87T Z31 auto w/ 88NA ECU + Z32 MAF... VQ curve off in Nistune, but OK in ROM...
Posted: Mon Jul 29, 2019 7:18 am
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)
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)