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The difference is entirely in the sensor, which is *far* beyond the skills of 99.9% of garage tinkerers. Then the gauges are built based on the characteristics of the sensor.
Narrow-band sensors have a very tight voltage range, and rapidly traverse the range in a very tight area around stochiometric. It is for all intents and purposes just an indicator of 'too rich' or 'too lean'. Which is really all a fuel injection computer needs to know. Too rich - lean it out a notch and check again in a half second. Too lean, richen it up a notch. it doesn't really care at that instant *how* rich it is, it just responds to the constant 'too rich' and 'too lean' readings. When operating properly the computer is bouncing around from rich to lean and adjusting the fuel up and down.
The wide band sensor, on the other hand, has a nice fairly even voltage signal from 0V to 5V, nicely coordinated with a mixture reading or roughly 10:1 (pegged rich) and 23~:1 (pegged lean), with the central 2.5V mark on stochiometric. An FI computer programmed for the on-off nature (over a different voltage range too, but I can't recall it) of a narrow band would obviously be confused by this smooth gradient - the computer has to be rreprogrammed. At which point it can be a little more responsive to off-mixtures - making larger adjustments the farther off the desired mixture you are. And obviously, this works much better when hooked to a gauge. You could get just a simple voltage gauge and hook it up. I think they are a little more complicated because they have reference voltages to make them more accurate and heater circuits. I'm not sure why they are so expensive even when DIY. All they really do is convert the 0 - 5V scale using a tableinto 10 - 24:1 readings.
The first WB sensors were rare odd Honda sensors off a somewhat obscure low production (and I think Cali only) 'lean burn' model - demand greatly outstripped supply once a few dozen sales a year to Cali were replaced by hundreds worldwide as people started using them for gauges. But newer sensors have hit the market, used on newer, more common cars and I think the price spike on sensors is over, as long as you have a newer kit. I'm stuck with an older Techedge unit that uses the rare Honda sensor.
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I'm JohnMc, and I approved this message.
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