How to Install a Boost Gauge

One of life’s great joys is feeling the power surge of a turbocharger. It does all the sutututuuuu and pshhh you could ever ask when the throttle blade slices closed – it’s pure childish joy. The only way to improve is to have a boost meter buzzing excitedly in your peripheral vision as the boost builds and releases. For that, I’m going to show you how to put a boost gauge in any car.

There can be no greater service to the gods of 2000s car culture than installing a big old boost gauge in the cockpit of your machine. Luckily, it’s extremely simple and only takes a few inexpensive tools and parts with a bit of ingenuity.

The first thing to do is to acquire a boost gauge. The options vary widely as you can spend as little as $20 on a boost gauge from Harbor Freight all the way up to $250 for most legitimate Japanese Domestic Market (JDM) Challenge gauges. The installation process for either is more or less the same, so the choice is primarily based on quality and aesthetics.

Mechanical or digital

There is an important distinction that separates all boost gauges: mechanical and digital. A mechanical boost gauge uses a boost reference to physically move the needle in the gauge. A digital gauge takes a boost reference from a sensor which sends data to the gauge via wiring and displays it on a screen or with an analog dial via a stepper motor.

Mechanical gauges have incredible response and accuracy (when properly calibrated) and are simple to install. The accuracy and response of digital gauges, however, vary widely. Inexpensive digital gauges can be slow to respond and inaccurate. In my experience, brand name products like Challenge, AEM, Stack and Greddy all have mechanical gauge response while having the style and diagnostic benefits of a digital gauge. Stuff like Prosport doesn’t quite match up.

The main reason you would want a digital gauge rather than a mechanical one is the ability to store peak values. This can be useful for seeing when you are under or over boosted. The digital gauges also have cool gauge sweeps on startup that add drama to the car’s startup. It’s not strictly necessary, but for a tuner like me it means a lot. That’s why I have a Défi oil temperature gauge in my car.

Preparation

For this installation I will be using a Newsouth Performance mechanical boost gauge, which means we will be wiring and routing a boost reference from the engine compartment to the cabin. This type of work is more tricky than difficult, but it’s usually straightforward and shouldn’t take more than a few hours. Before I begin, I’d like to run through the wiring diagram for your favorite boost gauge and start figuring out where you can hook up your car’s wiring.

[Warning: For safety purposes when working under the hood and with wiring, it’s a good idea to disconnect the battery terminals and to use safety glasses and gloves.]

It sounds scary because it’s scary. This is the only permanent part of the installation, but it can be made as painless as possible with a few connectors and courage. At the very least, you’ll need some basic wiring supplies. I know there are several schools of thought with wiring, but we go for cheap and easy, so I used basic connectors (yes, butt) and spade connectors to get the job done with a combined wire cutter/stripper/crimper .

Each gauge will come with a small instruction booklet that explains how to install it. The most important part of this will be the wiring diagram. Most gauges will have three to four wires, depending on the type of gauge. Because mine is mechanical, it has three wires for power, ground, and dimmer. A digital type gauge will add an extra wire for the boost pressure sensor signal. The diagram will show which wire is which – keep this in mind in the future. Also consider where you want your gauge to live in the car to determine wiring length and routing.

Installing the wiring

Take these wiring assignments and start digging into your own car to find a suitable power source, ground, and dimmer. For a power source, you want to use a spark ignition source so that the gauge turns off with the car. Ground can be installed anywhere there is metal, I usually choose a small bolt and grommet to ground my wiring. Alternatively, you can use the ground wire on the car harness if there is no metal nearby. The dimmer is the only wire without free choice; there is usually only one dimmer wire for a given component.

For the purposes of this installation, I unfortunately (for me) use my 2010 Volkswagen Golf GTI. Fortunately (for you), this means that I am doing this installation on the most finicky vehicle possible. Most people will have cars with much simpler electrical systems. On any car, a good starting point for finding switched ignition power will be a headlight switch, 12v cigarette lighter socket, or the radio. Some power sources may be constant and others switched on the same connector, so be sure to find the switched power. The best way to find out is to use a wiring diagram and a voltmeter.

Use the voltmeter terminal to probe the back of the connector where the wire enters and ground it to metal. If it shows no power when the ignition is off and 12 volts when the ignition is on, you have turned off the power. If it shows power regardless of ignition position, it is constant power. I recommend always testing the wires you want to use, no matter what the schematic says. Often the diagram is wrong and it’s best to test things out for yourself. You can also use this method to find a suitable power source by manually testing the wires.

Now comes the scary part. Unless you want to risk a bad connection by using a quick splice terminal, you need to cut the wire. Quick splice terminals can be great, but sometimes they don’t cut deep enough to make electrical contact. My low cost technique of splicing into a wire harness requires an old fashioned butt connector with heat shrink. I cut and strip the desired wire and place one end into the butt connector, then get the other end of the cut wire with the wire I want to splice. I twisted the two together and placed it into the other end of the butt connector. Crimp it, shrink the heatsink and the job is done. Rinse and repeat, as they say.

I also like to add an individual connector to each wire for future use. It would suck to have to cut and reconnect the wires with a butt connector if the gauge were to come out. Some of you may ask why I don’t use solder and the answer is simple: solder is no good in the vibrations and conditions found in a car. A crimp is much stronger and more flexible, even if it is a basic crimp. I could have gone crazy and used Deutsch connectors, Raychem heat shrinks, and done it “correctly”, but it’s inexpensive and works well for most of us.

Installing and positioning the gauge

The last thing to do is route the boost reference line from the engine bay. A mechanical gauge will require the hose to go all the way to the gauge, while a digital unit will have a box you can hide under the dash. Finding a boost reference should be simple: anywhere in the intake system after the turbocharger will give an appropriate reference. Most cars will have additional ports on the intake manifold. In my case, I bought a boost valve that replaces a PCV pipe fitting and used a catch box. Route the hose through a grommet in the firewall. Don’t be afraid to poke a hole in the rubber. Plug it in and you should officially have a boost gauge.

I would take a moment to start the car and check that everything is working. If the gauge reads vacuum at idle and moves with a kick of the throttle, everything is fine. Check the dimmer and other functions, then consider where you want to finalize the gauge mounting. I chose the steering column for visibility, but some mount in an air vent or in the center console. It’s up to you. Drilling shouldn’t be necessary, and I use 3M VHB double sided tape to mount the gauge pods. For this installation I used a Newsouth cast column cover which fits over my factory steering column and has a mounting hole for my gauge.

Make turbo noises as you like. I love watching the needle go crazy and the child inside us will too.