HOW TO: Install Boost Gauge into Drivers Vent

Hey-- here are the steps I took to install my boost gauge into my drivers side vent with photos.

Car:2007 Mazdaspeed3
Gauge: Defi Link Meter BF Amber Boost in PSI, Defi Control Unit II

Tools Needed:
wire stripper
wire cutters
wire crimpers
pliers
zip ties
wire snake or wire hanger
flat head screwdriver
philips head screwdriver
Dremel tool w/sanding bit (for 60mm gauges)
automotive fuse taps
female terminals
ring terminals
patience and time

Note: I developed this guide using my own knowledge as well as information researched from resources such as specialized online forums. The information on this page is meant to be a GUIDE and in no way should be considered official installation instructions. Use this guide at your own risk. If at any time you are not sure that you are doing something properly, please seek the advice or services of a professional.

1. Pop the hood and locate the vacuum tube running from the manifold to the bypass valve.
2. Cut the tube using wire cutters and insert T connector into each end and into one end of the supplied vacuum tubing that came with your gauge.
3. Zip tie all 3 connections tightly
4. Re-install vacuum tube onto bypass valve and secure with clamp using pliers.
1.jpg

5. Route the other end of the supplied vacuum tubing to where you are going to be mounting your boost pressure sender. As you can see I mounted mine with a nut and a screw to a hole I drilled in my battery box.
2.jpg

6. Under your drivers side dashboard, follow the trunk release cable and locate the point at which it passes though the firewall. There will be a rubber grommet around the cable. Pull the rubber grommet out of hole and feed a wire hanger or wire snake through the hole in the firewall. It will come out inside the engine bay near the drivers strut tower.
7. On the engine bay side, tape your boost sender wire to the other end of the wire hanger and slowly pull the hanger back through the firewall, being careful not to snag the wires. Once though the firewall, you can carefully feed the entire length of wiring from the engine bay into the cabin. Re-mount the grommet back into the firewall, adjusting it around the boost sender wires as well as you can.
3.jpg

8. Pull up the drivers side scuff plate (the piece that says mazdaspeed) and put it somewhere safe. The scuff plate is held in by tension clips, so be very careful when removing-- apply even steady pressure as you pull--too much stress on one clip could crack or break it.
5.jpg

9. Remove the drivers door kick panel (more tension clips and one 'pop' clip).
10.Using a flathead screwdriver release the hood release lever by sliding it in through the top, and releasing the tab. The lever should pop off into your hand and allow you to access the phillips head screw behind it.
4.jpg

11. Remove the phillips head screw, and then the lower drivers side dash. The dash is held in with tension clips.
12. Once the dash is free, remove the plug connectors for the DSC, Dimmer, HID Level (if equipped) and OBDII port to remove the lower dash completely.
6.jpg

13. Now comes the really tricky part- removing the vent. This step was very hard and painstaking as I wanted to be sure not to damage any of the vent parts. To remove the inner vent, I got a good grip on the louvers with both hands, applied steady even pressure, and it popped right out. (passenger side vent shown for photo demonstration)
7.jpg

14. Removing the inner vent was even harder. With the lower dash removed, you can access the inner vent cup on each side. I used a very large flathead screwdriver to push the tabs in that release the cup from the opening. Pictured below is the underside of the cup (marked with white writing) that you want out. This is not the best pic and I know it doesn't show you much. The tabs your need to put pressure on will be obvious when you get to this point.
8.jpg

15. I worked the outer vent cup on each side with a screwdriver until I was able to pop it out of the vent opening. This was the hardest part of the whole install process, because it took a LOT of pressure to pop it out, to the point where it felt like you were breaking it. Just go slow and be careful. Once you get the two vents out, the opening will look like this:
9.jpg

Here is what the vent cups looks like when out of the car- outer vent on the left, inner vent on the right:
10.jpg

16. Using the wire cutters, carefully snip the louvers out of the inner vent cup. After the louvers are removed, cut away the honeycomb patterned grating behind the where the louvers were.
11.jpg

17. Using a Dremel tool with a sanding bit, carefully begin to sand the inside of the inner vent. For my 60mm gauge I needed to take out as much material as possible to make it fit. If you are using a 52mm gauge, at this point you will need to figure out how to mount and hold the gauge inside the inner vent cup. Be careful at this step, one mistake could send you to a dealer for a new $50 vent assembly.
12.jpg

