I know, I know, folks know me as a dieselhead, but one of the few good things one can enjoy as a Brazilian-born is the experience with ethanol
One thing to consider about the intake manifold is that it can freeze when the ethanol is sprayed from the carburettor into the manifold. In Brazil some dedicated-ethanol cars had coolant flow passing thru the manifold to heat it, preventing it from frozing under that circumstance, just like a cab heater core. If you can't get a heated manifold, insulate the one you're going to use. Making a shorter way from the carburettor to the chambers is also a good way to overcome that freezing. When Volkswagen released its air-cooled dedicated-ethanol engines, the ones with dual-carburettor were more successful for that reason, since the carburettors sit lower than in a single-carburettor setup. No wonder when Chevy released its first fuel-injected dedicated-ethanol car in Brazil it featured MPFI even though the gasser still relied on a TBI unit...
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Originally Posted by Aguila1
If it was pure ethanol, perhaps 16:1 or more, but I'd rather be conservative and sneak up on the compression, based on experience, than regret going too high. I decided 13:1 was high enough to show a difference.
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With 16:1 compression, you wouldn't even need spark plugs
Lots of farm trucks and agricultural machinery in Brazilian sugarcane plantations run on ethanol instead of the regular Diesel fuel they were supposed to use. In older engines only some oil is added, while newer ones with electronic controls require an ECM reflashing. The highest compression I saw some folks using in spark-ignited liquid-cooled naturally-aspirated engines with Brazilian ethanol (E96h - 96% ethanol with 4% water) was 14:1.
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Another factor to consider is dynamic vs. static compression. On the contrary, the cam might have lowered the dynamic to the point that efficiency will suffer and maybe I could have gotten away with a higher CR.
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Slap a supercharger on it and play with a longer intake valves opening. Miller cycle FTW
