z32 vs z31 afm.. resistors removed

[G-E]

My '88 z31 ecu has the resistors removed to use the z32 afm, but it looks like mine crapped out and until I source another I was thinking...

What if I plug in the z31 afm, without those resistors will the vq map for it be wrong or is that something seperate?

I'm not clear about whether the vq map is pre-amp or independent, will the values need to vq be different with and without those resistors? If it is post-amp is there a way to rescale the whole vq map?

[Matt]

Need the resistors back in going back to Z31. Opamp drops Z31 MAF 2-7 volts down to 0-5 which ECU needs

[G-E]

I thought it boosted the afm signal by 2 volts?

What's the z31 config2 vq map for?

[Matt]

Nope. Not sure where that piece of misinformation comes from

Definitely drops it... the RB30/VG30 MAFs put out a higher voltage from factory in these older ECUs. The HD46510 A/D converter chip runs a 9 bit A/D converter with 0 - 5 volt range. Directly putting over 5V from the MAF would blow up the input on this chip as we found out in the early days

VQ map is calibrated for 0 - 5 volt input from this chip and turns it effectively into TP.

Nissan early ECUs use a 16K masked ROM chip and 1K PROM chip. Back in 1984 when these ECUs started coming out memory was expensive. Nissan programs were put into the masked ROM chip in large quantities

PROM chips were smaller and therefore would have been cheaper to program these adjustments in smaller quantities I guess.

Calibration changes were done in the 1K PROM chip (Program Once only). There effectively are two sets of VQ maps, TP and load scalers defined in the masked ROM. The calibration chip has a configuration parameter (feedback flags I think from memory) which tells the ECU which set to use. From what I have found all ECUs use the first set of maps. The second set must have been for another different MAF setup with different calibration curve. I've never seen them used

[G-E]

My z32 afm crapped out, was showing max volts no matter how much airflow after a week of fighting with this... during that time I had a bad distributor, a bad battery, intake leak, and rechecked my timing belt twice to be sure

I am using the stock 260cc z31 turbo low-imp injectors with 6ohm@10w resistors for each with the 88 non-turbo ecu, and I was having a realy hard time trying to find the ideal k-const

Normal turbo rom value is 607, but changing the afm in the menu drops it to 515, and this still seems wrong, even with o2 feedback off on the map/flag, I was getting afrs around 9.9-10.3 at idle, and low 13's at low load in neutral

I tried playing with the latency, lowered k-const to 500 which brought me closer to high 13's at idle, but then the first few columns of the map stays around 13-14afr with medium throttle, except when I let it settle back to idle, it climbs up to 18afr and dies

Since my engine is from an 87T I tried using most of the values from that rom, but I've even tried using the 88T/88SS rom values for the injector latency/const etc, don't know what I'm missing

As an aside I have no logs as my LM2 refused to connect to my laptop, I just got a new usb-serial adapter...

[Matt]

If you are using the Z31 AFM you need to reverse any previous modifications otherwise it wont run properly. You should be using standard K value for 1987 effectively after that to get it running right again

[G-E]

No I have another z32 afm coming tomorrow