You can also directly feed the compressed air into a cylinder (or even the intake manifold!) to force the engine to turn. No extra turbine required, though the

You can also directly feed the compressed air into a cylinder (or even the intake manifold!) to force the engine to turn. No extra turbine required, though the plumbing might get a little odd. [https://en.m.wikipedia.org/wiki/Air-start_system https://en.m.wikipedia.org/wiki/Air-start_system] That tends to be for very large engines, where the extra plumbing isn’t a problem.