If the combustion chamber is hotter you need a colder plug to keep the porcelain on the plug at a temperature where it self cleans without overheating
Regards
pat pprimmer@acay.com.au
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You said that LPG burns hotter than gasoline. My gut reaction is that this is incorrect, but I am unsure of the actual result. As you get more complex hydrocarbons, I believe you get higher flame temperatures. Thus if this thinking is correct, the gasoline will have a greater combustion chamber temperature. Where this might be incorect, is if the propane, in its vapor state, may mix with air better than the gasoline in its liquid state. Thus the fuel/air mixture with LPG may burn better. However I have had one experience with a gasoline to LPG conversion, and I thought you took a horsepower reduction because of the lower BTU value of the propane versus gasoline.
Does someone have a textbook website handy to answer these questions?
Now if you asked me the diference between propane and natural gas, I could give you a confident answer immediately.
If you visit the link below, most of your questions regarding propane and gasoline temperatures, etc. will be answered.
As you will see, the peak flame temperature of propane versus gasoline is not significant. A properly selected spark plug for a gasoline fueled engine should be fine for propane as well.
One of the greatest attributes of LPG is it's clean burning.
The combustion chambers are always very clean and crankcase oil contamination is generally very low.
This leads to another interesting question about lube oil specs that may not have to meet certain requirements that gasolene imposes on oil.
Agreed that plug heat ange would be very little different than gas since it is mostly a matter of heat dissapation and little to do with deposits from LPG as both fuel have no great difference in BTU content for the average engine use.
The problem is that exhaust gases temperature is consistently higher with LPG than with Gasoline(this have been reported for several sources, I think Franzh could help me on this). Whether the reason for this is only incorrect ignition time advance or the way fuel is burned that’s what I will find out soon. But meanwhile I just want to make sure the engine runs cooler.
The Jennings link details a visual clue of excessive advance. Something similar appears in Kevin Cameron's performance manual. It's not insulator color.
