Quote:
Originally Posted by ultraTwist  No this is a purely thermal issue associated with the ration of the volume to surface area. Thermal guys can jump in. But there's no free lunch, if lots of small pistions are better, you then need to pay for more fiction in the way of more values, cams and chains. |
Lots of small pistons moving fast are better for generating HP for a given displacement (due to a higher rev ceiling), not necessarily for better fuel efficiency. For fuel efficiency in today's engines, you want a slow turning engine operating at WOT under heavy load, at the engine's torque peak, all the time to reduce pumping losses. This is one of the reasons why diesels are so efficient, they run slowly (compared to gas engines) and have no throttle to restrict airflow. They also run best under a heavy load (at least 70% of their rated output)
The latest Cycle World magazine has a great Kevin Cameron essay about improving efficiency of gasoline engines. He's a MA native (I'm pretty sure) and one of my favorite writers.