03-22-2015, 11:01 AM
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
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