I have to open this thread by letting people know that I am extremely skeptical of this.
I live just off Woodward Ave in Michigan where they are currently having the Woodward dream cruise (oh joy! :rolleyes: ). Many of the cars and bikes driving around are so noisy it is unbelievable.
Does this really improve the performance of the car, or are there people just being jerks. Some cars are highly tuned and produce lots of power and make noise, I know. But when I see a Honda Civic with a huge tailpipe making loads of noise I have to wonder.
The best results I’ve seen in car magazines indicate that it’s a cheap way to boost your engines output by maybe 15 HP. That’s it. It does, however, have the “benefit” of enabling you to call attention to yourself. (Perhaps the driver’s compensating for something missing?)
A bigger engine is naturally going to sound louder, so if someone takes the muffler off their “sewing machine” powered car, it’ll sound like it’s got a bigger engine. (Why am I suddenly reminded of a peacock and it’s plumage as I write this?)
I’d have to say that it’s mostly for show, in the end. After all, if you’ve got a 1000 HP engine under the hood, the loss of a measely 15 HP caused by putting a quiet exhaust on the car isn’t really that big of a deal. My brother once told me that if you’re smart, you’ll drive a very fast car that’s quiet (AKA “a sleeper”), because if a cop hears a loud car, he knows you’re liable to speed. However, if the cop doesn’t hear your engine, he’ll have no idea that you’ve got a ton of horsepower under the hood.
I’ve heard it’s a safety measure. The rice rockets are small enough that their owners fear they’ll not be noticed in a world of SUVs. Of course, that only makes it easier for the SUVs to find 'em.
The muffler fell off my pickup truck last fall, and it was several weeks before I got around to replacing it. My gas mileage went up by 10-15% until I replaced it.
Never mind cars, over here we have a problem, (OK, I HAVE A PROBLEM) with small 2-cycle motorcicles, the guys remove the muffler in hopes that it will increase the HPs, (HAHA!!), the only result is a very idiotic looking guy, leaning on the handle bars as if doing 180 Km/h that you can hear coming from 3 blocks away, in fact the thing moves at a maximum speed of about 30 Km/h so it takes an awfully long time to pass by, meanwhile the shrieking noise is so loud and disturbing that the idea of getting a sniper riffle and taking pot shots at those bikers seems very reasonable
I don’t know if it’s still a problem these days, but removing backpressure from an exhaust system was once thought by some of my friends to lead to burned valves.
Having enjoyed the straight-pipe experience in a poor little Subaru GL (which had an ultra-expensive, single-piece exhaust running from the damned heads to the tailpipe, so I ran without an exhaust until the next inspection cycle), I have to agree that if you don’t mind pissing off the neighbors, a freer exhaust flow can dramatically improve a car’s performance, especially a little four-banger. Ten extra horses (I’m guessing) out of a 90 hp car is a major improvement.
But it pollutes on many levels, which isn’t very cool.
As every little m&m “gangska” wannabe knows it’s not the size of the maxwell house can you glue to your mom’s (borrowed) civic, it HOW MANY DECALS YOU STICK ON IT. Remember, if it’s not an affront to NASCAR it’s not fast.
Backpressure on the engine. The faster the exhaust gets out of your engine, the quicker it can cycle over to the “burn” phase again. So, the quicker you can get the exhaust out of there, the sooner you can inject gasolene to make a boom. More RPMs, mean more HP (though not in all cases, of course).
Simply said, the more air you can pass through an engine the greater it’s potential for making power. There are a few problems though. You must insure that the air fuel ratio is within the limits, neither too rich or lean, and insure that the engine retains its derivability. An engine needs three things to run. Fuel, Compression and Spark. (if it doesn’t run, it is missing one or more of those three things.) Air is part of the first of those three. Unless you plan the engine build to include attention to all three areas, you can actually decrease performance when adding performance parts. The exhaust is an example. If you simply add a free flowing exhaust system, and nothing else, it is doubtful that you will gain much if any power. Add to that an increase in the ability to ingest (free flowing intake, cleaned up heads, cam) air, and the exhaust now adds what it was always capable of. Think of it as part of a package that doesn’t come alive until the other parts are present. If your building an engine, save your money until you can do the package. Typically you get a better deal, and you get a proven system.
Think back to how a four stroke engine works. Intake, compression, expansion, exhaust. If your exhaust is at pressure (because you’re forcing it through a bunch of noise attenuating baffles) part of the power produced during the expansion phase will be used to compress your exhaust and push it out of the cylinder rather than make your wheels go roundy-roundy.
The bad thing is that in cheaper/smaller/lighter engines everything has been engineered down to such a low safety margin that exhaust backpressure it required to keep valves from being slammed into their seats and/or to open fully. Eventually your valves will get so deformed that they don’t seat properly (or fail to unseat) and you get a fuel/air mix bleeding into your exhaust system. You end up with a groovy tar-like sludge building up on your exhaust valves, which don’t have enough spring pressure to open (because your engine is engineered to have exhaust backpressure help open the valves, remember?) so your exhaust stoke turns into another compression stroke and all sorts of terrible things begin happening.
Of course, your engine exploding is a lot louder than your muffler-less car, so then you’ll really attract some attention.
Also, on some of the modern cars, if you tamper with the exhaust system too much, you must have the car’s computers adjusted or the car won’t run right.
