I couldn't find much information about intake air temperature sensors similar to the stock FC one so I thought I'd share my findings skimming through datasheets.
Most affordable and widely available sensor I found: Bosch 0280130039. Fits right in the acceptable IAT sensor resistance range (at least for S4, not sure if S5 uses the same sensor).



Generic GM/Delco Sensor on the other hand sits just above the acceptable range. Readings will be off by about -10°C in the 0-60°C range. Not too sure but I think this will make you run richer? Maybe in a worst case scenario better than nothing.

 

Excellent sleuthing. One thing I'd like to add is that the IAT sensor is also used on 13B and 20B Cosmos too. Identical in every manner. One thing the Japanese manuals have over the North American ones is a really thorough ECU Terminal Chart with graphs for sensor calibrations, PWM waveforms for things like solenoids, BAC valve, injectors, etc. Now if only there was some clever guy that could read Japanese and translate it...wait that's me

 

Happen to have those? Would love to get the stock sensors on the S4 set up in Megasquirt properly

 

I've found that the IAT for an R34 skyline is also within range and pretty cheap

 

Nissan Part number 22630-44B20, it looks like in the US we get 22630-ED000? if i looked that up right

 

Just installed the Bosche sensor #0280130039 on my 88 NA. Mounted in the bend up of the intake hose just before the TB and the car runs just fine. I was having a heat soak issue with the stock sensor because I live in the central valley and even at night it's in the high 90s. I have yet to see my idle fluctuate due to heat soak. The sensor definitely seems to work without making the car run strangely though.

 

https://www.fcpeuro.com/products/por...SABEgIQVfD_BwE

 

Help me understand the advantages to running 0280130039 over the stock IAT on my S4 turbo?

 

There isn't an advantage. They are looking for acceptable alternatives that will work with the stock ECU due to (non) availability of FC IAT sensors.

 

when I search nissan part number 22630-44B20 it appears to be the cheaper alternatives from the bosch
my research also lead me to the mpv air temp sensor.
looks like there are two types and hope this once also works
The same day. We might just have to change the connector.
Im hoping their both messure the same ressistant.




@j9fd3s did you use the r34 sensor? When I search part number appears as a coolant sensor. Might be wrong description.

 

nope, i think i ran across someone saying it would work, and then ran down the part number

 

@j9fd3s thanks for the reply. Its a desert in the forum these days. I'll definately get the bosch sensor instead. Was there no problem with the bosch sensor afterall?
Maybe ill try the mpv sensor and give it go too to rest.
@ryou did the bosch sensor give you any issues?

 

I posted on this topic a couple years ago (https://www.rx7club.com/2nd-generati...ensor-1159930/). I don't know where the above curves came from, but they don't meet the FC3S specs given in the FSM. Here are the Mazda specs from the FSM:

The S4 FSM gives these specs for the IAT resistance:
20C (68F) 41.5 +/- 4.15 kohm
50C (122F) 11.85 +/- 1.19 kohm
85C (185F) 3.5 +/- 0.35 kohms

The S5 FSM gives these specs for the IAT resistance:
25C (77F) 33 +/- 4 kohms
85C (185F) 3.5 +/- 0.4 kohms

Most likely, Mazda used an Amphenol NTC Type MS type RL0503-17.56K-96-MS thermistor for the S5 IAT sensor (https://www.amphenol-sensors.com/hub...032114-web.pdf). This thermistor has Ro@ 77 °F (25 °C) (ohms) of 30k and uses a F9.61 materials system.

Plotting these data, we have S4 (blue), S5 (red) and Amphenol NTC Type MS type RL0503-17.56K-96-MS thermistor (black). Dashed lines are the tolerances given by Mazda.

The Mazda FSM only give a couple data points for S4 and S5, which makes it difficult to match-up with a specific thermistor material. I've attached the Amphenol data sheets. If one is interested, than they can go through the entire 83 pages and perhaps find a thermistor material that more closely matches the S4 and S5 IAT curves, assuming there is a better material.

If you're handy with a soldering iron, the original IAT sensor may possibly be retrofitted with a replacement thermistor. Alternatively, a brass plug, having the same threads as the manifold, may be able to be fabricated to accommodate an appropriate thermistor. The brass plug can drilled with two small holes for the thermistor wires and those holes can be sealed with a high temperature silicone sealer. Seems that there are not many choices available.

 

@Hot_Dog thanks for the reply. This is an actually pretty cool idea to solder in.

I have a S5 n/a my IAT sensor broke one of the blade connector by accident 🤦‍♂️ I think I could probably fix it by grinding it down and soldering a wire to make it work in the mean time. I soldered new wires to my oil level sensor too and it worked out.
I would really like to find a replacement or find a way to make our own fix.
this would be a cool project and would help everyone else

 

I found more part numbers cross references

The stardard motor AX96 looks like it has the thermistor. I wonder if we could remove this and resolder it in our sensor.
if it matches the same tenperature that is.

 

I had to make a temporary fix on my iat sensor
the blade connector bent off so I had to solder a new male connector. This should hold as long as I dont bent it.

 

That looks like it'll hold.

Just FYI: I verified that the threads on the IAT are 1/8" BSP with 28 TPI. The major diameter of the thread is 9.728 mm with a pitch 0.907 mm. So, they are not M10 x 1.0 mm as somebody had posted earlier.

 

went to the junk yard and found the iat from a mpv. The 91 mov uses two options for a IAT. The thermistor version like our rx7s and the more modern version without a thermistor.
im betting it has the same temperature readings.

I tried installing it but looks like its a bit bigger. I tried to use a 1/8 27 die and didnt work so I stopped too orevent hurting the threads.
I saw your reply and I missed the its a 1/8 28 die instead.
I wonder where I could find that die size.

Im using this reference from rock auto


@Hot_Dog

 

On Dec 11, 2022, I wrote in a post on this forum (https://www.rx7club.com/2nd-generati...sor-1159930/):

"I've got a little bit more information to contribute to this topic.
After searching related threads regarding thread size:
Aaron Cake wrote that the IAT thread size is M10x1.0, which is the same as the oil pressure sending unit and the coolant temperature sending unit.
However, threads on oil pressure sending unit thread size were generally agreed on as 1/8" BSP (British Standard Pipe).
RotaryEvolution wrote that the IAT thread size is 1/8" BSP. The diameter of 1/8" BSP is 9.7 mm with a thread pitch of 28TPI, which translates to thread spacing of 0.91 mm.
So, who's right? I don't know, but thread size and pitch are so close that you can probably interchange devices between the two thread sizes with doing a great deal of damage if the threads don't match up."

Earlier this year, I bought a used IAT sensor for my S5 from Rotary Resurrection. I checked the threads using my tap & die set and IIRC, the tread was 1/8-28 BSP. So, the person from Rotary Evolution was correct.

Also, you need to check the resistance vs temperature specs for the MPV IAT sensor as they might not be the same as the S5 RX7.

 

The WVE 5S5856 is the IAT that the S5 uses. The two different p/n's might be for different engine sizes.