DME WIRING FOR 924s MEGAJOLT CONTENT

[Dean924s]

I have all but got the ignition set up in my car (say good by to the speed and reference sensors for good!!!!)

I will do a proper write up hopefully as soon as tonight when it actually runs. For now I need a good switched source of power for the unit.

Obviously it needs to be on when cranking but switched with the ignition. I was thinking of either using the power for the coil or preferably the power for the dme. In either case I need a wiring diagram for the DME in my 87 924s with a pin out diagram would be the best.

[Dean924s]

Note to self search AFTER you have a cup of coffee



The sadder part is that I knew I had seen this. For those that are interested it is in Justin's Microsquirt thread.

Ok: Off to Megajolt this darn thing!!!!

[JamesO]

Just as a heads up that looks like the chart I did when full of painkillers, if it is then double check it as some of it is wrong. Try this thread Microsquirt stand alone ECU installation guide

[pdx944]

So this megajolt only controls spark? Why not just use megasquirt?

[Dean924s]

Simple. Cost!

The whole guiding factor of this project was to come up with a way to eliminate the need for the speed and reference sensors and do it for less than or equal to the cost of replacing them (Current Pelican price is $186.50 each). Pelican Part # 944-606-115-00-M14

Hint: Go get the position sensor for a 87 BMW 535i here at pelican. Part # 12-14-1-708-619-M14 Your cost $77. The exact same sensor but the BMW one has a slightly shorter cable making it easier to install.

Anyway. This morphed into a simple get it done for $300 or less. I tried to make this budget work for the MS as it does allow for you to down the road add fuel control. And with the real budget of around 150 as the real threshold. the MS was out of the question completely.

How the project evolved.

I have been putting off the replacement of my speed and reference sensors for quite some time. I have always been able to get it running by wiggling the wires. Well I finally got sick of that feeling you get in the pit of your stomach when the cars is cranking and you are looking at the tach praying for that little wiggle/bounce. You all know that feeling????. . . . It really sucks! So finally I decided to do something about it.

As noted above the first and foremost issue was to get it done for close to the cost of replacement sensors. Now $150 was a tad on the cheap side but hay let’s see what we can do. Here are my costs.

Autosportlabs >> http://www.autosportlabs.com/ <<<
MJ Kit
TPS Kit $74 - Assembled - $144
MAP Kit $89 - Assembled - $161
I went with the MAP Kit.
Data cable and converter plug = $6.00
Optional Mounting Fins for the box $6.00

(a side note here the unit was shipped very fast, packaged very well and great communication through the process. I had it in 4 days!!!)

Car McMaster:
Custom 72-2 toothed gear $42.
(zero communication but cheap and had it to me in 3 days)

Ace Hardware:
Misc. Hardware bolts mounting etc. $10

Radio Shack:
Shielded wiring from RadioShack $9.00 (50 ft roll - enough for 5 cars)
Misc. welding supplies $2.00

Junkyard:
EDIS stuff from 94 Ford Escort (enough to do three cars) Two VR sensors from a FC RX7 This included the sparkplug wires, the mounting brackets and all the associated plugs with pigtails and as much of the wiring harness as I could get at. I also grabbed a bunch of vacuum lines from the newest car I could find. I got about 20 feet of it with all sorts of connectors and stuff. Grand total for the hall $40s.

The trick here is hold up a mess of wires. In my case they only counted the coil packs and then cut me a break. Three for the price of two. My friend at the counter told me they get $20/coil pack. I in essence got all the other stuff for free.

Let’s see... . . Add the 6, carry the one and I get. $204. Well under the $300

Now subtract the two complete EDIS systems I got and will sell on eBay and use the real cost of the wire (about $2) and I hope to be down to about $150 my target amount!

Other expenses that may be coming are another set of sparkplug wires. I will probably eventually go get some from a 4.6 V8. Again another case where a complete set will do two cars. I want to mount the coil further away from the motor. Either on the fender or the firewall. I was even thinking of mounting it to the upper radiator support.

Anyway. When I have it up and running I will post the complete set of photos (start to finish) and some of the blunders I made as well as some of the ideas I have for future modifications / changes. There is also a whole bunch of other possible "side bar" things that you can do with the 5 "ports" that the unit has. Sequential shift lights and redline LED's. Temp sensor timing adjustments. Then there are all the things you can do based on either RPM or MAP. Fire other injectors, meth injectors, water injection, spray an IC with water. I have not focused on this much but I know it is all there waiting for you to play with once the unit is up and running.

Other things I was thinking about / goals of the project is as follows (in no particular order)

1. Get rid of the speed and reference sensors. (Already said that)
2. Do it for less than the replacement cost of the speed and reference sensors. (Already said that)
3. Make it simple. The Ford EDIS is about as dumb as a stump simple as you can get.
4. Make it so if you have to maintain it. It uses Ford parts. Most from the second generation escort. There are thousands of them in the yards. Any junk yard is you new parts supplier for you ignition system. Did I note that the stuff is cheap? Even new the parts are very reasonable
5. Separate the system from the DME.
6. Have the ability to use either a MAP or a TPS system.

