TECH: PLX Devices SM-AFR

After my Innovate LC-1 wideband failed, it was time to get a new wideband... But because I was on a budget, I couldn't get another LC-1... So a cheaper alternative that I found was the PLX Devices SM-AFR.

Let's have a look at it!

The PLX SM-AFR is in a smaller package than Innovate LC-1. The features that they list on the PLX Devices website includes:

• Soft start technology
• 2 analog outputs
• 1 digital input, 1 digital output
• Bosch LSU 4.2 Sensor
• Compatible with multiple fuels
• Sensor is hand tested
• Digital precision

For under AU$200, what could go wrong?

Installation was a breeze, but I noticed something.... They had one linear wideband output (0-5V) for a wideband gauge and another analog output (0-1V) for basic narrowband....

You can't re-configure any of the outputs..!

The Innovate LC-1, you can re-configure any of the outputs and give it a different scale. This allowed me to use a normal volt-meter AFR gauge and reconfigure the output of the LC-1 so that it would read as accurately as possible as an indicative wideband.

Because the SM-AFR can't be reconfigured, you either need a Universal Exhaust Gas Oxygen (UEGO) gauge, that specifically takes the standard 0-5V linear wideband input or you have to settle with 0-1V narrowband output...

My gauge is the 0-1V type so I thought about being engineery and design an inverter circuit that can take the 0-5V linear output, reverse it and step down the voltage. Not difficult through the use of an operational amplifier and a voltage divider resistor network but I decided to keep that in my back pocket for now.

Well at least in the narrowband mode it will give me an indicative reading whether I'm running lean or rich...... Not by any means accurate however.

With everything installed I gave it a try and everything works as it should. Unfortunately, my AFR gauge now swings lean to rich like a windscreen wiper, but at least when I do go into boost, it creeps up to the rich zone and holds there which is comforting.

Perhaps I should invest in a cool new UEGO gauge ;3

Well for now I am happy with the SM-AFR's operations. The product is excellent and just plugs and plays. It's great that you don't need to setup firmware or require calibrating the O2 sensor. My only comment is that you can't re-program the outputs.. But then again, the 0-5V UEGO output is standard and is common to dataloggers, other UEGO gauges and even the AEM FIC. So for under AU$200, this is a great little product!