Ford MAF porting

Last Updated on July 23, 2024 by Mutiara

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Most Ford MAF (mass air flow) sensors with an aluminum housing have a post that restricts air flow inside it, such as the SN95. By removing it the vehicle can gain horse power by having better flow. Actual Dyno test have not been recorded for this modification, but all users agree that there is a clear increase in performance. This modification has been performed on 5.0 l and 4.6 l SOHC Mustangs, and 2.0 l SOHC Escorts.

Table of Contents

Procedure

Remove the air box assembly, start by removing the air filter and air silencer (if you still have it in place, its a good time to get some extra HP by discarding it), and disconnect the MAF electronics from the wiring harness.

Disassemble the air box and get the MAM out. Remove the meter tube back plate and discard it, you will not use it again.
Remove the Torx BIT screws (T20 size Torx bit) that secure the Metering electronics to the MAM housing (shown in black in the picture). Be careful not to touch or break the wires. If the torx bit screw is filled in with hard plastic or if they are secure bits, grinding them away and using vise grips to grip them when possible may be a better solution. Replacement screws can be obtained from Acre Hardware.
To cut, loop a hack saw through the Mass Air Meter housing , be careful not to scratch the housing, leave as little material as possible. The MAM has a round sample tube, be careful not to cut it.
Use the Dremel tool with a medium grinder to remove the excess material. Remove all material around the sample tube, leave it as round as possible to avoid turbulence.
Start to sand the MAM circumference, use the 200 grit sandpaper to remove the unevenness of the surface, use the 400-600 grit to give the surface a polished feel.
If your filter came with a metal screen, don’t disregard it, as it provides with added protection against particles and also straightens the air flow.

Technical info

WOT fuel is calibrated to a point 6-10% RICH of LBT (lean best torque) in an effort to inhibit detonation and protect catalysts to be destroyed by overheating. That means there is some power to be had by LEANING out the A/F from the originally calibrated point. By removing the post you HAVE reduced pressure drop across the air meter and lean shifted the WOT fuel.

Removing the crossbar and enlarging the cross-section of the meter (porting it) can affect the WOT (open loop) in 2 ways: first by permitting MORE air to pass per given voltage than the EEC realizes, you have shifted the transfer function lean. And at WOT, there is NO feedback Air/Fuel, so desired A/F is assumed to be correct, and is not actually measured. (We will cover closed-loop A/F in my next point.) and second, you can very likely (in a high horsepower application) reach the Vmaf clip (~4.9V) SOONER so injector pulse width is not updated with airflow info and the system leans out.

Now, for closed loop, it is very possible that the error in the Voltage MAF signal can be “corrected” within the confines of the adaptive fuel strategy. The EEC will do its best to stay at 14.7:1 A/F and has the ability to iterate about that point by correcting the commanded fuel pulse-width a certain percentage. So it wont be a surprise if you don’t experience idle problems, fairly low airflow at idle, times an error signal means not much error at idle.

Now, if you are using an open filter element, HOT under hood air is perceived by the ACT sensor and the spark signal is modified to prevent tip-in detonation and steady-state detonation. There will be GREATER effect of fan wash and other turbulent air sources on the transfer function than the hot air does at speed since the system cools down to some point not too far above ambient. Not exactly ambient, but not the 180F you can see sitting still.

Not all cars are created equal, some variations can occur, one of those is the fact that not all 94-94 (5.0) have the same PCM (EEC) versions.

Each version would have some different variables programmed into it, and those would be the result of software bugs found by FORD or improvements to the stored look up tables or part of the programming.

Some SN95s (5.0) are notorious for engine detonation , which in some cases has to be solved by changing the PCM or by adding a custom chip. In such cases of a SN95 presenting some degree of detonation this modification is not advisable.

It would be a wise idea to try this modification with a junk yard MAF, go buy one and test it.

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