Originally Posted by
dieselpilot
YS does very well with crankcase supercharging in their four stroke engines. It is effective and efficient. It has been attempted one way or another many times over then last 30 years. I found maybe a dozen patents for such systems.
Greg
Doesn't YS use a supercharger to pressurize the crankcase ? That's not using the engine's piston to 'supercharge' the the intake air/fuel like DP was thinking of. I suggested to DP that using an external supercharger to pressurize the crancase would work well. The YS engines have the supercharger built into the back of the engine, but it is still external (or rather seperate from the piston)...
Originally Posted by DP-buggyboy
Hmmm. I thought it was a good thought experiment. I understand the crankcase is not efficient at pumping, but it's how many high-peformance, high-RPM 2 stroke intake systems work....
Two stroke engines do move the intake charge through the crankcase and into the cylinder via ports, but don't 'supercharge' the intake charge. I didn't say the engine you proposed wouldn't run at all....just that it wouldn't have an advantage over a conventional four stroke that breathes straight from the carb to the intake valve (and certainly not one that has a supercharger).
I believe the 4-Mix engines that Stihl makes (for some of their string trimmers, brush cutters, and backpack blowers) breaths through the crankcase some how. It does have valves....is a four stroke....and doesn't have a seperate sump of lubricating oil. It runs on premix...