Spark plug heat range requirements, preignition limits, and ignition voltage requirements were investigated in several liquefied petroleum gas (LPG) fueled engines. These tests show that ignition voltage requirements both for cold starting and for running are considerably higher than with gasoline. It is also shown that very cold running spark plugs are both undesirable and unnecessary with LPG fuels.
Spark plug design can be utilized to reduce voltage requirements and to improve the overall performance of these engines. Projected core nose type spark plugs may offer additional performance benefits in LPG tractor engines.
