Anyone have this expansion?

Looks like it is good.
You prolly need to make a pipe to come off the exhaust port.
The length of the pipe before the chamber sets the timing of the pressure wave.
You will have to adjust that length to get the Range you want.

Don't open the hole in the end where the muffeler is too big.
That could cause the motor to run too hot.
I put a 1/2" NPT long skinny lawnmower muffeler on mine.
Knock the plate out of the center.

4 now i'd leave the stock muffeler on it.
It looks really nice.

Let me know how it works out.

The taper of the cones is what gives the pipes there chareteristic along with tuned length.

what motor u got i can tell u the port timing.

also " MERRY CHRISTMAS "

I just gave you a month worth of my work.

None of it is borrowed from anywhere except my own brain.

I Can't wait to see how it turns out.