Lambda heater

[Andrew Heggie]

Excuse me if this query is a FAQ, if so would someone point me at a
suitable information resource. I have lurked here a little while and
admit most of the discussion is technically beyond me.

I wish to monitor the exhaust of a vehicle that has been converted to
run on LPG (propane). The fuel is a by product of natural gas
transmission as well as from refineries and is lightly taxed for road
use here in  UK, as it is clean burning, though of only 75% of the
calorific value of gasoline.

The gas mixture control appears rather basic so I want to monitor it,
the carburetted engine is way under stressed so damage is unlikely but
I would like to optimise fuel consumption.

I have purchased an aftermarket 3 wire sensor. Two wires are for the
heater circuit and the third the signal with ground through the body.
I chose a heated sensor as I wish to mount it fairly well down the
exhaust.

With that premise I have a number of worries.

1) from the UEGO thread it seems possible that the heater will not
take 12v without some thermal shock? If so what should I drop the
heater voltage to. As the exhaust will have cooled further down the
system I take it the heater must maintain the temperature at about
300C?

2)I am guessing the lambda sensor is effectively two oxygen zirconium
cells back to back, the voltage generated from the ambient air side
acts in opposition to that generated from the exhaust oxygen?

3) Is the thread standard on these things? mine appears to be 18mm by
1.5mm pitch, is marked "Japan 5350 03B13".

AJH

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