Megasquirt + IAT/AIT sensor query
 

Hi guys

Greetings from NZ.

I am currently getting my bits together to turbo my 1990 MX5/miata, and have ordered a Megasquirt from a guy within NZ.
When I made my initial queries with him about the MS and my turbo goals he mentioned he had a supercharged MX5 running 6psi, and had a good tune/map he could put on for me, which he would edit a little to suit my injectors etc.

This guy has since said that he was not running a Air Intake temp sensor on this car (is this even possible with the MS?) and I plan to fit a GM style IAT from DIYAutotune.
What I'm wondering is will taking his preloaded map/tune and running it with an IAT cause any issues? Will I need to change anything in MS to account for the additional sensor etc?

Before you say anything, I did search, but couldn't find anything helpful for my exact situation.


Thanks guys

Martin

He's most likely using the built in ait sensor in the miata's AFM/MAF, that huge box by the filter. It requires different settings than your GM sensor, and is obviously more bulky and more restrictive.

Download the mspnp map from diyautotune.com for your year and no AFM. Change the req. fuel setting (there's a built in calculator) and tune from there.

Thanks curly, I'll do that.

The guy said he wasn't running the factory AFM/MAF on his setup, and when I asked him about if I needed a AIT sensor he said

"The ECU doesn't need a Air temp sensor to run
My wife's supercharged MX-5 has been running without an Air
temp sensor for about two years now .
The only real benefit of the Air temp sensor, is if you are
running very high boost, or no intercooler, then the ECU can
reduce the timing as the air intake increases.
A good intercooler and/or keeping the turbo under 15psi
negates the need for a Air temp sensor."

Is he just full of shit? or is it possible to run the MS with no AIT at all?

Your fueling won't be correct without an air temp sensor. You didn't specify what kind of MegaSquirt this is, but if MS1, the air temp calibration is imbedded in the firmware. If it's MS2 or MS3, air temp calibration settings are in the tune file. My opinion might be a bit biased, but I'm kind of thinking run don't walk...

The stock AFM has an AIT built in, and most people running MS with an AFM are just running two wires to that AIT. You can actually yank it out and glue it into the charge piping if you're super cheap. As far as I know, MS w/AFM setups don't use the flapper portion of the AFM. Could be wrong though.

Air temp effects density which in turn effect AFR. No air temp sensor is possible, but without correcting for air temp, you need to tune for the hottest conditions to get the AFR correct, meaning in colder air conditions, the tune will be too rich.

Probably doesn't impact a track pig too much.

To the OP, instead of buying an IAt just rip the stock one out of the AFM and use it.

Joe Perez authored a write up showing exactly how this is done. I bet it will come up with a google search.