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cause of timing drift

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I'm wondering what's the cause of that when using hall effect sensors.

When using VR sensors, switched polarity can be one cause, but what about hall effect sensors?

I've seen this happen now on two different engines (not on stock hall sensors though) with Haltech's Platinum series ECUs.

Changing the trigger edge and using the variable trigger angle map sure helped cure the issue, but I'd really like to know the cause.

I have to say, that in both cases I didn't have an oscilloscope or any tool like that handy at the time.

I ve heard of this mentioned alot lately with haltechs, it been big topic on social media at the moment. I haven't tried yet my self but according to other tuners its not the crank triggering which they had verified with an oscilloscope, it must be in the code written in the ecu. Sad because I really liked the haltechs until I heard all of this.

All reluctor sensors with Haltech ECU that I saw caused timing drift. The variable trigger angle solves the problem. My guess is that variable trigger angle is the same tuning parameter as Link G4+ and Vi-Pec trigger delay. So the problem not with Haltech but with reluctor sensors and timing drift is an ordinary thing.

BTW, changing rising edge to falling or sensor polarity does completely nothing with timing drift, is even doesn`t make drift less

both engines were equipped with hall effect sensors, not reluctor.

but anyways, we all know it occurs and how to fix it, but not knowing were it's coming from drives me nuts :)

Hall sensors generally have a faster response on either rising or falling so it gives the ecu more accuracy if it is set to trigger of the faster edge. This is normally given in the data sheets for the sensor but is not very easy to find on OEM items.

I think the drift you maybe seeing is related to ignition delay. It is usually a parameter you can enter into the ECU to compensate for the time delay of the actual spark event after the command to fire. (the type of igniter module and coils used will have an impact on the value needed to compensate for this delay. 50 - 80 ms seems to work on most of the setups ive seen.

Timing drift as we would normally refer to it is an aspect of a reluctor sensor where the polarity has been set incorrectly, or alternatively the triggering edge if this is selectable. It's quite common and will result in a very large timing drift - Perhaps 20-30 degrees or more.

Even with everything set up correctly we will still see the timing shift slightly as the rpm increases but this time only by a few degrees. This is the result of the ignition delay which is the time it takes from the ECU outputting an ignition event and the actual spark occurring. There is an inherent delay in the electronics, no matter how small. Although the situation is a little different you could almost liken it to injector latency.

The delay or latency should remain consistent, but the effect it has over the ignition timing will be dependent on engine speed. For example if the delay is 50 micro seconds, this is the equivalent of 0.3 crankshaft degrees at an engine speed of 1000 rpm. At 8000 rpm though the same delay would equate to 2.4 degrees. If this isn't accounted for the timing would appear to drift by about 2 degrees as the engine was revved from 1000-8000 rpm.

Andre, is the trigger delay perfectly linear with rpm rising? So one cell value corrects the timing "drift" through the whole rev range, for the ecus that have it like Link and AEM?

Yes it should be linear. If you think about how the cycle time works, this reduces in a linear relationship with rpm so if the ignition delay is a fixed value then the drift can be corrected by accounting for it.

Andre, do you know how it works? Is it degrees detracted from the trigger angle dynamically with rpm rising? So for example, if the trigger angle is 48 degrees, i am 6 degrees behind at 7000rpm and i need 45 degrees advance, can it be corrected? Or there isn't enough room for the trigger delay correction and the max advance i can have is 42 degrees no matter the delay number? Would i have to move the trigger angle one tooth behind? It is only 12 tooth count and moving one tooth behind would make the trigger angle 78 degrees, i am not sure this is ideal

Ok first of all let's assume there is some small amount of timing drift present. Let's assume it's in the order of a couple of degrees across the engine's useful rev range (much more than that shouldn't be occurring if the trigger system is sound). While it's nice to know what the timing is and we will obviously use this to help develop our timing map, ultimately it's the torque output from the dyno that tells us if the timing is right or wrong - We're simply optimising the timing to achieve MBT.

If the ECU offers an ignition delay setting then this is simply accounted for in the ECUs ignition output. As I noted above, the delay remains fixed so the effect of this delay at 2000 rpm compared to 7000 rpm is different since the cycle time of the engine is varying. This is how the ECU corrects for the drift. You don't need to move the trigger angle. What ECU are you using here?

Hi Andre, i think i confused you. Ofcourse i would not change the trigger angle to account for the ignition advance falling back. This would be wrong anyway, it'd fix the drift in one area and ruin all the rest of the band. I asked if you know, if this is what the trigger delay does in the code of the ecu, in the software. We enter a delay number, the ecu software uses an equation to fix the advance. I guess it is either adding the calculated advance onto the table plus any corrections, or change the trigger angle with revs rising to fix the drift.

In my case, it's an F20C (Honda S2000). The ecu (Ecumaster) is falling back 5-6 degrees at 6000rpm, and everything is correct with wiring and setting up. AEM has 150us delay in their base map and Haltech is adding more than 5 degrees at high rpm, so my timing light isn't far out. The trigger angle is 48 degrees, which will obviously be the max ignition advance too. But, at 6000rpm it's falling back 6 degrees aprox. This means that the max advance i can have there is 42 degrees instead of 48?

Plus the issue that i am investigating is that when i try to align the ecu timing with the actual, i don't see any difference above 100us aprox, and at that point, it's still about 3 degrees behind. Sure, this doesn't sound too important because the numbers can be whatever in the tables as long as they make the power on the dyno and MBT is achieved, but i don't really like to see 33-34 degrees advance in my tables at high rpm (it ends up there on a dyno), plus i tune it on the street, and this confusion with the timing drift is annoying.

And one more thing. Why does the same engine and trigger wheel, but with a hall sensor instead of the VR, has less trigger delay? About 40% less. Is it because of the waveform and the edge of the VR that's changing slightly with the sensor voltage rising at higher rpm, or something else? The K series engines and even the F20Cs built after 2006 which have Hall sensors have much less timing drift around 60-70us.