MAF

[alerocity]

what is a MAF? :huh:
could u show me some pics of it?

[overdrive75]

Mass Air Flow sensor. It is used in determining which part of the fuel maps to operate the engine, as well as some other things, even relating to transmission behavior.

Oh yeah I noticed you have the Ecotech

2.2L Eco-Tech has a MAP sensor Mass Air Pressure

3.4L LA1 has the MAF

Basic differeces

MAF has more functionality, monitors air flow, and pressure

where as a MAP can only monitor pressure, not air flow.

[Aleromaster]

Its the box pointed at by the arrows. I hope who's ever car that is dosn't mind that I borrowed the pic
Edit: whoops also just noticed that you have the eco so I guess it dosn't help you to much

[Fast Eddie]

Originally posted by overdrive75@Feb 26 2004, 07:25 PM
Oh yeah I noticed you have the Ecotech

2.2L Eco-Tech has a MAP sensor Mass Air Pressure
MAP is usually the manifold absolute pressure sensor, not sure if this is true on the eco or not but I've seen AFMs, MAFs, MAPs and a few other ways for EFI to determine the pulse width and a mass air pressure is a new one on me, probably just another name for what Im thinking of.

Oh yeah a MAF cannot determine pressure, at least not any i've seen. It only determines the velocity of the air entering the intake then it calculates the amount of O2 entering the engine based on several factors.

Sorry blabing, you got the answer to ur Q.

[overdrive75]

Air pressure can be calculated from air flow, very acuratly. However, it is extremely difficult to get accurate air flow from air pressure. In the case of a MAP sensor it relies on speed density tables for the air flow values, where the MAF can directly measure air flow and acuratly calculate air pressure.

[Fast Eddie]

provided you don't change the volume of the area the computer is programmed to ;) otherwise the results can start to waver, and air velocity can be used to calculate the pressure yes (once again provided the volume is a known), but the truly important thing for the computer to know is the pressure, as that will tell how much air will enter the chamber when the valve opens, thus determining how much fuel to mix with it. In other words air flow is nice to know but from the ECU/FMU perspective it is really useless.

[overdrive75]

I am not going to get into an arguement nor am I flaming, but your statement holds true for a MAP, not a MAF. A MAF is extremely tolerant in changes in volume.

I deal in this stuff day in and day out. A MAF system has the ability to learn the change in volume and comprehent it, where is a MAP system is always referencing tables.

[Fast Eddie]

I'm not trying to flame or whatever either I'm just trying to understand.

I know GM probably has there own algorithem for the EFI system, I thought you were a tranny guy :P, but the formulas i'm familiar with utilize the manifold pressure, independent of the method to determine it, not the air flow, basically- (MAP*VE*CYL disp) /absolute temp -tells how much air is in the cyl. Then goes through some other computations to determine the pulse width for the injectors. In other words no table look ups for the MAP system I'm familiar with. If you know how GM does it I'd love to see that, whether here or off board. I'd be especially interested to see how the MAF system determines the manifold pressure, if it needs it, w/o knowing the volume of the manifold, my little brain just can't figure out how it would work w/o knowing that, even w/ the volume I cant figure out how it would work....

Once again, im just trying to understand how various systems work and I know FI is one that can totally change the way are car performs.