A turbocharged car without a boost gauge is no fun. It's not that you really need it, but knowing what's really happening with your engine helps a bit, and the pressure surges when you mash the pedal sure are entertaining.

My car was among those unfortunate Saabs that came without a boost gauge (not that the standard one is very useful though), and I long wanted to fix that. Here's a detailed (maybe too detailed) description of the installation process. (And I did wash the engine a couple of days after performing this work ;)

The measurements I'm getting from a 1999 Saab 9-5 2.3t with a low pressure turbo are: the vacuum is 18-20 Hg at idle, 15 Hg while driving, up to 24 Hg when coasting. With the stock engine the boost during the moderate acceleration settled around 5 psi, the highest I've seen at WOT is 9 psi. An ECU upgrade from BSR raised these numbers to 12-13 psi in second gear and 14-15 psi in third.

17.04.2004
The kit

A Cyberdyne Ultragage boost/vacuum gauge kit (part #A213E061Y) bought on eBay. It contains a gauge, a sender, some tubing and other stuff.
17.04.2004
The gauge

I know I could've gotten an analog gauge for half the price, but I'm a digital freak, I like numbers and precision ;).
17.04.2004
The sending unit

The sending unit is sealed for good, it has a nipple for the vacuum hose and a signal wire for the gauge.
17.04.2004
The hose

The tees are a buck a piece from your favourite parts store. This one is dirty as I've just tried to fit it on a car.
17.04.2004
The engine

Our primary points of interest today would be the intake manifold and the big fuse box. The engine is filthy, and I'm sorry for that. Should have done the spring cleaning first.
17.04.2004
Disconnecting the battery

Always a good idea when you're planning to mess with wiring.
17.04.2004
The lower dash

To find a suitable place to get through the firewall, remove the lower dash cover. There are three T25 torx screws holding it.
17.04.2004
OBD-II connector

Remove two more screws, unless you want the cover hanging on the OBD-II connector wires.
17.04.2004
Holes in the firewall

A sysadmin would be shocked by a sentence like this ;). In our case in only means there are two clusters of wires coming through the firewall.
17.04.2004
Fuse boxes

Looking from the engine side, the access to one cluster is blocked by the strut tower and the fuse boxes are blocking the other. I pick the fuse boxes.
17.04.2004
Small fuse box

First, remove the cover from the smaller box.
17.04.2004
Disconnecting the cables

Then unbolt the cables using a 10 mm socket.
17.04.2004
Removing components

Push the latches, and the smaller box pops right up. The bigger box is secured with three nuts -- two are in the open, and the third one is under the master brake cylinder.
17.04.2004
Almost there

Move the fuse boxes out of the way and remove another connector assembly (lift the rubber trim to get it out).
17.04.2004
The cable sleeve

The rubber sleeve around the cables is ziptied and wrapped with dirty vinyl tape. We'll get rid of that.
17.04.2004
A handy pipe

The sender cable is rather soft, so I will use this plastic pipe to get the wire through the sleeve.
17.04.2004
The engine side

After some pushing and wiggling the pipe comes out on the engine side.
17.04.2004
Inserting the wire

The wire goes in...
17.04.2004
Coming through

...and comes out under the dash.
17.04.2004
Pipe removed

Find a good way to pass the cable to the top of the dash to the A-pillar and fasten it.
17.04.2004
Engine cover

Now we need to find a place to tap for the boost pressure. First, remove the engine cover.
17.04.2004
Cover removed

A nipple on top of the intake manifold looks very promising.
17.04.2004
Front view

There are two hoses coming out of it, and the top one is so inviting!
17.04.2004
Side view

It usually is not a good idea to cut the hoses on a car, and fortunately there's a conveniently placed tee we could tap into.
17.04.2004
Removing the hose

First, remove one of the old hoses from the tee.
17.04.2004
Old hose to new tee

Then connect it to the new tee we prepared during the step 4.
17.04.2004
New hose to old tee

And finally connect the short end of the hose to the original tee.
17.04.2004
Lots of hoses

This piece would be easy to remove later in case you'd want to sell the car. The long end in the right now runs to the sending unit.
17.04.2004
The sending unit

Time to connect it to the unit and secure the new hose so it doesn't rub against anything.
17.04.2004
Pulling the wire in

Pull the remaining cable through the sleeve leaving only a short end. Seal the sleeve with a new ziptie and some tape.
17.04.2004
Securing the unit

Fasten the sending unit well and bolt the fuse boxes back in place. Check if everything is connected properly.
17.04.2004
Connecting the wires

The gauge needs the ground and the 12V power. The ground nut is right at hand (10 mm again) and the cigarette lighter fuse would donor the power.
17.04.2004
Test drive

Out for a test drive. A healthy 20 Hg vacuum at idle is on display.
17.04.2004
Wiring done

Everything is put back together, and the wires are coming out at the base of the A-pillar.
17.04.2004
The gauge

The gauge comes with a memory button. Why haven't they just built it right into the face plate?
17.04.2004
Button installed

Ah, well, an aluminum bracket will do.
17.04.2004
Plastic bottle

I didn't get a pod for the gauge, and now I didn't want it dangling on its wires while I'm driving in search for one, so I cut the top of a plastic bottle.
17.04.2004
Masking tape

Painting it inside looked like a good idea.
17.04.2004
All black

Luckily, I had some black paint too.
17.04.2004
Mounted

The wires are connected, and the gauge sticks surprisingly tight between the pillar and the dash. It should hold until I find a suitable pod.
17.04.2004
Night

It's a bit too bright at night, but we'll adjust that.
18.04.2004
Day

Good visibility in the daylight.

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