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Idahome
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James cancer treatment is going very well! He is more active and gaining his weight back, so he has also been in the shop turning wrenches more, in fact we have also been building a new pad back here where James plans to build his own shop this summer!! Woooohoooo more shop space at the house.
Anywho we had some major progress on the sport trac in the last few days, the last major hurdle for this 02 trac 5.0 conversion was getting the speedometer to work, at the same time making the ABS, cruise control and 5.0 engine computer happy with the speed signal
We did this by wiring in the Dakota Digital SGI 100BT Speedometer calibrator and now we have it working.
The Dakota box gets mounted behind the stereo, near the GEM module. I chose this location because 3 of the 4 wires we need are available there
The Dakota speedo signal converter is used when doing a 02 Sport trac 5.0 (02+ Ranger will be similar) because in 2002 the old v6 PCM used to do the "buffering" of the speed sensor signal for the truck. We removed the v6 pcm.
WIRING IN A DAKOTA BOX:
The speedometer/speed signal goes like this in a 2002 sport trac
OSS (output shaft speed sensor in the transmission) feeds the V6 PCM a speed signal
The V6 PCM "buffers" the speed signal to adjust for tire size and sends the corrected signal to the trucks modules, GEM (for 4x4 shift), Cruise control, and instrument cluster
These modules use the same old 8000 ppm as most Ford speedometers want to see. PPM is pulses per mile
Since the 5.0 PCM is now in the truck and the v6 pcm went bye bye we needed to add a module that can do these calculations for us.
Otherwise the speedo, cruise, PCM and Gem modules would not be happy.
There is one other module in the truck that needs a speed sensor signal also, the ABS pump motor. IN 2002 the 4x4 ABS pump is still using the vss mounted in the rear axle. This is the only module on the truck that still uses the 8.8 mounted sensor.
From 2002+ the OSS in the transmission tail housing is the speed sensor for most of the truck
So lucky for us Dakota digital has been making speedometer signal "buffers" for some time. Now there are other options on the market, you can use a GPS enabled converter as well but it does require a GPS antenna. GPS is not always available, so we chose to use the dakota box.
Plus the new SGI 100bt is bluetooth! so you can change the speedometer settings on your phone or tablet...cool right?
This unit replaces the old SGI-5 which many people have tried to use before.
So how the heck do you wire one of these things in?
Well that was the challenge, I finally sorted it all out.
A few minutes of wiring was all that was needed after weeks of research and a few sleepless nights we now have a working speedo.
I had to purchase the 2002 Sport trac wiring book to figure this out and do a bunch of question searching online. Looking back it is all very simple really. Here is how we did it:
The Dakota box needs 4/5 wires:
It needs a speed sensor input (1), a speed sensor output (2), power (3) and a ground (4). The speed sensor ground wire is optional and found to not be needed (5).
So for me I wanted to use the VSS signal from the rear axle, because almost every truck I build has a 8.8 rear axle with a VSS mounted in it.
The VSS wires in a 2002 sport trac go from the rear axle sensor directly to the ABS Pump under the hood. The wires are pink/red (+) and light green/black (-)
WE TAP INTO the Pink/Red + wire (1) and run it into the cab and up behind the stereo next to the gem module. DO NOT CUT the wire as the ABS brakes still need this signal!!!!!!!!
This is the VSS feed and it goes to spot Speed signal input + on the dakota box
Next we need a VSS output, you can find this wire circuit 679 grey/black (2) at the Gem module pin 14 on connector C20001a
Ignition power (hot in start or run) is found at the GEM (3) as is a good ground (4)
So the wiring is the EASY part. Figuring out how to setup the Dakota box to do our buffering calculations is the hard part.
This took a little experimenting!! (driving back and forth on the driveway 4000 times trying different settings did not work)
Basically here is the secret everyone wants to know, you see there are SEVERAL threads online for how to use the VSS signal from a 8.8 into a hot rod, or 5.0 Ranger or Jeep or anything...and no real clear answers.
Not one thread where somebody came back and explained the wiring and how it was done and why. Well here it is!
I knew this going inL: Ford speedometers want to see or are calibrated to a 8000 ppm signal
So how do we get there? How many pulses per mile does a rear axle VSS sensor send?
That answer goes like this
Our sport trac has 29" tall tires. A 29" tire makes 720 revolutions per mile.
The speed sensor reads a tone ring mounted on the ring gear in the 8.8 axle, the tone ring has 108 teeth (I know I checked and counted) The ring gear turns once with every revolution of the tire
so 720 (tire revolutions per mile) x 108 (tone ring teeth) = 77760 pulses per mile generated to the ABS pump motor.
Now we need to turn 77760 PPM into 8000 ppm using the dakota box.
If you look at the dakota instructions seen here: https://www.dakotadigital.com/pdf/sgi-100BT.pdf
Any signal over 32000 ppm is considered a HIGH signal
Any signal under 32000 is considered a LOW signal
So we need to setup the Dakota box to use a H - L setting (high signal converted to a low signal)
This is listed as "application 3" in the instructions.
With the dakota box we are able to take the HIGH input signal of 77,760 and calibrate it with a factor of .25 (25% of the signal) all the way up to 4.0 (400% of the signal).
You can enter any number from .025 up to 4.0 and change it while driving to dial in your speedometer to be accurate.
The dakota box will take your input signal and multiply it by your chosen CAL or calibration number and send the corrected output to the wire hooked up on terminal OUT1
We need a signal of 8000pmm to make our speedo happy.
If you multiply 77,760 by 25% or 0.25 (the lowest setting available) you can see it is still nowhere near 8000 (25% of 77,760 = 19440)
The dakota box gives you more options! Hooking the output wire up to terminal 1 and a CAL of 25% still results in over 19000ppm!
But Hooking it up to output wire 3 is 1/16 of that value, output wire 4 is 1/32 and output 5 would be 1/64 of the value (sent to output 1).
So now we have math to do, we are getting somewhere.
I know that 1/16 = 0.0625 converted from a fraction.
So lets take the VSS signal of 77,760 ppm and figure out how to make 1/16 of that number close to 8000
I found if we first multiply 77,760 by 1.65 and then take 1/16 of that we get close
77,760 x 1.65 = 128,304
1/16 of that is 128,304 x 0.0625 = 8019
YEAH!! Still Following me?
So the Dakota box is setup like this, First you know you need to use the High to Low conversion, so application 3. In the Dakota box you adjust the base setting to be H-L
Next you set your CAL value at 1.65
Finally using output wire 3 we will be using 1/16 or 0.0625 of the calculated value and sending that to our VSS wire
IT WORKS!!!!!!!!!! Now we can drive around and actually dial in our speedometer using a simple GPS to check speed.
VSS signal of 77,760 PPM is input to Dakota box
The CAL value is set to 1.65
77,760 x 1.65 = 128,304
We need 1/16 of this value sent to the speedometer (1/16 of something is X 0.0625)
128,304 x 0.0625 = 8019
Test drive = Accurate speedo!!!
Confused yet? I was....for a few days, losing sleep, walking around all bitchy and pissy because I couldn't figure this out, this happens with me I live and breathe these trucks so until I sort this out I'm like a zombie nobody wants to be around. Well now I'm back to my chipper happy self because we WON THIS BATTLE
Now I will make a post that puts this into layman's terms
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I build custom RBV, specializing in drivetrain conversions, wiring, suspension and complete custom trucks