87T Z31 auto w/ 88NA ECU + Z32 MAF... VQ curve off in Nistune, but OK in ROM...

[turbodan]

Hi all,

This is my first post here. I've done some digging around and haven't found anybody with quite the same problem, but feel free to direct me to an existing thread if there's something that I have overlooked.

I just recently switch to Nistune after spending a while doing things the old way and burning ROM chips. I felt like I had my tune most of the way there on the ROM chips, and just needed to iron out some details, which I thought would be done easily enough with Nistune because of the ability to make changes in realtime. Here's where things fell apart... The VQ curve I'm using (for a Z32 MAF, same one that's packaged in-box with the Nistune software) and K value from my ROM tunes don't behave the same way when I load them on the Nistune hardware. My VQ curve is just about bang on when I run the car with a ROM chip that I've burned. But it goes from too lean at the bottom (<2V, 1-2 points lean) to too rich up top (1-2 points rich), crossing over somewhere around the 2-3V mark where it's actually "right" (WBO2 readings are what I would expect) when I load it into the Nistune hardware. I fail to see why any of this should have changed just moving from a ROM chip to Nistune, as all of the ADC and whatnot should be taken care of elsewhere in the ECU. So... what am I missing?

Here's what I've noticed/tried so far...
- When I first sync'ed the Nistune software to the car, I selected the 88-89 address file, but the software forced me to use the 87 address file. I'm guessing this has to do with the base image that was loaded onto my board (I didn't do this, I bought it from a vendor who did... I provided them with my ECU part #)? Looking at the .adr files, it would appear as if there is no difference between 87 and 88-89, but just wanted to call this out to be sure. Anybody know if this matters?
- I've reviewed the Nistune software + workshop training docs. I noticed a brief reference to difficulties tuning larger MAFs on the Z31 ECUs in the software docs, but no info on how to fix it, other than "talk to us". With, I suppose, is what I'm doing now. Again, I am unclear on why this would work on a ROM chip, and not on Nistune, which should just be emulating a ROM chip.
- I've spent some time poking around these forums and the FAQ, to find anybody with similar issues. Other than the generic "big MAFs are hard to tune on Z31/early RB ECUs", I haven't found much. Definitely not anything to explain why I'm seeing this disparity between my ROM and the Nistune hardware.

Here's some basic info about the car...
1987 300ZX Turbo
88NA Auto ECU, part# A18-A01 M85
Auto trans with Level 10 mods, new stock converter
Z32 MAF, 440cc Mercedes injectors
T3/T04E-57 turbo
Lots of other related stuff...

I've been through the electrical system, including reverting the injector wiring to pre-recall, and fixing up a bunch of stuff that was buggered by the previous owner. I'm confident that all signals are getting to where they should go, reliably. I was running my own datalogger off of lines I had tapped into the ECU connector prior to installing Nistune, so I'm confident that things are working as they should on that end.

I'm pulling my hair out at this point, and about ready to go back to burning damn chips, because I feel like I was much closer to having a functioning tune via that method. At least my VQ curve matched up.

Any help is greatly appreciated. I can provide logs if needed, but feel like this isn't a log type problem, I don't want to be trying to tune around some other problem in the system, when I know these table values work in an actual memory chip...

Thanks!
Dan B. (turbodan / dan86turbo / Dan86T)

[Matt]

Need some more information...

1. can you tell us what the ROM image (BIN) is that you are using on your chips. Is it a 1988 or 1987 file? Can you post the file here?
2. what is the ROM image (BIN) on your Nistune board. This depends who programmed the board, and the ECU ID: 23710-????? displaying in the software

Yes there are differences between 1987/1988 ROM files. Nissan moved some of the addresses. You cannot just load or switch 1987/1988 files and ECUs

Nistune should run identially to the ROM chips you are burning assuming you are using the same ROM image on the board, as you were burning.

What we would normally do on a consult ECU is compare ignition timing and injection time, but with a ROM chip and Z31 ECU that is not possible without the board and consult comms.

