have the 5.0 engine. would like to put the 5.8L engine in. will the 5.0 cpu and harness acomidate the 5.8? (91 F250 L.D.)

 

The wiring harness, definitely. The computer yes, with reservations. It will run the 5.8, but a computer for a 5.8 will be better, and it'll plug straight into the 5.0 harness.

 

You'll need to modify the injector harness to fire the "windsor" order over the stock 302....i.e 4-8 compared to 7-8 order on last 2 cylinders. Unless you are getting the 5.8 harness with the engine.

I'd recommend getting a Mustang EEC. If you are staying speed density, get one from an 87-88. If you are going MAF, get one from an 89-93. The stang EECs are more agreesively programed with better fuel mapping and timing curves....more bang for the buck! Salvage yards let them go for about $60.

I've done several swap with great sucess.

 

hey if its a 91 then hes speed density. That means the computer and wiring harness will both work. I would know. I just did this same thing. Im still trying to figure out how to get the EGR routed in but it's running. I think it's running on all cylinders. hehe.

 

^^ there is a lot of wiring that has to be done in order to run a mustang computer. Running the stock truck computer, nothing needs to be done to the wiring harness - the injectors are wired the same on both engines for both firing orders.

The 5.0 computer will run the 5.8, but if you can get your hands on a 5.8 computer, it will work better.

 

EPNCSU2006,

I just did this whole swappola thing. Not much wiring at all. In fact, I got the FMS MAF conversion kit. I wasted my money. It comes with either a A9L (stick) or C3W1 (auto) "Mustang" EECs, a wimpy 55mm stock Mustang MAF, overlay harnes to swap the last two cylinder firing order, and air box lid to adapt the MAF.

The only difference between the SP and MAF computers from the truck to the Mustang is the truck certain year trucks use a knock sensor, Mustangs do not, and the Mustang uses dual O2 sensors and the trucks through 93 use one. SD sytems use a bank firing order vs. sequential and the injectors will need to be rewired. On SD, 3 wires are used to fire the injectors....thus a ground, one for left bank and one for right bank. On MAF, 9 wires are used. One for ground and one individual wire per injector from the EEC. I've run both the C3W1 and A9L without issues. It don't need the knock sensor so don't need the wires. It could use the extra O2, but since the y-pipe only has one, it don't miss it BECAUSE it is upstream of the cats.

A stock 5.8 truck computer will not make it run any better than a Mustang 5.0 computer. Many people are running 302, 331, 347, 351, 383 strokers off of the 5.0, Mustang computers with great results without additional tuning or chip burning (of course natrually aspirated). Much of it is based off of the "windsor" firing order and MAF...more balance firing order and adaptable to airflow changes.

Now knowing what the kits consit of, I would have just spent $100 for EEC (at most), $20 for wiring, $40 for a used MAF, and $10 on PVC pipe to tie it together over $650 I did spend.

Don't mean to start a long thread of disbelief, but I have and am running the configurations listed above.

 

I know what it takes, I'm running an A9L in my truck, and I re-wired to account for quite a bit of differences - Injectors, MAF wiring, O2, TAD and TAB are different, I wired in the mustang A/C cutout relay, and canister purge solonoid.

As I said before, I know what is involved, and it's more than what you think. There are also speed density mustang computers which sequentially fire the injectors - the truck system is the only one that batch fires the injectors. The injectors get a common +12V and the computer grounds them to fire them. The O2 sensors on the mustang do not monitor catalyst performance - there's no O2 sensor after the cat on mustangs with the A9L family of computers - that didn't happen until OBD-II. There is an O2 sensor in each exhaust manifold to keep track of how each cylinder bank is doing. The computer does miss it, and I guarantee there will be a code in the computer for it if you aren't running it.

I never said the stock 5.8 truck computer would be better than a mustang computer. I said it would be better than the stock 5.0 truck computer. I realize the capability of the mustang system, as I am running that computer in my truck. The ability to run larger/modified engines has nothing to do with the firing order - the sole reason it can adapt to upgrades is because it uses a mass air sensor.

That's what I did on my truck.

I don't mean to be rude, but I want to get the correct information out there. I've spent considerable time trying to understand Ford EFI, and modifying my truck wiring harness to work with the mustang computer, and feel I know what I'm talking about.

 

EPNCSU2006,

Could you elaborate on the "bank injector firing" issue. This all seems exactly right. I noticed years ago that my 86 mustang has individual circuits to the injectors which obviously fire them in the firing order. I also noticed that my 86 bronco has fewer wires to the injectors, namely, what looks like a common hot wire per bank and a common ground. Are you saying that the entire bank fires its four injectors at the same time!? If so, no wonder the performance and economy of the trucks is much worse than the stangs (as well as other obvious reasons). If that is the case then only one cylinder per bank would be getting its fuel at the proper time. Or are you saying that the grounds for the "bank fired" injectors are actually separate circuits back to the EEC which supplies the needed ground in the firing order sequence?

 

Bank fire actually a little bit misleading, so that's why I call it batch fire. There are three wires going to the injectors on the batch fire system. There is common power to all the injectors (just a switched 12V source that is hot when the key is on - powered by the EEC relay), and two control wires to the computer, which grounds each circuit to fire 4 injectors at a time. The injectors are grouped together 1-4-5-8 and 2-3-6-7. All four in each two groups fire simultaneously. This does cut back fuel economy considerably. I'm not sure why Ford chose not to use sequential injection on the trucks.

Sequential EFI has a common power to all injectors, and 8 individual control wires going to the computer, which grounds the injectors in the firing order of the engine. For lower rpm applications, sequential EFI will be more efficient. Once above a certain rpm, the injectors are firing almost constantly, so the difference between batch and sequential is less noticeable.

 

Then converting my batch fire bronco to a true sequential injection scheme would require the mustang injector harness and the mustang EEC harness or at least the additional wires from the injectors to the EEC?

 

You do need the additional wires to convert from batch fire to sequential.

Batch fire vs. sequential does not a huge difference in fuel economy. If it did, the automakers would have adopted it sooner. All the GM TPI engines used batch fire on Corvettes and Camaros right on through 1992.

In a sequential fire system, the injector is timed to fire during the intake stroke, which is what you would think you want. Getting it right requires some means to tell the computer which cylinder is which, so you need the Mustang distributor as well. The batch fire system fires some of the injectors against a closed intake valve, which sounds weird, but gains the benefit of using the back side of the hot valve to vaporize the gasoline. This compensates to some degree for the loss of optimality in the injector discharge pattern. And as EPNCSU2006 pointed out, it doesn't matter above a certain RPM.

The Mustang computer is also MAF, which at least in Ford's implementation, is better tuned than the speed density setup.

You could certainly switch it over. The Mustang system trades cost and reliability to get better idle and throttle response. You might get 0.5 mpg better fuel economy. But a heavy truck with the aerodynamics of a brick is never going to do as well as a car on gas mileage.

 

jcarson, you'll also need the mustang computer - the computer is what makes it sequential injection. The first EFI mustangs were speed density, but still used sequential injection. So, if you wanted to convert, may as well go to mass air while you are doing all the wiring.