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Ignition Timing varies although it is locked

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I'm currently having trouble tuning my SR20 properly. The engine was built by a renowned engine builder in my area.

However as I was setting up my ECU (a old Sport 1000 but brand new, box sealed) I ran into problems setting the base timing. I locked it at 15° which I have at idle, but if I increase rpm the timing swings to roughly 30° and stays, not just a short blip. As if I wouldn't habe activated the lock function.

I restarted the ECU several times and installed a new cam sensor, but no change.

Anyone experienced something similar once?

What happens if you change the ignition table to have 15° in every cell?

Reversed polarity on crank sensor can have that effect if it is reluctor.

I will second dynodom's response. Sounds like reverse polarity on a reluctor type sensor.

If you are using the stock CAS with the Optical sensor, it's to be configured the same as a hall effect.

I would try what David said and also make sure that there is no ignition correction applied (idle, IAT, warmup...)

EDIT : Make sure that when log your final timing value (or whatever it is called in the software for this ECU), that it reflect the locked angle.

Haltech ECU's only use the low-res CAS windows for triggering (the 4 slots on the inner ring). If your SR20 is a COP model then those 4 slots on the CAS disc will have 4 different widths. If its a distributor engine then usually 3 of the slots are the same width and 1 is wider than the rest. In most Nissan CAS's the rising edge of the varying width slots is evenly spaced, the falling edge is not.

If your software allows you to change the trigger edge I would try that just to eliminate the potentially variable edge spacing as the cause. I dont know how that ecu syncs/homes/resets so it may not even run with the edge reversed but it is worth a try. If there is no trigger edge setting in the software then pull the disc out and flip it upside down. I have come across a few Nissans now that had the disc fitted upside down, still ran with the factory ecu but not with ours.

I just resolved mine with that issue timing not staying still. This is what I found. I disconnected the injectors and using a plane Jane timing light, the timing locked at 20° in tuner studio. I cranked the engine and checked the timing and found it off quite a lot. I changed my off set from 137° to 100°, rechecked to see where timing was. Timing was now moving closer to TDC, I kept changing the number to get the mark at TDC, that number was 113°. Connected injectors and started the engine timing mark now was solid and not moving around but was off around 5°, I add more to the 113° until the mark was at TDC running. The final number was 118.5°. The timing mark did not move. This worked for me. The first time I did it was with a setback timing light which had a broken knob on it, I thought I had the knob set to zero, that was not the case. Going back to the beginning proved that and also resolved the problem. Good luck.

Oh one other possible cause I forgot to mention in my last post- most people know this already but just in case: Dont use the "timing loop" at the back of the engine for connecting the timing light, many timing lights will trigger off the wrong side of the dwell when you do this and show incorrect timing with significant drift. Always best to remove #1 coil and fit an HT lead between the coil and plug and connect your timing light to that.

Hi Guys,

Really sorry for the late response I was sick and couldn't check.

Thank you very much for all the suggestions! I'm a bit overwhelmed actually :-)

So setting all the tables to 15° didnt change anything.

The problem solver was actually really hooking the timing light up to a seperate timing cable and hooking it up to the coil. Rookie mistake on my end i guess but I'm really happy I found the mistake.

Would have been weird if the locked timing didnt work cause that what the function is for.

Thank you very much guys! Especially @ Adam

Keep on tuning folks

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