[V8] O2 sensor

Mon Oct 4 13:40:18 EDT 2004

The rusty exhaust system, if my understanding is correct.

Tony Hoffman 

-----Original Message-----
From: v8-bounces at audifans.com [mailto:v8-bounces at audifans.com] On Behalf Of
Kneale Brownson
Sent: 04-Oct-2004 11:57 AM
To: dsaad at icehouse.net; v8 at audifans.com
Subject: Re: [V8] O2 sensor

So the V8 OEM sensor is a three-wire, isn't it?  Where does the original
wiring ground the O2 sensor?

At 08:57 AM 10/4/2004 -0600, dsaad at icehouse.net wrote:
>The O2 sensor is "analog". It generates a very small voltage from zero 
>to around
>1 volt based on oxygen content. Normal operating voltage for a proper 
>mixture is about 0.7 volts.
>If there is a difference in the ground reference voltage between the 
>ECU and the engine block then this voltage adds algebraically to the 
>actual generated voltage - thus offsetting it. This offset voltage can 
>really cause problems because the sensor output voltage is not linear - 
>it is exponential - so a small voltage change can mean a big mixture 
>change by the ECU. If the ground reference changes - as it could by 
>normal engine movement and vibration on a one or
three
>wire setup (think rusty exhaust pipes/bolts, etc) then the ECU will 
>never be able to stabilize mixture.
>The software in many ECUs can detect this and make allowances but our 
>vintage of Bosch software (I think version 1.2) does not do this. Any 
>little thing out of whack causes the ECU to overcorrect too quickly and 
>that shows up as "the surge".
>The O2 sensor also "ages" meaning that over time it responds more 
>slowly to mixture changes. This can also be compensated for by more clever
software.
>
>The O2 is not the only sensor that can do this either. The MAF, engine 
>temp, and air temp are all also susceptible.
>
>On the V8, the engine speed and crank reference are analog as well (I 
>think they come under the magnetic reluctance catagory) however they 
>are converted from a sine wave into digital pulses before being 
>processed by the ECU. A voltage offset here can cause very wierd 
>problems - like engines that will not run
over
>2000 RPM.
>btw, the brake wheel sensors are the same type as engine speed.
>
>The cam position sensor on the right head is a digital type sensor. It 
>outputs a
>5 volt digital (square wave) pulse so no conversion needs to be done by 
>the ECU.
>
>
>Guess I should get to work now... but this is more fun :-)
>
>
>Dave
>
>
>Quoting Tony and Lillie <tonyandlillie1 at earthlink.net>:
>
>> I'm not saying the fourt was disconnected ever, rather, I switched 
>> mine and Zay's cars to 4-wire using the auxilary fan ground on the 
>> drivers strut tower as the ground for the fourth wire (gray). This 
>> cured the "surging" the cars both did (mine was worse). My question 
>> is why the different grounds would give diffierent signals. Also, 
>> where the ECU sees the reference to be, and how an O2 sensor works.
>>
>> Tony
>> ----- Original Message -----
>> From: "Buchholz, Steven" <Steven.Buchholz at kla-tencor.com>
>> To: <v8 at audifans.com>
>> Sent: Friday, October 01, 2004 7:18 PM
>> Subject: RE: [V8] O2 sensor
>>
>>
>> ... well, if you don't have the fourth wire connected to anything it 
>> is as if there is an open circuit ... I'd expect the ECU would 
>> generate codes to this effect ... but yes, I'd expect your car to run 
>> like crap this way!
>>
>> Connecting the fourth wire to *any* ground is better than *no* ground 
>> ... as was pointed out, one of the OXS heater leads is in fact 
>> grounded ... this would not be a terrible place to attach the ground 
>> wire ... be extra careful to determine which pin is grounded because 
>> the other gets power when the engine is running ... this would 
>> probably be a bad thing for the ECU to see as a reference and might 
>> well damage the ECU.  This also fits with the esthetics of building 
>> an adapter for the Ford sensor ... the 4-3 wire adapter would then be
self contained.
>>
>> Steve B
>> San Jose, CA (USA)
>> >
>> > It is an interesting theory, where to ground the fourth wire.
>> > I'm going to
>> > get out the MM and check the voltage drop from the block to the fan 
>> > ground (in my free time, of course :-) ). However, the car runs 
>> > about 100% better since I put the 4 wire in, and Zay has reported 
>> > the same for his car. Both use the fan ground for the fourth wire.
>> >
>> > Can anyone explain the theory of why the engine would be better if 
>> > there is a voltage drop. The O2 sensor is not connected to the 
>> > engine, but rather the ECU, so I don't see the difference anyhow. 
>> > BUT, if one of you can educate me, I'd be happy to hear how it 
>> > works.
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>
>
>
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