Biofuel Engine Technology

Glow plugs and control

Extending glow periods

Many vehicles have an engine mounted temperature sensor that is connected to the glow plug control and is used to determine the amount of time the glow plugs are activated before (pre glow) and after (post glow) engine start.

The signal from the engine sensor can be modified by adding a resistor which gives extended pre and pst glow periods.  Adding a temperature activated switch to the coolant circuit allows the resistance to be switched out of circuit once the engine warms to reduce battery drain for warm restarting when the extra glow period is not required.

60°C Temperature switch for mounting
in 16mm coolant hose

For some vehicles glow plug control relays which extended post glow were released to improve combustion and emissions after starting.  Some of these relays use a engine temperature sensor to determine glow periods.  The signal from the sensor can be modified or interupted to extend the pre and post glow periods.  Extended after glow relays can be wired in to replace most other glow plug control relays.

Extended afterglow relay to fit some VW, Audi
and Ford vehicles can also replace other relays

Extended glow plugs

When cold starting is degraded, due to a change in fuel, improvements can be made by fitting glow plugs that extend 2mm further into the combustion chamber.

For some vehilces glow plugs from a different engine will offer the desired protrusion for other vehicles standard glow plugs can be modified to extend further into the chamber.