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S15 Boost Gauge install

DIY: Boost Gauge Install on a S15 200SX

One of the perks of owning a JDM S15 200SX is the handy and free boost gauge sitting in the A-pillar.
As pretty and flush it may be, there will come a day when you want some variety and/or a gauge that displays more than 1 bar worth of boost.

Good news! Replacing the stock gauge isn’t that difficult since there is already a holder and you can use the existing T-piece. Bad news is… well, it is a little fiddly… but that’s why this guide is here to help you!

Bear in mind the stock gauge size is 52mm so if you go for a 60mm gauge (like me) you’ll need to do some filing to increase holder size.

Tools required: Electrical tape, coat hanger, Philips screwdriver, side cutters
Difficulty: Low
Profanity Level: High

  1. Pull off the front face plastic on the boost gauge, just clips holding it in.S15 boost gauge

  2. Pull off the A-pillar plastic, again just clips holding it in place… use the force!S15 boost gauge

  3. Unplug the wiring from the boost gauge and unscrew it from the A-pillar.

  4. Locate the T-piece in the engine bay, a hose will be going from it to the factory boost sensor.S15 boost gauge

  5. If your boost gauge has a boost sensor of it’s own, unscrew the factory one and screw in the new one. Connect the existing hose from the T-piece to the new sensor.S15 boost gauge

  6. Now this is the fun part, running the vacuum hose from the T-piece straight into the cabin. In the case of the Defi gauge, it is a signal wire instead of a vacuum hose.

  7. There are two firewall rubber grommets available to run the hose into the cabin, it will be either via the firewall or wheel guard.

  8. The firewall grommet size is tiny, only about the size of a 10c piece and chances are there are plenty of wires already going through there so it’s going to very difficult. Do try your luck by taping the hose to a coat hanger and putting it through, you never know it could be your lucky day. Go to step 14 if you’re lucky bugger and can penetrate through.

  9. The alternative is going through the guard like what I did. Remove the plastic guards from inside the wheel arch, they will most likely be held on by clips and screws (don’t lose any!).S15BoostGauge_5

  10. You will see a rubber mounting (grommet) that would have some wires going through it, this is your passage into the cabin.

  11. Feed the wire/hose through the opening located on the top left of the engine bay.S15 boost gauge

  12. Pierce a small hole with the coat hanger which is where the wire goes through.S15 boost gauge

  13. Tape the wire to the coathanger and feed through the small hole you just made. Push through as far as you can so it will be visible somewhere underneath the driver footwell.  Jiggle the wire and look through the spaghetti until the wire is reachable.

  14. With that elusive wire now in your grasp you can take detach the coat hanger off the wire and turn your attention back to the A-pillar mount.S15 boost gauge

  15. Test fit your new gauge into the holder, file as required (great arm workout). Don’t worry too much about doing a clean job if your gauge is a 60mm as the face will cover the rough edges.

  16. Fit the gauge into the holder and now it’s time to hook up the power. Best way it to splice it off the +ve ignition barrel for power (each car will vary in terms of wire colour) and as for the illumination, just splice the +ve off the light behind the cigarette lighter socket, which usually is dead simple to locate.. It is suggested a fuse be connected to the power source.

  17. Connect vacuum hose (or signal wire) to the gauge and clip the gauge back into the A-pillar mount.

  18. Run through enough cable so that you can pop the A-pillar mount back into place. Tuck wires at the side behind trim.

  19. Finalise gauge position, cable tie loose cables and enjoy!S15 boost gauge

No more being limited to 1 bar!

Did you find this guide useful? What gauges have you mounted in the stock A-pillar holder?

About Flop

Open minded car enthusiast who appreciates most things on four wheels although JDM is where his heart lies. Wannabe racecar driver but having trouble fitting into his bucket seat since he's also a dedicated gym goer.

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  1. where do you splice the wire? inside the cigerate wire? must open the centre console?

    • Flop

      We spliced power off the ignition power under the steering column so that it only turns on when the cars on (step 16). For illumination we got power off the cigarette lighter so yup surround has to come off. Remember to use the appropriate fuse!

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