Researched by: Jerry Holmolka
Edited by: John Forshaw

Purpose: To locate the optimal locations for the mounting of *5* gauges (yes I said five... three in the pod and two in the center console underneath the ARC-2).  

(Note: Credit for much of this page should go to www.grandprix.net, however the very professional installation was done by none other than the inimitable Mike Bouchard. )

Here is what it looked like before:

Here is what it looks like after:

How its done:  I ordered the boost gauge, transmission temperature gauge and the oil pressure gauge and also bought an air/fuel ratio gauge from Frank to better adjust the ARC2.  TO compliment the A/F gauge which is a SPORT COMP model, I ordered and installed a SPORT COMP voltmeter beside it underneath the center console ashtray.

Installation of the Gauges:

Boost Gauge:
Most gauges come with a "kit" to install the gauge. Additionally, you may need the following (this is what I needed to complete my installation - Brian):

1) Extra vacuum line length (I bought 10 feet of rubber 1/8" inner-diameter vacuum line and used most of it)
2) A "T" adapter - small, 1/8" inner-diameter rubber which can be found in the "HELP!" section of most auto parts stores
3) Two small 1/8" plastic vacuum line connectors - one for connecting the "T" fitting to the rubber line you bought and one extra should you need it in an emergency; they come two to a package anyway

You will need to decide the location. My choice was a Lotek Engineering A-pillar replacement 3-gauge mount.

The best place to tap into a source that will realize boost is the vacuum line running to the MAP sensor. Now where is the MAP sensor? There is a vacuum line routing diagram on the underneath side of the hood. Or look at the back of the engine with the cover off. The line runs from just under the nose drive assembly as shown below (click picture for a larger view):

Install a "T" into this line as shown below:

and route into the cabin. There is a wire harness that runs through the firewall just above the passengers footwell. This is an easy location to use, but if you use rubber vacuum hose to reach that far you may have a few problems. Keep at it (jacking the car up may help you pull it through) and you can do it!

Run the line to the boost gauge and supply a switched power source for the backlight.

For those wanting to use a CYBERDYNE boost gauge, here is the info you need:
Cyberdyne boost hook up. 0-15 ONLY- 0-30 psi requires sending unit!

Green on gauge ----- green on map
Red on gauge---------- + 12v
Black on gauge------- ground
Yellow on gauge------- not used
Purple on gauge------ dimmer- does not have to be connected
(Thanks to David Singley and the GPML for this info)

Transmission Temperature Gauge:
Begin by locating the throttle body. Just below it is the transmission. On top of the transmission you will be able to see two "nipples". The lower and closest to the firewall is what we are concerned with. This is a pressure test port that can be used. There's a simple threaded plug in there. Simply remove it with a ratchet.

Install the provided sending unit into the threaded port as shown below. The small copper-colored sender with the gray wire is what we're looking at here:

-- it should be the same thread size as the plug. Make sure it fits snugly. Here's another look. You can see it in the back of the transmission:

Install the signal wire and route it securely away from the transmission.

Run the signal wire into the passenger cabin. There is a wire harness that runs through the firewall just above the passenger's foot well that is a good location for this wire.

Run the wire to the signal input of the transmission temperature gauge inside the cabin and supply a switched power source for the backlight. 

Don't forget to hook up 12V power. Why do you need 12V power? Because the gauge is an electrical (unlike a boost gauge, for example, which is mechanical). But I already hooked up my gauge lighting - isn't that good enough? No - the power for the lamp is used only for the lamp. The gauge needs an electrical signal that's not variable (unlike the dimmer you already hooked up - it's not always 12V and varies with a turn of the dimmer dial) so that it converts the signal from the sender into a mechanical movement of the gauge needle. Here's how to do it.:

Pop off the cardboard panel under the dashboard on the driver's side. Pop the light out of the panel and move the panel out of the way. Directly under the steering column, you'll see a small blue connector with a few wires on it. Find the hot pink wire that is located as shown below (it's hard to see in the small version, so click the picture to view the larger version). Notice the position of this wire is the last in the connector. There is only a small portion of this wire exposed, so take care to do this right the first time. Tap into this line, and connect this to your gauge for the power source (12V).

Oil Pressure Gauge:
The port for either mechanical or electrical installation is located about six inches behind the oil filter towards the engine. To find it, remove the passenger side front wheel. You will see the filter. Just behind it is the factory oil pressure switch. It is silver in color with two wires running into the electrical connector.

This switch only goes to an idiot light on the dash. There is no signal to the PCM. The reason for noting this is that the switch will be permanently removed. If you are scared about not having this light on the dash, think of it this way. You will now be able to see the actual pressure. That switch closes at or below 5 psi of oil pressure. This is lower than you want to be. So the new gauge will be a better solution.

Also, GM decided to use a normally closed switch that opens when the pressure comes up. I was curious as to why GM would do this. If the connector came off or a wire was cut, the light would never come on with the current configuration.

So, after draining the oil, remove the electrical connector off of the pressure switch. Next remove the switch. It is threaded into the housing and comes out fairly easy.

The rest of it is up to you depending on what type of gauge is being used, either mechanical or electrical. I would suggest an electrical since only a single wire needs to be run from the sending unit to the gauge. Whereas the mechanical one would require tubing to be run into the car with the chance of a leak. Warm oil on the carpet inside the cabin is not a good thing.

