JewFro297

Hello,
I'm doing a VAF to MAF conversion without ECU swap (Microcontroller based conversion) and I want to verify what I've gathered so far from probing and looking at the schematic. The sensor has four pins, in this physical order: 8V Ref (ECU 26), Ground (ECU 33), VAF Sensor output (ECU 31), Temp Sensor (ECU 30). I find it strange that I measured 8V coming out of the harness, but I'm assuming that the potentiometer is basically a voltage divider and will output between 1V and 5V based on the flap position.

I'm guessing that the temperature sensor is measured from the ECU using a pull up resistor or something, and that the VAF sensor output goes straight into an ADC pin. Is everything I've said correct? My biggest worry is the 8V, considering that's a really strange voltage, and I would expect 5V or 12V.

Edit: I'm pretty sure at this point that the reference is supposed to be 5V (or 12V), and that something must be wrong with my ECU grounding or possibly a voltage regulator. Any suggestions?

Edit again: According to this site, http://www.injectronics.com.au/asset...Bulletin57.pdf it looks like my measurements are actually correct, and the ECU supplieds 8V. So Yay!

Sorry for the sea of edits... I measured the output of my air flow meter with a scope, and the output was between 0 and 1 volt... Does that seem correct? I would expect between 0 and 5V or something along those lines...

NismoPick

I commend you for your research and efforts. Seems like a lot of work though, since there's already a simple solution of running a Z31T ecu and maf with just a few wiring changes. Since the AFM measures quantity and the maf measures mass (as you have already learned) it's fairly complex to make a bunch of conversions work together for no real gain by itself. Perhaps used with a VPC it might be beneficial, but by that point the project will have far outweighed the time and money invested over going the Z31 ecu / maf route. Just food for thought. I don't mean to discourage, just add some alternative views / advice.

JewFro297

Thanks for the suggestion, I think I plan on doing the z31T conversion in the future, but I wanted to do this conversion first to save money and for fun. I figured out the pinout and everything, set everything up in a test fixture, and was able to map the n62 MAF output to match the VAF output. Unfortunately, my assumption that I could fake a constant temperature with a resistor to the ECU was wrong, and I wasn't able to get the car to do anything other than idle. I've also learned that faking the intake system is a bad idea anyway, since many systems depend on it. My next step will be to characterize the sensors and figure out what physical value each voltage corresponds to, then attempt to convert the MAF sensor to a volume sensor by accounting for temperature. I realize this is kind of pointless, but I'm already this far invested so I feel like finishing the project. If anything, I could post the values I get online and maybe someone could make use of them for another purpose. I guess another problem I'm having, and the whole reason I started this in the first place, is that my car seems to run lean, as if it isn't sensing all of the air coming in. There's a lot of things it could be, but I think I've narrowed it down to the CHTS, AFM, fuel pump filter (not the normal fuel filter), or injection system being clogged. Anyway, most of the z31 swaps seem to be missing details about how to do them, and there's a lot of parts needed: At least two wiring harnesses, the ECU itself, a distributor, part of another distributor, and an oil pump shaft (which I'm not even sure how to change or where it's located)

JewFro297

I've attached the results of my first attempt at room temperature (2KOhm temp sensor resistance). The top yellow signal is the MAF raw output, the blue is the VAF raw output, the pink is the converted MAF output, and the bottom purple is the difference between the converted signal and the original VAF signal. The MAF curve changes with temperature, so that's most likely why it didn't work when I loaded it into the car.

NismoPick

There's a clear write-up on HBZ that has been used for years, I also have a zip file of all steps and diagrams needed to complete the swap ( https://www.zdriver.com/forums/attac...cu-swap-v3.zip )

No wiring harnesses are needed, only the MAF & plug, and Z31 ecu plugs with a few inches of wire (you can get the same pin connectors from many other Nissan's too). The 81T does need the 82-83T distributor and shaft, and swap in the VG30 encoder disc (chopper wheel). Run the new wires, and on the 81T you bypass the drop resistor pack. That's it. I actually sell Z31T ecu swap kits. I've done it to ~10 different 280zx Turbos... it's cake, and worth it. No mess, no fuss, straight forward.

Also useful: https://www.zdriver.com/forums/280zx...-timing-40948/

JewFro297

Oh awesome, you sell kits? How much, and what's included? Also thanks for the completed links, I've been looking for those for a long time. I'm still probably going to hold off on the conversion for now (money and time is an issue) but I'll consider it for the future

NismoPick

$300 shipped for a complete kit that includes everything needed: turbo ecu, ecu plugs, maf, maf plug, new crank angle sensor, and VG chopper wheel. I also sell just the MAF & connector kit for $100 if you already have an ecu, or want to source your own.