Guys,

My donor drive train is a 1990 Ford F150 5.0 liter with AOD. I pulled the entire wiring harness including computer from the vehicle when I pulled the drive train as well.

However, considering the vehicle is 17 yrs old , I’m a little hesitant to use the under hood portion of the harness – essentially the entire SPEED DENSITY EFI harness. It’s old, the connections are grungy, it’s been cooked in 17 yrs of engine compartment heat….

Been looking for a replacement harness.

So far, the only Speed Density harness I have been able to find is one made by Centech in Pennsylvania and they want $610.00 for it.

Is anyone aware of anyone else that sells a speed density harness for a 1990 5.0 liter? For what it consists of, $610.00 looks a bit steep.

Don’t try to sell me on going to MAF. It ain’t happening.

Don’t try to convince me to make my own. I was born handsome , not smart.

Thanks,

 

Fergy;

There must be 100's of donor cars that may have harness in better condition than yours, have you tired the re-cycle emporiums in your area. I am using the original 90 EFI harness from my Crown Vic, will make some splices and adjustments, but it will all be in wire loom afterwards anyway. I'll use bullet connectors and some solder as required.

I think I saw a supplier of connectors that could replace wornout ones.

Tom

 

Why not go MAF. Mass air is much better than speed density. You could get the harness from Painless or out of a junked Mustang

 

Ez-wire has them. But they are a bit on the high price side. Every one I've found is $400 or more. I'm going to make my own. I have MAF on mine, I bought a book to show me how. We will see!!!!!!!!

 

The main problem you will have with finding a harness is that you have a truck computer which is wired different than the Mustang computers. All the aftermarket harnesses I've seen have been tailored for the Mustang computer.

If you had a Mustang computer you can use a speed density computer with a mass air harness, you just have to ignore the MAF wire.

 

Quite frankly, it is foolish to stay with SD. There is a reason that Ford dropped SD and only uses MAF now. If I were the OP, I would look for an engine harness and ECU out of a Mustang and use that. Not only will it solve his wiring harness problem, but it will also be easier to tune as everyone and their brother can tune a fox body Mustang.

 

http://www.painlessperformance.com/w...rchField=60510

Or pick up one of these guys and an A9L or A9P

 

I'm not tryin to start an argument, I'm just asking so dont get mad. But why did Ford drop Speed Density, and go to MAF, and GM started with MAF and then went to Speed Density? I know the difference and all, but I just wanted to know the reason's why?


I also have several old Speed Density engines, and would like to find the cheapest route to EFI and stand alone engine harness's? I'm certainly not tryin to hijack this thread, I'm just glad someone brought up the topic.Thanks Fergie!!Is there any EFI genius's out there who could provide us non EFI guys with a schematic of what the least we can get by with to make these engines run? I've heard that the SD systems are smoother and easier to deal with? Any takers?

 

There are a few sites that deal with this topic, I can't remember the truck specific ones but here is one for MAF conversion

http://www.fordmuscle.com/archives/2...sion/index.php

 

Let's see if we can clear this up. Speed density and Mass Air both work fine. It all depends on your application on which is required. So lets start with the basics:

Speed Density uses several sensors and compares their readings to a chart to calculate the amount of incoming air which in turn is used to calculate the required fuel. This method works fairly well as long as a compatible camshaft is used. The cam has to have a lobe separation of 114 with intake duration under 215@0.50 and exhaust under 220@0.50. Any different lobe separation affects the vacuum signal for the Manifold Absolute Pressure sensor and higher durations make a rough rich idle.

Now with Mass Air it uses a "heated" sensor to measure the amount of air entering the engine. This is a more accurate way and it more tolerant of changes. You can change almost change any component on the engine with the exception of the mass air sensor and injectors. The computer will adapt to the new engine configuration and update the stored tables. Speed density will do this also to a certain extent.

