How to install a boost Gauge in your CX-7

[Raider]

From Superstretch18
I have been meaning to write-up my full boost gauge install for quite some time now, so I guess now is as good a time as any. Before starting, please note that this is only a guide. If you screw up during the install, neither I nor Mazda CX-7 Club are responsible for your issue. Credit goes to MAZOOM and shadow1 for inputs and a couple of photos. Now that the disclaimer is out of the way, here we go:

Tools/Supplies:
Flat head screwdriver
phillips head screwdriver
power drill/driver
Misc. wrenches & sockets
Straightened wire coat hanger (I'll explain a little later)
Owner's Manual
extra 16 gauge wiring (you can buy a 25' spool at autozone for like $5; don't even start the project without extra wiring on hand)
soldering gun or wire connectors of your preference
zip ties
boost gauge
mounting bracket or cup
3x Add-a-fuse adapters (again, you can find these at autozone) Littelfuse Add-A-Circuit Fuseholder for Mini Fuses | Parts-Express.com
3x 7 amp fuses

Before you start, make sure that your engine is cool and you have some shade to work in (I almost died in the S. Florida August sun doing this!).

Step #1: Disconnect the negative terminal on your battery. Be sure that you secure the loose battery cable, so that you don't accidentally complete the circuit while you are working. While you are at it, go ahead and remove the plastic intercooler cover from the engine. There are two or three press tabs that need to be removed with a flat head screwdriver. Pop them up and pull them out. The cover should pull forward with little to no resistance once these are out.

Step #2: Determine where you want to place your gauge. I chose to mount mine on the left hand side of the dash, to the left of the standard instrument panel.

Step #3:
Determine how you want to route your wires. Start from the top and work down. Once you are underneath the dashboard, you can literally reach up and touch the underside of the dash. Once I knew that was a possibility, I simply took a drill bit, marked a hole on both sides and went for it (not for the faint of heart!). In any case, there are other options. I just recently stumbled on this how to that outlines removing the plastic trim on the front A pillar, which may be a better option for some:


Step #4:
Fortunately, it is not far from where I mounted my gauge, so I actually didn't need to extend the gauge to reach the internal fuse box, which is just to the left of the steering wheel, immediately above the hood release. The connectors that I used to tap each fuse line are available at any autoparts store and are called Add-a-fuse or something similar. Basically, they plug into one of the fuse slots and give you an additional fuse slot for whatever you need to connect. Below is a shot of the manual showing which wires I tapped. I used fuse #10 for both the power and white light leads and fuse #12 (dash lighting) for the orange light, to match the rest of the dash.

Step #5
Now, you’re ready to move to the engine compartment. Here’s where I needed to start extending the gauge wiring. I added a good length of wire so I had some room to work with. I originally wanted to use the hood latch release to get through the firewall, but the cable runs through the fender and exits at the front of the engine bay, so I wasn't able to string the wiring completely through. Basically, I had to run the cables under the center console to the passenger side of the dash and through the existing hole that is used for the A/C compressor. Here’s where the coat hanger came in handy. A little tape and a straightened coat hanger works wonders for working wiring through tight areas! Don’t forget to lock down the gauge’s ground point as well.

**Edit: shadow1 recently made a good suggestion to use the firewall exit for the main wiring harness on the driver’s side. If I had to go back, I would probably do it this way, but after drilling the hole in the dash, I was a little hesitant to go messing with the stock wiring harness!

Step #6:
Now that you are in the engine compartment, you are ready to start connecting the sending unit. There are four connections that need to be made:

- Airline to the stock BPV.
- Ground to any stock ground point on the chassis
- Power connection (I tapped the A/C fuse for this)
- Connection to the gauge proper


For the airline, you need to cut the SMALL hose coming off of the BPV and “T” off of there. Here’s a shot of an aftermarket BPV, so you have some idea what you should be looking for. It is on the forward right corner of the plastic intercooler cover:

Here’s a shot of the engine fuse bank after all wiring:


To mount the sending unit, I used the plastic battery shroud. It is close to all connections and is very easy to bolt onto.

Step #7:
Bridge the gap between the sending unit and the gauge. Since I came out on the passenger side of the firewall, I needed to wire across the stock strut tower bar to get to where I needed to be. Fortunately, the wires tucked well and when you pop the hood, you can’t even see them! Clean up the wiring with zip ties and wire shrouds (make sure you are not contacting anything that gets HOT!).

Step #8:
Once everything is connected and you have checked everything twice, you can reconnect the - battery terminal and get ready to start her up!

Here are some shots of the final product:
Day:

night:


Couple of notes; since the negative terminal was disconnected, you are going to need to reset all of your radio presets and your power windows as well. Also, I got a cel code for about 10-15 miles, but it went away on its own on my first drive to work.

Observations:
Honestly, this thing sees very little boost in first and second gear. I have yet to get over about 6 or 7 psi at that point. From third on, I have hit highs of about 15 psi, but average closer to 12. Opportunity? Absolutely. We’ll see where that goes…

Hope this helps anyone looking to make the plunge. Feel free to ask any questions…

[dgillie]

is there a rest of this how to to see where to tap into for a boost line?

[Raider]

Yeah. it looks like that pic got lost. Just T into the hose coming off the top of the BPV

[dgillie]

thanks for the pics. they make this look easy. this will probably be doable very soon

[BobThe]

Well I don't mind saying that this was a serious PITA to do. Naturally it was a billion degrees in my garage so that didn't help.

I spent WWAAAAYYYY too much time trying to get that screw back in the vent (I bought one of those side defroster pods). I dropped more than a few down in to the black hole of the dash. Some of them came through the dash and ended up on the floor mat. Then popped the whole wiring harness rubber boot off as I tried to get a hole in it to pass through the hose for the gauge (I have a mechanical gauge). That was no fun trying to get it back on that plastic ring thing and back secured.

But in the end, I got it completed thanks to this write up. Thanks! If I were to do it again, I would not even try to put the screw back in. I don't think it's possible without taking the dash off. The only thing I can figure is that part was installed before the dash was installed. It's not possible to put it back in again. I tried bending a wrench, 90 degree needle nose pliers, a socket with a u-joint. I even tried to use one of those plastic push pin things. It's NOT POSSIBLE to put it back in. Don't even try. It's not worth your time, patience, hair falling out due to frustration, and so on. I ended up using one of those interior plastic push pins to get the vent pod reconnected to the gauge pod screw hole.

[Dntbh8n]

What kind of boost gauge is installed?