I need to replace my air temperature sensor

[Gavin]

As part of my ITB project I’ve ditched my factory AFM in favor of an alpha-n/MAP hybrid scenario. I had planned to rip the air temperature sensor out of the factory air box and mount it elsewhere in the engine bay, but as my project nears completion I can see that this may not be possible; I can’t see how I’m going to get that sensor out without damaging it. So my question is: Is there a different air temperature sensor that I could wire in, in place of the stock one, which would behave like the factory sensor (i.e. no air temp fault code)? Maybe something out of a different BMW, with a removable ATS?

[Gavin]

Nothing yet ea'

As a parallel question, is anyone able to inform me as to the functional modality of the M20's air temp sensor? That is to say, do our computers modify fuel based on a temperature gradient the ATS reads back, or does the ATS function in a closed/open mode (cold/hot) simply switching between winter and summer fuel maps?


I'm hoping to turn this girl over before end of day Sunday, so if anyone is able to offer some advice it would help me a lot.

[rs4pro3]

The stock sensor can be removed it just takes some skill. It is hot glued in place with two plastic rivets holding it in, carefully drill out the plastic rivets, and pry it out. Also the GM air temp sensor like used with megasquirt is very close to the stock sensors output.

What piggyback etc.. are you using for the alpha-N setup?

[nando]

Nothing yet ea'

As a parallel question, is anyone able to inform me as to the functional modality of the M20's air temp sensor? That is to say, do our computers modify fuel based on a temperature gradient the ATS reads back, or does the ATS function in a closed/open mode (cold/hot) simply switching between winter and summer fuel maps?
.

it does the first thing. IAT is pretty important to your ECU.

what engine do you have? On the 325i, the IAT is inside the AFM, not the airbox. you'd have to pretty much destroy the AFM to get it out, but it should be possible.

[Gavin]

Thanks for the input. If I mangle the ATS while pulling it out, it's good to know I can drop in a $12 (available everywhere) GM unit:D.

What piggyback etc.. are you using for the alpha-N setup?

I have a URD (Underdog Racing Development) signal calibrator tackling the alpha-n portion of my fueling. I have it modifying a 0-5v variable TPS signal running into the former AFM input. So far I've been very happy with it (great adjustment resolution). This portion of the fuel set up will passively control the stock 6 injectors. The up-stream 6 will be actively controlled via Megasquirt, keying on MAP signal from the vacuum manifold I've plumbed in. But I'm not even going to start thinking about that until I've got this girl idling happily.

what engine do you have?

I've got a SETA, my ATS is in the AFM also, I just misused my terminology in my first post.

[rs4pro3]

almost forgot the 318i's had the air temp sensor mounted outside of the AFM so you could probably use one of those. The GM sensor isn't exactly the same. I'd have to find the resistance/temp curves again.
I'd realy consider just going megasquirt as a full standalone. I highly doubt you'll need 12 injectors with your ITB's, I'm only running 19lbers on my setup right now and having no issues at all with it idling good or not.