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Re: [T3] ethanol, more power


On 22 Apr 2002, at 23:32, Jeff Palmer wrote:

> If I recall the 'regular' gas that includes ethanol is 89  and regular
> without ethanol is 87 octane?  I always thought ethanol added power too.

You can vary the blend to get whatever octane you want with either alcohol 
additive. Different gas brands will also do this differently. You will also find 
different practices in parts of the country.

Alcohol DOES provide some degree of anti-knock protection, but I assume 
that this is taken into account in the octane rating on the pump. 

Note also that pump gas is sold in different parts of the world using different 
Octane standards. In the US I only see it sold by (RON + MON)/2, but the 
requirements on the filler flap of our cars specifies only one of these. I can 
never remember which it is, however. From this I assume that this is the way 
gas was sold in Germany at that time. Is it still? (Was it ever?)

I guess I really don't know how the power of an engine will be affected by 
gasohol since a change in viscosity will also change the amount of fluid that 
is delivered, but alcohol and gasoline seem to me to have pretty similar 
viscosities and so a 10% addition of alcohol should not make much 
difference in the overall viscosity.

The energy content of alcohol is, however, still somewhat less than that of 
gasoline. The difference is not large, it's maybe 80-90% of gasoline, but it is 
known. Still, a 20% energy reduction in 10% of the mix is only a -2% 
change, and most people won't ever notice that.

-
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054
USA

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