A stock speed density system is pretty much limited to a max amount of 300 hp as that is the max the 19lb injectors can support (Crown Vic/Cougar/T-bird engines only have 16lb injectors so its 225 hp). The aftermarket hasn't embraced the speed density system since the better mass air system is easily attainable. The only modifiable speed density computer is the 1987 Mustang DA1 which will allow a forced induction and bigger injectors. Speed Density is good for stock and mild applications.

A stock mass air system still has the same fuel injector limitations but 95% of all these computers are modifiable. These also can be trickier to setup. Sure you can install bigger injectors and have a "recalibrated" mass air sensor but in reality your are just tricking the computer to add the right amount of fuel. It's best to use a tuner to change the injector size and you can keep the same mass air sensor till you "peak" it's airflow. You then need to change to a bigger mass air sensor and change the mass air flow table but that is another discussion. So pretty much you can any engine combination from a 292 y-block to a 460 big block. You only have to go to an aftermarket setup once you have a "heavily" blown engine which requires low impedance injectors as the stock computer is incapable of running them.

As far as computers go pretty much any computer can work, you just need to find the right one for your application. Don't be fooled by the Mustang computer "Myths" that you need a A9L or A9P and that the california tune is better. There maybe is just 1-2hp difference between them all on the same engine.

This really didn't help Furgy but maybe answered some peoples questions.

 

Fergie,

I have no easy solution for the wiring harness. I would say using one from a decent donor is your cheapest bet.

As for the whole speed desnity/mass air flow bit....go with what you are comfortable with.

I recently got myself all worked up again about fuel injecting my old Caddy engine. I will have to build my own engine harness, shouldn't be too bad (famous last words). I will be using the MegaSquirt brainbox as a controller (as soon as I can save my pennies up to order the danged thing)

Good luck
Bobby

 

Gentlemen,

I’m well aware of the benefits of the MAF system over the Speed Density system (and the limitations of the SDI system). I very carefully reviewed the merits of both a couple of years ago and determined that the SD system was sufficient for my purposes. My engine has been completely spec’d and rebuilt with the SDI system in mind.

In my particular situation, I do not need the added benefits of the MAP system.

That portion of the discussion is closed.

As I stated, I have the wiring harness from the donor vehicle. I could clean it up and use if a have to. However, given 17 years of cooking under the donor hood, the grungieness of the connectors and it’s obvious used appearance, I would prefer to replace it with a nice, spiffy new one if it is not too pricey.

Centech offer one for $610.00 which in my mind is too pricey (certainly for me) considering what you get.

I’ve just heard from an outfit called The Detail Zone and they have one that runs $525.00 but requires the 86-88 Mustang computer. It is definitely for Speed Density but in using that particular computer converts it to sequential firing instead of bank firing. In my mind, this would be a wise improvement. In my mind, it should provide better mileage.

I’m still interested in finding other sources – ideally cheaper.

So if anyone knows of someone……

 

Fergie, Dont be quick to overlook what you have like tip49 my 88 model SD motor is using the original harness. 16K later it is still running. Again the SD vs. MAF is a matter of preference. IF you plan a bunch of mod for power and speed probably go MAF. The computer will work with you easier. If you are an easy cruiser looking for gas mileage and reliability like me consider SD and using that original harness. Just my $.02,16k of mileage and 4 years driving experience.

 

Very good explanation. I have one comment on the injectors. You can get driver boxes to run low impedance injectors with the factory computer. However, once you get to that point you are usually better off going to a standalone such as a F.A.S.T or Haltech for other reasons. Good work, I left you rep.

 

If I were in your position I would simply cut off any tape and convoluted tubing that covers the harness and go over all the individual wires with a rag and some soapy water to clean them up. Get some electrical contact cleaner when you come to connectors. Take them apart and clean up the connector shell as well as individual conductors and you just might find that you don't need a new harness. If anything looks really bad you could go to the junkyard and cut off a pigtail and splice it into your existing harness. Then, wrap everything back up with the convoluted tubing and good electrical tape and be done with it. Taking the harness apart also gives you the opportunity to do a wire tuck and clean everything up under the hood.