94-95 & 96-97 MAF Delete Discussion - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-19-2007, 08:51 PM   #1
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Default 94-95 & 96-97 MAF Delete Discussion

Alright... I figured we should start a seperate thread for technical discussion on how to remove the 1.8L MAF without throwing a CEL.

Here's where I've gotten so far. When looking at the plug on the MAF:
1 2 3 4 5
( - - | - | - - )

(color codes for '97)
1) Blk/Lt Grn = Chassis Ground

2) Blk/Blu = Sensor Ground

3) Red/Blk = 5V

4) Red/Wh = Signal

5) Wh/Red = 12V (KL15/IGN SWITCHED)


Resistance between:
4&1 = 26 k-ohm
4&2 = OPEN
4&3 = OPEN
4&5 =1.66M-ohm

I haven't the foggiest clue how this unit works, so I'll leave this for comment from someone who can at least suggest some tests. I can get an oscope from work and know how to use it, so don't feel shy about suggesting tests.
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Old 11-19-2007, 10:21 PM   #2
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Does no one really know the science behind MAF. I mean I am sure they are all identical.

Without even researching or googling I bet that as it heats or cools the resistance in reference to pin 1 and 5 changes either one way or the other. That differential is what tells the computer how much air is passing.

edit: this should get us going http://www.autoshop101.com/forms/h34.pdf
http://en.wikipedia.org/wiki/Mass_flow_sensor

Quote:
Originally Posted by WIKI
This is achieved by heating a wire with an electric current that is suspended in the engine’s air stream, not unlike a toaster wire. The wire's temperature increases with the wire’s electrical resistance, which limits electrical current flowing through the circuit. When air flows past the wire, the wire cools decreasing its resistance, which in turn allows more current to flow through the circuit. As more current flows, the wire’s temperature increases until the resistance reaches equilibrium again. The amount of current required to maintain the wire’s electrical resistance is directly proportional to the mass of air flowing past the wire. The integrated electronic circuit converts the measurement of current into a voltage signal which is sent to the ECU.
I dont think I was completely off.

edit 2: So to mimic this we need two resistors. One to mimic the heated wire and one to control the outputed voltage to mimic how much voltage is needed to keep it at a particular temperature. I think, I dunno, im guessing.
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Old 11-19-2007, 11:03 PM   #3
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I'm still certain if you give it resitance signal for the AIT (stock ecu & MS share signal) and you put a resistor between a ground and the MAF signal you should be ok.

you'll already be wiring the AIT through the AFM harness if you remove it, so that's easy enough, and since it's unplugged you can jump a resistor right there. it's a quick test and completely reversable.
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Old 11-20-2007, 05:56 AM   #4
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??

I just unplugged mine, tucked the wires away and threw it in the garage. No lights, no CEL's nowt?
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Old 11-20-2007, 09:54 AM   #5
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Richy: What year car?
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Old 11-20-2007, 11:02 AM   #6
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1996
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Old 11-20-2007, 11:10 AM   #7
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you would at least get a cel if there is no AIT signal. did you share the signal with the stock ecu?
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Old 11-20-2007, 11:25 AM   #8
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Quote:
Originally Posted by richyvrlimited View Post
1996
Damnit, more information man.
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Old 11-20-2007, 11:44 AM   #9
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Quote:
Originally Posted by Braineack View Post
you would at least get a cel if there is no AIT signal. did you share the signal with the stock ecu?
nope, no sharing, I use a GM IAT and GM CLT sensor.

No CEL's nothing, I just unplugged the MAF and carried on as normal

Quote:
Originally Posted by Saml01
Damnit, more information man.
?? What more could I possibly add to the question, "what year is your car?" than the year of my car?
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Old 11-20-2007, 11:49 AM   #10
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Quote:
Originally Posted by richyvrlimited View Post
nope, no sharing, I use a GM IAT and GM CLT sensor.

No CEL's nothing, I just unplugged the MAF and carried on as normal



?? What more could I possibly add to the question, "what year is your car?" than the year of my car?
Well I kinda hoped you were gonna answer what Braineak asked without him asking it, but the details really. Just unplugging it, is kinda vague.

GM CLT, did you replace the Mazda one or are you using two?

You sure your CEL isnt burned out?
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Old 11-20-2007, 11:58 AM   #11
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Quote:
Originally Posted by Saml01 View Post
Well I kinda hoped you were gonna answer what Braineak asked without him asking it, but the details really. Just unplugging it, is kinda vague.

