Mass Air Meter article in 5.0 Mustang

[frank3si]

I was just reading an article about mass air meter calibrations in the new October issue of 5.0 Mustangs. This line in the article particularly caught my eye:

"Any changes made in front of the meter - such as eliminating the factory airbox or even swapping to a high-flow filter - can significantly affect meter calibration, creating A/F ratio inaccuracy."

Then in a caption showing Pro-M testing, the following appears:

"Making no other changes than replacing the cone with a typical factory 5.0 airbox, the monitor indicates the setup would immediately be about 18 percent rich unless recalibrated to correct."

This has me now a touch paranoid, wondering about one of the first things many of us do on our Cobras, which is toss in a K&N filter. I'd be interested in seeing any comments any of you have in regards to these statements, and if there is a serious adverse impact on A/F metering in the Cobra by using the K&N. I haven't really noticed any negatives since installing the K&N, but then again I didn't really notice a huge gain either. If there is a potentail negative impact, that, coupled with the possibility of long-term oil buildup on the mass air meter wires from the filter, may have me reversing course back to regular filters...

Frank

 

[Shadowgray03]

Lets see, the MAF measures the volume of air going through it and in turn, based on the way it is calibrated will send a voltage to the EEC. The EEC in turn has the MAF tranfer table data in it so it knows if the MAF is sending it 1volt that "X" amount of air is comming into the engine. With that in mind, what happens if you restrict airflow going to the maf by 50% or simply remove the air filter all together???? The MAF will see less or more air and in turn send a voltage to the EEC that corrosponds to the amount of air going through it, restricted or not. I dont understand their reasoning myself.

 

[frank3si]

Yes, the main point of the article seemed to be that regardless if huge amounts of air flow pass, the max voltage is 4.95 - and that's the need for major recalibration if you're passing flows like that. Still, I was surprised to see the part about air filter changes potentially requiring recalibration...

Frank

 

[Shadowgray03]

Originally posted by frank3si
Yes, the main point of the article seemed to be that regardless if huge amounts of air flow pass, the max voltage is 4.95 - and that's the need for major recalibration if you're passing flows like that. Still, I was surprised to see the part about air filter changes potentially requiring recalibration...

Frank

Well, I do agree that the EEC only gets data in a 0-5v DC range from the MAF but changing the amount of restriction to the MAF should make little difference.

As for requiring a differently calibrated MAF, the only reason to do that would be if you are making so much power that your pegging the MAF and even then going with a MAF that is calibrated differently is a questionable solution at best and here is why. If you rely only on the MAF to deal with A/F changes and you recalibrate it so it reports a lower voltage for a given airflow to prevent it from pegging then you through off all the load tables in the EEC. This is a very bad thing. If you change out the MAF to one that is calibrated differently it is VITAL that you also input the new MAF transfer functions into the EEC so it can do its job properly.

On a side note, when the MAF pegs, the EEC assumes failure and falls back to set parameters, if these set parameters are modified for your combo you can not only make great power, but safe power. SUre your MAF pegs, but only under WOT conditions and if tuned properly it wont matter. Often times going with aftermarket MAF cause a tuning nightmare, drivability isseues and in the end dont necessarily improve your performance or safety.

 

[Got Incon?]

Any changes you make in front of the MAF can cause huge differences because they change the flow pattern through the meter. Things such as placing a bend in front of the MAF (ala the demolet whatever its called) Which is why some had good results, and some had nigthmares.


Anyway, it does make a huge difference, and if you did recalibrate the maf, you would want to send in your entire intake tract up to the TB and have them reassemble it in the exact manor it would be in the car.

 

[mike79]

This is interesting. Im going to have my car dyno'd in a week. I have the CAI and exaust done, ill check it n see.

 

[frank3si]

Yes, the article did address issues such as a bend in front of the meter, and other things that can cause turbulence and affect how the flow is read.

