Quote:
Originally Posted by redyaris
The basic problem is matching the cam timing to the engine speed to optimize the air/fuel flow through the engine. It is possible to design an engine that has very high rpm, large amounts of valve overlap and very good fuel economy. but it would only be good for a narrow range of rpm...
If you wanted to design a motorcycle engine for better fuel economy you would start with a long strock engine that did not need very high rpm to produce the power you needed, so that there is less rpm change with change in road speed, so that the engine stayed very close to its optimum rpm for FE most of the time...
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Excellent point. Bikes like my Buell do this rather well, up to 60mpg out of 1200, same with BMW 1200s.
This cam idea would not work well for town driving for the reasons you describe above, but people like myself who do most of their miles could potentially see good gains in the rpm range that they cruz at. Like you said, the problem is getting that rang right.
Could a stock cam be ground to achieve the desired effects or would you need to start new with a blank?
If It could be ground, it seems like it would be worth while research to play around with this and possibly come up with a formula that could be duplicated on a new cam.
Just an idea...