Author Topic: Wet Sump Two Stroke Engine  (Read 189 times)

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Offline joe_indi

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Wet Sump Two Stroke Engine
« on: February 07, 2023, 08:47:30 am »
This might seem a crazy idea, but I have been worrying it for years now.
I read an article about why two stroke are highly polluting the reason being they need oil in the fuel mix for lubrication because they use a dry sump and ports through the cylinder interconnecting the combustion and intake areas.  Having valves would help but then valves would need to run at crankshaft rpm causing valve float at working rpm.
I thought why there are two stroke diesels that run without this issue. But they need turbo chargers to supply the air and they use  valves only at the exhaust, but  the porting is still complex with lots of overlap. But in spite of all this the two stroke diesel is claimed to be more efficient that its four stroke counter part.
If i were to think of an alternative my priority would be to get the cam down to half speed of the crankshaft, but that would open and close the valve at the four stroke speed. Well, I thought why not add another valve that works directly opposite to the first valve?
For the past 10 years this had been a thought but seemed an impossibility when complex camshafts, timing belts or chain and head ports were even thought of.
But then this morning I was worrying this issue around like a bone because our two strokes seem backed up against the wall, because since yesterday the whole country is going for E20.
I had read this article  that claims anything above E10 is not going to do any good to two strokes with carbs
And this adds more to the gloom
I had been theorizing about making the chainsaw and brushcutter engines "inefficient by adding thicker cylinder gaskets or retarding the ignition timing to meet this issue , when the keyword inefficient hit me and then I thought of side valve flat heads for wet sump two strokes .
 Why not use the same set up as in those old flat head side valve engines that had inlet and exhaust on the same side. And, very importantly, simple wet sumps that never even needed an oil pump, but a simple splasher. Both the  valves in this design could work alternatively as exhaust valves. And, valve timings just cannot go wrong because both valves are activated by the same cam lobe. The only work here is to make both valves and their ports equal/identical.
Then the thought was what about the inlet?. I dont think a turbo is necessary only some kind of blower to give a higher positive pressure than atmospheric pressure. Maybe some kind of injector could 'charge' the air. Some kind of valve maybe a simple butterfly could help give the required variable throttle.
I have all this in my mind now, but, I dont know where that inlet should be. That flat head with only a spark plug seems the ideal place, or should it be a port on the cylinder wall that is opened when the piston is on the downward stroke. Mechanics, engineers, I would welcome suggestions on this.
Someone might say "You have not thought of ignition" , well I have thought of ignition and I know it needs no work because these engines have the cdi or pointless ignition system usually mounted at the flywheel so that it generates sparking current at every stroke.
I am already eyeballing a locally available Chinese side valve engine, probably a B&S clone.
Right now as a first step all I want it to do is run like a two stroke, without oil mixed in the fuel (naturally)   for a few seconds, using a small blower and a soaked ball of cotton to do the function of that air fuel mixture.
Do I drill a port on the cylinder wall or on the head, that is where I need advice and why

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