Ideal engine speed for highway FE?

[arcosine]

55 was chosen because thats the slowest they thought people would drive. Speed limit was 45 mph during the war.

[zonker]

Originally Posted by Frank Lee

Optimum piston speed?

There seems to be a point of lower rpms at which engines don't get more efficient.

phew, now thats getting way up into that engine cavity in the search for better mpg.

i'll bet that at a certain point, the speed in which the combustion explosion propels the piston down it's bore has an ideal.

I'd guess that's probably related to why under-square motors (greater stroke than piston bore) are more efficient at lower rpms than over-square motors (larger bore than stroke).

[zonker]

another update...

did my 90 mile loop tonight, but with lowered speeds.

92.6 miles, 50F, 50-55 mph, 2.57 gallons used.
36.03 mpg!

the previous run, same 92.6 miles, 55F, 65-70 mph, 2.90 gallons used.
31.93 mpg...

that is a 4 mpg difference between 52 mph and 67 mph. pretty substantial.

[Sularus]

Good results zonker! I found out my GP does much better in the 50 - 55 region last year. Of course it makes my 50 mile trip to and from work about 10 mins longer, but oh well, at least I am saving some money in gas. Or at least I am not burning that money uselessly.