Efficiencies might seem bad, but thermodynamics limits the efficiency of any heat engine (of which an ICE is one) according to the absolute temperature of the hot and cold side of an engine. This is called the "Carnot efficiency" and it's comparable to a no-friction mechanical system, or a no-resistance electrical circuit.

For an ICE, assuming combustion temperatures of 550K and assuming the radiator can cool the system to 50C, the Carnot efficiency is (1 - Tc/Th) = (1 - 333K/550K) = about 40%.

That's a hard theoretical limit that assumes all processes are reversible. Real engines have irreversible thermodynamic processes so the Carnot limit can never really be attained.

In other words, your complaint isn't with the engineers, it's with thermodynamics.

(note: ICE engines are modelled using the Otto cycle rather than the Carnot cycle, but that's a bit more complicated and leads to efficiencies that are even worse. The Carnot efficiency is an upper limit for all heat engines, including steam engines, Stirling engines, turbines, etc.)

550k is a low combustion temperature. “Modern military jet engines, like the Snecma M88, can see turbine temperatures of 2,900 °F (1,590°C).” https://en.m.wikipedia.org/wiki/Turbine_blade

That’s like ~1850k assuming 2900F was rounded.

Absolutely. But I read the comment as complaining about efficiencies of automobile engines, not modern military jet engines. The combustion temperature of gasoline is 553K.

https://hypertextbook.com/facts/2003/ShaniChristopher.shtml

https://www.quora.com/How-much-heat-does-it-take-for-gasolin...

Ignition temperature is just the point when something starts to burn, it has nothing to do with the temperature inside an engine after ignition.

https://www.quora.com/Which-engine-has-higher-temperatures-a...

I am aware of the Carnot efficiency, my issue with the engineers is that they can't make big gains anymore, exactly because of the Carnot limit.

Best way of making a gasoline car (not the engine - the car) efficient is taking the throttle of the engine out and attaching a hybrid/regenerative generator/motor to it.

The best way of making the car efficient is doing something about the fact that we use two tons of steel to move 100kg of human.

Yes, but that's a market problem ;)

Maybe the electric scooters/mopeds are the solution?

Combined cycle thermal efficiency’s are breaking 60%. https://en.m.wikipedia.org/wiki/Combined_cycle_power_plant

But, for very long term storage efficiency is not that import. If you’re buying at an average of say 1c/kWh and selling at 20c/kWh in 6 months it’s mostly a question of what your storage costs per day as well as maximum output is.

I first worked that out in response to a claim that solar thermal plants were better than PV because they can store energy as molten salt and produce power at night. What sinks that claim is solar is cheap enough that you could heat your salt with electricity from solar panels and be ahead.

At the point there is no need to use salt. You can use a referable electrically driven gas turbine and get about 70-80% round trip efficiency.