18. I blocked off the vent by cutting an old tupperware lid to size and taping it inside the vent tube with electrical tape. I don't know for sure if it is necessary to block of the vent, but I did it just for peace of mind.
13.jpg

19. To wire my gauge and control unit, I decided to use the fuse panel found behind the glove box.
20. To access this fuse location, first remove the strip of plastic trim that surrounds the Radio LCD display. Again, these are tension clips so be careful!
Pop the clips from left to right or you will snap off the tab that holds the trim in on the far right side.
14.jpg

15.jpg

21. Take out the two black phillips head screws that hold the glove box in.
16.jpg

22. Just like the lower drivers side dash, the glove box is held in by a series of tension clips. Apply even pressure and pull the glove box out slowly and carefully. There will be a wire that connects the glove box lamp, you can
disconnect this if you like, but it isn't really necessary. This picture shows the wiring that I ran from my gauge to the glove box in order to wire up my Defi Control Unit-- they wont be there if you are removing your glove box for the first time.
17.jpg

23. Run your wiring--For a stand alone style gauge, you will need to run your boost sensor harness (from under the drivers dash) into the drivers side vent opening. Then you will need to run the power harness behind the center console and into the fuse compartment behind the glove box. Defi Link Gauges are a little more complicated. For my gauge there is a harness that comes from the sending unit (under the hood) and goes to my control unit that I am mounting in my glove box. Then another harness runs from the control unit to the back of the gauge. Finally there is a 3rd 4 wire power harness that comes from the control unit that I need to wire into the system: Black (ground), Red (constant 12v) Orange (switched 12v) and White (Illumination). These wires may vary depending on the brand of gauge you have, however any gauge will need at least a switched power, illumination power, and ground. To tap for power, I used Radio Shack automotive fuse taps (about $2/4) and blade style female terminals (about $2/10).
18.jpg

The fuse taps 'piggyback' onto an automotive fuse and allow you to run a blade terminal off of the same circuit. This is a great option for people like me that don't want to bother with cutting, splicing or soldiering wires. If you ever need to remove the gauge or rewire it, you just disconnect the connectors and remove the taps-its very clean and easy.
19.jpg

24. Because my gauge is tinted- it needs to be constantly illuminated while the car is on or you cant see it, so I stripped both ends of the switched and illuminated power and crimped both on a single female terminal. I then stripped and crimped another female terminal onto the constant power wire.
25. Using a fuse tap, I tapped the F43 fuse (cigar lighter) for the illumination and switched power. This will turn the gauge on and light it up when a key is in the ignition or the engine is turned on. I tapped the constant power wire to the F75 fuse (drivers door locks) This allows the gauge control unit to have constant 12v-- required if you have a gauge that needs to save settings or remember warning/peak levels. If a constant 12v is connected to a switched
source, it will lose all settings when the engine is turned off. NOTE: The radio fuse is NOT a constant 12v source from this location (I learned this the hard way and had to rewire it to the door locks). Every fuse in this location is numbered and easily located in this Connector Pinout document. If you have a traditional gauge that needs switched and illum wired separately, you can use the F43 cigar lighter fuse (switched power) and the F82 dash illumination fuse separately.
20.jpg

26. I stripped and crimped the ground wire to a ring terminal and attached it to a ground bolt right above the glove box on the dash frame (my terminal is the blue one):
21.jpg

27. Connect the gauge to the harness plugs (do not install it into the vent yet) and turn the car on to test for proper gauge illumination and function.
28. Secure all wiring away from moving parts and heat sources with zip ties.
29. Feed the boost source harness (from engine) and power harness (from fuse terminal) up behind the drivers vent and through the vent opening. Carefully reinstall the glove box, lower drivers dash, drivers kick panel and scuff plate.
30. Install your gauge into the inner vent cup, snap the inner vent cup into the outer vent cup and plug in the wire harnesses that are feeding out of the drivers vent opening.
31. Finally, snap the whole gauge/vent assembly into the upper dash vent hole and hope that you didn't make a mistake. I,for one, never want to have to take the vent out again...
32. Enjoy your new super-clean boost gauge vent install!
22.jpg

23.jpg

24.jpg
 
Last edited:

Powerslave

Banned
:
mps 3
nice write up looks sleeek, i still like mine on the steering collum though it doesn't block anything and it's perfect to see your boost while your moving through the gears
 

2ManyCars

Member
:
2008 MS3 GT (SOLD)
Good writeup. One tip I gleaned from someone on another thread was using the mini "Add-a-Fuse" connectors. This allows you to tap into the fusebox in a similar way but to put a fuse on the line as well.
 
