BENDIX ET-2 ELECTRONIC THROTTLE Manual

®
® ™
Bendix ET-2
POTENTIOMETER
PIVOT SPRING
MOUNTING BASE
™
FIGURE 1 - ET-2 ELECTRONIC TREADLE

DESCRIPTION

™
The ET-2 is an electronic throttle. On electronically
controlled diesel engines, the ET-2
function as a conventional mechanical throttle. The ET-2
treadle controls engine speed by interacting with an
electronic fuel management controller on the engine, rather
than transmitting a mechanical force from the throttle pedal
to the engine governor.
The main components of the ET-2
aluminum mounting base and treadle, a rubber treadle cover,
a potentiometer (variable resistor), and a roller assembly.
The potentiometer is specific to each engine application.

OPERATION

™
The ET-2 treadle provides smooth, graduated throttle control
through the function of its variable resistor, or potentiometer.
™
The ET-2 treadle receives its supply voltage from the engine
control unit. The lever shaft connects the roller assembly
to the potentiometer, so that any movement of the treadle
rotates the potentiometer. As the potentiometer rotates,
its resistance changes. This way, the potentiometer
communicates the throttle position to the fuel control
Electronic Treadle
TREADLE
COVER
DOUBLE RETURN
SPRING
ROLLER
CABLE ASSEMBLY
CONNECTOR
™ treadle fulfills the same
™ throttle are a cast
system by changing resistance, returning more or less of
the supplied voltage back to the electronic engine controller.
If the driver does not request engine power, the throttle is in
the idle (or "closed throttle") position. In this state, the
potentiometer significantly reduces the amount of supply
voltage returned to the engine control unit (See Figure 2).
As the driver depresses the ET-2
increases (see Figure 3). The potentiometer allows an
increased amount of its supply voltage to return to the engine
control unit, which in turn increases the engine's speed.
In the full (or "open throttle") position, the driver has fully
depressed the ET-2
potentiometer resistance. The ET-2
maximum percentage of supply voltage to the engine control
unit (see Figure 2).
Engine
Manufacturer
CAT
Cummins
™
Detroit Diesel
Mack
FIGURE 2 - ET-2 ™ TREADLE OUTPUT VOLTAGE, AS A
PERCENTAGE OF SUPPLY VOLTAGE
8V
7
6
™
ET-2
5
TREADLE
OUTPUT
VOLTAGE
4
3
2
1
0V
CLOSED THROTTLE
™
FIGURE 3 - ET-2 TREADLE OUTPUT VOLTAGE
™
treadle, output voltage
™
treadle. This is the state of least
™
treadle returns the
Idle Throttle Full Throttle
(Closed) (Open)
13 - 21% 79 - 89%
8 - 18% 70 - 80%
6 - 14% 86 - 94%
10 - 20% 70 - 85%
DETROIT
OR CUMMINS
DIESEL
OPEN THROTTLE
CAT
MACK
1