Cheap expansion chamber

[DAMIEN1307]

No kidding.. that's ridiculous

That's bikeberry...lol.

U think you are getting an mz65 clone like the nasty jack. But you will receive this little guy instead.

 

[ImpulseRocket]

So the wave usually travels back and forth 4 or 5 times before it is taken in by the engine?

A longer intake would then reduce the harmonics. Right?

Yes and no to both.

The wave travels back and forth the number of times the engineer set the harmonic number to which is determined by intake length.

Let's say I did all my math for an engine and the first harmonic, aka the most ideal and best one that could be used, requires a distance between the node and anode of 18ft.

Sound ridiculous? It is, which is why I said that the first harmonic is unrealistic for most applications, even though it is the most ideal as the resonance wave is the most powerful.

(The following is over simplified, but will get the point across)

So, to make it fit we have to divide the distance of the intake. The distance the wave needs to travel before the node opens again is still 18ft, so the easiest way to make sure the wave still returns at the right time is to make sure the distance it travels is the same. Half the intake length means that the wave still travels the 18ft needed, but has to travel between the node and anode twice. This means it is on the second harmonic.
9ft is unrealistic, so we halve it again. (3rd Harmonic) 4.5ft is unrealistic so we halve it again. (4th harmonic) 2.25 is starting to be more realistic, but still a bit long, so we halve it again! (5th harmonic) 1.125ft, aka 13.5 inches, is actually feasible.

The catch is, every time you cut the distance down and the wave reflects between the node and anode, it loses some energy, so the more harmonic steps you go, the less effect you see from the resonant wave tuning.

The other catch to resonant wave tuning is that it is for a specific RPM point, and outside of the region of the RPM range it is setup for, there is no benefit, and if done wrong, can be detrimental. This is why for a while car companies messed around with intake valve systems to change between short and long runners, such as the Mazda VRIS (Variable Resonance Intake System), which had a set of butterflies in the intake runners that opened and closed off the intake runners to alter the resonance and intake velocity to help boost low RPM power while the runners themselves were tuned for high RPM. The Mazda KL V6 engine, the ZE in particular - 2.5L V6 - utilized this system to great affect, and with the intake resonantors removed and an open exhaust, sounded like a mini Formula car (and were used for a time in Formula 3). Honestly, it's the best sounding V6 engine I have ever heard.

Skip to the 40 second mark to see what I mean. Has a note closer to a straight 6 than a V6, and he isn't even revving it out as high as it can go. These things at 9000rpm sound ridiculous

 

[DAMIEN1307]

Yes and no to both.

The wave travels back and forth the number of times the engineer set the harmonic number to which is determined by intake length.

Let's say I did all my math for an engine and the first harmonic, aka the most ideal and best one that could be used, requires a distance between the node and anode of 18ft.

Sound ridiculous? It is, which is why I said that the first harmonic is unrealistic for most applications, even though it is the most ideal as the resonance wave is the most power.

(The following is over simplified, but will get the point across)

So, to make it fit we have to divide the distance of the intake. The distance the wave needs to travel before the node opens again is still 18ft, so the easiest way to make sure the wave still returns at the right time is to make sure the distance it travels is the same. Half the intake length means that the wave still travels the 18ft needed, but has to travel between the node and anode twice. This means it is on the second harmonic.
9ft is unrealistic, so we halve it again. (3rd Harmonic) 4.5ft is unrealistic so we halve it again. (4th harmonic) 2.25 is starting to be more realistic, but still a bit long, so we halve it again! (5th harmonic) 1.125ft, aka 13.5 inches, is actually feasible.

The catch is, every time you cut the distance down and the wave reflects between the node and anode, it loses some energy, so the more harmonic steps you go, the less effect you see from the resonant wave tuning.