I may go to MS eventually but this is baby steps. Get this up and running and give people a alternative to the replacement of the speed and reference sensors.

Continued to next post due to size. The list software made me cut this into two posts due to the size. I wrote it in MS word thus the very long post.

[Dean924s]

Continued form above:

I may go coil on plug, but one thing at a time. I have 7-8 coils on the shelf for my expedition that I could use.

MS is really cheap compared to any other programmable ECU. It was just not cheap enough for the goals I set.

As for the technical aspect of this there will be many of you out there that will say I could have and should have. And you are right. But again, understand, I am doing everything possible to keep it simple and cheap. Make this so it can be installed in a couple of hours with no special tools.

For this reason I have elected to mount my timing wheel to the cam not the crank. Yes you lose a bit of precision due to belt stretch but it makes for a much better mounting location as you will be eliminating the cap and rotor anyway. However this lead to some interesting problems. The biggest is that the EDIS has to see a 36-1 signal wave for every rotation of the crank. The cam rotates half the speed of the crank so I could not use a standard 36-1 wheel from a ford (I have a couple from the junk yard and from motor swaps in my wife’s mustang). This meant getting a 72 tooth wheel and removing two teeth 180 deg out from each other. That is where Carr McMaster comes in as well as the FC VR sensors. I got a suitable 3" dia 72 tooth spur gear. Due to its configuration, it will allow me to bolt it directly to the end of the cam by replacing the stock cam pulley bolt with a longer metric grade 8 bolt. Now I have the reference wheel taken care of. The sensor from the FC was used due to it being proven to work with wheels with very fine teeth (much finer than mine). They are also much smaller than the Ford making them a little easier to mount and more compact. Lastly since I knew where there was one in the local yard I grabbed them. I have the OEM Ford units as well and will probably try them as well at some point.

The rest is just very basic wiring (Why I needed the DME wiring) and mounting of the coil pack and the EDIS units.

The system will run in limp more without the MJ so of there is a failure you can drive the car it will just be down on power as you only have 10 deg of timing.

This is also a good way to test the EDIS and its associated wiring before you connect the MJ to make sure that the car runs.

The really bad part at the moment is I had family things come up today and I did not complete the install. Depending on the weather up here I may have to wait till the weekend to get the car in my friends shop. It was 68 yesterday and at the moment it is 36!!!

Anyway when it runs I will post up all the stuff. The end goal is to come up with a very easy / simple to install completely programmable ignition system that the average 944 owner can install and have up and running over a weekend (really a couple of hours). This system is all of this. The reason it took me so long as I had to figure it all out. To do it again would be a couple hours work once the parts are in hand.

The other thing is that MS is intimidating to those that have not done it. The MJ is much easier to understand. You get comfortable with it quickly. It is much easier for the person that is just getting into programmable engine management to wrap there head around the MJ. I have messed with MS and it is intimidating. There are so many options and ways to have it control the ignition that it can get confusing very quickly. MJ you just have to decide if it is MAP or TPS based system. The EDIS unit takes care of the rest. The hardest part is installing the trigger wheel and with my solution to this it is not really all that bad a deal. I am still trying to come up with a crank based solution but for now using the cam to trigger it works. Not as good as crank fired but many hundreds of times better than the stock cap and rotor set up. And you are going from a old style low voltage ignition system (10-12,000 volts I was told) to a high voltage system (40,000 volts) and it has no moving parts to ware out.

This reminds me. No more cap and rotors to by any more. Last I looked this was $60-$75 to repalce I think. No more $100+ wire sets. Between saving the cost of the sensors and the cost savings of escort wires versus Porsche wires and not having to purchase any more caps and rotors this is looking even better. IT may actually save $$$ over a couple of years once installed.

Now this is it is not a plug and play deal but by the same token it is very simple. The kit is assembled in an hour or two. Just solder it up on the bench. It is all surface mount stuff. Easly done with s 25W pencil iron.

The in car wiring is easy. You wire the sensor to the EDIS, The coil to the EDIS, EDIS grounds and the shielding grounds go to earth. A 12 V power for the EDIS (has to be on when the motor is cranking). You then run two wires shielded wires from the EDIS unit to the MJ (for the PIP and SAW). You then run power and ground to the MJ. Preferably the same power source and grounding points as the EDIS unit. And you are done.

I have the MJ in the glove box as it makes access for tuning easier. I don’t want loose wires around my feet while I am driving. The MJ unit is about the size of a pack of smokes. I will eventually end up mounting it next to the DME up under the dash. It really is that simple.

MS is definitely a great piece of equipment and an option worth considdering. I will probibly be adding one to my car eventially. But it adds at least $150 to the cost of things. And if you want the Microsquirt we are talking at least $200 - $250 more. I also feel that the assembly of the MS a step up in complexity as compared to the MJ. I found the MS assembly a bit intimidating. Whereas the MJ is so simple to solder together my 7 year old could do it. (she has been helping me on this project.

I guess it is all about baby steps and the MJ is a baby step compared to the MS but you definitely get what you pay for. Combined with the relative simplicity of the assembly and install and the virtual guaranty that it will fire on the first try make it a great project for the person just getting their feet wet with this stuff.

