MAF voltage in log playback issue

[DuoWing]

Hey I was just messing around with my ECU and consult and I had a question here. I've been trying to determine the running issues with my L28ET, so I was doing logs with idling and then comparing them to the running logs in my Z31. At first I thought I found a big issue with maf voltatge showing 3.56 or so at idle in the L28ET, compared to the Z31 idling with MAF voltage 2.06. I tried to do a log of the Z31 and it seemed like it was logging fine, on the display it was showing the correct voltage as the consult gauge, then when I did a playback it was showing for my Z31 the MAF voltage being about 3.5 or so at idle. Why is the voltage showing up so much higher in the log playback than what it's actively showing on my consult when the car is running?

[Matt]

shouldnt be doing that. there is a 1.5V MAF offset inside Nistune which is applied to the ECU hence the voltage difference.

On Z31/R31 the MAF voltage is dropped inside the ECU through an opamp board and then passed onto a A/D converter chip. What Nistune sees when reading the MAF voltage from the A/D converter chip is the dropped voltage. 1.5 volts is added to the consult MAF display gauge

We determine when to do this by looking if using a R31/Z31 ECU. We then look at the current VQ map and if standard R31/Z31 MAF detected then we add the extra 1.5 volts. If the VQ map was changed (say to Z32) then the ECU hardware would have needed to be mofieid to remove the opamp voltage drop, so we dont apply the offset

What seems to be happening is that the recorded voltage 2.06 volts on the Z31 is not applying the offset for some reason (software error) but applies it on playback

The 3.56 volts should be what you see on the MAF signal wire if you were to put a meter on it

[DuoWing]

Ok, makes sense. Thanks for clearing that up. So like you said I'll go by what I see on the log playback vs the consult gauge itself. I was at first thinking there was some big error between my two MAFs.

[Matt]

Resolved

[bachig24u]

shouldnt be doing that. there is a 1.5V MAF offset inside Nistune which is applied to the ECU hence the voltage difference.

On Z31/R31 the MAF voltage is dropped inside the ECU through an opamp board and then passed onto a A/D converter chip. What Nistune sees when reading the MAF voltage from the A/D converter chip is the dropped voltage. 1.5 volts is added to the consult MAF display gauge

We determine when to do this by looking if using a R31/Z31 ECU. We then look at the current VQ map and if standard R31/Z31 MAF detected then we add the extra 1.5 volts. If the VQ map was changed (say to Z32) then the ECU hardware would have needed to be mofieid to remove the opamp voltage drop, so we dont apply the offset

What seems to be happening is that the recorded voltage 2.06 volts on the Z31 is not applying the offset for some reason (software error) but applies it on playback

The 3.56 volts should be what you see on the MAF signal wire if you were to put a meter on it

I thought the address file applied the offset 1500 to the gauges/log file not Nistunes detection of a recognised VQ MAP.
This maybe causing me grief when I correct the MAF translations, I noticed that sometimes the 1500mV is not applied.
Is this correct?

[Matt]

When Nistune detects VQ map is Z31/HR31/R31/VL then the MAF_OFFSET parameter is used (normally 1500mv) otherwise ignored

This is used when you use say a VL address file with the offset. When VL VQ map is detected then the offset is applied, but once changed to something else then the offset is not used in the software for the display/logging

[bachig24u]

in essence, if I change a value in the MAF translation, the offset is not applied even though the MAF is still requiring the offset to read correctly in gauges and log files?

[Matt]

If you alter an original R31/Z31 MAF translation curve, it will ended up dropping the offset since Nistune cant determine what MAF is currently in the ECU any longer

[bachig24u]

ahaa, this answers another 'strange happenings' inside nis that has been driving me batty lately.

So the question now is,
how can I re-apply the 1500 offset to make things look correct after tweaking the VQ?

[Matt]

As explained before Nistune looks at the VQ map and if its one in the Z31/R31 listing then the offset from the address file is applied, anything else then it is not used

This is so when the MAF is changed to say something like Z32 without an offset, Nistune drops the offset as it is no longer required. Before we got people to manually adjust the address files but this got confusing for people having to edit them in notepad so I added in automatic detection to help

If you are altering standard Z31/R31 VQ maps then the only thing I can think of doing is forcing the offset use by using a right click tickbox on the VQ map window. Does that sound like a feasible workaround?

[brett_32i]

so to make it go back to offsetting as required, i would just open up a base vl file, copy maf translation, then reopen my file and paste it in?

it will then see a std vl translation and apply offset as necessary?

at idle, maf(in nistune) is currently reading 2 volts is that where is should be for vl board?
the attached shows it looks ok to me up higher in the revs/load. about 85% load and about 85% maf voltage.

[Matt]

I've added a change in. Right click the VQ map graph and tick 'Enable MAF offset' to add it manually

[brett_32i]

so do my values look ok?
or should my value under that much load already be up over 5v (with offset)?

[Matt]

That probably is okay since your MAF reads between 2-7 volts physically on the MAF signal line.

[brett_32i]

ah thats good. checked the tick box option and offset is disabled, so yes, approaching 5volts under that load makes sense to me. thanks