miked Posted October 18, 2022 Report Share Posted October 18, 2022 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. Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 18, 2022 Report Share Posted October 18, 2022 How are you measuring injector timing? What trigger mode and sync mode are you using? Quote Link to comment Share on other sites More sharing options...
miked Posted October 18, 2022 Author Report Share Posted October 18, 2022 Im using an oscilliscope to record crank signal, ignition, and injection at the same time. Using the multi/missing tooth 12-1 with no sync, crank only. Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 19, 2022 Report Share Posted October 19, 2022 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. Quote Link to comment Share on other sites More sharing options...
miked Posted October 19, 2022 Author Report Share Posted October 19, 2022 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? Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 19, 2022 Report Share Posted October 19, 2022 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. Quote Link to comment Share on other sites More sharing options...
miked Posted October 19, 2022 Author Report Share Posted October 19, 2022 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. Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 19, 2022 Report Share Posted October 19, 2022 Can you attach a pic of your scope capture and your map. Quote Link to comment Share on other sites More sharing options...
miked Posted October 20, 2022 Author Report Share Posted October 20, 2022 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. Sorry, just realised there is no identifying each waveform. FUEL AND IGNITION Quote Link to comment Share on other sites More sharing options...
miked Posted October 20, 2022 Author Report Share Posted October 20, 2022 Here is one with Direct Spark ignition configuration Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 20, 2022 Report Share Posted October 20, 2022 If you want the fuel injection event phased to the engine cycle the injection mode will need to be sequential. Multipoint group just fires the injector drives alternatively in two out of phase groups. Quote Link to comment Share on other sites More sharing options...
miked Posted October 20, 2022 Author Report Share Posted October 20, 2022 Ok, looks like ill have to add a cam sync. What position in the cam rotation would recommend? Or does it not matter? It is a single cam 2v Thanks again for your help. Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 21, 2022 Report Share Posted October 21, 2022 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. Quote Link to comment Share on other sites More sharing options...
miked Posted October 21, 2022 Author Report Share Posted October 21, 2022 Ok, Ill keep trying. Would it be worth upgrading to the g4 firmware? As in would it make all this easier? Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 21, 2022 Report Share Posted October 21, 2022 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. Quote Link to comment Share on other sites More sharing options...
stewartb Posted November 16, 2022 Report Share Posted November 16, 2022 miked, why not inject with the spark timing? Intake is closed then, fuel gets heated and vapourised ready to be pushed through the port when valve opens??? Quote Link to comment Share on other sites More sharing options...
miked Posted November 16, 2022 Author Report Share Posted November 16, 2022 Hi Stewart! I have it sorted and running now. I ended up scoping the stock ecu and finding a configuration that was close and worked from there. Fired right up. Thanks for your idea though. Quote Link to comment Share on other sites More sharing options...
stewartb Posted November 18, 2022 Report Share Posted November 18, 2022 Wow! So what did you do? Did you use the spike after you fire the coil or at the long gap? Interesting stuff. Quote Link to comment Share on other sites More sharing options...
miked Posted November 18, 2022 Author Report Share Posted November 18, 2022 I actually had it right with 2 piston configuration injecting 1/2 cycle and direct spark. Only issue is it only starts 50% of the time as with no cam sync it doesnt know which phase its in. But it doesnt bother me. Quote Link to comment Share on other sites More sharing options...
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