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Old 02-22-2004, 09:10 PM   #1
Hit Man X
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Default Tuning A/F off stock O2 sensor?

I'm considering upgrading from my TXS Unichip to the UTEC setup. I have AutoTap Enhanced currently and am wondering how close can I get in the mV on the regular O2 sensor? I've got my two trucks tuned via the stock O2 then put on a wideband and they were very close (off by about .1-.3) so I was wondering if anyone has had good luck w/o a wideband on the Subaru end?

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Old 02-22-2004, 09:20 PM   #2
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I don't think so...
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Old 02-22-2004, 10:26 PM   #3
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the stock front O2 sensor is only able to read down to around 11.73 to 1 and is NOT very accurate.
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Old 02-22-2004, 10:34 PM   #4
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Ah well, thanks guys.
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Old 02-23-2004, 07:52 AM   #5
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I use the stock front O2 as a check that I am not lean. The OBD software that I use reads down to 11.3:1. I just make sure that I don't go over that. After tuning my car on the road with UR600's and a 16G the A/F on the dyno was 11.2-11.0 from 4800-6400 droping to 10:1 at redline.

TMS
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Old 02-23-2004, 09:06 AM   #6
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how do you read off the front O2? a basic A/F gauge?
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Old 02-23-2004, 09:43 AM   #7
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DeltaDash
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Old 02-23-2004, 01:15 PM   #8
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My harrisonR&D OBD scanner does it too.

TMS
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Old 02-23-2004, 03:15 PM   #9
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AutoTap reads in mV's and I have based A/F off those. All I'd need to do it sounds like is to get someone to give me a reading of their O2 who's been tuned already to give me a target mV.
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Old 02-23-2004, 07:00 PM   #10
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You could use the rear O2 (narrowband) just as you did on your previous cars. Its true that if you're careful, you can get a decent tune from a narrowband O2. It won't be exact, but pretty close.

-- Ed
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Old 02-24-2004, 03:29 AM   #11
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Vaus is correct. You can get a decent tune from the rear O2. If you know what values to look for then you are all set. I even tuned my RS-T only on the rear O2, poeple said I was crazy. 2 years later of driving a 245 wheel horsepower and 285 ft/lbs of torque and people started to think otherwise.

I will admit a really good O2 helps a lot. But don't rely on it, because it will get dirty and in the end becomes less accurate much faster than one that is a little more vague. As it will get dirty but will still be in the same ball park for tuning.

Cheers,
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Old 02-24-2004, 10:27 PM   #12
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does anyone know what the values would be? as in how many mV's equals roughly what af ratio?
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Old 02-25-2004, 04:20 AM   #13
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A lot depends on the O2 sensor and if it is dirty, wether there is a cat in the system or not? Etc...

The only way to really know from the start, is to turn the car on and let it idle. You know this is about 14.5:1 A/F ratio. Now get the narrow band reading from that.

Drive down the road in cruising condition and get the average reading for the narrow band, here, the car will be anywhere from 13:1 to 14.5:1. You can then deduce what is 13:1 as you know what 14.5:1 is.

Now you have an idea of that range. Next try flooring it, if it is a stock WRX, they like to run RICH!!! So your O2 sensor will be some number again, but you know the A/F ratio is at least 10:1. So you know have the range and what is important and not.

Add in a fudge factor for safety and you should be all set. Go to the dyno and see how accurate you were with the values, you might be very surprised.

Cheers,
Bill Knose
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Old 02-25-2004, 04:49 PM   #14
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which wire do I tap into for the front 02 sensor(assuming that that is the one to use).
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Old 02-25-2004, 05:02 PM   #15
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Quote:
Originally posted by Rickyh
which wire do I tap into for the front 02 sensor(assuming that that is the one to use).


Why would you tap into it? Use a program such as AutoTap to monitor the voltage to it to get the WOT A/F levels...
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Old 02-25-2004, 05:23 PM   #16
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because i do not have autotap. i have an safc and i can hook up one of the wires to the o2 sensor to read the voltage from it.
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Old 02-25-2004, 11:30 PM   #17
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Quote:
Originally posted by Rickyh
because i do not have autotap. i have an safc and i can hook up one of the wires to the o2 sensor to read the voltage from it.


I dunno what the SAFC is but I'd check the manual that came with it to see what wire is needed. I believe the WRX has a 4 wire O2 sensor, so if you can find the signal that should be the correct wire to tap into.

Good luck!
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Old 02-26-2004, 04:27 AM   #18
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Again...

I'd use the rear O2 sensor if you're used to tuning with standard narrow bands.

-- Ed
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Old 02-26-2004, 05:01 AM   #19
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Rickyh,

I would suggest NOT using the front O2 sensor, as this is wide band O2 sensor. The AFC from what I remeber does not work off a wide band it works off a narrow band. you could damage something if you try using the wideband.

So my suggestion is to use the rear O2. If you want to find out which one it is please goto. www.northursalia.com

Cheers,
Bill Knose
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Old 02-26-2004, 09:04 AM   #20
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Well, i admit i was really trying to get out of spending 350 on a wideband. I guess I will just have to suck it up and spend the money.
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Old 02-27-2004, 07:10 PM   #21
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Suck it up and get the DeltaDash. That is going to be the most useful tuning tool you have, frankly.
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Old 02-27-2004, 10:09 PM   #22
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What would be the ideal A/F ratio?
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Old 07-06-2004, 10:19 PM   #23
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can anyone tell me what the stock a/f readings are at WOT???

thank you
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Old 07-07-2004, 09:03 AM   #24
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Quote:
Originally posted by jugger
can anyone tell me what the stock a/f readings are at WOT???

thank you
~10:1
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Old 12-20-2004, 07:15 PM   #25
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Sorry for dragging this from the dead again

Going RS-T soon with the AVO kit, but really no money to spend on a Wideband...

1) The Link ECU doesn't take wideband, and my thoughts are tapping the rear O2 signal for the Link as a reference.
2) Front stock wideband is about a foot from the turbo on the downpipe, around where the bend towards to tail. I'm thinking of finding some cheap way to read of that.
3) Equal length headers are coming when the funds are available as well as the VSD Concept, and thus not really wanting to spend for an EGT and getting the probe welded to the stock headers
4) Supposingly the Link has a map already for the AVO kit

Given the above, should I try to do a first cut road tune after the kit goes in? What should I be looking for in case the map doesn't work too well in the colder weather up North? And lastly, while I'm kind of blind in terms of tuning (no EGT, read off the stock O2 front and rear), how handi-capped I'm with this kind of equipment to tune?

Thanks

Chris
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