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20cc Four Stroke Diesel

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Roger B:
After having experimented with my two stroke diesel for some time ( https://www.modelenginemaker.com/index.php/topic,5545.0.html ) I have begun to wonder if I am getting some specific 'two stroke' problems  :headscratch: I think it has a tendency to run on excess fuel that gets past the piston rings and is then inducted from the crankcase  :thinking:

I know that I have enough compression to ignite the diesel fuel (pump diesel). I know that the bottom end is strong enough, it even survived the passage of an M3 grubscrew through the system.

The next step will be to convert the current engine to a four stroke. I can use the crankcase, crankshaft and conrod. The cylinder and head will be based on the horizontal engine with a chain driven camshaft mounted under the cylinder. The head and combustion chamber will be a challenge to fit the valves, injector and water cooling passages. I am looking at two options at the moment, The standard bowl in piston and the Lanova type figure of 8 around the valves. The Lanova type seems to result in masking of the valves but makes fitting the injector easier. The bowl in piston will require some interesting water passages to allow a reasonably central injector.

Minh Thanh:
Hi Roger !
 4-stroke diesel engine is easily determines the efficiency of the pump and injector
  Good luck !

Roger B:
Thank you  :)

The first step on this conversion was to arrange a suitable camshaft drive. Studying the catalogues suggested that a 12 tooth 6mm pitch chain sprocket would fit in place of the injection cam. The boss on the crankcase cover had to be reduced in size to give clearance to the chain and the sprocket had to be thinned down to 7mm wide.

Roger B:
Finally I broached a 3mm keyway in the sprocket and put it all back together.

Great to see that you are moving forward again Roger  :ThumbsUp:

I'm wondering about your pump placement - will it still be crank-driven and if that is the case, what about the fact that you only should have one injection per 720 degree crank rotation ?


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