Thread: Modern 2 Stroke Engine Idea!

Hello everyone,This is more of a doubt than an idea because I'm not very learned or experienced in this topic.

In making modern 2 strokes,we have Fuel Injection,Sump-based Lubrication,Oil Injection.etc

Is it possible to completely eliminate primary compression in a 2 stroke ?

"Direct Compression Fuel Injected 2 Stroke Engine" :

My idea is to have a 2 stroke engine,head with a Fuel Injector and Spark plug,but the crankcase similar to 4 stroke,probably immersed in oil (better lubrication than premix coming there).Fuel isn't mixed with Oil and they don't get to the crankcase.You have a traditional intake with an air filter,Reed Valve going directly to the combustion chamber.So yeah,the thing goes like this :

1) Piston starts moving down from TDC,creating suction,pulls in fresh air inside the combustion chamber

2) Piston starts to compress,air starts to swirl,Fuel Injector fires JUST after the piston closes both the intake and exhaust ports (that's when compression actually happens) so the swirling air mixes with fuel easily and is fully detonated by the Spark plug,completely eliminating blowby or escape of unburnt fuel.Blowby still happens but that's just air,which is available plenty and is free of cost and not with Fuel,which isn't.

3) Piston starts to go down due to combustion,opening both the ports,The exhaust is pulled out to the exhaust port by the piston's downward movement,while fresh air is also entering the combustion chamber, 'pushing' out the exhaust gasses.

And the cycle goes on and on.

I feel that this fixes some problems of 2 strokes like complicated crankcase design,air fuel blowby,weak lubrication,Emissions,Efficiency.etc.But it brings its own problems like complexity of Fuel Injector,increases costs and weight.etc but I feel the advantages far outweigh the disadvantages.

Combine that with Modern Catalytic Converter,I think 2 strokes can be just as efficient,clean,still simpler,lighter,easier to build (and rebuild) than a modern 4 stroke.

What do you guys think ? Please comment your thoughts below!

Thread approved.

The problem with your idea is that it does away with primary compression (i.e. Crankcase compression). Primary compression plays a crucial role in how a 2 stroke makes power. Without primary compression it is difficult to efficiently fill the combustion chamber with air-fuel charge.

While the 2 stroke piston looks simple and crude compared to a 4 stroke piston, it is in fact a part that wears many hats. The crown of piston acts as a plug which compresses the air/fuel charge in the combustion chamber and captures the energy of the ignited charge to convert it to kinetic energy to drive the crankshaft. The sides of the piston act as valves as it moves up/down thereby opening and closing the ports. The skirt of the piston acts a like a vacuum pump to pull air-fuel charge in to the crank shaft and compress it in the first stage. The piston skirt the acts a compressor that will drive the air-fuel charge from the crankcase into the compression chamber through the transfer ports. What you have proposed does away with the crucial act of the piston acting as a vacuum pump to pull air fuel charge into the crankcase.

Originally Posted by abhimanyu31

The problem with your idea is that it does away with primary compression (i.e. Crankcase compression). Primary compression plays a crucial role in how a 2 stroke makes power. Without primary compression it is difficult to efficiently fill the combustion chamber with air-fuel charge.

While the 2 stroke piston looks simple and crude compared to a 4 stroke piston, it is in fact a part that wears many hats. The crown of piston acts as a plug which compresses the air/fuel charge in the combustion chamber and captures the energy of the ignited charge to convert it to kinetic energy to drive the crankshaft. The sides of the piston act as valves as it moves up/down thereby opening and closing the ports. The skirt of the piston acts a like a vacuum pump to pull air-fuel charge in to the crank shaft and compress it in the first stage. The piston skirt the acts a compressor that will drive the air-fuel charge from the crankcase into the compression chamber through the transfer ports. What you have proposed does away with the crucial act of the piston acting as a vacuum pump to pull air fuel charge into the crankcase.

Why I didn't take Primary Compression :

Piston going down creates suction and that opens up the reed valve,sucks in air,as the piston starts to come up,It starts compression and Air starts to 'TWIRL' so,The very microsecond which the piston closes both ports,The fuel injector sprays at high pressure,overcoming the pressure from the combustion chamber (which is the most difficult part)

Now I thought that the air,which is twirling at incredibly high speeds at this point,with the atomized fuel...'MIGHT' mix well with the already twirling air quickly,leading to a proper mixture and a complete combustion,we get power stroke,The piston comes down,Pushes out the exhaust gasses,while repeating the process as reed valve also opens,fresh air is in,Piston goes up,closes both ports,start compression,air twirls,injector fires at the right time,BOOM and the whole cycle repeats again! You can do away with with primary compression,Can submerge bottom end in oil,no more bearing failures or engine seizure.

There are too many guesses here.I wish I can test this twirling mix effect myself,if it works or if it doesn't.