S70 DIY: Boost Gauge Install - complete guide

[mecheng]

Ok, I realize this is not rocket science but there are some tricks and advice I can share and I haven't found a complete guide to step people through this. It is not hard, but takes a bit of patience to do the job cleanly and safely as you are taping into electrical wires and adding new vacuum line.

If you are like me, you want to know how your engine is performing and boost / vacuum is a key parameter that can help diagnose leaks, boost fad, not reaching peak boost, etc.

Here is a step by step guide.

1) Under the hood, locate the main fuse panel. Use a screw driver to release the tabs and move the main fuse panel aside.

Remove main fuse panel

2)You are now looking for an accordian like black tube with this rubber grommet on the end. To the right of the master cylinder. This is called the pass through. Remove the rubber grommet.

Pass through hose

3)Use a sharp sissors to cut one of the tentacles, just cut the end, there is a cutting line on the grommet.

Grommet cut to feed line

4)Inside the car, remove the lower kick panel under the steering wheel which is held by qty 1 torx screw.

Remove kick panel

5)Locate the same pass through and grommet by going on your back on the floor and looking up. It is near the base of the pedals. Cut grommet as you did in step 3, and feed your boost plastic line through the grommet until you see it in the engine bay. I used a bit of grease on the line to help it slide through the grommet.

Feed vacuum line into engine bay from inside the car

6)Inside the car, feed the plastic boost line above the hood latch and through the side of the dash board by removing the rubber molding. It will just pull away from the car.

Feed boost line

7)Remove the dash dimmer switch, be careful you can break the tabs. (Don't fret if you do, wrap the switch in electrical tape to make it 'bigger' and it will fit snug. Use two flat head screw drivers.
Unhook the connector and locate the pink and black wire.

8)Now you need to fish the new wires for your gauge behind dash to exit where the rubber molding attaches. For this, wrap ends of the wire with a coat hanger bent in a gradual U shape. Use some patience and feed the coat hanger until you see it poking out the side. You can get the bend right and it takes a minute or it might take a bit of trial and error. Hint: And no, you can not fish the wire through the speaker or vent, I tried.

Fish Electrical

Go Fishing

9)To make the connection, You want to gently remove some of the insulation from the wire without cutting the wire so be careful, use the correct setting on your wire stripper. (You can get quick connects but I prefer to add a solder joint with low resistance over a knife edge contact which isn't always guaranteed to be a good contact especially if you don't size it exactly. I was not able to remove the wires from the connector despite trying, otherwise I would have soldered to the upper part of the female connector.)

10)Wrap the wires together: positive from the gauge wire to pink, negative to black. This provides diming power: same as the dash assembly. The wire from my gauge was not long enough so I added a long section to make it easier to work with. Solder and then use electrical tape.

Connect power to dimmer switch: pink is +ve diming power, black is -ve

11)Dry test your gaugepod fit and mark a hole in the A pillar plastic for a hole that you need to drill. The Gaugepod from Lotek Inc. (same as sold by IPD but without the extras (see 12) should fit to the base of your dashboard. I got my gaugepod painted Tan to match my interior.

Mark hole to drill into plastic only

12)Lotek supplies a sheet metal screw for you to drill into the steel A-frame; this is not something I wanted to do. Instead after 30 minutes of searching through all my screws, I found a machine screw with a nut: nut on the back of the A frame plastic, screw into pod. The screw I found wasn't flat so I had to use my grinder to gently ground the surface of the screw so it would not protude and I can put the cap on it. The only hole I drilled was into plastic A frame; make sure you remove it so you don't drill into the existing wires or metal, and be gentle removing it or it will crack (don't ask me how I know: albeit a very small crack which I fixed). I believe IPD provides a plastic rivet so kudos to them, you may want their kit but it is more expensive. If anybody has the details of the plastic rivet, please post??

