Originally posted by ButtonPuncher:
Seawulf, thanks.


Swazo,
The PCM must be able to compensate for temperature changes. If it is a -10F Janurary day or a 180F August traffic jam day. The only way to do this is to take readings from the IAT and bias the readings from the MAF. Everybody is just flat out bitching that it won't work right. From what the Focus guys are doing, it sure seems to work. Is there proof that it doesn't work? If so, what temperature was the air when the readings became totally inaccurate?


Personally, I have seen 180+F intake temps while using the CTA intake in the summer. Nothing blew up, but it sure ran like crap. The PCM was obviously pulling all of the timing due to the insanely high intake temps. From that info, we can tell that the MAF can do it's job up to 180F.


BP



I don't disagree that people need to try things to see how they work. However, you are taking it to another level without doing and critical thinking on the subject.
The IAT is independent of the MAF. It ONLY tells the pcm the air temp.
The MAF is a hot wire "differential" type of measuring device. Meaning:
It measures the changes in resistance between two wires based upon the mass of the air striking the two wires AND on the amount of current that is being introduced. This was calibrated at 1 atmosphere of pressure, not 1.5 to 2.0 atmospheres like you would see in a turbo with blow through maf!
Basically, small difference between the two wires means less dense air, therefore LESS AIR MASS entering the engine.

Density is directly related to temperature so the maf is designed with those factors in mind. All this differential measurement is done by the sensor electronics. All the PCM does is determine air mass from the voltage it senses. If the air is already hot and compressed, that is going to really throw the voltages off no matter what temps the IAT is reporting.

So stop crying that no one posts anything, at least listen to the wisdom being passed your way, then go out and do what it is you think you should do AFTER you have weighed your options.
Remember, we don't have the data to post for MAF calibration voltage/mass at anything above 1 Atmosphere of pressure and a nominal temperature range.

And another thing: How many different variables are you talking about when you say the Focus guys can make it work right? 3, 4?
The end result is a good air fuel. If your maf reacts a certain way (ie always a bit lean under boost because of the error) then you can either fix the problem with the maf or you can change the fuel delivery by injecting more fuel. You can vary it due to throttle position, boost pressure, MAF voltage, and IAT. If you can program then you can compensate for a problem like that.
This doesn't mean that you picked the appropriate solution.
If it were me, I'd look into other ways to fix the stalling on the zetec.

Former owner of '99 CSVT - Silver #222/2760 356/334 wHP/TQ at 10psi on pump gas! See My Mods '05 Volvo S40 Turbo 5 AWD with 6spd, Passion Red '06 Mazda5 Touring, 5spd,MTX, Black