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Single cylinder injection timing trouble


miked

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Hi team! Ive install an old LEM G3 into my single cylinder tu250cc for a laugh.

This is my first jump into aftermarket ecus.

I am having trouble getting it to inject at the right time.

Got ignition nailed at 0⁰ for reference and solid signals all round but for some reason I cant get  injection on the right cycle. I have tried all sorts of configurations but no luck.

I am probably missing something here but I cant see it.

Currently configured to 2 piston (cant select 1)

Any ideas would be greatly appreciate.

 

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There is 720deg crank rotation in the 4 stroke otto cycle, but you only have a trigger capable of determining position is a 360deg cycle.  Without some unique event that occurs only once every 720 deg (usually a tooth on the cam), the ECU has no way of knowing if the TDC it receives every revolution is for compression stroke or exhaust stroke.    

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This is correct. However I have it to a point where ignition is firing at/slightly before tdc every compression cycle. If it knows when ignition is required, shouldnt it also know when to inject based on the engine configuration? 

Is there no way to achieve injection on the intake without a sync pulse of some kind?

 

 

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The injection should remain relevant to the same phase that the ignition is following.  The ecu will still run sequential and direct spark without a sync (cam), just you will only have a 50/50 chance of it syncing on the correct phase during start-up - depending on where the crank stopped last time it was running etc.  The other 50% of the time it will start sparking on the wrong stroke so will never start.   

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I would have thought so to. Ignition is set to direct spark and fires at the right time every 720⁰ consistently it will start and run on brake clean no trouble. 

Im going to try setting spark to distributor and check each injector output to see if one of the others I am not currently using is pulsing at the correct time. 

Thank you for your assistance.

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Here are a few captures with different configurations.

BLUE - Crank sensor

GREEN - Injector drive 1

RED - Coil signal

Waveform1

Configuration: Piston, 2 cyl, Firing 1,2

Trigger: Multitooth/Missing 12-1

Injection: Multipoint/GroupIgnition: Distributor

Waveform 2 

Same as one but 1/2 engine cycle

Waveform 3

Same as one but 2 stroke, 1 engine cycle

 

Fuel and ignition tables have not been looked at. Ignition is locked at 0 degrees.

waveform 1.png

waveform 2.png

waveform 3 .png

Sorry, just realised there is no identifying each waveform.

waveform 1.png

waveform 2.png

waveform 3 .png

FUEL AND IGNITION

fuel table.png

ignition table.png

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sync pulse is not too critical - just dont want it occurring at the same time the missing teeth on the crank are going past the crank sensor.  

Note you can still run sequential injection with no cam sensor just like you are using direct spark ignition above - but it will only sync on the correct phase by pure luck.  approx 50% of start attempts it will sync on correct phase and start.  The other 50% it will sync on the wrong phase and crank forever with no start.   

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No, With any ecu you will need a trigger system with some unique event that only occurs once every 720deg.  Typically something on the cam. 

G4X can use a MAP sensor connected to a single intake port to detect when the valve opens instead of a cam sensor.  

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  • 4 weeks later...

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