Quote:
Originally Posted by serialk11r
I haven't completely thought this through but with E85 especially and boost, wouldn't it be better to spray E85 into the manifold or something rather than the ports, assuming the direct injectors are maxed out? That way it evaporates before it hits the valves, and with boost it will help cool things down too. Reducing available air mass isn't a big deal since the lower temperature and pressure will allow more air to come in anyways.
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arghx7 gave you the technical reason but I'll break it down simply for you.
If the fuel evaporates before it reaches the combustion chamber you will not have as much cooling effect. Therefore if you spray the E85 directly into the combustion chamber you have a greater cooling effect along with the extra cooling effect you get from the evaporation of ethanol vs. gasoline.