A New Platinum Tipped Spark Plug Extends the Lean Misfire Limit and Useful Life

Higher compression ratio and lower air-fuel ratio tend to raise the required break down voltage. Various types of electrode configurations were examined. It was found that a very thin platinum plate attached to each elect-rode was effective in reducing the electrode wear. This newly developed platinum tipped spark plug uses a small sized center electrode and an enlarged initial spark gap. The lean misfire limit and the torque fluctuation at partial load are improved with the platinum tipped spark plug. After a durability test, the break down voltage became lower due to the grained platinum surface. The spark gap was almost unchanged during an 80 thousand kilometer durability test run.