Date: Tue, 15 Sep 1998 14:01:50 -0700
Reply-To: t bill <tbil@YAHOO.COM>
Sender: Vanagon Mailing List <Vanagon@vanagon.com>
From: t bill <tbil@YAHOO.COM>
Subject: Re: Vanagon fuel requirement
Content-Type: text/plain; charset=us-ascii
>
> When the fuel mixture explodes all hell brakes loose between the
piston and
> the cylinder head.
True, that's why we have octane: so we can talk about burn rates
instead of explosions. If it explodes, you have a knock. That's what
a knock is.
Pressure waves expand quickly and resonate in different
> directions. If you graph this process then you have a curve which
goes up
> steeply and then declines with a couple of bumps (the different cross
> waves). If these cross waves become stronger, then you have what is
called
> knocking.
Knocking is not just stronger waves. It is a violent explosion. Kind
of like burning dynamite (it burns somewhat like a flare) and
exploding it.
It rattles the engine, produces more wear and makes the whole
> process less efficient. The higher the compression in gasoline
engines, the
> more pronounced it can be. That's why higher octane fuels have
inhibitors to
> actually slow down the combustion process somewhat and therefore be
more
> gentle on the engine.
The fuel quality need also depends on your load and
> driving habits. The more you go full load the higher the need for more
> Octane because the pressures in the combustion chambers increase.
>
> The detergents are supposed to prevent carbon deposits in the
engine. This
> is particularly important for fuel injected engines since carbon
deposits
> can change the spray pattern and clog up injectors.
Carbon does not clog the injectors in a fuel injected car, other
things in the gas clog injectors.
This is a major problem
> for people who drive mainly short distances since uneven
temperatures and a
> richer mixture cause more condensation.
Condensation of what? Water? This is not a problem as to carbon or
knocking.
>
> Some companies add alcohol. Mohawk advertises "mother nature's fuel"
in
> Canada because they add ethanol. In Brazil there is a whole network of
> alcohol propelled cars. Some racing cars like CART series use
alcohol for
> mainly safety reasons. Alcohol is water soluble (it actually
attracts water)
> and therefore fires can also be extinguished with water. Alcohol burns
> cleaner but does not quite have the energy of gasoline.
Actually, quite a bit less energy.
>
> My rule of thumb:
> When I am doing daily driving with little load I use regular from a
company
> using detergents. I also make sure that the engine gets a good long
run once
> in a while. When I load up the car or go into the mountains or off
road,
Actually, if going up in the mountains mean gaining altitude, you can
down grade your octane. The reason is that with the thinner air (at
10,000 ft you are above 70% of the atmosphere) your compression is a
lot less. You could run 85 octane with no problem.
TBill
***If everything seems to be going well, you have overlooked
something.***
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