The weight added by a super/turbocharger is nearly offset by displacement. If you look at the saito 120/150/180 4-strokes you will see that they weigh about the same as the YS110 and the YS is roughly equal to the 150 so for the same weight you could buy the saito 180 and get MORE power for that given weight. Know the idea of running a velocity stack up behind the prop, the problem is that you do not get any sort of constant flow. It is too turbulent to make work properly. The idea of a TURBOcharger I feel is the best way to go if you are looking for huge power gains because they like high RPM's. Turbos spin up around 100,000 RPM's and need high pressure from the exhaust to get enough energy to rev them up and make boost. In reality it is just WAY easier to up size the engine. You also get rid of all the related tuning hasels that go with a pressurized intake.

I would love to see a 4hp .46 2-stroke though.

Dave