Wideband O2 sensor

[maineSS]

I recently got my PLX Devices Wideband O2 sensor hooked up, along with a Vacuum Gauge to complement my Tach. Now I have a triumvirate of instruments to stare at, just like a Ricer....

Pic #1 shows the gauges on the dash. Left to right, O2 sensor reading 12.8 A/F ratio, Tach reading 700 rpm, Vacuum Gauge at 20" - engine at idle.

Pic #2 shows the lighted switch used to power up the unit. There are 3 contacts- Power in, Load, and Ground. Power in and Ground are wired direct to the battery terminals to avoid voltage spikes, with an inline fuse on the Power in side. The unit is normally wired to the ignition switch to start the O2 heater immediately on engine start, I turn it on just before, and shut it off after engine shutdown.

Pic #3 shows the control box. I mounted on the passenger side as I'm running out of room to mount stuff on the driver side. My machinist made up a nifty slide in mount, normally it's mounted with Velcro or double side tape.
To be continued...

[Gordon Maney]

Pretty soon you will need special qualification/certification to drive your truck!

[maineSS]

Continuing on, Pic #4 shows the O2 sensor mounted in a stainless band exhaust clamp available from NAPA. The bung was Tig welded into the band. You can get these premade from O2 sensor manufacturers, I decided to make one.

Pic#5 shows the threaded bung plug used to seal the hole when the O2 sensor is removed. My engine burns oil, so I don't drive around with the sensor in all the time.

The sensor is supposed to be located in a lower temp area than the typical narrowband sensor, usually 24" downstream of the exhaust port. My IR gun showed my exhaust to be lower temp than the sensor limits even close to the engine. The recommended mounting is 15 deg from vertical to 10 deg above horizontal on either side of the exhaust pipe. This allows any condensed water in the sensor element to drain, and keeps the sensor wire out of the high heat area direcly above the exhaust pipe. Mounting the sensor at the pipe bottom is a big no-no, as liquid water can flow into the hot element, instantly destroying it.

Air/fuel readings need to be correlated with engine speed and load for maximum value. Carburteted engine show bigger swings than fuel injection due to no feedback correction, but using the readings intelligently makes tuning a lot quicker. We'll see how it reads the Fish carburetor.