1. Electrical Systems
  2. Converting Turbo I to Turbo II Electronics

Parts of this article were researched at the MiniMopar website.
Using a custom ECU tune (available from several of the vendors and several members of this site) usually requires that your engine be equipped with what is known as "Turbo II" electronics.

"Turbo I" engines did not have an intercooler, and ran about 6-8 psi of boost, stock, though they had air/fuel maps for up to 1 bar (~15 psi). "Turbo II" cars had an intercooler and ran about 8-12 psi of boost in stock trim. Because turbochargers heat the air they force into the engine, and because the Turbo I engines lacked an intercooler to reduce the temperature of the air charge, the Turbo I engines were not equipped with an Air Charge Temperature Sensor . (It was assumed that the turbocharger would add significant heat to the intake charge; therefore, the battery temperature sensor and the coolant temperature sensor could be used to determine intake temperature.) Turbo II engines were equipped with an intercooler, which used ambient, outside air to cool the temperature of the intake charge before it is forced into the engine. So, Turbo II engines had the ACT sensor, since the intake charge could be significantly cooler than the air coming directly out of the turbo.

Because your engine did not originally have an intercooler, you need to install an ACT sensor before you can install the Turbo II computer. This will allow the computer to know how cool (and thus dense) the air is entering into the combustion chambers. Basically, installing an intercooler onto a Turbo I engine will prevent detonation because of the cooler air, but the computer has no way of taking advantage of this cooler air, because it assumes that it is still hot. So, installing an intercooler onto a Turbo I engine prevent detonation (good thing), but you do not get any more power out of it (bad thing).

You cannot simply install the sensor, unfortunately. Turbo I cars were (usually) not wired for the ACT sensor. So, you must install the wiring for the sensor, including the requisite pin on the ECU.

Here are the materials you will need for this project:
  • Air Charge Temperature Sensor (available from Mopar or Dodge Dealers, from Turbo Mopar Vendors, or at a junkyard, though I recommend just getting a new sensor)
  • ACT Sensor Wiring "Pigtail" (available from Turbo Mopar Vendors or from a junkyard)
  • ECU Pin (get a whole plug from the junkyard)
  • Miscellaneous wires, solder, etc.

The first thing to do is to get an ECU plug from a junkyard. Just cut the thing out of the harness. It looks like this:



See those little copper circles? You want one of them.
You're going to need a sharp tool for this; I used a sharp pick-like object from an electronics tool kit.

First, you need to remove the rear of the plug, exposing all the wires. It is just held on by a few clips and pops right off:


Next, you need to remove that red clip on the "front" of the plug; that is what's holding the pins in. Use that sharp too to carefully remove the red clip:


Now, all of the pins are exposed. Using that sharp tool again, carefully guide on of the pins out of the "front" of the plug:


That's it; you're done with the junkyard plug, though you may wish to hold onto it in case you need a pin for something else.
Now, go to your vehicle and remove the battery so you can get to the SBEC/SMEC connector. The connector is held in with an 8mm bolt. Carefully separate the connector from the computer module so as not to bend any pins.

Again, remove that backing plate from the plug, exposing the wiring. Carefully remove the red retainer clip. The Turbo II computers use pin 21 for the ACT sensor. You will probably notice that there isn't a wire (or even a hole!) for that pin on your connector. That's OK, because we're going to add it.

Using a good electric drill, carefully drill a hole into the back of the plug where pin 21 will go:



Now, make sure you get any plastic debris out of that hole!
Take that pin that you removed and carefully slide it in through the back of the plug:


Slide it up so it is even with the rest of the plugs:

Reinstall the red clip:


Using solder and heat shrink, extend the wire on the back of that new plug, giving it enough length to reach the sensor location. Reinstall the back of the plug, and replace it into the ECU, carefully tightening the 8mm bolt.
On Turbo II engines, the ACT sensor is installed on the intake manifold. The port that is used doesn't even exist on Turbo I manifolds.

Here is my Turbo I manifold. Next to the Fuel Pressure Regulator, there is a vacuum port, and to the right of that port is a small raised area. That is where the ACT sensor would go on a Turbo II motor.


You've got several options here. First of all, you could remove the manifold, and drill and tap a hole to install the ACT sensor. This is probably the "best" way to do it. Secondly, you could install some sort of bung to your charge piping right before the throttle body and install it there. (To do this, take your ACT sensor to the hardware store and find a nut that will screw on it. Then drill a hole onto your intercooler piping right before the throttle body, weld the nut in, then install the sensor.)
The third option is for lazy people like me:


Figure out a different place to hook up that vacuum line and just screw the ACT in there. (Fortunately, that hole is the correct thread size for the sensor.)
Regardless of where you installed the sensor, you must now install the wiring pigtail. The correct pigtail has two wires on it: black with a red tracer (signal) and black with a green tracer (ground). Run the black/green wire to a good signal ground, such as the fuel rail bolts. (As an added bonus, the fuel rail bolts are only inches away.) Connect the black/red wire to the pin you installed earlier.

That's it--you've installed an ACT and done the necessary modifications to run a Turbo II computer. You may wish to leave that sensor UNPLUGGED until you install the new computer, though, as it may cause a CHECK ENGINE light on a Turbo I computer.

Congratulations! You just modified your car's ECU!



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