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Timing Drift w/ Timing Locked

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I'm having trouble figuring this one out. I have a Syvecs S6 PnP. When I went to confirm the ignition timing on my 2jzgte (non-vvti motor). Here are the the steps I've taken to test this:- Enabled the test mode to lock my timing at 10°. - Verified the timing remains at 10° on the Syvecs with logs and watched with my timing light, up to 1500 rpm. All good there. - I rev the motor up to ~4500 rpm and I notice the timing drift to the 5° mark with my timing light. - I reviewed the logs and confirmed the Syvecs is still showing 10°, which is what I would expect. - I added the camRaw value to monitor and log. That value was solid at 334° the entire duration of the test. - The sync log shows me that my sync is good and the VR sensors are wired correctly, based on the shape of signal wave in the log.- Trigger is set to falling edge and no filters. I tried enabling filters and no difference. Has anyone come across this before? Jason

sounds like you may have a incorrect ignition delay set up. (there is a delay from when the ecu requests spark untill it actually fires) this delay is dependent on the coil. around 20-40 uSec should get you close. if you have a scoope you can messure it.

I'm not familiar with Syvecs, but agree this sounds like it could be due to the delays inherent in the ignition system. From what I've seen, there may also be additional delays inherent with VR sensors that may not be present with hall-effect or optical sensors. The timing light could also be a factor, make sure it's not doing any sort of dialback. If you're not already using a spark plug wire extension (between the coil and the spark plug) to check timing, that's a good idea as well.

This is one more reason you should tune your vehicle's ignition map on a dyno; other people's timing maps might have been tuned without using a timing light to verify all these settings.

Thanks for the feedback, fellas.

I am using a spark plug wire extension, so all good there. Let me check the settings on my timing light. First time using this one and it has a few features I didn't even think to look into.

It's possible that the polarity of your trigger input may be wrong. This will result in the timing drifting relative to engine rpm. You can use the syvecs scope feature to visualise the cam and crank waveforms to confirm what is going on.

Hi Andre,

Thanks for the response! I actually learned to check that from one of your videos. I verified the wiring is correct via the Syvecs scope. I was hoping that was the issue because that's an easy fix, but no luck.

The sync log shows me that my sync is good and the VR sensors are wired correctly, based on the shape of signal wave in the log.

In my experience often with evenly spaced trigger wheels (with no missing teeth), it is difficult to tell from a scope trace if the sensor polarity is correct as the waveform is almost symmetrical, there is no clear way to tell which zero-crossing is a tooth edge and which is a tooth centre. I have often found what I thought was the most vertical zero crossing was actually the wrong edge.

So I think it would be worth trying the opposite polarity just to rule that out. 5deg drift sounds too much to be ign delay to me. If your ecu allows you to select the trigger edge then just try changing that.

Thanks for the advice. I have tried swapping the trigger side and still no luck.

"sounds like you may have a incorrect ignition delay set up. (there is a delay from when the ecu requests spark untill it actually fires) this delay is dependent on the coil. around 20-40 uSec should get you close. if you have a scoope you can messure it."

Is anyone aware of this setting within a Syvecs S6?

Can anyone advise whether or not it is safe for me to move on and continue the tuning process with this "drift" condition present?

For clarification, I've tried everything I'm aware of - reversed polarity of sensor wires (car wouldn't even start), changed trigger from falling to rising on both sensors in multiple scenarios (one rising, one falling, both falling, both rising, etc...didn't resolve the condition) and tried a new, non-dial back timing light.

I have confirmed the static timing value is correct. I.E. - at idle, reading is accurate. At 4000rpm, reading is accurate - etc...The "drift" is only during transition when the motor rpm is increasing. I can post a screenshot of some logs if that would help anyone provide some feedback.

Just to confirm your last post, you're saying that when you hold the engine speed steady, you see the correct 10 degrees BTDC of timing, you only see it drift when the engine speed is changing?

How quickly are you revving the engine up from idle to 4000?

It happens with a steady rev up from 1500 to 4000 and is worse if i rev it faster. It is always correct once settled.