My real question, though, is the statements about something as simple as putting a K&N in place of the stock air filter. Can the flow of a K&N in our Cobras really pass such a greater volume of air as to cause the issues referred to in the article (see top of this thread)?

Frank

 

[Shadowgray03]

Originally posted by frank3si
Yes, the article did address issues such as a bend in front of the meter, and other things that can cause turbulence and affect how the flow is read.

My real question, though, is the statements about something as simple as putting a K&N in place of the stock air filter. Can the flow of a K&N in our Cobras really pass such a greater volume of air as to cause the issues referred to in the article (see top of this thread)?

Frank

As I mentioned above, they measure flow weather its increased or decreased has no bearing, the MAFs job is to measure, the only thing that affects it is turbulence etc.

 

[Got Incon?]

Originally posted by Shadowgray03
As I mentioned above, they measure flow weather its increased or decreased has no bearing, the MAFs job is to measure, the only thing that affects it is turbulence etc.

As I mentioned above, by changing what is in front of the meter, you change the flowfield through it, so that what the meter measures is not indicative of the total flow anymore. A meter is calibrated with the configuration it will run in. A known amount of air is passed over it, voltage readings are noted, then you can correlate an increase in voltage to being the measured amount of air. However once you change what is in front of (or directly behind) the meter, you change that air vs voltage curve to a different one. Now your readings are off. In cases like a bend in front of the maf, the calibration can be so far off the car will not run correctly any more.

 

[Got Incon?]

For some more tech, the reason this happens is because a maf meter samples just a small section of the airflow, then ASSUMES flow to be nearly the standard turbulent flow cross section (people misuse turbulent air, as all air in a intake tract of a car is turbulent with what they are actually trying to say as being non-uniform and non-steady [in-time])

Such meters as the new meter from pro-m with all the ports all the way around the whole maf try to sample the entire flow, which means changes can be made to the intake tract and not bother anything because now the meter does not have to assume that the air flow is uniform across the entire cross section, it is actually measured.

 

[Mojo03]

For what it's worth the MAF on the s003 Cobra is good for 500RWH. More than that, you're already replacing injectors, throttle doy, etc, so reaching above 500 tells you it's time to replace the MAF meter, too

 

[Shadowgray03]

Originally posted by Got Incon?
For some more tech, the reason this happens is because a maf meter samples just a small section of the airflow, then ASSUMES flow to be nearly the standard turbulent flow cross section (people misuse turbulent air, as all air in a intake tract of a car is turbulent with what they are actually trying to say as being non-uniform and non-steady [in-time])

What bothers me is the fact that these aftermarket companies say they will set you up with a calibrated MAF but what they are referring to is calibrated to injectors and NOT calibrated to your intake, which is whats important.

Originally posted by Mojo03
For what it's worth the MAF on the s003 Cobra is good for 500RWH. More than that, you're already replacing injectors, throttle doy, etc, so reaching above 500 tells you it's time to replace the MAF meter, too

Most people with a KB are well over 500rwhp and running stack MAF. Does it peg...sure, does it need to be replaced....no.

 

[Got Incon?]

Well both are very important. One thing you can do is run a straight section to a symetrical conical air filter in front of the MAF. This generally means that the assumption that the MAF makes of uniform turbulent flow is correct, and everything works out nice. Just don't put bends in front of the MAF like the desecharger unless you plan on custom tuning the MAF by sending everything to pro -m.

 

[94SVT Coupe]

Originally posted by Got Incon?
Well both are very important. One thing you can do is run a straight section to a symetrical conical air filter in front of the MAF. This generally means that the assumption that the MAF makes of uniform turbulent flow is correct, and everything works out nice. Just don't put bends in front of the MAF like the desecharger unless you plan on custom tuning the MAF by sending everything to pro -m.

Exactly. I don't think a cone filter on the MAF is going to screw up the MAF readings, even without a stright piece. The stock filter is a cone filter, bolted right to the maf.