than another vehicle with no muffler at all, then the muffler in question is not a muffler at all. There are plenty of places that ban the use of straight pipes on motorcycles. So are there any places that also ban the use of mufflers that don’t actually muffle?
I don’t know how many cars you’ve heard sans muffler but there is a substantial difference between that stattaco BLAAATTTTT! - BRATTTTT! sound and
a loud “performance” type muffler which is (typically) more of a growly noise.
And some places do have ordinances which address the noise level. Back in the 60’s “glass packs” (fiberglass packed pipes substituting for mufflers) were illegal in some areas.
I’ve heard this argument before and it usually comes from people who do not know what a car without a muffler sounds like. Those performance mufflers that you call “Why Bother Mufflers” are actually quite good. An unmuffled engine can be excrutiatingly loud to the point of physical pain. I don’t think you can even yell over an unmuffled V8 within 10-20 yards.
Badly matched mufflers can actualy reduce the power output from an engine, and extremely bad ones can result in engine damage.
For any muffler to work effectively, first you have to decide what you want it to do, do you want torque, power at high revs ?
To get the best from it you may well need to consider differant air filters, differant carburetter jets, or differant engine mapping, and maybe to change the way the spark retardation works.
Simply fastening on a noisy can is not likely to improve performance.
The OP is actually very familiar with cars without mufflers. There’s no denying that any muffler is better than none. Particularly a V8 with no muffler when compared to a small 1.9 liter DOHC with no muffler. I’m also glad to see that the word “performance” was put in quotes - as **casdave **points out, wide open mufflers don’t always improve performance. And, I admit, most “performance” mufflers I’ve heard are actually quite effective - at idle speeds. But anyone who has heard these things speed through their neighborhood can testify that they can be brought to window-shaking decibel levels with relative ease. But none of that actually addresses the question at hand…
Why is such a device, which can achieve pretty high decibel outputs (and me without my A-scale slow response sound meter handy), allowed to be sold as a muffler, and are there any places that actually prohibit their use?
Ol Peculiar
Stattaco? Is that like really fast Mexican food? I know, I’m sorry…
In CT at least, the motor vehicle code doesn’t require mufflers, per se. They require that your car does not exceed the “Maximum Permissible Sound Level”. For something like a modern car going > 35 mph, the limit is 81 db at 50 feet. There’s a whole chart of values for various cars/trucks/buses/motorcycles, covering a range of 72-92 db.
Since we don’t actually have mandatory auto inspections in CT for new-ish cars, the only way you’ll actually get busted is to annoy a police officer.
I don’t understand. How can a muffler improve performance over no muffler? I was under the impression performance mufflers were essentially mufflers that reduce performance less than stock mufflers do.
I’m not sure I understand the question, but removing the muffler doesn’t mean you’re going to improve performance. I have a Suzuki 3-Cylinder that won’t idle at all without a muffler. I don’t understand the mechanics of it, but I was told that that particular engine has to have back-pressure to run properly.
I don’t understand mechanics of it either and that’s what I’m asking. The less resistance the piston encounters during the exhaust cycle the better - or so it would seem. I mean, I’m a software engineer, I can only handwave these things, but the only even reasonable theories I can think of are:
a) Engines are designed with mufflers in mind and the exhaust valve doesn’t close properly without backpressure… Seems like an easy thing to fix were you inclined to run without a muffler.
b) Engines are designed with mufflers in mind and the more rapid/severe pressure change without a muffler causes a bigger temperature gradient that screws with the engine…
I am not inclined to believe either one of those as viable reasons for keeping a muffler if you can get away with not having one. If I had to guess I’d say ‘backpressure helps performance’ is a myth perpetuated by muffler salesmen.
Amen. I think similar thoughts about the whale-tailed Fartmobile pulling away from a traffic light with almost double the horsepower of my Lawn Boy mower.
Whilst there is a certain amount of exaggeration about what a replacement muffler can do, the use of the word ‘myth’ is too strong.
The reality is that rather than back pressure improving engine performance, its actually the low pressure waves returning back into the manifold that really makes things happen.
During the period in the second stroke in the upstroke, burnt gases are being vented into the exhaust system, and low pressure waves returning from the muffler scavenge these gases from the cylinder, and becuase of this you can use differant cams to change your valve timings, and also you can run at higher revs.
Except, perhaps on a two stroke, which is an entirely different beast. No valves. Not sure of the dynamics, but my understanding is that an expansion chamber (needs to be ‘tuned’ to the engine)provides back pressure at the right moments.