What is Speed Density EFI and what does it do?
Many Bronco owners are satisfied with their engine power output. For those of you who are not, you have probably already considered adding a new cam, exhaust or heads/intake. In 1986, Ford switched to EFI on 5.0 Bronco engines. 1987 brought the first EFI 5.8. The EFI Ford used for almost all Broncos is what is called speed density. Speed density EFI uses a manifold absolute pressure sensor (MAP), a throttle position sensor (TPS), an air intake temperature sender (ACT) , and the knowledge of the factory intake/exhaust tract which gives your engine certain volumetric efficiencies over it's RPM range. This allows the EEC-IV (Electronic Engine Control IV) to determine the mass (different than volume) of air coming into your engine, and hence the amount of fuel needed to go with this air. Speed density EFI also uses what is called bank fire injection. 4 injector are fired at one time on each side of the engine (only 2 wires for firing injectors from EEC-IV).So why do I need Mass Air EFI?
The problem with Speed Density EFI is, that changing many of your engine components, will change this volumetric efficiency. Speed density can detect some changes with it's MAP, TPS, and ACT sensors. It can not detect that you have changed the volume of air coming in and out of the engine. This is where mass air comes in. A mass air sensor directly reads the mass of air (or number of molecules of air). By doing this, it can detect the changes in the volume of air, in addition to it's pressure and temperature. Mass air EFI is usually what is called SEFI (Sequential Electronic Fuel Injection), which has one separate wire for each injector and fires them twice for every power stroke of the engine. This makes the injector timing more accurate and will help emissions along with power.So what mods can I do?
Speed density EFI will usually run well with just about any exhaust modifications. There are also mild head/cam swaps designed for speed density EFI systems. One list member is running the stock speed density computer/intake with Windsor Jr. heads and a stock 351W lightning cam. Claim is that it runs very well and the key is the lobe separation of the cam, which should be kept above 113 degrees. Lighting Cam specs:.198 intake, .208 exhaust @ .050
.416 intake valve lift, .445 exhaust valve lift
114 degree lobe separation
Stock 351W cam:
.206 intake, .221 exhaust @ .050
.440 intake valve lift, .450 exhaust valve lift
115 degrees lobe separation
Anything else, like moderate to wild cam/head/intake swaps or any forced induction will usually require a swap to mass air. Some guys on the Mustang 5.0 lists have run fairly wild combos on speed density and have had no problems, others have had huge headaches with the same combo. Therefore, a swap to mass air should be in your plans (at least your backup plans) if you plan on any engine mods. This swap can be bought from various sources, but it costs $1000 or more.
Is that all I need?
Keep in mind, that while swapping in mass air will help when doing modifications , once you get beyond the flow capabilities of your stock injectors and/or mass air flow meter, you will need bigger one's. The stock mass air sensor is pretty big, so you will probably run out of injector before needing a mass air sensor swap. You can get mass air flow meters that flow more and/or are calibrated to bigger injectors. This way of doing it is again a gamble, as sometimes it works, but many times it does not. Part throttle timing curves can be disrupted tremendously by trying to fool the EEC-IV with recalibrated mass air sensors. This usually leads to massive part throttle pinging and possible engine damage. Piggyback chips can be custom done for your application (about $225) and will allow running bigger injectors (or even bigger mass air meters) with the same mass air voltage curve that the stock mass air sensor uses. Check out our Sources listed at the end of the article and their websites for more info on the "whys" of piggyback chips and what they can do.So, how do I do it?
Below is information I have gotten from the Bronco mailing list or found myself in regards to this swap. I have not done this swap and I do not even own an EFI equipped Bronco.- All transmission controls have 8 wires except 94-95 5.0's which are supposedly mass air and have 9 transmission control wires. Not sure if this is a CA. thing or not. 89 could have an E4OD trans, which is also controlled by the EEC. It seems all EEC's that control the E4OD have the same number and color wires, except as noted above. Above 89 should have an E4OD (E).
- Mass air conversion from 95, 5.8 processor (processor number BIO0, last digit zero!) would require running 6 new wires for injectors. Pins 12, 13, 14 ,15 and 38, 39. 2 new wires for mass air sensor at pins 9 and 50. Other mass air sensor wires are power and ground. Pin 2 must be run to brake switch. Switch pin 28 to 18 and 19 to 9 (diagnostic wires). May have to add second O2 sensor, relocate pin 29 to 43 and run pin 44 to second O2 sensor. Stock mass air sensor on 95 CA models is 70 mm, which should flow well over 400 HP.
- 96 models all had mass air, but they use Fords' EEC-V, which is under the rules of OBD II (On Board Diagnostics II). this EEC is much more sensitive to engine mods and is also 104 pins, vs 60 pin on the EEC-IV. Not a good candidate for a swap.
- It is highly recommended that any swap be preceded by ordering Fords factory electrical diagrams for what you have and what you want to swap in.
- 87-89 (or any year) models that do not have electronic transmission controls, may have problems using an EEC that wants to control a transmission. This can be fixed by using a 5 Speed Mustang EEC and a piggy back chip. The piggy back chips can even control engine size, so a 5.8 (or even a 410 ci) won't be a problem. These EEC codes should be OK for the swap. A9L, A3M, A3M1, D3D1, X3Z, S0Z. Use of Mustang EEC may require swapping several pins for cruise control wiring. It will also require the wiring changes described in part 2, mainly converting the injectors to SEFI, running new O2 sensor wiring and running new mass air wires.
- It was also suggested that a "Lightning" truck EEC (processor number c3P2) may be used as it is mass air, but can double the amount of fuel that it provides as it bank fires the injectors twice for every power stroke, effectively making 19 lb/hr injectors seem like 38 lb/hr. I would say a piggyback chip would be more satisfactory than this method, but it is another idea.
- Speed density EFI uses bank fire injection. Due to this, the distributor supplied with this motor does not need to know when it reaches the number 1 cylinder. Converting to SEFI requires that the EEC-IV know where the number 1 cylinder is. The distributor may need to be changed to the one supplied with SEFI engines that has one smaller tooth in the hall effect sensor built into the distributor. Some list members have converted to mass air using a mass air kit and have had no distributor problems. Early EFI owners, especially 86-87, should have the excitor ring on distributor checked and make sure the #1 identifier is present in your distributor.
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SOURCES
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Auburn Performance
Equipment 230 Rear SW Cutoff Worc ester, MA 01604 (508 ) 797-9728 |
Johnson
Motorsports 128 Carondolet Court East Mobi le, AL 36608 (334 )344-2621 |