Date: Sat, 3 Feb 2001 23:14:54 -0700
Reply-To: gary2a@TELUSPLANET.NET
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: gary2a@TELUSPLANET.NET
Subject: Re: Voltage/mixture sensor, testing O2 sensor
Content-Type: text/plain; charset="iso-8859-1"
----- Original Message -----
From: "Courtney Hook" <chook@nisa.net>
> Hi Gary, I'm Courtney out here on Vancouver Island, and would LOVE to have
a system as you describe. I take it that the LED's read out the incremental
> voltage, which they receive via the O2 Sensor? I am building a
Hiperformance
> engine for my Type1 right now, and would love to have the ability to check
> the mixture at the pipe. What would it cost to purchase one from you minus
> the sensor (already have a no. of them) ?
> Many thanks,
> Courtney Hook
> Nanaimo BC
>
Hi,
I just built a few for myself and friends.
You have the right idea about how it works. Just a 0 - 1 volt voltmeter. I
use them when I do propane conversions to set up the mixture. Other than
that, I don't feel the need to have one permanently attached to the vehicle.
At the moment I just have a cheap digital voltmeter temporarily connected
directly to the oxygen sensor. I haven't even bothered to use the LED bar
display meter.
A couple of points to consider:
As you probably know, O2 sensors need to be hot to work, so if you are more
than about 1 - 2 feet away from the exhaust port at the head, you need to
use a heated 02 sensor. The CDN digifant vanagon uses a heated sensor.
System gets to closed loop faster.
Over the past year, I have gotten over 2 dozen used O2 sensors from the
junkyard. It turned out that over 70% of the used sensors I got were
bad --where I live, we don't have emissions testing.
Do the propane torch test to check your sensor.
Attach a digital voltmeter to the sensor. Hold the flame of the torch on
the sensor and watch the meter.
What you are looking for is how fast you get a reading, how quickly the
voltage climbs, how quickly it falls when you move the flame away, how
quickly the voltage climbs again when you put it back in the flame and what
the maximum voltage is.
A good sensor starts to show voltage after about 5 seconds in the flame, and
climbs up to a maximum of just over 1 volt in about 3 - 4 seconds. After you
move the flame away voltage should drop quickly (1 second), and rise quickly
again when heated again.
Also, hold the sensor in the flame for 30 - 60 seconds. If voltage remains
constant the whole time and does not flicker, than that may suggest that
there are no heat related intermittent problems.
The only way to know for sure that you have a good sensor is to use a new
one. But most people feel confident that the above test is effective. If I
were fixing someone else's car for money, I would just use a new sensor.
However, if it fails on any of the above you at least know for sure that it
is bad. After you test a couple, you will know what to look for.
Gary Lee
Calgary
>
| 
