Engine Sound

[JustPassinThru_imp]

If noise is power wasted, then why are racing cars/motorcycles so loud?

Motorcycles are loud because some primitives, who IMHO didn't get enough attention when they were toddlers...like to compensate for it in the present. Notice I didn't say "as adults." The assumption, juvenile IMHO, is that because THEY like the noise, that I, in my bed at two in the morning, will ALSO appreciate that noise that so thoughtfully woke me up.

So they pull off the mufflers.

Racing cars are loud for the same reason - no mufflers. I doubt there would be any performance loss if a racing engine was engineered for some back-pressure; but obviously the racing fan-base likes the sound as punctuation for the display on the track.

And so long as it STAYS on the track, I'm fine with it.

Noise...is energy. It's air compression into sound waves. Noise off an engine, is energy that MIGHT have been used to push the piston but instead was vented off as an explosive report, 10,000 of them a minute.

There isn't - YET - the technology to harness that wasted energy; but it IS waste, the same way friction and thermal loss are wastes.

[aschem_imp]

If mufflers restrict flow then is that also restricting power output; possibly even more so than noise? I found an interesting article about engine exhaust here: http://www.cycleworld.com/2015/02/13/ask...gp-racing/
Very detailed oriented and I learned something new about how exhaust sound waves
The trumpet player analogy of how just a little pressure generated can make so much noise was interesting.

[redbirds_imp]

Any motorized device that is used in the general enviroment, whether that be city, suburbs or rural, should be quiet enough that people are not unduly disturbed. When on vacation last summer in Manasota Key, FL the constant roar of un-muffled or barely so Harley-Davidson bikes cruising by our condo at all hours put a damper on what would have otherwise been a restful time. To make things worse, these childish idiots would clutch in and rev their motors just to make sure they did not go unnoticed. I'm happy that I can cruise by my neighbors on my bike and they will not have noticed my passing unless looking my way.

[JustPassinThru_imp]

If mufflers restrict flow then is that also restricting power output; possibly even more so than noise? I found an interesting article about engine exhaust here: http://www.cycleworld.com/2015/02/13/ask...gp-racing/
Very detailed oriented and I learned something new about how exhaust sound waves
The trumpet player analogy of how just a little pressure generated can make so much noise was interesting.

Again: An engine is operating at optimal efficiency when it is operating in its design parameters.

If you eliminate backpressure on an engine that is designed to work against backpressure...you don't have more power. You run the risk of burning valves, as hot exhaust rushes out against less restriction than is designed.

There seems to be some desire here to twist arms to get the response: Yes, taking the muffler off REALLY DOES make MORE POWER. Sorry, in a closed-loop EFI world, what that does is muddle the signals and send the FI into a default mode - thus DROPPING power as well as fuel economy.

Like losing your vacuum spark advance in the old days.

I am wholly opposed to those persons who seem bent on making noisy nuisances of themselves and their motorcycles. It makes us all look bad; it gets lawmakers more involved. It annoys ME - I do NOT want to hear that noise, except in rare circumstances, such as a dragstrip show.

What it is, again IMHO, is childish misbehavior to get noticed - even if that notice is negative and hostile and even inviting retaliation.

[Guth_imp]

If mufflers restrict flow then is that also restricting power output; possibly even more so than noise? I found an interesting article about engine exhaust here: http://www.cycleworld.com/2015/02/13/ask...gp-racing/
Very detailed oriented and I learned something new about how exhaust sound waves
The trumpet player analogy of how just a little pressure generated can make so much noise was interesting.

Again: An engine is operating at optimal efficiency when it is operating in its design parameters.

If you eliminate backpressure on an engine that is designed to work against backpressure...you don't have more power. You run the risk of burning valves, as hot exhaust rushes out against less restriction than is designed.

There seems to be some desire here to twist arms to get the response: Yes, taking the muffler off REALLY DOES make MORE POWER. Sorry, in a closed-loop EFI world, what that does is muddle the signals and send the FI into a default mode - thus DROPPING power as well as fuel economy.

Like losing your vacuum spark advance in the old days.

I am wholly opposed to those persons who seem bent on making noisy nuisances of themselves and their motorcycles. It makes us all look bad; it gets lawmakers more involved. It annoys ME - I do NOT want to hear that noise, except in rare circumstances, such as a dragstrip show.

What it is, again IMHO, is childish misbehavior to get noticed - even if that notice is negative and hostile and even inviting retaliation.

