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#Post#: 89802--------------------------------------------------
Wet Sump Two Stroke Engine
By: joe_indi Date: February 7, 2023, 7:47 am
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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
HTML https://blog.stihl.co.uk/how-will-e10-petrol-affect-your-stihl-chainsaw/
And this adds more to the gloom
HTML https://blog.stihl.co.uk/e10-fuel-faqs/
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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