[stromer]

I'm looking to install an Air Fuel Ratio gauge in my car so I can be a little bit more informed of what is going on under the hood. I have decided I will mount it in the glove box so its out of the way when I want it, but I can gain access by just opening the door.

The biggest problem so far is trying to get Saab specifc info on how to wire it up. I get the impression its a model specific install as every car is a bit different. Searching these forums isn't too much help because air cannot be searched for being too short of a word. So having just fuel and gauge returns a lot of irrelevant information. So from people who have done it before, what are the steps involved in this install process? Were do you tap in wires? How many wires are there to tap?

I already know about the steps to have the gauge illuminated, so I just need to know where to tap to get the actual A/F info for the gauge.

If I get good responses, I'll try to do a write-up and forward it to Cleve for the tuning FAQ.

Oh, and pictures are always helpful.

 

[ricot83]

mark 900se did it and told me which wire... it is the green wire on the ecu side of the harness that plugs to the front o2 sensor in the engine bay

 

[Stalker]

Yea, that wire and the best place to tap it is right below the TB (fairly certain its the only green wire that runs right there. I remember there are 2 groups of wires under there, this is the one closest to the engine block.

Pics complements of Mark's cardomain page

 

[stromer]

I reccognize that as being where the O2 sensors plug in. So knowing which O2 I want, I can just follow it up to figure out which green wire.

g96 has sort of talked me out of doing this install. For one, he said that the normal a/f gauges aren't very accurate because they are 1v. And that a wide band is the only one that is accurate being a 5v. (Maybe those voltages are mixed up?) Seeing as a wideband is considerably more money, maybe I'll hold off.

And its not like I'll be able to adjust anything myself if my ratio is off.

 

[Marks900SE]

Whaoo, they are finially put to good use! Hope they helped.

 

[Tboy]

Here is a bit more accurate one for 58 bucks. Not a gauge install, but pretty unobtrusive unless it needs to tell you something.

http://www.dawesdevices.com/airfuelmeter.html

Tboy

 

[Stalker]

Whaoo, they are finially put to good use! Hope they helped.

Ive personally used the "Mark's Manual" for all my gauge installs :cheesy:


Well except the mounting part...

 

[stromer]

I like that Dawes Device version just because of the cleanliness that would come with the smaller unit to be installed.

This is the part that I like, all for $58:

"Each meter is individually tuned using internal potentiometers and a calibrated DVM (compared to the mass produced gauges which use resistors--and are not individually calibrated) to give the most accurate results available from a narrow-band O2 sensor"

And a DVM is? And a potentiometer for that matter? I'm not so sure. I trust its better, but I know somebody is just waiting to explain this all to me. I imagine somebody like Adrian knows.

 

[Shaft]

Now I dunno where I read it, but I was informed that tapping into the exisitng O2 is a no no.

However I only have 1 O2 in my car. Is that weird? Its on the downpipe before the cat.

I'm going to install a universal 02 after the cat to tap into for my A/F gauge.

 

[hunt.dogshome]

I tapped in on my 1st O2 sensor no probs. I also only have 1 - later versions here have 2, which caught up with US law.
I used a screened cable to be safe in case of noise pickup back into the ECU. That's also what sort the loom to the ECU is. The gauges take very little current on their input or supply and so used the same earth as the sensor rather than looping it around to the car body and potentially (pun) causing a noise problem there.

Used the O2 heater supply that comes on with the fuel pump to supply the meter. What this all means is all my 3 connections (12V, earth and signal) are all in the O2 Sensor wire. This means I didn't have to cut the main loom, just the one from the sensor which will get cut anyway if the sensor needs replacing.

DVM - Digital Volt Meter. Most resistors are 1% anyway, so I think there is some kiddology here; especially since the reading will be all over the place "up-down-up-down-up-down" normally as you drive anyhow.

Potentiometer - adjustable resistor or twiddler.

 

[Shaft]

I tapped in on my 1st O2 sensor no probs. I also only have 1 - later versions here have 2, which caught up with US law.

I used a screened cable to be safe in case of noise pickup back into the ECU. That's also what sort the loom to the ECU is. The gauges take very little current on their input or supply and so used the same earth as the sensor rather than looping it around to the car body and potentially (pun) causing a noise problem there.

Used the O2 heater supply that comes on with the fuel pump to supply the meter. What this all means is all my 3 connections (12V, earth and signal) are all in the O2 Sensor wire. This means I didn't have to cut the main loom, just the one from the sensor which will get cut anyway if the sensor needs replacing.

DVM - Digital Volt Meter. Most resistors are 1% anyway, so I think there is some kiddology here; especially since the reading will be all over the place "up-down-up-down-up-down" normally as you drive anyhow.

