Motorcycle Repair: about 2stroke and 4 stroke, top fuel dragsters, exhaust gases

Question
hello

i was wondering why , when we incrrease performance for a 2 stroke , we always try to restrict the flow of exhaust gases

and whereas we, make free flows ,bigger valves, multi valves for a four stroke to make sure that exhaust gases to go out.

why this opposite way to increase power?

Answer
For more info that you probably wanted go to:
http://tsrsoftware.com/redesign.htm

Except for top fuel dragsters and stock cars, most tuned 4 cycle exhaust systems are not just sewer pipes trying to dump out all the gases. There are powerful pressure waves that move back and forth inside the exhaust pipe that can cause a timed suction wave at the exhaust port at certain rpms.

The same is true on 2 cycle engines, but because they fire EVERY stroke instead of EVERY OTHER stroke, there is less time to do what needs to be done... intake, compression, power and exhaust. If you read the above article you will see how complex these tasks are for the 2 stroke tuner.

Bill Silver