Bret Ludwig wrote:
>>How can alcohol "increase engine power?" It can't. Either the engine is
>>optimized for alcohol (and yes, you can extract a great deal of power
>>from engines that use alcohol as fuel) or an engine is NOT optimized to
>>burn alcohol. There's no direct comparison without changing the fuel
>>system and compression ratio.
>>
>>Now if you do allow changing the fuel system, how do you compare?
>>Probably the best way is on engine size. For any given engine
>>displacement, setting it up to burn gasoline will net more horsepower
>>out of the engine since more chemical energy can be pulled into the
>>engine in the form of air/fuel mixture because the energy density of
>>gasoline is higher. Its arguable that in the case of turbocharged or
>>supercharged engines, you could run more boost with alcohol and
>>therefore extract more power, but that is tantamount to simply
>>increasing engine displacement anyway.
>
>
> In the late 1970s and early 1980s the USAC cars were putting out 1000+
> bhp out of the 166 CID Turbo Offy. On gasoline it is doubtful much more
> than 200-250 hp would have been possible.
Again, an engine DESIGNED for that fuel. I don't argue that if you're
limited by an engine's cooling capacity, you might be able to do better
with alcohol. Or maybe not- gasoline with water injection might work
better.
> Alcohols allow radically more power to be produced in certain cases
> because of alcohols' higher octane rating, and also the alcohol fuelled
> engines can be run very rich which allows the alcohol to act as a
> cooling medium.
That's really no different than feeding a gasoline engine a lot of water
injection (ADI) to slow the combustion rate and control inlet
temperatures and detonation. The Reno air racers have probably taken ADI
further than just about any other motors****t- they run Rolls-Royce
Merlins at over 140 inches of manifold pressure (the race teams and
engine builders won't publish the actual number) with NO intercooling-
just ADI. Years ago, one of the Reno air race teams attempted to set up
and run a Wright R-3350 on alcohol because of all the assumptions you
just mentioned. It never worked, the engine always made more power and
was more reliable on avgas with ADI. Later, the Pond Racer was designed
with alcohol in mind, and would *probably* have worked except that it
didn't have adequate fuel capacity for the full race length, plus pace
laps and cool-down. Switching it over to avgas resulted in perpetual
overheating because the cooling systems were inadequate for the higher
power density (among a lot of other problems that aircraft had that were
unrelated to the fuel, not the least of which was trying to use
automotive engines in a high-stress aircraft application).
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