long stroke efficiency

[javajunkie]

I have a question about the theoretical maximum stroke length of an engine and the resultant efficiency. With direct injection it is possible to keep the intake valve open during part of the compression cycle. In theory then, we could take an engine with a 10cm stroke length and 10:1 compression and double the length of the cylinder yet keep the 10:1 compression ratio. Then during the power stroke the piston would move 20 cm and make more efficient use of the available energy. Of course, a cylinder could be made too long and after the piston has traveled so far no more energy/pressure is available to move the piston and friction would begin to reduce efficiency. So my question is, how long in theory can a cylinder be made to make use of all available energy and by how much would this increase efficiency over today's engines? Thanks for any help -- I'm new to this forum.

 

[GregLocock]

That's an Atkinson cycle. You need to model the frictional behaviour of the piston and bearings to see the tradeoff.



Cheers

Greg Locock

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