Interesting Issue running wasted spark module on L8 ECU

[CossieFan]

Hi all,

My first post here so hopefully its a good one!

I was helping a mate convert his focus cosworth to a wasted spark configuration.

After modding the ECU we couldnt get it to start, checked all the obvious things like incorrect wiring on the mod etc. But the problem proved much deeper.

I cracked out the scope and discovered the aftermarket crank pulley was actually causing double detections when decoded by the ECU.

The crank pulley was an aluminium one that used grub style allen screws as a ferrous metal for the inductive pickup.

Replaced the pulley with a decent one that had a solid steel pickup wheel with teeth and it fired straight up.

I've attached a photo of the scope trace for anyone that has a similar problem. The blue trace is the inductive pickup and the yellow is what the ECU CPU saw. You can see a small blip in the middle of the blue trace and a double detection on the yellow.

[Miniliteman]

Good find! TEK scope?

[CossieFan]

Yeah TEK TDS 2014! Oldie but reliable

I'll try and get a scope trace of the new crank pulley!

[katana]

The crank pulley was an aluminium one that used grub style allen screws as a ferrous metal for the inductive pickup.

I wonder if the trigger pick-up is so sensitive that its seeing the Allen wrench recess in the grub screw as a gap - it appears like it on the scope!
I like using mini earth magnets but no one tells you about getting the polarity correct - re did some wiring 3 times before I twigged and flipped the magnet around DOH!

[stevieturbo]

I wonder if the trigger pick-up is so sensitive that its seeing the Allen wrench recess in the grub screw as a gap - it appears like it on the scope!
I like using mini earth magnets but no one tells you about getting the polarity correct - re did some wiring 3 times before I twigged and flipped the magnet around DOH!

You would think the allen key recess would be too small...but it does almost look like that is what is happening. Or maybe sensor gap needs tightened up ( or grub screws moved out )

Was this pattern on all 4 teeth ? or just one ?

A little square headed grub screw might be more suitable ? or a regular bolt then trimmed off to suit.