I was on cars.com just now comparing the civic hybrid and insight gear ratios to the regular civic and corrolla. Given the stock tire sizes, here's what I found:
At 70 mph in od/5th the civic hybrid is running at 1,958 rpm; an '06 insight is at 2,396 rpm; the regular civic is at 2,947 rpm; and the corolla is at 2,767 rpm.
If you multiply the rpm by the length (inches) of the piston stroke, you get number that doesn't correspond to anything specific like actual piston speed, but it allows for a direct comparison among the four engines. The higher the number, the faster the pistons are moving in the cylinder walls.
civic hybrid: 6,167
'06 insight: 7,692
regular civic: 10,138
corolla: 9,961
So we can see that at 70 mph, the pistons in the regular civic are moving 164% faster than the pistons in the civic hybrid.
Now, according to my admittedly limited understanding of engines, as piston speed increases beyond the point at which it makes peak torque, the burn is actually chasing the piston down the cylinder. This requires greater and greater inputs of engery (fuel) inorder to make more power, which is why engines start consuming much more fuel as they rev higher and higher.
So the rpm x stroke numbers I just posted above should be a major factor in the improved fuel economy of the hybrids, which just goes to show that if the manufacturers would give us 6 speed trannies with really tall overdrives we could see huge FE gains in regular cars. But, no, evidently they want us to think we have to pay an $8,000 premium for fuel efficiency
Now, perhaps a straight comparison of the rpm x stroke numbers isn't a fair comparison, because the various engines might have very different cam timing and duration, as well as ignition timing. If someone knows more about this please chime in. However, I'm still struck by the huge differences in engine/piston speed between the hybrids and non-hybrids.
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