[theonewithin]

It's not the firmware.

The code works fine using that trigger pattern.

If you have a spare arduino you can test it yourself using Ardu-sim.

Your log looks like mine did before i switched between trailing/leading.

This is using the original VR sensor with the engine on a 8-1 wheel.

Pulling spark plugs helped a lot to lock things down as compression slowdowns were minimised.

See my attached screenshots.

Using the same sensor each time. Just changing polarity, leading/trailing edge and removing spark plugs.

In the end went from completely useless signal to one that i don't need any filtering on and get no sync loss up to the redline of 13500.

Stock VR sensor on stock 8-1 wheel running original unshielded wiring.

[NickZ]

you need to pull the trigger signal to ground on the speeduino, it relies on going from 5v to 0v (ground), i would put a pull down at the speeduino then.

I think having unequal size gap/teeth would be a large problem, they have to be equal.

Im using August 2nd version firmware.

[mian3010]

@theonewithin, your reply was an interesting read. I will try to play around a bit more, with trailing/leading.

@NickZ The board with the IR-sensor already contains this pull-down resistor.

I do not quite see how uneven gaps can affect the signal. As long as the double-sized gap is significantly bigger than the others. However, i will try with the VR-sensor instead, and that one has perfectly equal gap sizes, to rule it out.

[NickZ]

Uneven gaps will be a problem, speeduino counts the time between the teeth to rule out noise or triggers, So if it keeps getting different time between the teeth it wont be able to sync and lock in to a pattern.

[mian3010]

Now i finally had time to look at this again.

I have changed back to the VR-sensor, and it seemed to give a consistently good signal, however, after running the engine for about 1 minute or so, it read some inconsistent data, and i could hear the engine stumbling. Just once, then running fine again for another minute or so.

The VR-sensor does not give consistent results at all at leading, so i set it to trailing.

It now looks like this:

Tooth error VR.png (9.27 KiB) Viewed 10289 times

[PSIG]

The VR-sensor does not give consistent results at all at leading, so i set it to trailing.

A VR sensor with correct polarity, reading the tooth trailing edges correctly for missing-tooth wheels, and using an inverting VR conditioner (MAX9926) should be set to Leading Edge (or Rising Edge in the new code).

If you get garbage with that setting, your VR polarity is incorrect. You previously said you tried swapping VR wires, but got "nothing". Swapped wires should simply give you the same signal, but inverted/reversed. This may indicate you swapped the wrong wires (VR+ and shield?). Using the wrong polarity and/or the wrong edge setting will cause timing errors even if it runs, for multiple reasons. Note the latest code release has changed the terms Leading and Trailing to Rising and Falling in order to reduce confusion between physical tooth edges desired (in this case trailing) and signal edge settings required (in this case rising).

David

[mian3010]

Thank you for a great reply. I will try this out the next time i have time to work on the car.

I will admit, that my response to what happened when switching wires were purely based on memory, and my memory might not have been correct. I will try swapping the wires as well. I think this might be the culprit, as the red wire is VR- in my current setup.

[740Schneb]

Hi, I've been working on a 1990 740, I went through tons trying to get the vr rpm signal working. I eventually switched to a hall sensor. I drove it for a while but I'm still having tons of issues.
Wondering if you ever came up with a solution to your issues?

[theonewithin]

Hi, I've been working on a 1990 740, I went through tons trying to get the vr rpm signal working. I eventually switched to a hall sensor. I drove it for a while but I'm still having tons of issues.
Wondering if you ever came up with a solution to your issues?

I suggest you start your own thread as your issues will likely have nothing to do with the issues here.

Make sure you post your tune and log of problem.

[Jakobsen]

So did you get the car running ?