There have been huge improvements since the first petrol engine, and huge improvements in the last 20 years as well. Petrol engines are some of the most studied and meticulously engineered things ever created.
What do you mean? The amount of improvements in standard ICE engines are mind-blowing. The fuel efficiency and power they manage these days is insane. You’re quoting that 60% figure and neglecting that most of the losses from that are thermodynamic and mechanical losses at transfer points that can’t really be overcome. At some point you have to lose some heat along the way.
There is a fundamental limit to ICE efficiency dictated by the laws of thermodynamics. You can push that theoretical limit up, but it is dependent on having a higher compression ratio. Diesel engines use higher compression ratios for ignition, but they are dirty (in comparison). Higher compression ratios tend to result in more NOx emissions too, so for the regular car makers there is a direct trade between efficiency/emissions/reliability. But even if you aim for highest efficiency at all cost, you'll never get close to 100 percent, as the theoretical max never goes there (or does it at infinite compression ratio?).
Petrol engines can physically only achieve around 55-60 % efficiency, so getting up to ~35-40 % vehicle efficiency is actually really good. Large scale Diesel engines get really, really close (within a few points) of the hypothetical frictionless-no-heat-radiation-no-flow-losses efficiency possible with their parameters.
Turbochargers do exactly that. They take waste gas/heat to turn a pump and provide more oxygen for combustion. Also look into the F1 ERS systems that recover waste energy.
One big limitation is the Carnot efficiency - for any heat engine (which internal combustion engines are) there's a maximum upper bound on the efficiency, which for gasoline and diesel is around 37%. Beyond that point you can't extract any more energy out of the waste heat without removing energy from somewhere else in the system.
There is, especially in Racing. In Formula 1 some engines have reached 52% thermal efficiency [1], but the amount of hardware required in order to capture the excess heat (see MGU-H)[2], makes this costly and difficult to improve upon, and currently with the new F1 engine regulations they are dropping some complex systems so the barrier to entry is less expensive.
The term to google for is cogeneration. Sometimes all people need is the correct search term.
The problem with cogeneration is its usually incredibly heavy and there aren't many uses for very low temperature process heat in most real-world applications.
Another problem with cogeneration is you might get a small percentage boost by connecting a backup generator to the HVAC system but the capex can be VERY high if done safely and reliably, and system complexity seems to scale at an exponential rate. It seems a no-brainer to dump the radiator heat from a backup generator into an office building thereby burn less natgas to heat the building; however you factor in that you have to frost-proof it all and its going to be hundreds of gallons of anti-freeze in those pipes which is expensive and all pipes leak eventually with has ecological issues, and you can't have exhaust leaks into the building and over half the time you need cooling not heating anyway and the HVAC cannot be made smaller because you still need to heat even when the gen is off and the HVAC system will be less reliable because it'll be more complicated and the backup gen will be less reliable because its more complicated, perhaps making the backup gen less reliable than wall power. So shrug shoulders and dump the gen heat using an air cooled radiator, even in the winter.
It's amazing what we do have. Just the computers alone are more than anyone could have ever imagined. But as for flying cars, they do exist, but we just don't need them.
Isn't this called a helicopter? Aside from the noise, etc. issues with them, what would be the difference between a flying car and a helicopter? The need for a pilot's license to fly one?