Wastegate Control Valve Quick Pressure Release


This page describes a method to eliminate the problem of turbo spool-up between shifts when using wastegate control valves (WCVs).  To read more about WCVs, see the Increasing Boost With Wastegate Control Valves page.  In order to prevent spikes when using WCVs, the pressure relief bleed that is required to close the wastegate has to be kept small.  However when this bleed gets too small, it causes the wastegate to stay open.  So during fast shifts, you will not get good spool-up between shifts because the wastegate is still lingering open.  This is especially apparent with smaller turbos (which are also more prone to boost peaking).  The way this system works is to eliminate this delay by installing a solenoid controlled by a pressure switch or an Electronic Engine Performance Controller (EEPC) to relieve the pressure in the wastegate actuator quickly.  A small restrictor is still required so that the pop-off valve can still regulate the pressure.  Without the restrictor, the valve will just "pump-up" the actuator and the result will be less boost than desired.

Using A Pressure Switch

Using a pressure switch for this is quite simple.  Install a solenoid near the location that the bleed is located.  You can install another "T" fitting, or use a "cross" fitting for the bleed and solenoid.  Connect the hose from the new fitting to the center barb on the solenoid.  One of the remaining two barbs will need to be blocked off.  Which one depends on how you wire the pressure switch.  I will assume that the switch and solenoid will be wired so that when the solenoid is on, the bleed is closed.  In this case, the normally open barb on the solenoid will have to be blocked off.  For more information on solenoids, see the Understanding Solenoids page.  Your configuration will then be something like this:

To calibrate this setup, you need to set the pressure switch so that it turns on at a few psi below your boost setting.  So, if you set your pop-off valve to about 14psi, then you want to set the pressure switch to around 10-12psi.  Setting the pressure switch pressure too close to the desired boost may not give the pop-off valve enough time to open the wastegate.  The result would be boost peaking.  You can also just set the pressure switch to 0 psi, so that the pressure release will only take place when the engine is in vacuum.

Using The EEPC

The configuration for adding the quick pressure release feature with an EEPC is basically the same.  The only difference is that the solenoid is activated by the circuit instead of pressure switch.  I trust that you can envision this minor change.  Since the EEPC is generally used for multi-stage WCVs, I have provided a diagram for a 3-stage WCV with quick pressure release.  As with most EEPC setups, 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 1A should work.

The calibration procedure for this setup is the same as the pressure switch.  You want to adjust the EEPC output for the quick pressure release (purple wire) to a few psi below the low boost setting.  Again, you could also just set it to 0 psi (about 2.5V on a 2 bar MAP sensor) and not worry about it.  For more information about install the EEPC, see the Multi-Stage Wastegate Control Valve Using The EEPC page.
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This page is maintained by Russell W. Knize and was last updated 04/19/99. Comments? Questions? Email minimopar@myrealbox.com.

Copyright © 1996-2003 Russ W. Knize