Woodward GECO, Technical Manual, Page: 9 / 90

Manual 03554 GECO

Stoichiometric
Woodward 1
Chapter 1.
General Information
Welcome!
This manual describes the GECO™
 and GECO Vista Stoichiometric controls.
The GECO  Stoichiometric control provides precise air/fuel ratio control for
engines using three way catalytic converters to reduce exhaust emissions. It is a
more sophisticated exhaust oxygen feedback control system because it includes
continuous oxygen sensor diagnostics, catalyst over-temperature & differential
pressure protection, and failsafe operating modes.
Available Woodward Stoichiometric Controls
Woodward Control P/N Enclosure Type
Touch Display /
Handheld
9907-865 – GECO
Stoichiometric
Hoffman Enclosure Handheld
9907-867 – GECO
Stoichiometric
Panel Assembly Handheld
9907-879 – GECO Vista Hoffman Enclosure Touch Display
GECO

Stoichiometric System Features

Microprocessor-based
o
9–30 Vdc supply operation voltage for GECO Stoichiometric
o
19.2–28.8 Vdc supply operation voltage for GECO Vista

Pre-catalyst, closed loop, exhaust oxygen feedback control

Post-catalyst, exhaust oxygen feedback, cascade control allowing
adaptation to changing catalyst performance

Post-catalyst exhaust oxygen control set point variable with engine load

Adjustable fuel valve dithering algorithm for better catalyst control

Catalyst temperature monitoring to protect the catalyst from engine fueling
malfunctions (2 K-type thermocouples)

Catalyst differential pressure monitoring to indicate ash build-up and help
meet regulatory requirements

Open loop valve positioning in event of critical oxygen sensor malfunction or
large transient load changes

Self-learning capability that “remembers” appropriate fuel valve positions
over engine load range providing near-perfect failsafe operation

Capable of driving up to two fuel metering valves for “V” engine
configurations

Utilizes low-cost L-Series fuel trim valves capable of “Full-flow’ fuel trim
strategy that extends the AFR adjustment range

RS-485/Modbus
®
* communications support for data transmission

Full color HMI screen, enabling monitoring without hand-held terminal
(available on the GECO Vista model)

Comprehensive diagnostics including continuous oxygen sensor health
monitoring

Manual closed loop enable switch

Alarm relay

Shutdown relay

LED Driver for Power Indication, Alarm & Shutdown