Expansion chamber

[YetiWoodz]

The formula that worked very well for me that StreetRyderz posted is.....

1700×160
-----------------
Desired rpm at top of powerband

= length in inches from piston face to 3/4 through baffle cone

1700 is speed of sound at temperature. 160 is port timing. Varies by a little with different cylinders, but shouldn't affect the result too much.

 

[YetiWoodz]

The powerband range I heard can vary from 2000 to 4000 rpm. The jog pipe is about 4000.

 

[DieselTech]

The formula that worked very well for me that StreetRyderz posted is.....

1700×160
-----------------
Desired rpm at top of powerband

= length in inches from piston face to 3/4" through baffle cone

1700 is speed of sound at temperature. 160 is port timing. Varies by a little with different cylinders, but shouldn't affect the result too much.

So its 1700×160÷by your desired rpm correct? What's the ¾" through baffle cone mean? Does it mean your length will end 3/4" into the cone?

 

[DieselTech]

The powerband range I heard can vary from 2000 to 4000 rpm. The jog pipe is about 4000.

So you have a 4000rpm powerband window correct? With the jog pipe. So will just say your powerband will be from 9000-13000rpm. That's what your referring to?

 

[Chainlube]

I know header length & size play into it. Longer header more torque. Shorter header equals more rpm. I think this is somewhat right.

Not really applied to 2t, the total length of the system is though. The divergent cone angle and length dictates the exit speed and the convergent cone shape dictates the return pulse speed.

 

[Chainlube]

So its 1700×160÷by your desired rpm correct? What's the ¾" through baffle cone mean? Does it mean your length will end 3/4" into the cone?

Actually that is 3/4 way through the baffle (convergent) cone.

 

[Chainlube]

The convergent cone shape is used different maximum rpm. A steep angle will reflect the pulse across the chamber more and fizzle out quicker where as a more gradual angle will reflect it back down the middle.

 

[DieselTech]

Not really applied to 2t, the total length of the system is though. The divergent cone angle and length dictates the exit speed and the convergent cone shape dictates the return pulse speed.

That's the answer I understand! I'm a dummy. Lol So if the convergent cone is at a steeper angle the return pulse speed will be faster to return it towards the cylinder. Is my thinking correct?

 

[Chainlube]

That's the answer I understand! I'm a dummy. Lol So if the convergent cone is at a steeper angle the return pulse speed will be faster to return it towards the cylinder. Is my thinking correct?

Nope. If the end of the chamber was capped off flat, the exiting pulse would slam into it and die.
I would like to make a chamber with removable convergent cones and try different shapes and check the top rpm for each.

 

[DieselTech]

Nope. If the end of the chamber was capped off flat, the exiting pulse would slam into it and die.
I would like to make a chamber with removable convergent cones and try different shapes and check the top rpm for each.

I'm not saying capped off or at at 90°angle or nothing. I'm saying if your convergent cone was at 30° originally & you changed it to a say 55° angle, wouldn't that angle change on the convergent cone increase your return pulse speed to the cylinder.