Controlling Cold Start Injectors With The EEPC

Description

This page describes how to control your cold start injectors with an Electronic Engine Performance Controller (EEPC).  Cold start injectors can most easily be found at salvage yards on European vehicles that have mechanical fuel injection with the Bosch fuel control system.  These include Saab, Volvo, and Volks Wagon.  There are two sizes that are out there, but there seems to be no easy way to identify them.  They are usually located in the center of the intake manifold; and on mechanically injected vehicles, they are the only injectors with wires coming out of them.  When removing them, cut the fuel line about 2 inches or more from the injector because you will need it.  Also cut off the wire harness with the connector on it, so that you can use it to make the electrical connection.  Remove a couple different ones to try out.

According to Gus, the easiest way to identify them is to apply 12V across the pins and blow through them.  Assuming you found at least one of a different type, you'll find that some are easier to blow through than others.  According to Gus, the injectors that flow better are good for 4psi of additional boost (or 30 HP), while the more restrictive ones are good for about 2psi of additonal boost (or 15 HP).

This page details the installation of 4 injectors.  Your installtion should be adjusted to suit your needs.
 

Building The EEPC

In order for this system to work, you need to build the Electronic Engine Performance Controller for it.  The following page contains all the information you need to do this:

EEPC: MAP Sensor-Based Fuel Injector Controller

Be sure to read all of the information on that page and to follow all the testing and calibration procedures before installation.
 

Parts

In addition to the parts needed by the EEPC, you will also need the following parts for the 4-injector setup:

Installation

The best place to install the injectors is in the air duct near the throttle body.  If you have an intercooler, they have to be installed between the intercooler and the throttle body because the intercooler would cause the fuel to condensate.  About 2 - 6 inches from the throttle body is a good place.  The reason for this is that the turbulence generated by the throttle body ensures that the atomized fuel mixes evenly with the air.  The actual position around the duct that you need to mount the injector will depend on where you have room.  You will have to install it at an angle that will clear the valve cover, hood, etc.  The diagram below show 4 injectors with one above (blue wire), one below (violet wire), and one on each side (green and yellow wires).  This exact configuration is probably not possible on most engines because of clearance issues.  You can always stagger them or put them one in front of the other.  Just try and make the distribution as even as possible.

The fuel supply needs to be tapped off of the line to the fuel rail.  This is a 5/16" I.D. hose for our engines.  You will then have to figure out how your are going to distribute the fuel.  3 hose T-fittings will work, but looks sloppy and increases your chance of a leak.  I would buy some brass 1/4" pipe fittings and assemble a type of manifold with one input and four outputs.  You can even use steel tubing to supply the manifold with fuel and have four 3/16" hose outlets.  Your configuration will then be something like this:

This EEPC needs the output signal from the MAP sensor.  Please use your vehicle wiring diagram to locate these wires.  I highly recommend soldering into these wires, rather than using wire splices.  A reliable connection is very important.  If you have an 1987 or earlier vehicle, these wires are already available in the passenger compartment in the harness to the logic module (see your wiring diagram).  For 1988 and later vehicles, the wires go right from the engine to the 60-way connector on the SMEC or SBEC (see your wiring diagram).  You will have to run two wires from under the hood back into the passenger compartment.  The EEPC will be wired like this:

Calibration

To calibrate this setup, you need to set the EEPC so that injector 1 turns on at the point where your mixture tends to lean out.  If you are using a zener diode or pop-off valve on the MAP sensor, you should set it just above the point where the MAP sensor stops responding.  Then set injector 2 to turn on at 2psi or 4psi above the first one (depending on what type of injector you have), and so on.

All MAP sensors for our engines have an output voltage range of near 0V at full vacuum to about 5V.  The stock Chrysler MAP sensor for turbocharged engines is a 2 bar sensor.  Below is a table showing the manifold pressure and its corresponding output voltage for the 2 bar MAP sensor.  The range shown is the reliable voltage output range of the sensor.  It can go higher than 4.90V, but the sensor manufacturer does not gauruntee anything about it's output.
 
 
Manifold Pressure
(relative sea level / absolute)
2 Bar
MAP Output
14.31psi / 29.01psi
4.90V
14.00psi / 28.70psi
4.84V
13.00psi / 27.70psi
4.67V
12.00psi / 26.70psi
4.50V
11.00psi / 25.70psi
4.33V
10.00psi / 24.70psi
4.16V
9.00psi / 23.70psi
3.99V
8.00psi / 22.70psi
3.82V
6.00psi / 20.70psi
3.47V
4.00psi / 18.70psi
3.13V
2.00psi / 16.70psi
2.79V
0.00psi / 14.70psi
2.45V
5.00inHg / 12.24psi
2.03V
10.00inHg / 9.78psi
1.61V
15.00inHg / 7.33psi
1.19V
20.00inHg / 4.87psi
0.77V
25.00inHg / 2.41psi
0.35V
29.10inHg / 0.40psi
0.02V

Once you have the unit installed and calibrated, take it out for a spin.  You can tweak the stages if you see lean or rich spots.

For further details on this installation, see Gus Mahon's web page, which includes a pictures of the installed injector:

Adding Fuel, by Gus Mahon (skip to the 5th section)
 
 
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This page is maintained by Russell W. Knize and was last updated 04/23/99. Comments? Questions? Email minimopar@myrealbox.com.

Copyright © 1996-2003 Russ W. Knize