[Homestead] Ethanol / Biofuel
don.bowen at earthlink.net
Sun Mar 8 14:53:52 EDT 2009
> Well, then they need to switch to high compression engines like the diesel
> engines. Ethanol is produces more MPGs if run in a high compression
Ethanol has a higher octane rating so can withstand much higher compression
ratios but not Diesel engine ratios. Higher compression ratios cannot make
up for the lower energy content and higher fuel volumes required.
Racers use alcohol because they can run much higher fuel volumes. These
high fuel volumes are used to cool the intake charge for greater charge
volume and to cool combustion chamber so much higher compression ratios can
be used, 11:1 or so where Diesels start around 18:1 and most are closer to
> HOWEVER, this whole love affair with ethanol and gasoline engines to me is
> just so much stupidity. We have diesel engines which run for 500,000 to a
> million miles with few if any problems. Biodiesel has very little loss in
> MPGs and you can produce biodiesel from the same source(s) as ethanol.
Diesels get longevity from several sources. One is the extra large bearing
needed and the necessary oil flows because of the extra power outputs. A
huge reason is the Diesel does not have the cylinder washing problem of a
gasoline spark ignition engine. When a piston moves to top dead center the
wals are coated with oil. As the piston moves back down the oil control
ring scrapes off but a small film necessary for top ting lubrication.
During the intake stroke the fuel air mixture contains a strong solvent that
washes the cylinder walls clean so there is less oil on the next up stroke.
There are several other reasons for Diesel longevity, one is that Diesels
were mostly used in areas where longevity was important such as farming and
transportation. Look what happened when GM tried to make a Diesel engine
that would last the life of the typical automobile.
> Those little VW Rabbit diesels got well over 40 mpg.
The so called Common Rail Diesels are used in many European cars but are not
allowed here. US laws are designed for the typical US driver who treats a
car as an appliance. The world is filled with all sorts of small Diesel
engines that get great mileage but the US consumer has not been convinced
they are worth it.
Don Bowen KI6DIU
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