Speed density systems calculate load from the RPM of the engine, the Density of the air in the intake, and the temperature of the intake air. The Density of the air is calculated using a Manifold Absolute Pressure(MAP) sensor, which is attached to engine Vacuum. Intake air temperature is measured by a Air Charge sensor(ACT) or on newer vehicles they are called Intake Air Temperature(IAT) sensors. This setup relies on the fact you have not changed anything, the programming in the control module is specific to a certain engine/drivetrain, and is not very adaptable.

Mass Air Flow Systems directly measure the volume of air going into the engine using the Mass Air Flow(MAF) sensor. This sensor has a two wire element, the hot wire is heated to 200 degrees Celsius above the incoming air, the ambient(cold) wire serves as a reference temperature. As soon as air flows, both wires are cooled, the control circuits then apply more voltage to keep the hot wire 200 degrees Celsius above the intake air, this creates a voltage signal which is monitored by the Control Module. The greater the air flow, the more the wires cool and the higher the voltage.

As you have probably already gathered, the Mass Air system is highly adaptable, and is well suited for high performance applications, and gives fairly good drivability on a performance vehicle. On a Speed density system, just changing the cam can cause the car to be undrivable.

For this article, I will be doing a 93 Ford F-150, 5.0, E4OD trans. Because they don't make a kit for this, I will be re-wiring the harness, and using a PCM and MAF out of a 95 f-150, 5.0, E4OD. If you have a truck with a non-electronic Trans, like the old AOD's, or C-6's, etc, you can use a MAF conversion kit.

Ford racing part numbers:

PART NUMBER YEAR/VEHICLE/ENGINE TRANS

M-9000-A51 1986-88 Mustang 5.0L HO EFI only Manual
M-9000-B50 1986-88 Mustang 5.0L HO EFI only Automatic
M-9000-T50 1987-93 F-Series 5.0L/5.8L EFI Truck only (Will not fit Lightning) Manual
M-9000-T51 1987-93 F-Series 5.0L/5.8L EFI Truck only (Will not fit Lightning) Automatic — AOD only

These kits come with the processor, MAF jumper wire harness, MAF sensor, hoses, clamps and brackets. The truck kits also come with SEFI wire harness, and the upper airbox.

I gathered some of my parts from a salvage yard, the mass air meter and air-box anyway, I couldn't find the air-tube, it runs from the throttle body to the MAF, so I made one, but I think I you look long enough you are bound to find a used one, it seems that most salvage yards discard this part. K&N also makes a air intake kit for the F-150 that would work well for this. I also couldn't find a used PCM, so I bought a new one, it has to be a 95 5.0 with Mass Air and a E4OD trans, keep in mind there are some 95 5.0 SD PCM's out there. The catch code on the one I got was WAY1, VEX1 will also work. I also needed the MAF sensor pigtail, I was able to find one at the local dealership, part # 3U2Z-14S411-CA.

The speed density systems on the trucks are "batch-fired", what this means is that all 4 injectors on each bank are fired together, and then the other bank is fired. In a Sequential Fuel injected(SEFI) car, like the mustangs(sd or MAF), each injector is fired sequentially in the firing order of the engine. Also another note is the firing order will change, the newer MAF trucks use the 5.0 H.O/5.8 firing order (1-3-7-2-6-5-4-8), but the older SD trucks use the old 289/302 firing order (1-5-4-2-6-3-7-8). I am using a mustang H.O. camshaft in the trucks engine anyway, so this works out great.

Ford PCM part numbers

AKC0 - 5.8L - F8TF-12A650-NA (MAF conversion kit EEC) BIO0 - 5.8L - F5TF-12A650-BYA (stock 94-95 MAF 5.8L/E4OD) VEX1 - 5.0L - F5TF-12A650-HB (stock 94-95 MAF 5.0L/E4OD) WAY1 - 5.0L - F5TF-12A650-JB (stock 94-95 MAF 5.0L/E4OD)

Part 2: "putting it all together"