Quote:
Originally Posted by teoman
I would have thought that direct injecting it would be beneficial for performance as it also cools the intake charge and should be easily controllable. Not sure why they prefer gas injection.
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Direct injection doesn't really cool the intake charge, since it doesn't vaporize at the intake manifold and is injected directly to the combustion chamber at the liquid phase instead. But if LPG was fed in the liquid phase through a regular port-injection it would freeze the intake manifold. Some older Fiat engines and dedicated-ethanol ones from other manufacturers featured a heated intake manifold which had some ducts where the engine coolant would pass in order to avoid the risk of freezing due to a similar effect while running on ethanol. Anyway, LPG is not road-legal in my country, allowed only for special machinery such as forklifts and some tractors, but most of the illegal conversions that I have already seen were based either on dedicated-ethanol or Fiat engines exactly due to the intake heating provisions.