An "expansion chamber" as used on a two stroke does not connect two separate pipes together. There is nothing in common between the two. That is a jump I cannot make. Also, while there are one or two companies that play around with smaller versions of expansion chambers on four strokes they are smaller and closer to the exhaust valve. In general the further away from the valve the smaller the cross section of the pipe should be (to a point) to maintain velocity.
The "expansion chamber" on the Daytona (we called it a colostomy bag) was not for improved power (it hurt power output) but for noise emissions reasons. by replacing it with a proper cross over you can gain power. By replacing it with a well designed collector you can gain even more power.
When you oversize the cross section of the pipe the flows velocity goes down. Lower velocity means reduced effect in terms of scavaging improvements from pulse timing. A cross over is already not as good at improving power as a collector, enlarging the cross section of the crossover only makes it worse.
I don't know if there is an improvement in power output with changing out the stock cross over, but if it is anything like the one on the Daytona then it would be hard to imagine that there is not.
The "expansion chamber" on the Daytona (we called it a colostomy bag) was not for improved power (it hurt power output) but for noise emissions reasons. by replacing it with a proper cross over you can gain power. By replacing it with a well designed collector you can gain even more power.
When you oversize the cross section of the pipe the flows velocity goes down. Lower velocity means reduced effect in terms of scavaging improvements from pulse timing. A cross over is already not as good at improving power as a collector, enlarging the cross section of the crossover only makes it worse.
I don't know if there is an improvement in power output with changing out the stock cross over, but if it is anything like the one on the Daytona then it would be hard to imagine that there is not.