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Removing 2 stage boost on a skyline R33 GTS-T

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  • Removing 2 stage boost on a skyline R33 GTS-T

    As you all know the standard R33 RB25DET boost solenoid (value controller) is 5psi until rpm is greater than 4500rpm and then its 7-8psi. Continue reading if you wish to always be in high mode (7-8psi). If you have an aftermarket boost controller then you can stop reading now.

    The standard solenoid has two wires running two it, one is constant power which is shared with the AAC value and some other components the other is a ground signal. The ground signal (black wire) is run to the ECU. This wire is grounded when rpm is greater than 4500rpm by the factory ECU. Basically if you give the wire a constant ground instead of the ECU's above 4500rpm ground it will always be open, thus allowing it to be in high mode aka 7-8psi.

    The mod:

    Cut the black wire and run it to your own ground on the car body somewhere. Find a local bolt/nut or metal chassis component and attach a lead wire to it, then run this lead wire the black wire on the standard solenoid. For testing you could run this to the suspension tower, is has a huge bolt/thread on top of it. The other end of the two wires (black and white) should run to the factory harness plug (black odd looking plug), which can be simply taped up so it goes nowhere.

    Be sure not to the modify the white one, as it's power for the solenoid.

    Basically the black wire goes to your new ground, the white wire doesn't change. Make sure you tape up the loose end of the black wire out of the plug and don't leave it dangling around. Now to test


    Start up your car, make sure you don't have any alarms or warning lights etc.. Safety is important!. Instead of your car going into 7-8psi above 4500rpm it will be in this mode all the time, this means when you take off in first you'll be limited to 7psi instead of 5 and thus applies for all driving thereafter. Take it for a quick spin and see the difference. You'll notice first is whole different feeling to it and each gear thereafter seems to have more stick about it. Your top end power output will not be changed, ie if you made 140rwkw and you've done this mode it will still be 140rwkw it's just the curve will be sharper as you'll be on more boost quicker


    If you don't notice any different then you've either done the wrong wire or the ground is strong enough. Be sure to pick a strong ground and make sure its secured properly. You can get gold washer clips which will hold a wire and provide a good ground for use on a nut.

    If in doubt you can simply unplug the black factory harness plug and your controller will be in closed mode which is 5psi all the time. With only a power signal the solenoid doesn't function and thus it will always be in "closed" mode which is 5psi

    Last edited by Bandit; 01-01-2010, 12:37 AM.

  • #2
    Further information supplied by Bandit well done this is very helpful

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    • #3
      Some really good information here Bandit!! thanks