Potentiometer - adjustable resistor or twiddler.

Hunt... so your saying your powering your meter, getting your meter's signal, and grounding it from the O2's wiring? And this is the original Bosch O2 right after the 90 on the downpipe? How long have u had this setup and can you post the wiring diagram of the O2? What about putting a switch on the A/F meter to avoid annoyance in times when its not needed.

Thanks!

 

[Marks900SE]

DO not tap the o2 AFTER the cat, it is only there to see if the cat is working. Pre-ODBII cars only had one sensor. Tap the first o2 sensor to get a correct reading no matter what the year.

 

[Marks900SE]

Hunt... so your saying your powering your meter, getting your meter's signal, and grounding it from the O2's wiring? And this is the original Bosch O2 right after the 90 on the downpipe? How long have u had this setup and can you post the wiring diagram of the O2? What about putting a switch on the A/F meter to avoid annoyance in times when its not needed.

Thanks!

I have also made a switch to turn the power to both gauges off if so inclined.

Seen as the green switch by the dimmer here...

The power to my A/F is taken from the cig lighter as it is turned on/off with the car, and the boost gauge light is from the light switch so it goes on/off with the headlights being turned on/off...but that is overruled by the little green switch if so inclined.

Headlights On
Switch on
-->both gauges on

headlights on
switch off
-->both gauges off

headlights off
switch off
-->both gauges off

headlights off
switch on
-->boost gauge light off but A/F on

 

[stromer]

I wonder what would happen if I tryed to tap into the first O2 sensor. My car says it is failed, by way of a CEL. That's the MP 3" dp for ya...

 

[Shaft]

Mark that install is very sweet! What I meant about a switch was to completely shut off the A/F meter.. sometimes night driving and having that LED sweep constently can be a pain. Is this possible?

 

[stromer]

Just put a switch on any of the wires that doesn't require a full loop. This would make the gauge not work.

 

[hunt.dogshome]

My connections (using O2 lead):-

BLACK / Pin4(green) is SIGNAL (---v-^---^v--^-v-^---v^---)
WHITE / Pin1(grey/white) is 12V Supply via F11
GREY / Pin3(black) is 0V common and signal ground

The other WHITE in the sensor lead to pin 2 is a switched 0V for the O2 heater. No connection to that.

I've had it about, what, 3 months?

My "night mode" is to shut the glovebox

All the boy-racer gauges live in the box.

 

[stromer]

You got a picture from the driver seat of this gauge? I was going to do it, but I was looking more and more at the angles and I wasn't sure it was such a good idea.

 

[hunt.dogshome]

Don't have eye-line piccy. You're guessing right; it's not perfect, the first gauge in the top corner furthest from you is, however, no problem and if I'd put one below that that would have been fine too. Wanted to keep width of box for legal briefs, embassy pouch, gold bars, whatever!

The second gauge along starts to be obscured - that's my A/F so not so bad.

I think if a third went in along from that, you wouldn't see much of it.

The pillar gauges are the most visible and look very good - but then I realised I didn't want to look at the actual boost or A/F for 99% of my driving. Only look if messing, fault-finding or 'testing'

Also thought that pillar gauges say "nick me" to prospective thiefs as they are very visible from outside the car.

As for dash-mounted multi-pods - OK for rally-stylee but bin-there done-that with Minis.

Did have boost gauge in the ashtray area, which was angled up and worked well, but then I was watching 2 needles (stock APC) go up and down when I booted it. Like I say, personally, 99% of the time I'm not watching the gauges anyhow.

 

[Marks900SE]

Mark that install is very sweet! What I meant about a switch was to completely shut off the A/F meter.. sometimes night driving and having that LED sweep constently can be a pain. Is this possible?

Thats what I meant by A/F gauge off..no LED's sweeping and it also cuts the light for the boost gauge.

The great thing about having an easy access boost gauge like where I have it is that I can continually tune the MBC+A. When I went on the run in PA with DeLorrean and them it was very handy since I could put it to max boost while keeping an eye on the road and being able to see where the needle was.

The dual piller gauge pod is great, I dont think Id put my gauges anywhere else.

Downs:
-Does creat a TINY blindspot only noticable when going around a sharp lefthander and it has the potential to block the oncoming traffic lane. But since I wont be in that lane anyway, its not bad.
-Draws attention from other drivers...stupid hondas and such have been known to see them and do stupid things on the highway. These people are just ignored
-Possible increased disliking form the police should I be pulled over. "See I have them turned off, I just use them for when I autocross and possible drag at MIR, I swear officer"