We are a group of 3 swedish students who are doing a project in our university. We wish to design a fuel efficient and low friction four stroke engine of about 35 cm3. The idea is to use the Atkinson cycle (http://en.wikipedia.org/wiki/Atkinson_cycle) with a over expanded power stroke using late inlet valve closing in the compression stroke.

The engine will be used in a hybrid powertrain, in a vehicle of about 100kg so the power requirements to keep the vehicle at constant speed (about 30km/h) is about 50 W.

These engine design parameters will be used as a start up in our engine design software (AVL Boost):

Compression ratio: 15:1
Bore: 34.2mm
Stroke: 38mm
Bore to stroke ratio: 0.9

The idea is to use the SI engine for 5-10 seconds and then turn it off for 10-15 seconds and then turn it on again. So the engine doesnt need to be cooled, instead it needs to be isolated to keep it warm.

So, my question to you is, do you have any good advice for us regarding the engine parameters and geometry design?

Do you have any advice of low friction materials, good lubrication, number and geometry of valves?

Use direct injection?

Homogeneous or stratified combustion?

What kind of ignition system?

Equivalence ratio?

Do you have any good ideas of manufacturers that can manufacture similar small four stroke engines?

References to good reading on the web or books?

Any kind of comments and advice is helpful. If you have some good information, please refer to the book or web page that you found the information (referenses needed in the report).

Best regards, Jim