Has anybody found these gauges to be of much value for a daily driver and are they all that accurate? I had a thought that since I have a threaded hole below my exhaust manifold (even though my van doesn't require an O2 sensor)I had the option at least to hook up a gauge if I wanted to.


thanks

The gauges themselves are accurate, they are a basic voltmeter.

The sensor itself on the otherhand - depends on the type of sensor used. "narrow" band sensors, the cheaper kind, are only accurate at 14.7:1 afr. These types of sensors will make the gauges bounce back and forth from lean to rich when your near 14.7:1, when your richer then that by a minor amount they stay at the rich side, and when lean a little bit they stay on the lean side. So you can tune lean, rich, or stoich, but nothing else.

"Wideband" sensors on the otherhand are accurate at usually 10-20 :1 afr.

Narrow band sensors usually can be hand under $50. Wideband sensors can be significantly more, and they require a controller you can't directly hook up to a gauge. A popular one, the Innovate Motorsports LC-1 is $200 including sensor and controller. The controller is awsome. Its programable with 2 outputs - you can program one output to match say your efi computer whereas the second output to match a cheap gauge that would typically be used with a narrow band gauge (by program I mean you can tell the controller when sensor sees this afr, output this voltage)

Widebands are a lot more useful in tuning, allows you to set your cruise to be leaner to save mileage, WOT/highload situaitons to be a bit richer without spitting fuel out the exhaust, etc. A narrowband, however, is still lots better then judging your tune by how the engine sounds when you turn the screw.

I used a narrow-band O2 sensor when I was tuning my motorcycle.

As it was temporary, I also used my digital voltmeter as the gauge. Just had to convert millivolts to Air/Fuel ratio. I wanted 850mv for power and 100mv for cruise, and it actually worked pretty good when I was seeing how the carb circuits kicked in. (I changed things to see if I understood what was going on, and if I could make the carb go rich or lean when I wanted it to)

http://www.conservatory.com/vw/manuals_ ... ETL-18.GIF

has a millivolt to lambda graph. Multiply lambda by 14.7 to get A/F

Note: narrowband sensors are only accurate around 14.7:1 (450mv), but can be used outside that range...........


If you want to see what happens, just install a O2 sensor (cheap as possible, but I recommend Bosch), and use your multimeter to see what happens. Then you can decide if it is of some benefit.

If you get real serious, you need a wide-band sensor (don't know how to use with multimeter though)

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Thanks guys for showing both sides of the coin and offering some great ideas. Id like to give it a try from square one at least since I already have a multimeter and it would be alright to just have the O2 sensor installed in place and check it when I tune up. Would it work to go for a three wire heated O2 for this setup?

yes

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

That spot on the manifold will not need a heated o2, so you can save yourself a few bux and get a standard one wire. Heated sensors are made for cars that put the sensor downstream in the exhaust pipe, or hearder installs where the header sheds a lot of heat and doesn't retain it like a cast iron log would.

And on the note of wideband - widebands can be OVERheated the innovate motorsports people sell a heatsink for theirs .

If you do use a multimeter - make sure its a high impedance, digital model. A cheap $10 jobber may get you in trouble with an o2 sensor, sink too much current and destroy it.

I figured he had a 3-wire just laying around...........

You probably don't need the heater hooked up, worth a try and easier wiring.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

thanks guys for your help. Its much appreciated.