WARNING: This procedure requires the use of an after-market boost gauge. If one is not available it is recommended that the fuel cut defenser, if you have one, be removed or disabled so that the ECU can control over boost accordingly. Failure to take adequate care during the adjustment phase could result in serious engine damage. Please also read the other sections in this document particularly the “Cautionary note” disclaimer at the beginning of these instructions aswell as the section on “How do I know if I have hit the factory bost limit ?” for advice on the effects of the factory boost limit.

THESE INSTRUCTIONS ASSUME THE VSV HAS BEEN DISCONNECTED. IF THE VSV IS CONNECTED DURING THE ADJUSTMENT PROCEDURE ENSURE THE VSV IS OPERATING NORMALLY AND BE AWARE THAT THE ECU CAN INDISCRIMINANTLY REDUCE BOOST BY AROUND 4PSI. IF THE ECU DOES THIS DURING ADJUSTMENT BE CAREFUL NOT TO OVER COMPENSATE OTHERWISE OVER-BOOST WILL OCCURR WHEN THE ECU RESTORES FULL BOOST – YOU HAVE BEEN ADVISED.

NOTE: These adjustments can be performed with the pipes connected to the relief valve providing the hose clips are not too tight – simply twist/rotate the knurled end of the relief valve inside the pipe as required.

Preparation

Drive carefully to a suitable straight road or dual carriageway where the car can be accelerated with no danger to you or other road users.
Ensure the engine is at normal operating temperature.
If you haven’t done so already, adjust the relief valve so approximately half of the adjuster threads are showing – be careful not to completely undo the relief valve as the ball and spring may drop out.
Perform a reference run to determine the current boost pressure – it is unlikely, with the valve half way, that boost will be above the factory limit however …
If the boost limit is reached proceed to Resetting the ECU
If you want to raise the boost higher proceed to Increasing the Boost

Increasing the Boost

Shorten the valve by 1 full turn or ½ turn for a smaller increase.
Perform a power run and determine the current boost pressure.
If the boost limit is reached proceed to Resetting the ECU
If more boost is required (DON’T BE GREEDY) carry on Increasing the Boost
If you have found a happy balance between improved power and the boost limit - stop increasing the boost and see how things go before performing further adjustments !

Decreasing the Boost

Lengthen the valve ½ a turn or 1 full turn for a larger reduction.
Perform a power run and determine the current boost pressure. If the boost limit is still reached proceed to Resetting the ECU
If more boost is required (DONT'T BE GREEDY) proceed to Increasing the Boost
If you have found a happy balance between improved power and the boost limit - stop increasing the boost and see how things go before performing further adjustments !

Resetting the ECU

Pull the car over to the side of the road.
Switch off the engine.
Remove the 15 amp EFI fuse from the fuse box under the bonnet near the battery.
Wait at least 30 seconds.
Refit the 15 amp EFI fuse in the fuse box.
Restart the engine.
Proceed to Decreasing the Boost