MAF

by Michael Decipha Ponthieux
Posted: 5-31-2014
Last updated: 9-13-2016

CLICK HERE for MAF Transfers

Basics

A Mass Air Flow Sensor Element is a hot-wire thermister thats regulated at a specific temperature. The more air that crosses the element, the cooler the element gets and the more voltage required to maintain its regulated temperature. The voltage outputted by the MAF (mafV) is directly related to its resistance. MAF sensors require 4 wires minimum. A +12v battery power feed, a dedicated ground, a grounded 5v reference ground (will measure +5v across battery 12v+) , and a signal return mafV for the ecu to correlate the amount of airflow to the ECU. The mafV is used by the ecu to lookup or "transfer" the voltage to an airmass, this is known as the Mass Airflow
Transfer Function FN036.

The mafV is the MOST CRITICAL tuning variable in a mass-air engine computer.

Extenders

MAF Extenders (such as the DIABLO Sport MAFIA), function by increasing the reference voltage from -5v to a higher voltage, typically -7v or higher. The return
signal is then scaled back down by the device to -5v and outputted on a linear slope to the ecu for tuning. The only caveat of doing so is that the regulator
must be able to maintain the reference voltage stable. This is not always practical in many "noisy" vehicles. HID headlighting and Electric Water Pumps are
notorious for causing issues with such devices. Most all MAFs are capable of supporting a 7v reference voltage with no damage.

Frequency

Some METERS operate on a frequency, such as GM and newer 2011+ ford MAFs. These meters operate on the same hot wire design but have an IC on board that
convert the voltage to a frequency output to be inputted into the ecu. The basics remain the same.

Element

All MAF Elements are basically the same design. In some applications (specifically on GM vehicles), the MAF element is backfeed power when the vehicle is turned
off to "burn-off" any contaminants on the MAF element. Ford is notorious for using the exact same MAF element on many different models of their vehicles.
Be mindful, they are not the same METER, they use the same element but have different housing which creates mutiple different MAF Transfers = Meters.

Housing / Pipe

The MAF housing is the largest contributor to the MAF sensors measuring range. The larger the diameter pipe, the more measuring range the meter will have.
The more commonly used MAFs are made in 3 typical designs. The first and most common is a slot style meter (ford 2005+) which is a "blade" MAF where air
flow is sampled in the center section of the pipe. This is the most accurate commercially available MAF's being used today. The second most common MAF
design is where the element is placed in a "sample tube" mounted to the edge of the inside diameter of the pipe. In this design only the outside edge of that
section of the pipe is being sampled (ford EEC-IV design). The 3rd most common MAF design can be found in some aftermarket MAF meters where the inside
diameter of the pipe has air passage grooves where the airmass is sampled. This is the least common design.

Meter

A "Meter" often referred to as the "MAF" is the result of the element AND THE HOUSING. Simply removing an element from it's housing and
placing it in a different sized housing/pipe will give you a COMPLETELY DIFFERENT METER or "MAF SENSOR". This means that your current
MAF transfer will not be accurate for your new meter. Thus it is not recommended to remove an element from its housing to be used in any other housing.

Screens

Unless you have 3x the pipe diameter of straight pipe before and after the maf, you should have screens installed. Contrary to some belief, a screen DOES NOT restrict airflow. Anything done to straighten out the airflow will increase velocity thus increasing airflow which at the same time increasing accuracy which provides much much more accurate fuel control giving better fuel economy. Another major benefit a screen can provide is a huge reduction in low airmass fluctuations which result in a bucking/trailer hitching sensation. See the PRE TUNE INFO for more details.

Stock & Calibrated MAF's

A "calibrated" MAF is an aftermarket METER designed to be used with a STOCK TUNE for a specific application. Thus, a 'calibrated'
meter for a Cobra WILL NOT BE ACCURATE for a GT. Nor will an 95- Mustang GT "calibrated meter" be accurate for a 96+ Mustang GT. A calibrated
meter relies on the STOCK TUNE to be accurate. This is known as "scaling." In order to create a "calibrated" meter, you must first have the stock meter or
MAF Transfer. A calibrated meter then has the EXACT SAME flow characteristics as the stock meter but at a higher air mass. This is the principles of scaling,
which means the ECU is no longer measuring the actual airmass but a percentage of the actual air mass. Two meters with the exact same flow characteristics
will have the exact same percentage of airmass difference. This percentage differentiation is the SCALING PERCENTAGE. By doing so, aftermarket meters can
be made to have a 'calibrated' scaling percentage equivalent to a higher flowing fuel injector at that same scaling percentage. For example, a stock 86-01
GT Mustang is equipped with 19lb injectors. If the injectors are replaced with 80lb injectors, the ecu will now be spraying approximately (80/19=) 421% more
fuel than needed. Since the ECU is now spraying 421% more fuel, a meter that flows 421% more air will return the air to fuel ratio back to the original equivalent
ratio it was previously. We can logically infer now that a 'calibrated' meter will have the exact same transfer function as the stock meter but with more airmass
at a given voltage. Calibrated meters are NOT NECESSARY when you have tuning capabilites, or if you are getting your vehicle tuned. If you do not have the MAF
Transfer curve for your "calibrated" meter, you can simply multiply the stock meters airmass flow by the scaling percentage. For example, if you multiply the stock
meters airmass flow by 421% (x4.21) you will now have the accurate MAF Transfer for an 80lb calibrated meter.

With this knowledge, it is not required to have a calibrated meter for an injector swap if you will be tuning your vehicle. If you have tuning capabilities,
I ONLY recommend buying a meter calibrated for 60lb injectors ONLY. I have found in my experiences that 60lb calibrated meters are the most accurate and
consistent of all 'calibrated' meters, and have a flow measuring range that will support up to approx. 850 hp, sufficient for most street engines.

If you have any questions post your concerns in the MAF thread on the forum.

Wiring Diagrams

CLICK TO ENLARGE

Special thanks to those who have posted the diagrams.


Read the Fuel Write Up for MAF Tuning details and
read the Scaling Write Up for MAF Scaling details or
CLICK HERE for MAF Transfers

Continue reading on to understanding how HEGOs work.

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