Wastegate – Fabricating and Installing Shims

Overview

This procedure explains how to fabricate and install shims for the wastegate on a Porsche 944 S2 with a 3.0L engine. Shimming the wastegate increases the spring pre-load, allowing it to hold higher boost pressure. This is useful if your wastegate isn’t maintaining the desired boost level, ensuring optimal engine performance.

Tools Required

• 6mm (1/4 inch) hex key or Allen head socket
• 8mm (5/16 inch) hex key or Allen head socket
• Source of pressurized air (e.g., an air compressor)

Parts Required

• Custom-fabricated shims (made from sheet metal based on the template)

Required Additional Procedures

Steps in these procedures are required to complete this process:

• Wastegate Removal and Installation

Step-by-Step Procedure

Step 1: Remove the Wastegate

1. Follow this link to ensure this step – Wastegate Removal and Installation – of the process is followed accurately to remove the wastegate from your Porsche 944 S2.

Step 2: Disassemble the Wastegate

2. Use a 6mm (1/4 inch) hex key or Allen head socket to remove the three Allen head bolts securing the wastegate diaphragm to the wastegate body.
3. Before removing the bolts, mark the orientation of the mounting bracket on the wastegate body with a marker or tape. Two of the bolts also secure the bracket, so this ensures proper reassembly.
4. Use an 8mm (5/16 inch) hex key to remove the wastegate valve by unscrewing the Allen head insert in the bottom of the valve.
5. Carefully separate the wastegate diaphragm from the valve body.

Step 3: Fabricate the Shims

6. Place the bottom flange of the wastegate diaphragm on a piece of paper and trace around it with a pencil to create a template.
7. Transfer the template onto a piece of sheet metal by tracing it with a marker.
8. Cut out two shims from the sheet metal using tin snips or a similar cutting tool, following the traced outline.
9. Ensure the shims match the shape of the diaphragm flange and have holes aligning with the bolt holes in the wastegate body and diaphragm.

Step 4: Install the Shims

10. Place the two fabricated shims between the valve body and the bottom flange of the wastegate diaphragm.
11. Insert the three Allen head bolts back into their holes. If the mounting bracket was left on the car, only install the bolt that threads into the tack-welded nut on the diaphragm flange at this stage.
12. Before tightening, ensure the remaining two bolt holes in the shims align with the holes in the wastegate body and diaphragm.
13. Tighten the bolts to 20 Nm (14 ft-lbs) using a torque wrench with a 6mm (1/4 inch) Allen head socket.

Step 5: Reinstall the Wastegate

14. Follow this link to ensure this step – Wastegate Removal and Installation – of the process is followed accurately to reinstall the wastegate into your Porsche 944 S2.

Post Procedure Checklist

• Check that the wastegate holds the desired boost pressure (e.g., test with a boost gauge and a source of pressurized air).
• Inspect the wastegate area for any leaks or loose bolts after reinstallation.
• Ensure the mounting bracket is aligned as marked and securely fastened.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manual, Volume 1
• Youtube