Either way, the port you will adapt to is a 1/4" pipe or NPT female fitting. If you are using an electrical sending unit, most come with 1/8" pipe threads. You will need to stop by the parts store and get a 1/8" female pipe to 1/4" male pipe fitting. Brass would be fine.

Install your fitting or sending unit, with adapter if needed, and run your signal wire or tubing to the gauge and supply a switched power source for the backlight.

Air/Fuel Ratio Gauge:
This gauge is quite simple to install.  It has 3 wires on the back of it.  Power (red), ground (black) and Signal (violet).  Care should be used when connecting the violet wire to the proper location.  You must tap into the wire that leads to the first O2 sensor, but NOT at the O2 sensor side, but anywhere between the connector and the PCM. 

 
Do NOT connect here!               This is the proper location.

This is normal operation for most computer controlled vehicles.

 I installed it in the back of the cubby hole of the center console.. the effects are devastating!  Here is a picture:

(click on a picture for the full-size view)

The A/F Ratio Meter is a voltmeter with a range of 0 to 1 Volt. The meter displays the output voltage of the vehicles oxygen sensor through 20 LED's. The first LED will come on at a voltage of .050V, the second at .100V, the third at .150V, etc.

The stoichiometric (STOICH) air/fuel ratio is the chemically correct ratio, theoretically all of the oxygen and all of the fuel are consumed. The mixture is neither rich nor lean. However, due to the fact that combustion is never perfect in the real world, there will always be a small amount of oxygen left in the exhaust. This small amount that is left is what the oxygen sensor measures. The smaller the amount of oxygen that is left in the exhaust, the richer the A/F ratio is, and the higher the oxygen sensor voltage is. The on-board computer or Powertrain Control Module (PCM) monitors the voltage from the oxygen sensor. If the PCM sees an oxygen sensor voltage greater than .450V, it immediately starts to reduce the amount of fuel that is metered into the engine by reducing the on time to the fuel injectors. When this happens, the A/F ratio starts to go in the lean direction, and the oxygen sensor voltage starts to go down. When the voltage drops below .450V, the PCM immediately starts to increase the fuel metered to the engine by increasing the on time to the fuel injectors to produce a richer A/F ratio. This occurs until the oxygen sensor voltage goes above .450V. This repeating cycle happens very fast (many times per second). The PCM is said to be in closed loop. It is constantly monitoring the oxygen sensor voltage and adjusting the on time of the fuel injectors to maintain a stoichiometric A/F ratio. This A/F ratio produces the lowest harmful exhaust emissions, and allows the catalytic converter to operate at peak efficiency, therefore reducing the exhaust emissions further.

Since the oxygen sensor output is non-liner and very sensitive at the stoichiometric A/F ratio it will cause the A/F meter LED's to bounce back and forth rapidly. A very small change in A/F ratio causes a large change in oxygen sensor voltage as can be seen on the graph. This causes the A/F ratio meter LED's to rapidly cycle back and forth, and is normal operation when the PCM is in closed loop and trying to maintain a stoichiometric A/F ratio.

The oxygen sensor is very accurate at indicating a stoichiometric A/F ratio. It is also very accurate at indicating an A/F ratio that is richer or leaner than stoichiometric. However it can not indicate what exactly the A/F ratio is in the rich and lean areas due to the fact that the oxygen sensor output changes with the oxygen sensor temperature and wear. As the sensor temperature increases, the voltage output will decrease for a given A/F ratio in the rich area, and increase in the lean area as shown on the graph.

During wide open throttle (throttle opening greater than 80% as indicated by the throttle position sensor) the A/F ratio will be forced rich by the PCM for maximum power. During this time the oxygen sensor outputs a voltage that corresponds to a rich A/F ratio. But the PCM ignores the oxygen sensor signal because it is not accurate for indicating exactly what the A/F ratio is in this range. The PCM is now in open loop, and relies on factory programmed maps to calculate what the on time of the fuel injectors should be to provide a rich A/F ratio for maximum power. The A/F ratio meter should indicate rich during this time.

During hard deceleration the PCM will command an extremely lean mixture for lowest exhaust emissions. This may cause the A/F ratio meter not to indicate anything. The A/F ratio is so lean that it is outside the range that the meter will indicate.

For those using a CYBERDYNE A/F ratio, here is the info you need:
Cyberdyne A/F ration gauge hook up Pt # 7009
Orange on gauge------ Purple on 1st O2 sensor (by rear spark plugs)
Red on gauge--------+12v
Black on gauge--------ground
(Thanks to David Singley and the GPML for this info)

Backlighting your Gauges:

So you've got your gauges installed, but you want to hook them up such that they'll:

1. Light up only when the dash lights come on, and
2. Dim when you dim the dash lights via the dimmer dial to the left of the steering wheel

There are two connections you need to make: ground and dimmer. First we'll connect the dimmer power connection.

Open the driver's door, and pop off the trapezoidal panel that's there on the side. It looks like this:

Once off, unplug the wire harness connector that connects to the headlight dial and dimmer dial. Flip the connector so the top of it is facing downward, and locate the wire on the row nearest you, second from the right (click picture for larger view) as seen here and tap into it:

That's it for the dimmer circuit. Make sure to connect this line to the appropriate input on your gauges.

All that's left now is the ground. I used a connector and wire right under the bolt that connects the dash frame to the car's chassis, because there is already exposed metal there, and it was very convenient. Choose a good ground anywhere you feel comfortable, and connect the ground to your gauges.