Diesel is not measured by "Octane", it is measured by "Cetane". The gas powered engine experienced the 'ping' because of the contamination of diesel which lowered the "Octane" value. That's why some say when your car starts 'pinging' to go from 87 octane to 93 octane to stop the 'ping'.
When gasoline is compressed, the spark detonates the fuel creating combustion. Diesel needs to be much more compressed to get detonation to have combustion.
In a gas engine...what creates this 'ping' is two flame fronts colliding on the compression stroke causing the metallic 'ping' sound. If we could slow down the compression stroke to milliseconds...I'll try to explain what happens. After the fuel charge enters the combustion chamber and both valves are closed. The piston moves up to complete the compression stroke. As the fuel becomes compressed it may detonate before the spark plug arcs to ignite the fuel. The pre-detonation is usually caused by a hot spot on the piston surface i.e. carbon specks, burr of steel, etc. These are usually glowing red hot after a short time from starting the motot.
The hot spot ignites the fuel and as this flame front moves accross the combustion chamber while the piston is completing it's compression stroke. When the piston has reached the length of its stroke the spark plug ignites the fue also. Now you have two flame fronts moving across the combustion chamber towards each other and when they collide is where you get the 'pinging' sound from.
For years many thought this sound came from metal parts 'clanging' angainst each other. Waukesha Engine Division in Waukesha, WI devloped a cylinder with a quartz window so they could view the combustion process. Using high speed photography they were able to see the two flame fronts colliding.
By adding diesel to gasoline you can not get "high pressure spikes and concentrated heat" because diesel needs to be really compressed to obtain that type of detonation. The compression ratio of a gas engine is not anywhere close to the compression ratio of a diesel engine. Therefore, the diesel contamination in gasoline will just foul the plug and soot up the catalytic converter.
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Today's Featured Article - Third Brush Generators - by Chris Pratt. While I love straightening sheet metal, cleaning, and painting old tractors, I use every excuse to avoid working on the on the electrics. I find the whole process sheer mystery. I have picked up and attempted to read every auto and farm electrics book with no improvement in the situation. They all seem to start with a chapter entitled "Theory of Electricity". After a few paragraphs I usually close the book and go back to banging out dents. A good friend and I were recently discussing our tractor electrical systems when he stated "I figure it all comes back to applying Ohms Law". At this point
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