Missfire detection, cylinder identification

[mattias]

It only seems to go up to cyl7.

Dave (NL) has solved this issue, it'll have to wait until 1.2.15+ firmware and new VemsTune is released.

[Erikk]

I have -400uS in cylinder 3+4    

The vr-sensor polarity is switched. As a result, you get a tooth retardation ( 6deg ) on two cylinders.
If you are using the vr-sensor from bmw m50, then connect yellow to primary trigger input and black to sensorground.

Black as signal is for m20 and m30 engines.

[GintsK]

Erikk - on some wheels first tooth after missing is little disturbed anyway (e.g. 1.8T IIRC)(Clio 2L 16V wheel by default). First trigger tooth defined some teeth later. Cylinder power shows significant time difference. Two questions:
1) why cylinder power do not use First Trigger Tooth + reff tooth table: that signals are evenly spaced?
2) in this particular case - I hope ignition events are based on given trigger tooth + reff tooth table and not disturbed by one not so good signal?

Gints

[Erikk]

Erikk - on some wheels first tooth after missing is little disturbed anyway (e.g. 1.8T IIRC)(Clio 2L 16V wheel by default). First trigger tooth defined some teeth later.

Is this the same 60-2 wheel that we install behind the flywheel on Audi I5 with hallsensor?
It has a tooth thats smaller than the rest, so it needs to be triggered from falling edge, else it will to the same as runninig bmw with wrong polarity.

[GintsK]

No, not that wheel...
But it does not matter. Questions is more about VEMS in general than about specific wheels.

[Matus]

I had cylinder that wasn't running from the beginning but I didn't realize that as you know it is not that obvious especially when engine is not tuned yet. I found out it coincidentally when was checking plugs .. one piston was shiny and the rest was black.

So this is nice and and really useful topic for me

This would be proper reading for V8.

    Ign_out0 ->individual power2
    Ign_out1 ->individual power3
    Ign_out2 ->individual power4
    Ign_out3 ->individual power5
    Ign_out4 ->individual power6
    Ign_out5 ->individual power7
    Ign_out6 ->individual power0
    Ign_out7 ->individual power1

As I understood value shown in time value is just difference but now major question is which values are differentiating.
Does it matters about aliment in the log ? for example.. lets say that I put together accidentally two bad cylinders together so difference might be small ?

Or does it means that value represent acceleration and "difference" is just optical result ?  ( I will bet on this one however I would like to be sure because nothing is worst than bad data interpretation    )
 
 

[Mads Lund]

Regarding individual power measurement, never use 1'th tooth as trigger tooth. I made a post som time ago on this topic. In short, the missing tooth will offset the voltage of the VR sensor slightly, compared to the smaller gaps between the othr teeth's. This will affect the analog signal a littel, and postpont the trigger event on the first tooth a few microsec, enough to make individual power useless.
So never use 1'th tooth as reference, use second or higher. On mine v6 duratec, did I have to ofset the complete cycle, and have cylinder 2 as the "no 1" cylinder, worked but anoying. So at the end did I rotate the trigger wheel 40 deg to solve the issue.