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Timing advancing with rpm, VR sensors tried both polarity

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Hello, I just got a rusefi standalone ecu uaefi setup recently and am having issues with timing drift as I increase rpm. The car is a 92 honda accord with an h22a engine. It has a 24 tooth wheel for the trigger rpm signal in the distributor and another wheel that has 1 teeth for sync. With a fixed timing angle, I can adjust the offset to match the fixed angle of 15 degrees at idle but any change in rpm dramatically advances the timing.

I have tried both a rising edge, and falling edge input capture, and also tried changing the polarity of the vr sensor then retested both falling and rising edge again. It is a distributor setup with a single coil, testing the timing with the light connected to the #1 spark plug lead. I have a few years experience with tuning but this is my first time wiring in a standalone ecu so the trigger input are still new to me.

I also tried adjusting the vr sensor threshold table up and down +-1.5v with no change

The car idles smooth with the rising edge input capture but I could hear audible detonation while driving

I have a hondata s300 v3 that I tuned previously with this car and switching back to it the car runs perfectly again and timing does what it's supposed to.

Pretty stumped at this point and would love some help, especially anyone who has a successfully running obd1 Honda on uaefi using the built in VR conditioners

Attached is screenshots of a trigger capture log, screenshots of my trigger settings, VR threshold and also the wiring schematic showing how I wired everything. Also the whole tune file in case there's a setting I'm missing. Thanks in advance!

Attached Files

Does your software have an "ignition delay" parameter? This is a fixed time from when the ECU triggers the coil to spark, and when the spark actually occurs. You tune this value so the ignition timing doesn't change with an increase in RPM. Typically values are 20 - 50 uS (micro-seconds).

Another possibility -- if you are using a distributor that still has a mechanical advance built in, then the ignition might not happen with expected.

Unfortunately my ECU doesn't have a spark hardware latency setting although I don't think that would fix my issue. That usually advances the timing further whereas I need to retard the timing. I think my issue might be related to the vr conditioner on the board. There's a special vr conditioner made specifically for the Honda OBD1 and Toyota 3sgte that I guess is the only thing able to pickup the signal properly on the stock trigger system. Has anyone heard of this being required before?

Unfortunately my ECU doesn't have a spark hardware latency setting although I don't think that would fix my issue. That usually advances the timing further whereas I need to retard the timing. I think my issue might be related to the vr conditioner on the board. There's a special vr conditioner made specifically for the Honda OBD1 and Toyota 3sgte that I guess is the only thing able to pickup the signal properly on the stock trigger system. Has anyone heard of this being required before?

What does a real oscilloscope trace of the crank and cam signals look like? I can't believe there would be any special VR conditioner, unless they are using a current-loop type sensor. Then you would just need a resistor to convert the current to a voltage you could monitor.

Unfortunately I don't have an oscilloscope to test with, I tried using the built in trigger scope function in tuner studios but it wasn't working unfortunately. I'm not too well educated about how the vr sensors work to know whether it's a current loop type. I found a thread on rusEFI's forum talking about how the cam sync inside the distributor is snail shape and can cause issues. I attached a picture of that maybe that's the issue?

Attached Files
  • distributor_labeled_05e12ecf0d63ef8c6cc59b96359777196611da8f.jpg
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If you believe the triggering waveform is the issue, viewing it would be the next step in diagnosing whether it's the issue or not.

A 2 channel automotive Picoscope is around $150 US, and if you can spring for a 4 or more channel unit they come in handy.

Reading your description this sounds more like an issue with the spark edge to me. If that is inverted you will be sparking at the start of the dwell period rather than the end, this gives a large amount of spark advance with RPM as the fixed dwell time becomes a larger crank angle at higher RPM.

It could be as simple as just the spark edge setting wrong in the software or it may be a little more involved such as the ecu hardware is misconfigured for your ignition system - for example a coil driver in the ecu triggering an ignition system that also has a built-in driver. Older Honda distributors typically have the coil driver built-in to the distributor and it sparks on a rising edge - note this is the opposite to 99% of common ignition systems.

Adam has probably identified the problem. You could figure this out very quickly using an oscilloscope and your Hondata vs Rusefi operation looking at the igntion output signals. Perhaps you can find a local shop that has an oscilloscope and could do that testing for you.

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