But much less efficient at 65 and 75. Pushing the wind eventually gets you.

At which speed a car is most efficient can essentially be chosen by the engineer designing it as far as I know.

For an engine rpm yes, for a moving body, not so much. Energy in a vacuum is proportional to velocity squared, and energy required with wind drag is iirc 4th power of velocity.

So even with an engine designed to be most efficient when the car drives 65 mph, the efficiency of the system will quickly be controlled by drag forces as speed increases.

Incredible. Thanks for sharing. I had no idea. What is “pumping loss “?

> What is “pumping loss “?

Unlike older scientific topics that have esoteric terminology, usually from the Latin, this one is pretty straight forward... It is the energy lost due to pumping. Basically, the overhead of keeping an engine running no matter how much distance of roadway you cover, but more on point, the extra losses due to running an engine outside of its peak power/performance range:

https://www.cycleworld.com/2015/10/12/ask-kevin-what-is-pump...

Would be very interesting to see some of the ideas that they wanted to base improved infrastructure on with older ideas of the future of technology. The convoys always fascinated me, and the entrenchment of older technology makes progression much harder when the existing infrastructure is heavily depended on and long term planning has never been a strength of the US.

Weird, does this apply to EV's, too?

> does this apply to EV's, too?

Not "pumping" losses, no. There is no intake air or exhaust gas to pump.

EVs may experience an effect that is similar in practice, albeit much smaller... Things like headlights, HVAC, entertainment systems, etc., will draw more power the longer it takes you to get to your destination, so reducing your speed from 30 to 15 MPH might not be an efficiency win.

No- those losses (less the engine idle speed) are relatively larger for electric, because alternator loss is already baked into the efficiency for ice engines.

No- electric motors generally perform better at lower speeds, gas at higher speeds. Especially so in direct comparison.

Which is why hybrids often switch from electric to gas past some determined speed.

That's only true because the electric motors don't have a gearbox but the gas engines do.

I believe due to motor efficiency and losses from AC, media system, etc., the most efficient speed for most EVs and hybrids is around 25 mph. I’ve heard 10 and 35 suggested as well.

its the opposite for EVs. Their range decreases as their speed increases due to the increased effect of wind resistance