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Guys, I've soaked up soooo much informtion over the years that I thought I would add something back to the knowledge pool. I know Apexodus just posted a similar thread, but mine was slightly different from another point of view. Hope this helps someone!

Speed of Sound dual gauge A-pillar installation guide (05-09 GT all)
Including Boost/Vac and Air/Fuel Ratio gauge install

Tools Needed:
• T25 Torx bit and driver
• 10 mm socket and ratchet
• Microtorch
• Soldering gun, solder, flux
• Adjustable wrench
• Tubing cutters
• Pliars

Parts Needed:
• Speed of Sound Gauge Pod
• ¼ inch vacuum T-adapter
• 2 1/16” gauges
• MINI add –a- circuit
• Colored wire - black, white, red
• Wire connectors
• Heat shrink tubing
• Zip ties
• Electrical tape
• Electrical quick connects
• Corrugated wire cover (optional)

Time for Installation:
Gauge Pod – 15 minutes
Gauge wiring – 1 day
O2 sensor bung – 30 minutes if you have a TIG welder and the skills, otherwise expect to pay someone to do it the next day.

If this is your daily driver (like me), be prepared to do this in stages so the car is buttoned up for the next work week. Start early and leave plenty of time for unexpected issues.

Step 1
On a convertible the first step is removing the driver’s side sun visor. If you have a fastback you can skip this step. The sun visor can be removed by taking out the two torx screws with a T25 torx bit.

Step 2
Once that is safely removed you can begin to remove the A-pillar. The A-pillar is held in place with mounting clips and a Velcro- type adhesion tab. The dash end has a slot and tab configuration that will work loose once the pillar if free. You just need to get your fingers under the edge and start to work it loose. I found a quick jerk (as you would use to remove body panels) was effective.

Here you get a good look at the mounting clip and Christmas tree aligning clip.

Now, let’s move on to the gauge installation.

I chose to install a vac/boost gauge and an air/fuel ratio gauge. I did this in preparation for a future supercharger installation. I currently use a blue color for my stock gauges. I wanted the new to match, so I chose the Autometer Cobalt series. They are LED lit and very nice. The Speed of Sound pod is also made specifically for 2 1/16” Autometer gauges. Several pictures online showed the Cobalt series, but they seemed too bright for me. The solution for this was a separate dimmer module for the Autometer gauges. This is an optional step, of course.

I installed the dimmer under the dash with double sided tape, as it is very light. The factory amplifier made a good spot that I could reach and adjust if necessary. The white wire goes to the power for the gauges, the black to ground and the purple to the car dimmer. I needed to split the white into two for both of the new gauges. I soldered and heat shrunk a Y type connection prior to beginning the install.

Step 3. Connecting the wires:

Boost/Vac gauge (mechanical)
- 12v power (white) and ground (black)

Air/fuel ratio (electrical)
- 12v switched power (red), ground (black), 12v dash lighting (white)

Note: your wiring may be different based on different gauges.

A. Black – from a well documented install online, I found that there are two good ground bolts behind the glove box. Just push in on the sides of the glove box and it will fall forward exposing these bolts. A 10mm socket will loosen them and allow your fork connectors to be paced under the bolt head. I needed a ground for the dimmer and one for each gauge. I put two on one bolt and one on the other.

Next, I fished the wires behind the center stack with a plastic rod (similar to pulling wiring on a home project).

I tucked the wires under the dash and used electrical ties to keep them out of the way. Be sure to put the glove box back as well.

Next I needed to get the wires from under the dash to the A-pillar. I tied a bolt to a shoestring and let gravity find its way down. I tied the wires to the string and pulled them up.

B. Purple – Also from a great install online, I found that the blue wire with yellow stripes will control the factory dimmer. If you are not using a dimmer, you can connect your white wires to this blue and yellow one as well. To get to this wire, just reach behind the dash and pop out the factory control. There are no bolts, it will just pop with some force.

Locate the blue and yellow wire and use a “wire-tap” for the purple wire.

C. White – The boost/vac gauge just takes a spade connector which I soldered and heat shrunk in place. The AFR gauge requires a soldered connection with heat shrink covering.

At this point I plugged in both gauges to the white wire and turned on the headlights to make sure the gauges lit up. If everything’s ok push the switch back into its factory location.

D. Red - The electrical AFR gauge needs switched power to start the heating process for the Bosch O2 sensor. The first thing I did was extend the wire with a splice of similar red wire. I then connected an “add-a-circuit” as the manufacturer recommended an inline fuse and this was the easiest way for me to do this.

The smart junction box is located in the passenger foot well. I routed the wire there to find an open spot. I initially chose one that was completely unoccupied, but it was powered with the key off. This would cause the O2 sensor to heat all the time and eventually fail. I found that spot 3 was only powered when the key was on.

Step 4. Boost/vac gauge installation

The only other connection to make is the vac/boost nylon line. This line needs to get through the firewall and into the engine compartment. Near the clutch pedal there is a rubber grommet that has an extra opening that can be cut to allow the line through.

To see the other side of this access you need to remove the fender well cover. It is held on by 4 plastic connectors. To remove them turn them counterclockwise with a Phillips screwdriver and then pull them out. I found it was easiest to do this with the tire removed. At this point feed the line into the engine compartment.

I found that tapping into the vacuum line near the fuel rail was the easiest. The T line connector that came with my gauge was too small, so I replaced it with a ¼” T adapter from an auto parts store. Simply cut into the line and make sure the connection is tight. I used corrugated wire cover to make sure the line was shielded from direct heat.

On the inside end, pull the line up though the A-pillar and connect the brass fittings.

Step 5. Air/Fuel Ratio gauge installation

The wiring harness has multiple wires but we only need the red, black, white and the O2 sensor. The other wires are for a data logger which I did not install. The first step is taking the wiring harness and making the connections to the wire that was pulled earlier. I soldered the wires and then used heat shrink for a neat appearance. The next step is feeding the wires down the A-pillar space. At this point I also “neatened” up the wires with electrical tape.

The Speed of Sound gauge pod comes pre-drilled for wire routing. I found that the AFR harness was too big to go through, so I opened it up some with a rotary tool.

Now I could put the vacuum line and wiring though the right hole and the AFR harness through the left one. I then carefully positioned the A-pillar gauge pod into place. The trick is to make sure the tab feet are situated into the dash area first. Make sure not to crimp the wires or kink the vacuum hose. Once you have it positioned well, make sure the mounting clips line up and then give it a tap to go into place.

The AFR harness will go through the firewall similar to the vacuum line. I placed it through the larger grommet and then fed it into the engine compartment. This harness connects to the O2 sensor which needs to be placed into the exhaust. I am not a welder so I had someone do this part for me. The bung needs to be placed on the upper half of the exhaust tubing so that condensation does not form on the sensor which could damage it. Mine was placed after the catalytic convertor on the driver’s side exhaust pipe.

There was a sensor already near this area, so I routed the AFR harness wire along it and used wire ties to keep it away from the exhaust. The sensor just screws into the bung. Make sure to use anti-seize in case you have to change the sensor in the future.

Step 6. Gauge Connection
A. Boost/Vac Gauge

All that is left is to connect the wires and the vacuum line to the boost/vac gauge. Make sure to wrap the threads with a little Teflon tape so that no leaks occur.

B. AFR Gauge
This gauge just plugs into the harness fitting.

Both gauges will seat nicely into the gauge pod for a professional look. Now turn on the car and make sure the vacuum reads correctly. For me, idle read 22 in/hg. The AFR will heat the sensor and then the reading should be close to 14.7 if your mixture and tune are correct.

Now go out and enjoy your new gauges!!

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