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MG MGB GT V8 Factory Originals Technical - Oxygen sensor

Hi folks,

In the 'carb replacement update' thread it was suggested that an oxygen sensor would help me to set the carb mixture.

Is simply a matter of getting an oxygen sensor, inserting it in the exhaust and watching the voltage with a DVM?

Where does the sensor go? Soon after the pipes from the two banks join together, I guess.

Anyone got a table of voltage to air:fuel ratio?

Anyone know where to buy an oxygen sensor in the UK? I know most 'injected cars have one, but can you just buy a 'generic' oxygen sensor?


Nick Wilson

A Bosch GM-type O2 sensor is what is meant by "generic". Apparently 95% or so of cars use this type.

If you use a plain old 1-wire sensor, it has to go up in the header collector, so it will get hot enough ... they require a great deal of heat to work. I forget what the voltage at "stoich" 14.7 is, but it's something like half a volt.

NB if you get a 3-wire (heated) sensor, you can put it anywhere along the exhaust you may find convenient. I do not know how much amperage the heater draws. I remember reading that 3-wire setups are considerably more long-lived because they are always burning off contaminants.

One hilarious thing about 02 sensors ... reminds me of what automotive rednecks we V8ers are ... you go into Pep Boys and say "... I need a 3-wire O2 sensor."

"... what kind of car?"

"... don't worry, just take me back to where you have O2 sensors."

You will find that while theoretically there are at least 25 different types of Bosch sensors, they are all absolutely identical except for the plastic connector on the end of the wires! The sensor for a BMW is identical to that for a Buick, albeit w/a different connector, and it's almost twice the price. Since you will probably be cutting off the connector anyway, just get the cheapest one.


Another thought about this. Could I get a gunson gas analyser and drive around with the sensor stuffed up the exhaust? Does it work while the car is driving (rather than idling)?


Nick Wilson

the voltage range of a lambda sensor (O2 sensor) is usually 100-900mV.
yes it needs heat to work, but to hot will melt the thing
best installed at or near your hefader collectors
a gauge is much eazier than using a volt meter whose neddle will swing around as you drive

This thread was discussed between 05/11/2000 and 06/11/2000

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