Drill hole through A frame plastic

13)Drill another hole to pass the connections through the A frame plastic with the same precautions. My Autometer gauge came with a rubber grommet. Use teflon tape on the threads, and if you use a ferule, be patient, it will slide onto the boost line: my ferrule setup was tricky. Tighten all the lines with a wrench, hand tight will casue leaks but don't overdo it. You will not have any room to mount the bracket, but if you are using the Lotek kit, the gauge will fit tight, so don't worry about it. If it doesn't wrap electrical tape around the gage. Make sure no excess vacuum wire is left in gauge pod or it will kink, I learned the hard way. I unkinked it so it is not leaking but I wasn't happy I did this. They should supply a rubber line, but I called them and Automoter only supplies hard plastic with all their lines. Keep your bend radius generous!

Drilled holes in Plastic A-pillar (don't drill into steel A Pillar)

Making the connections on the gauge, use teflon tape. Gage fits snug, no braket needed

14)Make the boost line connection to the vacuum tree. Using the supplied T with my autometer gauge, I used some vacuum hose and clamps to make the connection. It is far too complex so I will be purchasing a Volvo elbow (small to big) and connect the plastic line directly into a elbow with clamps.
I've read to cut a hole in one of the rubber caps and connect vacuum line into it, but that doesn't seem precise.

Overly complex vacuum line fit to tree

Does anybody know the Volvo PN for the small to large elbow (there is one on the vacuum tree)?

What is the PN? This would be a simplier solution.

Installed!

Done: action shot in vacuum sadly :(

at WOT @ 15°C ambient temp (Fall is around the corner) and 1/2 Turn on Waste Gate, original CBV and TCV, all new Vacuum hoses

12-13psi Peak - settles to 10psi (surprised with the Peak - but that explains how hard it pulls)
15 in-HG vacuum at idle in Drive
18 in-HG vacuum at idle in Park

Happy Boosting

[rmmagow]

Sweet write up. The boost numbers, when you hit the peak is it the TCV that takes over and cuts it back to 10 or so? Is the waste gate adjustment what lets the peak go a bit higher? That's a nice looking clean install. I think I'm going to try this on my 98 AWD.

[rspi]

I think every turbo car should have a gauge. Nice install. I usually pull those funny elbows from cars in the junk yard all the time.

[rspi]

Oh, how did you know which wires to tap into on the dimmer? Is the pink one a dimmer feed or just power?

[mecheng]

Sweet write up. The boost numbers, when you hit the peak is it the TCV that takes over and cuts it back to 10 or so? Is the waste gate adjustment what lets the peak go a bit higher? That's a nice looking clean install. I think I'm going to try this on my 98 AWD.

This is a good question, that I've asked but haven't got a definite answer so I will be testing shortly.

But the theory is: TCV will drop it back down to 10psi, by feeding air to the waste gate to open.
The waste gate adjustment is only done to build the boost earlier as my car was a dog in the mid range, only 1/2 turn made the difference I needed and how it should be from factory. There is a whole write up in the performance section but Volvo was very conservative with the HPTs (especially if you have a 16T turbo) and this adjustment. Pre-98 people go up to two turns for HPTs only with no codes, I kept it conservative.

https://www.matthewsvolvosite.com/forums ... =5&t=23391

[mecheng]

Oh, how did you know which wires to tap into on the dimmer? Is the pink one a dimmer feed or just power?

I used a volt meter and found that the pink wire is a dimmer feed, black negative. Tested it, dims perfectly. And for those wondering, yes I tried to fish the wires through the vent and speaker: no dice. That would be easy, but you can not; don't waste your time like I did.

[rspi]

I just installed another gauge and it was the dimmer power like you explained. My gauge is cheap and needs power at all time to light up the back so I think I need a full power wire or the light will not be on unless the head light switch is on.

[mecheng]

Robert: you must have a digital gage. My gage is a simple mechanical gauge.
I paid too much for it, I found Amazon sells them cheaper than my local performance shop but I had some spare time so I wanted to get it done. VDO is another good gauge that you can get a good deal on Amazon (use the link on this site of course!).

I simplified my connection to the vacuum tree. I found a vacuum line that fits snugly around the boost cable, I think it is 1/8" ID and I was able to slowly feed it over the vacuum tree nipple. I love how rubber expands!

Connection to vacuum tree

[rspi]

The first one is digital and the second is mechanical.

[erikv11]

Those look like the factory clamps on your IAC hoses, if so you may wish to remove them to pull it out and give it a good cleaning.