What is the difference between a narrow and wideband Air/Fuel Ratio gauge? I honestly have no idea lol. So I figured someone here must know.

-Dave

 

The difference is in the sensor itself, not the gauge.

A narrow-band sensor is used in the stock PCM control system. It has one purpose.... to help the PCM keep the closed loop (part power, moderate RPM) A/F ratio at the stoichiometric ratio of 14.7:1 for emissions. As a result, the sensor is only accurate over a very narrow range of A/F ratio, typically in the range of 14.65:1 to 14.75:1. It does that for the sole purpose of emissions, since the catalytic converter is designed to function with the engine operating at 14.7:1. Beyond those values, the sensor is more sensitive to changes in operating temperature than it is to changes in A/F ratio. Hence, it is not an accurate tuning device for max power/max torque conditions, where a much richer A/F ratio, typically in the range of 12.8 - 13.2:1 is required for NA applications.

A wide-band sensor is deisgned to be accurate over a wide range of A/F ratio values, typically in the range of 10:1 to 20:1. That allows you to get an accurate measurement at max power/max torque, even using nitrous or forced induction, where you might want to see values as rich as 11.0:1.

 

Wow. Thanks. So basically a wideband would be ideal for spray?

-Dave

 

If you are wanting to monitor your A/F ratio with a gauge and/or data logger, a wideband O2 kit is really the only type you can use.

 

Can't we just convert to a wide band in our cars from the narrow bands? I guess we can't all else we would do it. But why can't we. I'd like to know why? Is it the wiring? Voltage? or the responce time that the PCM can't handle?

 

A stock narrow-band sensor supplies the PCM with a non-linear signal that varies from 0 - 1.0 volts. The typical wide-band sensor operates in a fairly linear manner, over the range of 0 - 5.0 volts. Hence a stock PCM will not respond correctly to the signal from a wide-band sensor.

However, some wide-band controllers (the "box" that you need to have to operate the wide-band sensor) have an option that allows the controller to produce a 0 - 1 volt signal that emulates a narrow-band sensor. When you have a wide-band setup like that, you can replace the stock narrow-band sensors with wide-band sensors. Its going to run you about $500-750 to accomplish that. The popular Innovate LM-1 wide-band controller can function in that manner. I suspect the FAST dual-wide-band controller may work that way as well.

Aftermarket ECU's will generally accept a wide-band sensor output for closed loop A/F ratio control.

 

Closed loop with a wide band seems like a tuning panacea. But it isn't. Closed loop seems useful only under steady state condtions or when the load changes very slowly. With rapid increases in load and throttle, the system can't keep up and the AF mixture goes lean. So, I am not convinced of the utility of a wideband except as a tuning aid, unless you want to cruise at richer or leaner than 14.7:1. I have seen this with FAST, Electromotive, and other aftermarket DFI systems. I have also read that it is difficult to manufacture sensors with a consistent reponse time, which further complicates use of a O2 sensors to control AF ratios other than under steady state or near steady state conditions.

Rich

 

Thanks for the info. I knew there had to be a catch, but I didn't know what it was.