Objective:

Delete MAFS, and use Speed Density tuning with Haltech

Plan:

Weld in a bung for aftermarket Air Temp Sensor (IAT, or ATS, depending on who's software you use). As we know Nissan uses a IAT that is 'part' of the MAFS, so when you delete the MAFS, you lose the IAT, and you NEED it for Speed Density tuning

Hook Up:

Tap into the MAFS wires that go to the IAT inside the MAFS, and just use them for the aftermarket sensor.



PINOUT MADE FROM THE FSM INFORMATION:




This is my fancy drawing from info the FSM's have given for terminal designation. But it seems to be incorrect.

Apparently, the IAT sensor uses Terminal #5 as 5v supply, and #3 as return.
However, #3 is also the main ground for the MAFS, so I'm confused how the IAT can return it's signal through it sucessfully.

When I hooked up #3 and #5 to the aftermarket sensor, it didnt work.

I was left to do my own testing without concrete answers, unfortunately. And I observed the following:




I found a 5V reference on pin #2, and used what appears to be the ECM ground for the other wire. This ground didn't have continuity to chassis, which didn't make much sense. Either way, With a 470k resistor installed temp showed 70* C, sweet, I say, so I hook it up to the sensor, it reads -11* C, which is how cold it is outside!!!

SO I wire it all up, thinking it's good, and run the car. Well, the temp doesn't change.... Even as it gets hotter in the bay, I even pumped hot air at the inlet with a heat gun and nothing changed.
I'm not convinced it's not working, but I'm getting the general feeling it isn't.

More testing to come, I guess, but if anyone can help me figure this out, or simply knows how to hook it up, please chime in! And if not, hopefully this helps someone else in some way or another, either now or when I get it figured out myself

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Pics of the piping and sensor:

 

Pins 5 and 6 are the AIT in the MAF harness.

blue and y/g

the sensor just needs the 5V and the ground. Are you sure you have the calibration curve setup properly in your haltech?

 

My sensor is only 5 wire. Calibration is not done yet, no

 

well if you have it hooked to ground and 5V, then that's correct (pins 2 and 4 based on your multimeter). You just need to tune the calibration curve as its not the same, esp at extreme temps like you have.

 

Sweet, thanks man, I'll post results after I calibrate it and do some testing with infrared to test accuracy roughly. No more working in this weather though, lol, ridiculous

 

Sweetness, I am not smart enough to figure this out quickly.

Provided calibration for the AEM sensor:




Obviously I need the calibration in Voltage for this for my Haltech. I didn't consider this during purchase, perhaps short minded of me, I bought this sensor so I wouldn't have to wait forever and a day on shipping time.

Is there any way to figure this out? I've tried the obvious (to me) and I don't know how to calculate it. Voltage drop in the circuit is the entire source voltage at any resistance, when calculated. This doesn't give me a varying value obviously.

The only thing I can assume (having never dealt with doing my own calibration before based on resistance value) is that there is another resistor in the ECM after the point where the ECM reads the return voltage. This is a complete guess, but I don't see how else the ECM can read the return voltage otherwise.

And if that's the case, without the second resistors value, I cannot accurately calculate the return voltage after passing through the IAT, right?

Sorry if I'm just blindly missing something here, or over-complicating it, but how in the heck do I do this calibration?

 

The only other thing I thought to do was simply monitor the voltage the Haltech is seeing for the sensor, and then Infared the location of the sensor, and make my own calibration chart, easy, EXCEPT there is no way I see to monitor the voltage the Haltech sees for this sensor, plus the general PITA it would be to try and reach the necessary temps throughout the range, as these sensors are not Linear.

I suppose I could back probe my multimeter into the return wire directly from the sensor, but that's about the only way I can figure to do it right now, and that's still a big PITA.

 

Ugh, ignore the inquiry I guess.
I'm just "speaking"our loud. Since I have no way to find the "second" resistance its a moot point anyways.

I will have to manually check it throughout its temp range.

I just have lots of computer time, and no hands-on time right now for the car, she is on blocks under snow in the freezing cold. I was going for an easy way to stay inside where its warm lol

One plus, is apparently AVI2 input in haltech shows the raw voltage for the iat so that is one less thing to mess with at least

 

the older style haltech came with the GM AIT sensor curve. You just had to load it.

Otherwise, watch raw voltage with thermometer and make your own curve.

It just needs to be close. Most MAP cars dont even use a AIT. And unless you are making AIT trims, it doesnt matter either.

 

Ahh I see that now, thanks man, I found the calibrations but they obviously don't match up, despite this AEM sensor being an apparent 'GM style", maybe that just means the NPT thread size, who knows, lol.

Excuse my ignorance, I thought IAT was vital information for Speed density?
how does the ECM calculate Air Density without knowing the temperature of the air? If all it knows is pressure, it has no clue what the density is, as density of the air is directly proportionate to the temperature, right? Or doesn't it matter as much as I think it does? Maybe I'm putting too much stake in the label "speed Density" tuning.

 

MAF's calculate air density. MAPs run solely on pressure. The pressure it reads will change as a function air density. The computer doesnt calculate density, its being measured as part of the entire pressure component.

Like I said, you only use it for extreme cold/hot weather correction, and even then its only 1 or 2%.
Engine coolant is used for correction tables.