The other catch to resonant wave tuning is that it is for a specific RPM point, and outside of the region of the RPM range it is setup for, there is no benefit, and if done wrong, can be detrimental. This is why for a while car companies messed around with intake valve systems to change between short and long runners, such as the Mazda VRIS (Variable Resonance Intake System), which had a set of butterflies in the intake runners that opened and closed off the intake runners to alter the resonance and intake velocity to help boost low RPM power while the runners themselves were tuned for high RPM. The Mazda KL V6 engine, the ZE in particular - 2.5L V6 - utilized this system to great affect, and with the intake resonantors removed and an open exhaust, sounded like a mini Formula car. Honestly, it's the best sounding V6 engine I have ever heard.

Skip to the 40 second mark to see what I mean.

Not too different when in my youth, I used to be heavy into my amateur radio hobby...We always worked with "harmonic frequencies" and when we made our own antennaes, we needed to cut them very precisely for the proper "wave" length.

On older analogue radios you could tune in a station where it came in very strong, That was the actual station location on the dial, but sometimes you would notice as your sliding down the radio dial, you could pick up that same station multiple times within the bandwidth at weaker and weaker levels, that is what is called picking up the "harmonic" frequencies.

 

[ImpulseRocket]

Not too different when in my youth, I used to be heavy into my amateur radio hobby...We always worked with "harmonic frequencies" and when we made our own antennaes, we needed to cut them very precisely for the proper "wave" length.

On older analogue radios you could tune in a station where it came in very strong, That was the actual station location on the dial, but sometimes you would notice as your sliding down the radio dial, you could pick up that same station multiple times within the bandwidth at weaker and weaker levels, that is what is called picking up the "harmonic" frequencies.

Yes! That is the exact same principle at work.

 

[Scooterduder]

My bike does 50mph with my 220lbs butt on a steel frame. 40mm stroke, ported allaround, Piston crown ramps, needle bearing spacers, balanced crank, scooter cdi, advanced timing, 36t sprocket, expansion chamber, short intake, velocity stack, 6cc head with .02 squish gapView attachment 184998

Hey Jayraye39, I absolutely love your bike! I'm asking this question out of ignorance and curiousity. Why no reed valve?

 

[Wevil Knievel]

Hey Wevil Knievel, which flexible exhaust pipe are you using? Thanks!

The niome flex pipe.

 

[Scooterduder]

So I now have the Nasty Jack expansion chamber from Ebay on my bike and from Amazon the "BADDASS SHARKS 28mm Motorcycle Exhaust Muffler Pipe System................." It works pretty nicely. I pushed the muffler stinger into the expansion chamber stinger if I'm using the correct terminology. Didn't fall off yet... Thanks for the help ImpulseRocket89 and others.

 

[Chainlube]

So I now have the Nasty Jack expansion chamber from Ebay on my bike and from Amazon the "BADDASS SHARKS 28mm Motorcycle Exhaust Muffler Pipe System................." It works pretty nicely. I pushed the muffler stinger into the expansion chamber stinger if I'm using the correct terminology. Didn't fall off yet... Thanks for the help ImpulseRocket89 and others.

Here's the issue I see with that pipe, the stinger from the divergent cone should go all the way through the silencer, one piece. If you can stick the outlet tip of the silencer inside the stinger, then the stinger is too fat. The OD of your header pipe where it goes into the first convergent cone should be like 25mm and the OD of the stinger pipe should be around 19mm. I bet the header and the stinger are both 22mm.

 

[Whitewill1412]

Here's the issue I see with that pipe, the stinger from the divergent cone should go all the way through the silencer, one piece. If you can stick the outlet tip of the silencer inside the stinger, then the stinger is too fat. The OD of your header pipe where it goes into the first convergent cone should be like 25mm and the OD of the stinger pipe should be around 19mm. I bet the header and the stinger are both 22mm.

But wouldn't the back pressure from the muffler kinda correct the issue of the stinger being too big? I'm just guessing. I don't really know what I'm talking about.

 

[Chainlube]

Did you look through the muffler? Being that the muffler is smaller it will add some, just not the same as if the whole stinger was smaller, I'm talking diameter though.