Features

Theory of Operation

The Ford - Ignition Start Control (ISC) will prevent start up backfire during alternate fuel operation. The controller delays the ignition until the Ford OEM computer synchronizes with the cam sensor and no longer triggers the ignition coils in pairs.

The Ford OEM computer uses the crank and cam sensor signals to drive the ignition coils. The cam sensor generates a trigger every two engine-revolutions to determine which cylinders will be under compression versus exhaust. Under normal running conditions, one coil will spark while it is in a compression cycle. During the first two engine revolutions, the OEM computer will trigger two coils simultaneously before the cam sensor signal is detected. One of these coils will ignite in a cylinder in a compression cycle. The other coil will spark in a cylinder in an exhaust cycle, which is called a waste spark. On gaseous fuel conversions, the intake manifold and the exhaust cylinder may contain a combustible air/fuel ratio during cranking. A waste spark in the exhaust cylinder during cranking will ignite the fuel in the cylinder, and generate an intake backfire through the open intake valve. This waste spark is prevented by the Dual Curve ISC controlling the spark until the cam and crank sensor are synchronized and the OEM computer only fires one coil at a time.

A slight increase in crank duration may be noticed while the Dual Curve ISC controls the ignition firing. However, this delay is shorter and more reliable than other backfire methods such as EGR solenoids, which are no longer needed when using the Dual Curve ISC.