GM CLT, did you replace the Mazda one or are you using two?

You sure your CEL isnt burned out?
using two, you can see it here just before the heater Matrix



CEL light is definately good as I changed the bulbs not long ago when I fitted ArtWorks Dewa dials

Might have been vague, but just unplugging it accurately describes everything I did
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Old 11-20-2007, 11:59 AM   #12
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Well I can say now that I have unplugged my MAF, I do have a CEL. Haven't read the code yet to see what its throwing, but the only thing that has changed between pre and post turbo install is the removal of the MAF, everything else is still hooked up. My car is a 97, and MS is sharing the stock coolant sensor, but using the GM IAT sensor.
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Old 11-20-2007, 12:03 PM   #13
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I'll just remove the cat from the Pigeons.........

Just thought, my car is a Jap import, hence it's not got an OBDII ECU, it's only OBDI. I think that's probably why I don't get a CEL.
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Old 11-20-2007, 12:10 PM   #14
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ODBI will still get a CEL without a AIT signal.


look, the problem is only two things:

the AIT and the MAF signals.

the AIT is easy enough to solve....share the signal....the end. Wire the AIT straight into the MAF harness using both the ground and signal leads and you're done.

the MAF signal is what's in question only. I'm still going with the ecu needs to know the sensor will give it anything other than failed. so a simple resistor to the ground and signal should do it. Just so the ECU thinks something is there.


that's ALL we need solved here. figure out a way for the ECU not the miss the MAF signal and you're fine.
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Old 11-20-2007, 12:15 PM   #15
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Quote:
Originally Posted by Braineack View Post
ODBI will still get a CEL without a AIT signal.
why don't I get a CEL then?

CEL definately *isn't* broken btw.
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Old 11-20-2007, 12:32 PM   #16
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1 2 3 4 5
( - - | - | - - )
1 4 -resistor connects these two
3 4 -IAT wires go here (myIAT is non polar)-according to DIYAutotune site instructions
Scott, so what you are saying is that pin 1 and 4 need to be jumped via resistor?
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Old 11-20-2007, 12:36 PM   #17
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Quote:
Originally Posted by Braineack View Post
ODBI will still get a CEL without a AIT signal.


look, the problem is only two things:

the AIT and the MAF signals.

the AIT is easy enough to solve....share the signal....the end. Wire the AIT straight into the MAF harness using both the ground and signal leads and you're done.

the MAF signal is what's in question only. I'm still going with the ecu needs to know the sensor will give it anything other than failed. so a simple resistor to the ground and signal should do it. Just so the ECU thinks something is there.


that's ALL we need solved here. figure out a way for the ECU not the miss the MAF signal and you're fine.
Does the factory ECU really not need an accurate maf signal. Wont if affect the idle since it doesnt know the temp of the air coming in and the AIT gives a different output.
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Old 11-20-2007, 12:38 PM   #18
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Quote:
Originally Posted by whaaamx5 View Post
1 2 3 4 5
( - - | - | - - )
1 4 -resistor connects these two
3 4 -IAT wires go here (myIAT is non polar)-according to DIYAutotune site instructions
Scott, so what you are saying is that pin 1 and 4 need to be jumped via resistor?
That probably wont work because the ECU determines air volume based on current draw. If you plug your IAT into the 5v line it probably wont do anything if not burn out.

2 and 4 for AIT.

Jumping 1 and 4 probably wont do anything either.

What I need to do is get a maf and give it to my electrician, I bet he could figure it out in 15 minutes.
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Old 11-20-2007, 12:50 PM   #19
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sam, according to diy installation thats why i did pins 3&4 for the IAT
http://megasquirtpnp.com/models/mm94...495_manual.htm
look half way down the page...
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Old 11-20-2007, 12:52 PM   #20
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the ECU shouldn't care about a correct MAF signal, it can't do anything with it anyways, you took over the fueling. on the 90-93 installations, we completely remove the AFM signal and it doesn't care at all.

***Warning****I'm not a wiring whiz at all

In factory form, the 12v source heats the element, and it changes resistance values based on the temp of the air hitting it. 0-5v. I'd try a resistor to drop it below 5v and above 0v. So from position 5 to 4.

Last edited by Braineack; 11-20-2007 at 01:07 PM.
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