A/F Gauge
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Understanding a narrowband Air Fuel meter.


Disclaimer: Any performance upgrades or wire harness tampering to any engine component may have damaging effects and is solely your responsibility from any damage occurred. It is also a very good idea to study other information very closely and know what you will be dealing with before attempting any modifications. In other words,
don't blow anything up!

An A/F (air fuel) Ratio gauge can be very useful when enhancing the performance of any TURBO engine. A/F gauges range from 4 LED's to 20, it is your choice in which style you prefer. Dawes Devices makes a 4 LED gauge, (like the one above), that is only 3 times larger than a quarter and is easier to read than the Autometer, unfortunately I didn't know the Dawes Devices gauge existed when I bought mine, but I do like the way this one looks in a daily driver. Cyberdyne makes a 10 LED gauge that is also easier to read. This section is going to be focused on the Autometer SPORT COMP A/F ratio gauge with 20 LED's.

First to study a little on what to expect before you install.

This Autometer gauge has 20 LED's starting roughly from 0.1 volt and ending at 1.0 volt with each LED as an increment of 0.05 volts.

The LED colors consist of 4 red LEDs (Lean), 10 Yellow LEDs (Stoich), and 6 green LEDs (Rich). This is what the gauge looks like when cruising and a good O2 sensor is in use. (If the LED's move back and forth very slow it is the sign of a bad O2 sensor) .

 

This is not what you want to see under acceleration or WOT (wide open throttle), "THIS IS LEAN". If you see red or yellow lights under boost back out immediately and find the problem, (possibly a blown off vacuum hose or really bad fuel pump etc....).

 

 

"THIS IS A RICH CONDITION" When pushing higher boost ranges some people like to run real rich (.95 volt and above). Everything I've ever read on the "Turbo Dodges" suggested that .90 volts is optimum burn at WOT, but after the installing of my Innovate wideband, it would show mixtures as rich as the low 9:1 A/F ratio at that point.

After adjusting my fuel mixture at 20 psi of boost, the narrowband gauge would show closer to .84-.88 with no issues. Keep your mixture closer to .90-.95 if you are only relying on the narrowband for tuning. Different sensors on the same setup would show different readings between each other.

OK! Now you know what to expect from this unit, let's install it!

Installing the gauge

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Tuning video log