Multi-Stage Wastegate Control Valve Using The EEPC


This page describes how to install a multi-stage wastegate control valves (WCVs) setup using the Electronic Engine Performance Controller (EEPC).  To read more about WCVs, see the Increasing Boost With Wastegate Control Valves page.  This setup gives you multiple stages of boost, depending on throttle position.  It also has an output for the Quick Pressure Feature, which uses the MAP sensor to measure pressure.  The particular example implements 3 stages of boost.

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: TPS-Based WCV Controller With Quick Pressure Release

Be sure to read all of the information on that page and to follow all the testing and calibration procedures before installation.  In addition to the parts needed by the EEPC, you will also need the following parts for the 3-stage setup:


How you physically install the solenoids and pop-off valves is entirely up to you.  The most important thing to remember is that the pop-off valve that is to be set to the highest boost should have the shortest vacuum line path.  As you will see in the diagram below, the high boost valve goes through the shortest part of only one solenoid, while the low boost valve goes through the long parts of two solenoids.  It is important to remember this if you want a system that has good response.  If you are going to add more stages, just make sure the valve stages are lower and lower as you go down the chain of solenoids.

The EEPC circuit provides the ground to the solenoids, so each solenoid needs a common 12V source.  It's always a good idea to put a small fuse on this line, close to the power source.  About a 3A fuse should work well.  It is best to install the EEPC inside the passenger compartment, rather than under the hood.  Even if you seal up the case well with RTV, the extreme temperatures under the hood can cause the circuit to not behave properly.  Here is the diagram for the valve and solenoid setup:

This EEPC needs the output signal from the TPS and 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:


To calibrate this system, you need to think about how you want your system to respond.  The following procedure is a starting point and can be used as an example if you wish to change your caliration later.  The EEPC for this setup actually has three TPS-controlled outputs for three solenoids.  This can potentially be used for 4 stages of boost, but this example has been using 3 stages, so the 3rd output of the EEPC will not be used in this setup.

As far as I know the TPS for all of these engines has an output voltage range of about 0V at closed throttle to 2.60V - 3.00V at wide-open throttle (WOT).  You can verify this by measuring the voltage on the output of the sensor (the center wire) with the ignition key in the "on" position.  You must remember that the computer treats WOT as a special condition.  If you are not familiar with this, please read the 2.2L/2.5L Turbo Engine Important Upgrade Information page.  Now you must choose the throttle positions at which you want each stage to turn on.  Below is a table showing throttle position in degrees and the corresponding approximate TPS output voltage:
Throttle Position
TPS Output
Closed Throttle - 10 degrees
20 degrees
30 degrees
Half Throttle - 45 degrees
60 degrees
 Computer sees WOT - 79.3 degrees
Actual WOT (floored) - 90 degrees

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
14.00psi / 28.70psi
13.00psi / 27.70psi
12.00psi / 26.70psi
11.00psi / 25.70psi
10.00psi / 24.70psi
9.00psi / 23.70psi
8.00psi / 22.70psi
6.00psi / 20.70psi
4.00psi / 18.70psi
2.00psi / 16.70psi
0.00psi / 14.70psi
5.00inHg / 12.24psi
10.00inHg / 9.78psi
15.00inHg / 7.33psi
20.00inHg / 4.87psi
25.00inHg / 2.41psi
29.10inHg / 0.40psi
Once you have the unit installed and calibrated, take it out for a spin.  You can tweak your boost pressures and the boost stage references as you see fit.  Enjoy!
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This page is maintained by Russell W. Knize and was last updated 04/20/99. Comments? Questions? Email

Copyright © 1996-2003 Russ W. Knize