[AT] Mixing High Octane gasoline and Diesel fuel

[Gene Dotson]

    Pre-ignition and detonation are 2 seperate conditions.
    Pre-ignition occurs when the fuel charge, under pressure at
the compression stroke, is ignited prior to the desired time in
relation to the ignition timing. Pre-ignition is commonly caused
by a leftover heat source in the combustion chamber. Common
causes are hot carbon particles and a sharp edge on the cylinder
head or top of the piston.
    Detonation, or pinging, is the condition where the sudden
expansion from the initional ignition causes enough heat and
pressure at a point away from the desired ignition point that it
starts a second flame front that then travels back to the
initial flame. These two flame fronts collide with terrific
force and is what you hear as pinging. Detonation is always a
secondary condition after initial ignition has occurred.
pre-ignition can cause the onset of detonation.
    Contrary to many beliefs, the mixture in a cylinder does not
explode. It burns rapidly with a controlled flame that will
continue to burn till the piston is near the bottom of the power
stroke, applying a steady push on the piston and not a sharp
hammer blow at the top of the stroke.

    Back to your original question, yes, I have mixed diesel
fuel in gasoline for tractors. Typically about half a gallon to
5 gallons of gasoline and I do believe it developed more power
and certainly did no harm.

                Gene



----- Original Message -----
From: "Dean VP" <deanvp at att.net>
To: "'Antique tractor email discussion group'"
<at at lists.antique-tractor.com>
Sent: Tuesday, April 12, 2005 9:50 PM
Subject: RE: [AT] Mixing High Octane gasoline and Diesel fuel


: Gene:
:
: Thanks for the tutorial.  I guess I got the facts mixed up or
was given
: incorrect data. If I have understood you properly, the bottom
line is that
: there is a possibility one could get more power using the
right mix of
: diesel fuel and 87 Octane gas in a low compression, long
stroke engine. Then
: whatever mix gets it down to the equivalent of 72 Octane
gasoline would be
: optimum?
:
: So then by implication, "ping" is caused by the fuel igniting
too quickly in
: a very high compression engine or too early when timed
incorrectly in a
: lower compression engine. Or both is possible I guess if the
octane is too
: low.
:
: Dean A. Van Peursem
: Snohomish, WA 98290
:
: I'm a walking storeroom of facts..... I've just lost the key
to the
: storeroom door
:
:
: www.deerelegacy.com
:
: http://members.cox.net/classicweb/email.htm
:
:
:
: -----Original Message-----
: From: at-bounces at lists.antique-tractor.com
: [mailto:at-bounces at lists.antique-tractor.com] On Behalf Of
Gene Dotson
: Sent: Tuesday, April 12, 2005 5:47 PM
: To: Antique tractor email discussion group
: Subject: Re: [AT] Mixing High Octane gasoline and Diesel fuel
:
:     Dean;
:     Actually your information is flawed. High octane gasoline
: burns slower than lower octane. The additives slow down the
burn
: rate so it can be used in a high compression engine. Any
engine
: will develope the maximum power on the lowest octane fuel that
: it can use without detonating. Diesel fuel will cause a spark
: ignition to detonate if the compression pressure is high
enough.
: Diesel fuel mixed with gasoline would burn faster to make up
for
: the slower burn rate of the higher octane. Diesel fuel with a
: high cetane rating burns faster than fuel with a low cetane
: rating. Diesel fuel contains more BTU's per gallon than
: gasoline, so it makes sense that the faster burn rate of
diesel
: and higher BTU's would offset the slower burning high octane
: gasoline and result in more power
:     Or you can just use the cheapest and lowest octane in your
: tractors and still have more power.
:     Using a higher octane than required in low compression
: engines results in a burn rate that is often so slow that the
: fire is still burning when the exhaust valve opens and will
burn
: out the valve and seat.
:     You Never, never, NEVER gain power by using a higher
octane
: fuel than the engine requires.
:
:                     Gene
: