Post by prodigit on Mar 15, 2013 18:11:35 GMT -5
Since I have nothing else to do right now, but wait,
I thought it interesting to calculate the necessary length of an exhaust pipe before the muffler (or pot).
Because it includes a lot of difficult calculations I can really not do, I thought of simplifying the process a lot (I'm not an engineer) to get an approximate length for a pipe, with my calculations, close to what an engineer would find; but leave the more advanced and precise stuff for the real engineers.
Anyway, I came to the following results:
The speed of sound is ~340.29 m/s in air.
According to what I read, it is faster when under pressure (in air), and when the temperature is increased, so for easy sake, let's say at an exhaust it goes ~350m/s.
An scoot starts picking up speed ~1500RPM, but it's effective peak band (where you want it to be working optimally) is ~5k RPM most of the time. I calculate from 5k RPM, because the lower the RPM, the longer the pipe must be.
At 5k RPM, there are 2500 exhaust pulses per minute, or ~41 pulses per second coming out of the exhaust.
That means on one full pulse, the gas travels ~8.5 meters ( or ~ 25ft) in 1/41th a second.
You will want the exhaust valves to open at the moment a negative pulse is about to form (a sub pressure, or vacuum), so generally that means that the optimal pipe would be halved the result above, or ~4.25meter (~12ft) for a 4 stroke.
That's pretty insane!
If that's true, it means that most 4 strokes should have a 12ft pipe behind them.
I guess I'm missing something here?
I thought it interesting to calculate the necessary length of an exhaust pipe before the muffler (or pot).
Because it includes a lot of difficult calculations I can really not do, I thought of simplifying the process a lot (I'm not an engineer) to get an approximate length for a pipe, with my calculations, close to what an engineer would find; but leave the more advanced and precise stuff for the real engineers.
Anyway, I came to the following results:
The speed of sound is ~340.29 m/s in air.
According to what I read, it is faster when under pressure (in air), and when the temperature is increased, so for easy sake, let's say at an exhaust it goes ~350m/s.
An scoot starts picking up speed ~1500RPM, but it's effective peak band (where you want it to be working optimally) is ~5k RPM most of the time. I calculate from 5k RPM, because the lower the RPM, the longer the pipe must be.
At 5k RPM, there are 2500 exhaust pulses per minute, or ~41 pulses per second coming out of the exhaust.
That means on one full pulse, the gas travels ~8.5 meters ( or ~ 25ft) in 1/41th a second.
You will want the exhaust valves to open at the moment a negative pulse is about to form (a sub pressure, or vacuum), so generally that means that the optimal pipe would be halved the result above, or ~4.25meter (~12ft) for a 4 stroke.
That's pretty insane!
If that's true, it means that most 4 strokes should have a 12ft pipe behind them.
I guess I'm missing something here?
..BAD TO THE BONE..