Siemens VDO has developed an auxiliary engine control unit claimed to enable the cost-efficient conversion of gasoline engines to bi-fuel operation with natural gas.

Siemens VDO uses the existing gasoline engine control unit, adapting “classic” functions such as injection and ignition to natural gas operation and supplementing them with functions for onboard diagnostics.

An auxiliary control unit for natural gas operation has been added, which takes over the fuel switching strategy, signal detection, of additional sensors, control of actuators such as natural gas injection or cut-off valves, as well as the natural gas component diagnostics. Depending on the desired fuel, the auxiliary engine control unit forwards the injection signals calculated by the gasoline engine control unit to the corresponding natural gas or gasoline injection valve on a one-to-one basis.m