Out of curiosity, what qualifies as noisy by your standard and what passes as acceptable? Is there a decibel number associated with too loud?

[JustPassinThru_imp]

If mufflers restrict flow then is that also restricting power output; possibly even more so than noise? I found an interesting article about engine exhaust here: http://www.cycleworld.com/2015/02/13/ask...gp-racing/
Very detailed oriented and I learned something new about how exhaust sound waves
The trumpet player analogy of how just a little pressure generated can make so much noise was interesting.

Again: An engine is operating at optimal efficiency when it is operating in its design parameters.

If you eliminate backpressure on an engine that is designed to work against backpressure...you don't have more power. You run the risk of burning valves, as hot exhaust rushes out against less restriction than is designed.

There seems to be some desire here to twist arms to get the response: Yes, taking the muffler off REALLY DOES make MORE POWER. Sorry, in a closed-loop EFI world, what that does is muddle the signals and send the FI into a default mode - thus DROPPING power as well as fuel economy.

Like losing your vacuum spark advance in the old days.

I am wholly opposed to those persons who seem bent on making noisy nuisances of themselves and their motorcycles. It makes us all look bad; it gets lawmakers more involved. It annoys ME - I do NOT want to hear that noise, except in rare circumstances, such as a dragstrip show.

What it is, again IMHO, is childish misbehavior to get noticed - even if that notice is negative and hostile and even inviting retaliation.

Out of curiosity, what qualifies as noisy by your standard and what passes as acceptable? Is there a decibel number associated with too loud?

Like one learned Supreme Court jurist said about obscenity. It's hard to define; but I know it when I hear it.

I have my own test. I like to listen to podcasts when I'm on long rides; and I use earbuds under my helmet. If the engine noise drowns out the wind noise, my machine is too loud.

If I'm standing by the side of the road, or at home minding my business etc. - and the sound of the machine interrupts what I'm doing...it's too loud.

Not objective? Sure. Since LE isn't writing tickets anyway, what it comes down to is how loud is loud enough to torque me off and make me curse the misbegotten son-of-a-dog's parents for not making a trip to the drugstore....

[Pterodactyl_imp]

Quote:I am wholly opposed to those persons who seem bent on making noisy nuisances of themselves and their motorcycles. It makes us all look bad; it gets lawmakers more involved. It annoys ME - I do NOT want to hear that noise, except in rare circumstances, such as a dragstrip show.

What it is, again IMHO, is childish misbehavior to get noticed - even if that notice is negative and hostile and even inviting retaliation.
Could not agree more.

However, once again, you are confusing noise suppression and back pressure control. If I ran my exhaust into a large, complicated muffler system (they are not called mufflers for nothing), there is a possibility that the noise produced would be close to negligible. More efficient? The answer, simply, is no. The most efficient mufflers can only employ the same scavenging effect as a header, to help slightly overcome the loss of efficiency introduced into the system as back pressure. I have yet to see an engine that made more power with a muffler than an open header exhaust. In the design of all race engines header systems are important, any noise reduction is purely coincidental. MotoGP bikes have header systems that are in some instances very complex. Apparently the 4-2-1 system designed for the 2005 Yamaha 990cc irregular fire inline four was a real work of art! The lack of muffler is not associated with crowd pleasing, believe me. Any back pressure control system still requires pressure relief, producing noise. If you don't believe that put a cork in your muffler (and stand clear). You know, I used to love doing that in my delinquent stage . Noise is part of the internal combustion cycle. If an internal combustion engine can be built without friction, heat, noise or even mass, and could still produced power, then we would be quids ahead. Difficult design brief though.

In the words "back pressure control" there is room for misunderstanding. Any "back pressure" makes an engine less efficient. "Control" is the key. Back pressure control systems in standard four stroke engines, the CBs for example, produce tuned pressure waves to assist scavenging on the exhaust stroke and prevent spillage on the intake stroke, a task that assists the primary method of achieving this - valve timing geometry (cam profile etc.). However the header system, being of the fixed geometry type, cannot be effective over the entire operating rev range. That is one of the reasons race engines are lumpy, fart and misfire at idle yet sing like the fat lady when in the race RPM range. Over a standard engine's rev range a header system will produce an addition to power (torque and hp) in certain rev ranges, and a loss in others. The trick is to make sure the header system suits the primary operating range.

