Hello Guys, I have a small embarrassing question about my Car's MAF.

I have a 99 miata and i need my maf to work properly for my ECU (Ecumaster DET3). Short story about it: It's a ECU that can make a conversion from MAF -> MAP. I installed the MAP and cut the MAF wire going to the ECU, down (LG/B Wire colour (i guess)).

Now the problems.


With the MAF connected to the ECU, when i measure the voltage it's all alright ( 1.7v at IDLE -> 4.8V at full 7k RPM ). Now.. if i unplugg the wire from the old ecu and measure the voltage of the sensor it says 7.2 V. At this moment i thought that the wire is broken or something and i removed the MAF from the car.

My MAF has 3 wires, GND SIGNAL and 12V.

I added a battery to the GND AND +12v, all ok, and when i check the SIGNAL comming from the maf it says 7.2V. Even if i blow on it or put a fan on it, that damn thing does not change...

For my ecu to make the conversion i must have the maf working good outside the car becouse the MAF signall will enter in the ecu (DET3) and DET3 will output a given voltage to the original ECU.

The Question is WHY? why does my MAF have a good output only when connected to the OLD ECU ? What is simulating the ECU ? How can i make it work normal outside the car (not connected to the ECU).

I made a lot of research and i couldn't find a answer.


I want to make it work like this: MAF FORUM POST

Why that MAF is working outside the car and mine not. I guess my MAF is not broken becouse it would not start without it, and it's values are ok, i guess (car running good, maybe a little rich).


Thank you in advance and sorry for my language.

P.S. I don't want to change it unless it's truely broken and please don't tell me that the ECU will change IGNITION timing if i change the maf, the DET3 will handle it, i know this


I draw a scheme: MAF DRAW


*Could it be a frequency MAF ?

 

URL FOR MAF FORUM :

https://www.miataturbo.net/ecus-tuni.../#&gid=1&pid=9

 

@Joe Perez any idea?

 

I have here a photo of it. So i tried everything and now i am wondering if it is supposed to work like this or am i doing something wrong, or it's broken..? Help
* here i connected it to a +12v supply and the signal wire (middle) shows 7.2V

 

I found the same thing. I believe there is a pull-down resistor inside the ECU that scales the signal. Haven't tried it myself but someone mentioned that they did that to get it working on another forum. Was a 1k resistor from memory.
You could always probe the OEM ECU to work out if there is one and what the value is.

 

So can you give me the forum post? Or how did he connect it? I want to make it work outisde the car.
Thank you.

*but the thing is that the 7.2v does not change and i know that a resistor it pulling out the voltage. But if for example i pull down the voltage from 7.2v to 1 or 2 it will not change if o blow air on it either. I guess.

 

Found it
Megasquirt Support Forum (MSEXTRA) ? Some Mazda MAFs are NOT 0-5 volt devices (View topic)

 

Damn, thank you very much. I will try this today.
Thanks a lot. I posted on the other forums and nobody knew anything about it.
Will return with feedback

 

Hello,

I've just tested, it works very good.
I don't know if the values are good, if anybody have a table with the voltage of the maf on a given RMP will be very nice for me.

Thank you again!