[Hich]

Hi,

I am trying to setup my 1 cyl. 200ccm scooter engine with a Speeduino board (Blitzbox) and I am wondering about the correct trigger setting. The engine has on VR pickup coil at TDC on the crankshaft. No CAM sensor. So I get 1 signal per revolution.
The Blitzbox board (https://github.com/oelprinz-org/Blitzbo ... ree/master has a Max 9926 and VR+ is connected to the pickup coil, VR- to GND.
I have set the trigger decoder to "Generic Distributor" but that does not seem to do the job. When cranking RPM in Tunerstudio goes up to (unrealistic) values of 2000 and when the engine stops the displayed RPM slowly (within 10-15s) goes down to 0 RPM.
What would be the appropriate trigger decoder to use here?
The picture shows the trigger signal (blue curve) as measured on VR+. This occurs once every revolution.

Thanks a lot Karsten

[PSIG]

Thank you, Karsten. Please post your tune, and a log of cranking.

The o-scope image is odd, that the MAX inverts the incoming signal on the output. I assume that is what the yellow line is?

Basic Distributor expects 1 tooth signal per-cylinder, per-cycle. You have two per-cycle. Can you 'scope with Trigger Settings at Missing Tooth, Crank Speed, 2 teeth, 1 missing?

Typically, the Trigger Edge for VR with a MAX conditioner is Rising, to capture the VR falling edge, but yours isn't like that, or you probed somewhere else or reversed the probes. Please test with New Ignition Mode ON and OFF.

I am curious to see this run, and to get some timing accuracy info from logs, especially transition (accelerations).

[Hich]

Hi,
please find attached the current tune and a tooth log. Not sure if this is the correct log you need. Only in the first few seconds the starter is cranking the engine.
The yellow line is the ignition output from the ECU.
Later today, I can try to tap the MAX9926 output signal and put this on the scope.

Thanks a lot, Karsten

[Hich]

Ok, I have tapped the MAX pins directly and I think there are two problems:
On the scope is blue - VR+ as input to MAX9926 and yellow the output (pin 4).

1.Tunerstudio shows about 2000rpm while it is 1000rpm, so something is definitly wrong defined.

V+ (blue), Max9926 output (yellow) @ 1000rpm
20240805_Max9926_In_out_1.JPEG (1.19 MiB) Viewed 648 times

close up,
20240805_Max9926_In_out_2.JPEG (1.03 MiB) Viewed 648 times

2. When cranking stops there is no real signal (besides noise) on the VR+ pin, but there is still output from Max9926

with ignition coil connected
20240805_Max9926_cranking_with_coil.JPEG (932.94 KiB) Viewed 648 times

If I disconnect the ignition coil, the signal looks clean:

ignition coil disconnected
20240805_Max9926_cranking_no_coil.JPEG (1.18 MiB) Viewed 648 times

So obviously the Max9926 is catching some noise due to the induction of the ignition coil. The pickup is really close to the ignition coil, so maybe the noise is coming this way. Next I will try with shielded cables.

Would be great if you have any clue for 1.

Best regards Karsten

[jonbill]

you're using basic distributor trigger pattern, which for a single cylinder engine expects 1 trigger signal every 720.
But you actually have a single crank signal every 360. Hence, 2x speed.

[Hich]

Yes, I understand, but what would be the appropriate decoder to use? None of the other seem to fit as well?
Thanks Karstdn

[digmorepaka]

Yes, I understand, but what would be the appropriate decoder to use? None of the other seem to fit as well?
Thanks Karstdn

I would configure it as two cylinder(so it expects two pulses/cycle or 1/crank rev) with two injectors(so your required fuel stays the same).

[Hich]

Ok, nice idea. I'll try that.
Probably I can just set it to 2-stroke alternatively.

[Hich]

Yes, I understand, but what would be the appropriate decoder to use? None of the other seem to fit as well?
Thanks Karstdn

I would configure it as two cylinder(so it expects two pulses/cycle or 1/crank rev) with two injectors(so your required fuel stays the same).

The RPM reading looks good now, just wondering about the fuel (so far I did not think too much about more than one cylinder). Is the 'pulse width' defined per injector or is that a 'sum of all'?

Best regards Karsten

[digmorepaka]

Yes, I understand, but what would be the appropriate decoder to use? None of the other seem to fit as well?
Thanks Karstdn

I would configure it as two cylinder(so it expects two pulses/cycle or 1/crank rev) with two injectors(so your required fuel stays the same).

The RPM reading looks good now, just wondering about the fuel (so far I did not think too much about more than one cylinder). Is the 'pulse width' defined per injector or is that a 'sum of all'?

Best regards Karsten

To get required fuel calculator to behave with this workaround you need to set 2x displacement and two cylinders, retain the same flow rate. I don't remember how the fields in the engine constants dialog are divided but one of them *should* be total and one *should* be per channel per squirt, don't quote me on that I don't exactly remember how it is.