[Gmecm] One wire oxygen sensor to four wire

[Beau Blankenship]

Yeah, I got some real world experience. It works fine. Sends engine into
closed loop pretty quick and never drops out at idle. My bung is in the
collector of the passenger (full length) header. The old 1-wire unit used to
hunt around for the right AFR at idle causing a bit of an oscillation after
coming to a stop. I believe that most of the chevy's and most everything
American made for that matter, are the same size and thread pitch. Seems
like 14mm.?? The sensor element is exactly the same and produces the same
voltages as a 1-wire. The 4th wire for sensor ground is a good idea if your
sensor is mounted on the exhaust pipe behind some paper collector gaskets
and some rubber pipe hangers, which tend to give a high resistance to
ground. If its custom and you have any of these special needs, use the
4-wire. Stock cast manifold, 1-wire should be fine

Beau

-----Original Message-----
From: gmecm-bounces at diy-efi.org [mailto:gmecm-bounces at diy-efi.org] On Behalf
Of Jon Dods
Sent: Tuesday, June 05, 2007 6:43 PM
To: gmecm at diy-efi.org
Subject: Re: [Gmecm] One wire oxygen sensor to four wire

I've been patiently waiting for a reply top this topic as I'm also looking 
to change from a one wire to a 4 wire sensor.

I was hoping for somebody with some real life experience in this area might 
contribute some information however, in lieu of that, I will post what I 
have learnt on this subject so far.

Based on my research, I believe this would be ok provided the sensor was 
replaced with the same general type.  Since the most commonly used sensor is

a zirconium dioxide sensor I'm going to assume that's the one used in this 
instance.  These come in a number of varieties and sizes. Obviously, you 
need to choose one, which is the correct size for your bung.  Beyond that, 
my belief is that the only difference is the wattage and/or voltage of the 
heating element.  This is where I get a little lost as I've read that the 
heating element in some sensors must be current controlled by the ECU while 
others can be just hooked up to 12V.   Perhaps someone with more knowledge 
on this subject can clarify this..

The zirconium dioxide sensor should produce an average of 450 mV (0.45V) 
output if the engine is running at 14.7:1 air/fuel mixture and the sensor is

at operating temperature.  The key word there is average, as the output 
should actually fluctuate from around 225mV to 675mV in cycles taking about 
1 second to complete a full cycle.



Regards,

Jon.

----- Original Message ----- 
From: "Mike Hudson" <sonoma at shaw.ca>
To: <gmecm at diy-efi.org>
Sent: Sunday, June 03, 2007 8:27 AM
Subject: [Gmecm] One wire oxygen sensor to four wire


Hi
My setup is a full TBI system from a 91Chevy G20 including TBI intake and HD

TBI cylinder heads sitting on a 83 350/5.7 block.
A 3 wire oxygen sensor doesn't have a wire for sensor ground, it uses the o2

sensor body for the ground return path.

I welded in a bung for the o2 just below the connection between the exhaust 
manifold and the exhaust pipe. The ground for the o2 sensor would have to go

through that connection which is not the cleanest ground path. That's why I 
would like to go with the four wire.

The 4 wire has one wire for: o2 ground, o2 signal, heater positive and 
heater ground.




I was thinking of using something like a AC ASF-75 or NTK 21006(Narrow band)

Will the output from the 4 wire o2 output the same voltage at the same AFR 
as the 1 wire sensor (Narrow band) ???

Does anyone know which year and model vehicle the ASF-75 was used on?

Thanks...
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