AF Meter with stock o2 sensor

Our cars have two 02 sensors. The front and the rear. You should be able to use the rear with most any A/F ratio guage.

Schweet. Thanx.
One more Q about the Two o2s in our car... Why? Is this common? I'm assuming we have on in front of the cat, and one after.

OBD-II the first is the O2 sensor and the second is that catalyst effiency monitor.

and you can't hook it to the front O2 but you can hook it to the rear O2.

jeremy

someone told me MY99 O2 sensors front and rear are the same narrrow band O2....

HOK said:

someone told me MY99 O2 sensors front and rear are the same narrrow band O2....

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that's cause they are plugs are prolly different but on MY00-02's we have wideband front O2's

Hndatch627 said:

OBD-II the first is the O2 sensor and the second is that catalyst effiency monitor.

and you can't hook it to the front O2 but you can hook it to the rear O2.

jeremy

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Hooking it to the rear O2 would have you monitoring the Catalyst output, which will give some indication of the engine's A/F ratio, but not as good as an O2 sensor before the cat. Also, it is a bad idea to splice into the factory wiring, as any voltage spikes, etc that may possibly be generated in the A/F gauge will feed right to the ECU and could destroy it. They are quite sensitive to that kind of thing, that's why you only use high-impedence DVOMs on ECU wiring and not a gauge type volt-ohm meter.

Most mechanical A/F gauges work by having the O2 sensor "pull down" voltage supplied to the sensor wire, and this voltage could interfere with, or harm the ECU.

Short answer, yes you can do it, but I don't think it's a good idea.

So the best thing to do would be to weld another bung into the pipe near the front o2 sensor, and use a dedicated o2 for the AF gauge? Correct?

Skidd said:

So the best thing to do would be to weld another bung into the pipe near the front o2 sensor, and use a dedicated o2 for the AF gauge? Correct?

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yes this is the correct way to do it. As far as the damage goes...i have seen many done with NO problems...Autometers guages are 100% electronic and i have YET to see any single one cause an ECM/PCM failure. I plan on having a second bung added to the Downpipe once the turbo goes on so that i can guarantee a rich mixture. Andi do agree it's bad to splice into a factory harness but it happens all the time. As for voltage spikes, there is a built in limit, just look at everyone going turbo. They have at one time or another sent a nice spike thru the ECM/PCM.

can anyone recommend a wide band that you wouldn't have to weld on a new bung

arangov3 said:

can anyone recommend a wide band that you wouldn't have to weld on a new bung

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there are none, because they all use a standalone sensor

why is welding a bung such an issue? Literally takes 5 minutes to do, and anyone with a TIG can do it (even cheesy exhaust shops have this)

Wow, an 11(almost 12)-year bump! That might be a record!

There aren't any widebands that don't require a new bung to operate properly. That said, Skidd has since created a little Java app that can read the stock front O2. You just need a certain kind of OBDII adapter.

Hydrochloric said:

Wow, an 11(almost 12)-year bump! That might be a record!

There aren't any widebands that don't require a new bung to operate properly. That said, Skidd has since created a little Java app that can read the stock front O2. You just need a certain kind of OBDII adapter.

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by new bung do you mean one completely separate from the original front one or can you weld a new bung in place of the original o2 sensors place


and yea old bump I had a question might as well pick an oldie to bump instead of make my own thread

Hydrochloric said:

Wow, an 11(almost 12)-year bump! That might be a record!

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You haven't met George of the Jungle yet.

noTe said:

You haven't met George of the Jungle yet.

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shhhhh if he sees I've bumped an old thread he may start to haunt my old threads lol like 2 years old

arangov3 said:

by new bung do you mean one completely separate from the original front one or can you weld a new bung in place of the original o2 sensors place


and yea old bump I had a question might as well pick an oldie to bump instead of make my own thread

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most if not all widebands come with the bung, they drill a hole, weld, done. On turbo cars this goes in the downpipe.

I believe Skidds uses the stock front sensor, and pulls the values that the ECU is seeing and displays them.

Note: Front stock sensor is a narrowband, and doesn't read real well outside of 14.7 (if you were reading the original thread)

You *might* be able to find a wideband that uses the stock thread dia and pitch, and replace the stock front sensor. I know several wideband gauges have an analog 0-5v output that if you scale it just right can *work* to simulate the stock narrowband signal.

This being said, you'd save a lot of time and headache just having a bung welded in. Seriously, it'll cost you $10 to have an exhaust shop weld one in.

also, threadbump.

Z1 Performance said:

there are none, because they all use a standalone sensor

why is welding a bung such an issue? Literally takes 5 minutes to do, and anyone with a TIG can do it (even cheesy exhaust shops have this)

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I don't have a tig welder


a remember seeing somewhere(looking now) a wide band with a second pigtail for the ecu but now I can't find it or maybe i didn't know what I was looking at then

BRZCory said:

Note: Front stock sensor is a narrowband, and doesn't read real well outside of 14.7 (if you were reading the original thread)

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Negative. Some older Scoobs have a narrowband, but they have been using a WideBand for years now. my 2000 has a wideband. Not sure about the 1999 or prior though. To my knowledge, everything Subaru made after at least 2000 uses a wideband front o2 sensor.

If you want AF readings without welding or cutting, buy one of these
OBDKey :: OBD Bluetooth
and install this on your android phone
MyMPGTracker.com
(full disclosure... my software, some other companies OBD dongle).
In SSM Mode, you can get AF readings from your factory ECU on your android phone.

Side Note.. wow.. I've come a long way since 2002 in what I know about our cars. :loser:

BRZCory said:

Note: Front stock sensor is a narrowband, and doesn't read real well outside of 14.7 (if you were reading the original thread)

You *might* be able to find a wideband that uses the stock thread dia and pitch, and replace the stock front sensor. I know several wideband gauges have an analog 0-5v output that if you scale it just right can *work* to simulate the stock narrowband signal.

This being said, you'd save a lot of time and headache just having a bung welded in. Seriously, it'll cost you $10 to have an exhaust shop weld one in.

also, threadbump.

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I should have refreshed my page before I posted

I really just want to take advantage of using the factory location(OCD moment) so I could just grind off the factory bung and get a new bung welded on and use a wide band to work with the ecu.