Woodward GECO, Technical Manual, Page: 73 / 90

Manual 03554 GECO

Stoichiometric
Woodward 65
HEGO Installation

Location of downstream HEGO sensor should be:

In the exhaust stream after the catalyst.

As close to the catalyst as possible.

As far from exhaust outlet as possible; ambient air reversion from the
exhaust pulses or air leaks in the exhaust pipe can cause false lean signals.

On the top 160° of the exhaust pipe (to avoid corrosion and thermal shock
from condensation).

Drill and spot face 15.5 mm hole in suitable location.

Tap for 18 x 1.5 mm if pipe is at least 6 mm (1/4 inch) thick, or weld internally
threaded port around the hole.

Install sensor with anti-seize thread lubricant and torque to 40 N·m (30 lb-ft).
Catalyst Temperature Sensor Installation
Location of the catalyst temperature sensors should be:

In the exhaust before and after the
catalyst.

As close to the catalyst as possible.

Extended into the exhaust just enough to
give a true exhaust temperature, not pipe
temperature (very thin sensors and very
strong exhaust pulses can fatigue and break
the sensor tip).

On the top 180° of the exhaust pipe (to
avoid corrosion in the fitting due to
condensation).

Drill holes in suitable locations.

Weld or tap for temperature sensor compression fittings.

Install sensor with anti-seize thread lubricant and sensor tip at least 25 mm
(1 inch) into the exhaust stream.
Oxygen Sensor Poisoning
Lubricants and sealants of any kind must be checked for oxygen sensor
compatibility: Even for use on the intake or crankcase ventilation system.
Contaminants drawn into the engine can propagate through the combustion
process, and even small amounts can poison the activity of Zirconia-based
sensors. Common sensor poisons include silicon, lead, and excessive oil
contamination. Gasket sealers (RTV silicone), pipe thread sealers (pipe dope),
and solder or brazing materials will typically contain these materials. Most
products intended for modern automotive use are sensor-safe, but many
products common in industrial environments are not. Double check products
during repair or maintenance, and when in doubt, use automotive products and
procedures.