MAS Mod

I decided to do this mod after I noticed that my boost would drop from 17 PSI to 10 PSI as my RPMs got higher.   This hindered my car's performance at my first visit to the track by yielding me a 15 second quarter mile time at 94 MPH.  So this is what I did to remedy the problem, now I can hold a steady 17 PSI right up to redline.

            MasMod1.jpg (37049 bytes)    MasMod2.jpg (39937 bytes)    

Parts and Tools Needed

3 feet of speaker wire

100 kohm potentiometer

Soldering iron, solder and solder wick

Dremel tool

1 small cabinet hinge

1.5 inch square piece of metal or plastic

8 inch spring

2 small nuts and bolts

  1. First thing to do is to remove the MAS from your car.

  2. Take your dremel tool and cut away the bottom part of your MAS but remember to leave the part where the screws are attached.

  3. Drill a hole into the middle of the square piece of metal or plastic big enough for the bolt to go through.

  4. Screw the piece of metal or plastic to the hinge and smooth out the area where the hinge will be mounted.

  5. Once the area is smooth, screw the hinge into place.

  6. Take the spring and bolt it to the loop underneath the metered airflow passage.

  7. Measure the off to the flapper door so that it is closed at idle, once it is the appropriate length bolt the spring to the flapper door.

  8. Remove the passenger side center panel to gain access to the ECU. 

  9. ECU connector pin outs can be found here.

  10. Remove the 24 PIN connector and cut wire number 8 (green with orange stripe on my 1990 Talon Tsi) leaving about an inch and a half of wire before the connector.

  11. Solder the speaker wire to both ends of the number 8 wire.

  12. Re-connect the ECU and screw the passenger side center panel. 

  13. Run this speaker wire to a suitable spot for the adjustment potentiometer.

  14. There will be three connections that need to be soldered.  One is the ground connection and the other two will be the speaker wire.

  15. Reattach the MAS and start your car to ensure your a/f meter is cycling rich and lean.

  16. Do a few hard WOT pulls to ensure that you are not running too lean.  Increase the resistance in the potentiometer to richen the mixture up a bit or decrease the resistance to lean the mixture out.

This modification made fuel cut disappear, and cured my high RPM shudder.  I can also run 17 PSI no problem right to redline.  Once again I would like to thank Mike J. for answering all of my questions.

Any helpful insights, comments, and questions can be forwarded here .

 

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