Low Volatility Fuel Delivery Control during Cold Engine Starts

The intensity of a combustion flame ionization current signal (ionsense) can be used to monitor and control combustion in individual cylinders during a cold engine start. The rapid detection of poor or absence of combustion can be used to determine fuel delivery corrections that may prevent engine stalls. With the ionsense cold start control active, no start failures were recorded even when the initially (prior to ionsense correction) commanded fueling had failed to produce a combustible mixture. This new dimension in fuel control allows for leaner cold start calibrations that would still be robust against the possible use of low volatility gasoline. Consequently, when California Phase 2 fuel is used, cold start hydrocarbon emissions could be lowered without the risk of an engine stall if the appropriate fuel is replaced with a less volatile one.

A cold start fuel calibration that produced lower hydrocarbon (HC) emissions but was too lean for reliable engine starts using low volatility (high driveability index) fuel was tested with high driveability index fuel (DI = 1266) down to temperatures as low as - 12 °C. Successful engine starts even at these low temperatures were achieved by activating the ionsense cold start control algorithm.