Link ECU handling methods

[Anthony Parle]

Couple of questions in relation to the general Link ECU methodology,

I have a engine with 12 tooth Crank sensor and 1 Cam, It has a timing belt.  Does the Link ECU take TDC from the Cam Sensor every time or the Crank?

When we talk about a cycle we are talking 720 degree (Being 2 rotations of the crankshaft)?

If a injector has reached the limit of its duty cycle does it still open and close or does it just stay open?

Thank

[Scott]

Hi Anthony,

If the engine is a 4 stroke engine then the ECU will see 24 teeth on the crank and 1 tooth on the cam in a complete engine cycle (720 crankshaft degrees of rotation). When setting the base-timing the ECU is configured to know the relationship between the crank teeth, the cam tooth, and TDC for cylinder 1. 

If an injector drive is doing 100% duty cycle it will actually momentarily switch off between pulses, on an oscilloscope you would see this. However it is very likely the switch off time would be less than the time required for the injector to close, so fuel flow would not stop.

Scott

[Anthony Parle]

Hi Scott,

Okay so to ask in a different way,

Does the stretching of the Cam belt throw out the timing of the ignition because we firer off the Cam sensor?

or is it that we fire off the crank sensor? 

[Scott]

Stretching of the cambelt would change the relationship between the crank and cam pattern. Depending on how bad this is the ECU may incorrectly calculate the engine position or speed. This could lead to injection or ignition pulses occurring at the wrong time. Normally the 'Trig 1 Err Counter' would increment when this happens, and if looking at a log of the ignition dwell time you may see odd values.

When the ECU see's the cam tooth it then expects to see 24 crank teeth before it sees the cam tooth again. If it sees 23 or 25 teeth, or if the tooth moves far enough out of it's expected position the above symptoms could occur.

Scott.