Peter
I'm not sure about the effects on combustion - my chemistry is rubbish, but I know that acetone attacks quite a lot of plastics and some rubbers, so unless you are sure that the fuel lines and gaskets in your fuel system won't be affected, I wouldn't risk it.
I've used acetone as an 'injector cleaner' and it does seem to clean engines out very well, with resulting power and mpg benefits. Apart from that, I doubt it has any real effect on combustion itself, in modern engines.
When messing about with tiny model engines with LOTs of nitromethane the timing gets retarded. Nitromethane burns slowly. Adding acetone makes it burn faster or ignite earlier which amounts to the same thing. More power! I dont understand why it burns faster if it does but these little motors run at 30k rpms and obviously lack real advance curves! They use a glowplug. I doubt that adding acetone to a diesel is really beneficial though.
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