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Old 10-27-2002, 12:21 PM   #1
jfalcon001
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Default Installing A/F to ECU... need help

Hey all,

I have an Apexi Turbo Timer and A/F... the problem i am running into is that the ECU map of the 02 WRX has two signal wires... on + and one -. The Apexi TT/A/F only has one wire for signal... so which do i connect to?

Thanks for the quick response.

Justin
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Old 10-27-2002, 01:20 PM   #2
jfalcon001
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Come on guys really need some help here....
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Old 10-27-2002, 01:32 PM   #3
supermarkus
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You gave us an hour to reply on a Sunday, don't expect a mad rush to answer your question. A lot of people don't have computer access until the work week, or have families and lives to attend to. Patience.
Give the others some time to get around to the question. If you can't wait, an educated guess would be to tap off the positive lead.
As per the wiring guide on northursalia.com and in the factory service CD, wires D19(white) and D29(black) both give positive voltage to the ECU.
D29 should read between 2.4-2.7V and D19 should read between 2.8-3.2V. What range does the TT need for it's readings? Tap accordingly.

Last edited by supermarkus; 10-27-2002 at 01:41 PM.
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Old 10-27-2002, 02:16 PM   #4
jfalcon001
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I appoligize... i wasn't trying to be a little nagging bi.... well you know the rest... thanks for you help....

The wiring guide is great... but all instructions there say to tap off the Rear o2... which i don't want to do because its not accurate... yes i still have the cat in my car... but the APEXi TT and A/F Sensor doesn't have any documentation that say it accepts the 2.8 3.2 or 2.4 2.7 voltages... so i guess i will tap the rear o2 for now and then will call apexi on monday.
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Old 11-10-2002, 10:10 PM   #5
206WRX_GDA
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Any update on this?

Quote:
Originally posted by jfalcon001
I appoligize... i wasn't trying to be a little nagging bi.... well you know the rest... thanks for you help....

The wiring guide is great... but all instructions there say to tap off the Rear o2... which i don't want to do because its not accurate... yes i still have the cat in my car... but the APEXi TT and A/F Sensor doesn't have any documentation that say it accepts the 2.8 3.2 or 2.4 2.7 voltages... so i guess i will tap the rear o2 for now and then will call apexi on monday.
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Old 11-11-2002, 12:23 AM   #6
enewtabie
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If your using the autometer gauge..heres a lil info I heard..so dont quote me..The voltage is not right to use the front 02sensor and the rear is too late..(after the exhaust)..so really AF is really useless ..like I said..what a friend told me after I bought mine.
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Old 11-11-2002, 12:28 AM   #7
jfalcon001
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I have resigned myself to to having to install another o2 sensor to get the proper readings.
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Old 11-11-2002, 12:39 AM   #8
206WRX_GDA
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Good points, but how can the A'PEXi TT work in "auto" mode without these wires connected?
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Old 11-11-2002, 12:42 AM   #9
enewtabie
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I hadnt thought of that..hmm..
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Old 11-13-2002, 01:55 PM   #10
206WRX_GDA
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here's a question, how does the automatic timer calculate it's idle time if you have an O2 simulator to avoid the CEL on some downpipes?
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Old 11-13-2002, 02:42 PM   #11
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Or you can make a small ckt ( if I remember 1 or 2 opamp, 1 2.8V zener and some other discrets) to scale the 2.8-3.2 V signal for the front O2 sensor to 0-1V so the A/F meter can use it. I may still have my schematic let me look for it.

I used this for a Auto meter A/F guage and it seems to be close enough

WR-Xtasy
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Old 11-13-2002, 04:11 PM   #12
AKWRX
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With the Autometer A/F gauge, I just hooked a separate dedicated oxygen sensor (narrow band 0-1V generic Bosch) to drive it. Works just fine. But, now can put some feel for numbers to "das blinkin lites" from the UTEC A/F values from the OEM front oxygen sensor.
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Old 11-13-2002, 04:46 PM   #13
Jon [in CT]
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Quote:
Originally posted by WR-Xtasy
Or you can make a small ckt ( if I remember 1 or 2 opamp, 1 2.8V zener and some other discrets) to scale the 2.8-3.2 V signal for the front O2 sensor to 0-1V so the A/F meter can use it. I may still have my schematic let me look for it.

I used this for a Auto meter A/F guage and it seems to be close enough

WR-Xtasy
I would caution against trying this at home.

The "signal" that the WRX ECU is looking for from its front A/F sensor is a current. The WRX ECU measures that current to the nearest 1/8 of a milliamp and, if you're not VERY careful, you can change that current by trying to measure the voltage. And BTW, the WRX ECU is the source of the voltage on that line, so it has little relationship to exhaust A/F ratio.

Back on topic, I don't think the O2 sensor voltage that the Apex'i TT can report has anything to do with how long it idles the engine after you remove the ignition key. It's just a little "bonus." But I could be wrong. I suspect many TTs determine idle time based on recent RPM activity, which some of them try to deduce by watching the very tiny voltage fluctuations produced by the generator.

Last edited by Jon [in CT]; 11-13-2002 at 04:51 PM.
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Old 11-13-2002, 05:01 PM   #14
jjunior887
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just for reference my Blittz TT uses ignition pulses to calculate the auto setting. Basically what Jon said, it bases it off RPM not A/F.-James
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