Anyway I have typed way too much. What I really hope is that others will see just how easy it can be and how inexpensive it really is. And better yet. No more speed and reference sensors !!!!!!

[Dean924s]

The next question:

How does the DME calculate fuel? Is it based only on the AFM and the TPS? with corrections for temp?

[Schumi]

How do you plan on making the ignition map (10x10 isn't it)? Just street tune off of hte base map till you get what works best?

[Dean924s]

I will probably invest in some dyno time.

I also have a WB02 in the car and a Knock sensor from a 951 hooked up with headphones as well as a boost / vacuum gauge so I will probably give try a bit of street tuning first and see where we go.

I will probably end up with a couple of maps. One for the track & one for the street. High octane fuel, Low octane fuel. I may even see if there is any economy to be had and make a map for that.

This will be the fun part!

[Dean924s]

IT LIVES!!!!!!!!

I now have a Ford EDIS form a 1993 escort running my 924s.

http://www.youtube.com/watch?v=ufkbAqUPiAQ


Still needs tones of work but it runs!!!!!!

[Schumi]

coooooooooooooooooooooooool.

So are the reference and speed sensors on the flywheel totally gone?

I had my doubts about the 72-2 wheel on the cam but that's pretty awesome.

Does it rev up at all in limp mode?

[blown 944]

wow, This coupled with my knock counter could be just the ticket for the street car.

Thank you

[Dean924s]

Originally Posted by blown 944

wow, This coupled with my knock counter could be just the ticket for the street car.

Thank you

Ohhhhhh We need to talk!!!! I have actually come up with a way to wire in myWBO2's aux 0-5V V-out to the Megajolt aux input. I would was then going to have retard the timing based upon the lambda. IE if it gets to lean under load it will take timing out.

You obviously know where I am going with this. The knock would be just to cool!!!

I have lots of spare parts... .. In fact I know I have enough to build a whole second one. (edis units and coil packs the wheel as well as plug wires included) It just has not been welded up. I think All I would need is another mounting bracket for the coil.

[175mph951]

Originally Posted by Dean924s

Simple. Cost!

The whole guiding factor of this project was to come up with a way to eliminate the need for the speed and reference sensors and do it for less than or equal to the cost of replacing them (Current Pelican price is $186.50 each). Pelican Part # 944-606-115-00-M14

you could have gotten bmw sensors for $60 ea...

[fast924S]

We should make a LINK to here
Timing Map for NA car

For future use if anyone needs MAP info

[Dean924s]

Originally Posted by 175mph951

you could have gotten bmw sensors for $60 ea...

Ya but that is boring. My car is never going to be a show piece. In fact I look at it as a rolling laboratory to experiment with. Just replacing parts is no fun. Besides it is the stepping stone to getting rid of the DME all together and I have learned a whole lot and had fun at the same time. And I can say

"Look Ma no cap and rotor"

Ohya and then there is the bigger picture as well and it that involves an M62.

The megajolt is but a piece of the puzzle. >87 944S Supercharge I am very happy with the results so far and if this is all I was doing I would be very satisfied. But ther is a much bigger picture to this project.

[HondaDustR]

How does the DME time the injectors without the speed/reference sensors? and how does the tach work? Looks really cool, though. I may give this a try, especially if my sensors go bad.

[Dean924s]

Currently the speed and reference sensors are in place on my car. I am trying to figure out a way to get rid of them. There is a tack out form the megajolt or I was wondering if I could somehow process the signal from the VR sensor into something that the DME could use. This obviously is work in progress.

What I was really hoping was that the DME could just the tach out signal from the MJ unit. It has to process it for the stock tack so why not use the processed signal for the DME. If ti does all have to do is figure out where to hook up the tack out signal form the MJ in the DME. I know this is really optimistic but it would be so cool if it worked. You then would be able to adjust fuel with the DME and not have to worry about what the timing part of the DME setting is.

[HondaDustR]

Well, what kind of signal is the MJ tach output? I would imagine (hope that) it signals some kind of voltage spike once for every crank revolution at cyl #1 TDC. Doesn't the DME get the tach info from the DME sensor that gets one signal per rev from the set screw on the flywheel (can't remember which of the two it was)? Maybe the MJ tach output could input to the DME as if it were that sensor signal, assuming the MJ tach signal and the DME timing signal position are the same, or could be made to be the same. Does the DME still depend on any of the stock hall sensors for the fuel part.

I'm a little confused. Shouldn't you already be able to not have to worry about what the DME is doing for ignition timing?
Seems to me like whatever the timing is that the DME is doing, there's no ignition system being timed by it, so as long as the engine still gets correct timing from another source (the MJ system), it doesn't matter.

Found some info on the EDIS module. http://www.dainst.com/info/edis/edis.html
Looks like the EDIS module has a tack out signal, too.
Also interesting is the Ford EDIS system can do multiple spark discharge below 1800 rpm. I wonder if the MJ will ever have that implemented.

Maybe you could rig up a knock sensing setup like this http://www.megamanual.com/ms2/knock.htm
into the auxilary input of the MJ, only with 951 sensors.