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One of the most efficient engines on the planet has a bore of 3 feet and a stroke of 9 feet. Longer stroke works well for torque and horsepower at lower RPM.
In 1950 Alfa Romeo built a grand prix engine that was a 91 cubic inch (1.5) liter straight 8, which was actually two 4 cylinders bolted nose to nose. All accessory drives were gear driven off the junction of the two noses of the engines with two stage supercharging and 10k RPM red line.
390 HP at 2 MPG on the racing circuit.
It's like the difference between the old 225 slant 6 and a motorcycle engine that red lines at 15k RPM. The 225 had a stroke of 4.5 inches and a bore of 3.5. Lots of low speed torque. Geared right in a aerodynamic body with modern fuel delivery, the old slant 6 would still be competitive.
Best 5 speed gear ratios (overall) would give you red line engine RPM at 30,60,90,120,150 MPH in the respective gears. Considering a 6k RPM red line, that's 3k RPM at 75 MPH in top gear, just about exactly where the Civic VX final drive ratio was.
This doesn't seem to really follow the topic of the OP's thread which was about efficient engines which is a totally different subject.
regards
Mech
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