You say you looked at the address files and they look no different. Well I can tell you all the address locations are different, very different. You cannot use one image on a different year address. It will mess everything up

My suggestion at this stage is to copy/paste the values (RAW) from the current file into a default clean 1987 file (or whatever is loaded on your board)

[turbodan]

Hi Matt,

Thanks for the quick reply. Here's what I've done since my last post (and some answers to your questions as well)...

1. I'm using an 88 ROM image on my EPROM chips. I've attached both the .bin that I burned my ROM with plus the NIStune image that I built from it. The way I've built my NIStune image this time around is to load up the stock Z31_VG30ET_1987_21P01_MT.bin (I tried AT as well, and didn't notice any difference) in the main slot, and the image I was using on my chip in the compare slot, then used the map copy function to copy over all maps that were changed on my tuned image. This gave me the exact same results as previously... too lean in the bottom end and too rich up top.
2. ECU ID on my Nistune board shows as 23710-21P10. I find this strange, because it's a 1988 NA auto ECU (should be part # 23710-25P10). Could this be the source of the problem?

I also socketed and did the MAF resistor mod on a spare ECU that I had sitting around (another 23710-25P10 / A18-A01 M85) so I could stick my tuned EPROM back in and do a quick A/B compare to make sure I wasn't going crazy, without having to remove the NIStune hardware from the ECU in the car. It runs as I remember it. The wideband readings are what I expect given the tune.

Thanks!
Dan

[turbodan]

Just to add some more data, I went back and rebuilt my ROM image in the most OCD way I could. Here's what I did.

1. Loaded up NIStune, picked the 88-89 address file, and loaded the .bin that I've been burning onto ROM chips.
2. Copied and pasted every table, scalar, and flag out into an Excel sheet, in raw mode.
3. Closed everything out, re-opened NIStune, picked the 87 address file, and loaded the 21P01 base image.
4. Copied and pasted everything from the Excel sheet into my new image.
5. Saved this image and sync'ed it to the ECU.

And the results: Car still runs like crap... super lean down low and too rich up top.

Dan

[Matt]

Z31_VG30ET_1987_21P01_MT.bin
used the map copy function to copy over all maps that were changed on my tuned image

This will probably not work, since the other ROM image is 1988 26P01 and should have different map locations

2. ECU ID on my Nistune board shows as 23710-21P10

It matches the stock file you are using (1987) but if you are wanting to use the 1988 ROM (and even 1988 Feature Pack 26P0F) then I would get the board reflashed and updated

I find this strange, because it's a 1988 NA auto ECU (should be part # 23710-25P10). Could this be the source of the problem?

21P01 is a turbo ROM image, whilst 25P10 is a non turbo. K constant and map locations will be different and cause all sorts of confusion

Regardless the problem is not the 1987/1988 hardware part and ROM mismatch. We use the 26PXX ROM images in the 1987 NA and turbo ECUs all the time

It is likely using maps from 1988 BIN in a 1987 programmed board, using the mapcopy feature. You need to open two copies of Nistune
- one with 1987 address selection and BIN file matching your ECU
- other copy loaded with 1988 address selection and BIN file

Then manually copy maps (raw mode) from 1988 Nistune to the 1987 Nistune

[Matt]

Okay just read your second post, and sounds like you did similar to what I already suggested. K constant values (stock) are the same, so no issue there. Latency I noticed was different. Not sure why the switch over temp (60degC) was changed to 0 in your EPROM file so left that

Attached is 21P01 with maps copied in

You can do two things with this
1. Load into your board as is and see if it is the same as your copy/paste
2. Burn to a separate EPROM chip and try in your spare ECU and see if it runs the same as your 1988 EPROM BIN file

This will help work out if a problem with running on the board, or copying 1988 maps into 1987 file (should not be an issue here)

If a problem running on the board, then I recommend getting it reflashed to 26P0F (so you get feature pack too) and then can use File > Import to pull the EPROM maps straight in (without having to worry about using anything 1987 related in future)