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
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.
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.
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.)