Good writeup. One tip I gleaned from someone on another thread was using the mini "Add-a-Fuse" connectors. This allows you to tap into the fusebox in a similar way but to put a fuse on the line as well.

yeah I almost got those but after realizing that they cost $5 each I found these at radio shack for much much less. The Defi constant 12v has its own inline fuse anyway. In my opinion its a little overkill to fuse the illumination an switched power. I couldn't bring myself to pay $5 a pop for 2 cents worth of wire and fuse...
 
thanks been looking on doing this i put my boost gauge next to my cig light but i wanted to put my wide band a/f gauge in the driver vent. thanks
 

2ManyCars

Member
:
2008 MS3 GT (SOLD)
Hey one more question. Would it work for your install to access the fuse box from under the dash? When I did mine, I did not pull any of the dash off on that side to get to it. It just pops down from the panel under the passenger side dash per the owner's manual. Would that help simplify the steps a bit?
 
Hey one more question. Would it work for your install to access the fuse box from under the dash? When I did mine, I did not pull any of the dash off on that side to get to it. It just pops down from the panel under the passenger side dash per the owner's manual. Would that help simplify the steps a bit?

I don't know, maybe thats another fuse box? The one used definitely would not be able to be reached with the glove box in the car. There are literally hundreds of places you can tap gauges on wire harnesses on the car if you know the right colors and don't mind soldiering.
 

2ManyCars

Member
:
2008 MS3 GT (SOLD)
I don't know, maybe thats another fuse box? The one used definitely would not be able to be reached with the glove box in the car. There are literally hundreds of places you can tap gauges on wire harnesses on the car if you know the right colors and don't mind soldiering.

Looks the same as mine. Per the owner's manual, I accessed it via a removable panel under the passenger-side dash and a couple of knobs you turn so it drops down.
 

voiceKoil

Member
:
Mazdaspeed3 2007
I personally dont like how you took the vent out, the vent simply unclips from the inside, you just have to unistall the panels to get it out properly, prying it out with a screw driver seems like a pretty crude way to get it out, and not to mention the damage you could cause the the vent. Overall though it looks good and you actually took the time to do a write up on it. Looks nice! Love the guage though, I told myself I would spend the Big bucks once I start getting in depth. Now that my Greddy guage is sold and I may have to keep my car I could go this route ;)

Sorry I misread what you were prying on, so I guess you may be less likely to damage it, its really a peice of cake to just take the panel out and remove the vent that way though, vs trying to get in that tight area to get it out.
 
Last edited:

voiceKoil

Member
:
Mazdaspeed3 2007
I don't know, maybe thats another fuse box? The one used definitely would not be able to be reached with the glove box in the car. There are literally hundreds of places you can tap gauges on wire harnesses on the car if you know the right colors and don't mind soldiering.

No he's right it just lowers down, theres 2 plastic screw in peices and it pops down. I think theres a little shield that pops on and off too.

I put mine through the firewall right where the glove box is, so it kinda killed two birds with one stone by taking it out. But you dont have to take the glove box out, its just easier.
 
I personally dont like how you took the vent out, the vent simply unclips from the inside, you just have to unistall the panels to get it out properly, prying it out with a screw driver seems like a pretty crude way to get it out, and not to mention the damage you could cause the the vent. Overall though it looks good and you actually took the time to do a write up on it. Looks nice! Love the guage though, I told myself I would spend the Big bucks once I start getting in depth. Now that my Greddy guage is sold and I may have to keep my car I could go this route ;)

Sorry I misread what you were prying on, so I guess you may be less likely to damage it, its really a peice of cake to just take the panel out and remove the vent that way though, vs trying to get in that tight area to get it out.

You need to take that inside cup out if you want to have a clear shot to block off the vent completely like I did. If you dont care about blocking off the vent, getting the inner vent cup out isn't necessary.

I see what you are saying-- you dont need to take the outer vent out-- just the inner vent part (with the louvers) and then install the gauge into that.

I just took everything out cause I didn't know what needed to come out and what didnt--

I will be sure to update the guide so people that try this wont have to do more work than necessary--