Open systems (no header), without back pressure control, are less efficient than utilising exhaust back pressure to optimise used gas extraction (or scavenging) or escape of mixture prior to combustion. After that, a muffler adds nothing and, in fact, reduces power. As I stated above, a muffler designed to be part of the header (back pressure control system) is beneficial. Any dedicated noise reduction designed into the system means a loss of efficiency. If you are convinced that this is not so, better call the Honda Race Team, tell them.

Exhaust sound levels for street vehicles are legislated by most jurisdictions. The idiots ("hoons" in Oz) who modify systems and exceed these limits do so, in most cases, without heed to engine efficiency. They do it to satisfy their needs and to hel* with the rest of us. Not good, I agree. In me there must be some subjectivety in play though. I have heard H-Ds (mostly), Ducatis (sometimes) and others, straight from the showroom floor that would seem to have excessive noise levels. They irritate me. But they have the noise compliance sticker so I guess thats all OK. The standard CB is nice, give it a the PC tick. I use a Staintune.

Cheers

[JustPassinThru_imp]

Well, we're not that much in disagreement. And I didn't want to get in the weeds too deep, with engineering minutia - which I'm not qualified to discuss. I get the general principles; I don't have the specifics.

However a muffler need not restrict exhaust unduly. One interesting schematic I came across was of, IIRC, an early Yamaha system, that used a huge-bore pipe to turn sound waves on themselves. No baffling; just an engineered shape.

To "muffle" is to mute. If you talk to me through six layers of cloth, your voice is muffled.

As for the reaction some people show for compliant pipes on H-D and other bikes, where the SOUND recalls open pipes but is within noise-regulation standards....remember, some of this is a sort of dentist's-chair reaction. We hear that sound and immediately THINK of open pipes...some moron is bearing down on us, loud pipes. We THINK that because it SOUNDS JUST LIKE open pipes, just not so loud.

We react emotionally. Again, this is because so many imbeciles have made SUCH a nuisance of themselves with their loud pipes. I used to get the same reaction, in another part of the USA, just by riding a bike. Fully stock, noise-compliant...and apartment managers and business owners would tell me to "get that d*mned thing off my property NOW!"

Irrational? Of course. But after dealing with brain-dead troublemakers and their loud scenes, they just have a knee-jerk reaction.

Interestingly, I had a different sort of reaction when I was working temporarily in northern Michigan and staying at a good-sized, non-chain hotel. The owner was a former Chicago cop...and saw my bike and warned me that if I was in the parking lot, revving it and waking everyone, he'd "tune me up." I told him I got it; and he had nothing to worry about.

A week later, as I was warming it up (quietly) (cold mornings) he came up...he was curious. Wanted to know about the machine...it was a big thumper, with a carb...he was all questions.

Once I showed him I could behave like a civilized human; and once he understood that the muffler was on and working, he was nothing but friendly.

[ChipBeck_imp]

Gentlemen,

I am not a fan of unmuffled motors in anything. Especially boats. When I go to the lake and 1 or 2% of the boats are making 90% of the noise with wide open dry headers it's pretty aggravating. And every one of my vehicles (dirt & street bikes, cars, trucks, and boat) have mufflers. But in many cases it's not the stock muffler and they are louder than stock. More noise is not the objective however. A different and far more satisfying sound is what I'm looking for. Like Guth, I use a Staintune slip on and it's the best sounding exhaust I've ever had on a bike. The stock CB1100 muffler has the exhaust make 2 complete 180 degree turns before exiting that pipe and with modern noise regulations that's about the only way to meet them. The Staintune is straight through. Same for the pipes on my HD. Stock HD pipes are ridiculously quiet because that's the law. At the other end are straight pipe bikes that are obnoxious. And just outside of legal are muffled bikes and cars that are music to my ears, but not everyones.

But hey, a lot of folks would like to see the internal combustion engine banned and force us into electric cars charged by wind mills. Technically, almost any aftermarket exhaust is illegal. Don't you love the box they come in that says "For off-road or closed circuit competition use only". How many people use a Harley Davidson Road King for off road or closed circuit competition?? Using a Power Commander or a fender elimination kit is illegal too in several states.

In any event, I love my bikes with all of their mods, legal and illegal.

Chip

[aschem_imp]

Speaking of noise and getting off topic, I find my neighbor's weed eater (gas), leaf blower (gas) and lawn mower (gas) running for 25-45 minutes each is more annoying than a loud motorcycle that is only heard for a few seconds.