In games you get a better result for the cycles by cheating rather than doing a physical simulation.
Live for speed IIRC did have a fully synthesized engine sound but most games now have samples and some clever interpolation / synthesis as mentioned by others.
Live For Speed also sounded pretty average, although it was still highly appreciated that they simulated it instead of fauxing give the type of game it was.
GTA used a combination of pre-recorded real life audio and their own granular synthesis engine. (Granular synthesis uses sampling, but cuts up the samples into tiny pieces and processes them in various ways.)
Automation Game (car tycoon) features engine design and stimulates sounds from a combination of individual parts snippets iirc as you move around you can hear the valve train clicking or the cylinder firing
