Manual

ManualsBrandsBendix Commercial Vehicle Systems ManualsEquipmentET-2 ELECTRONIC THROTTLE 6/04

MACK

CAT

DETROIT

DIESEL

DESCRIPTION

The ET-2

™

is an electronic throttle. On electronically

controlled diesel engines, the ET-2

™

treadle fulfills the same

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

™

throttle are a cast

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

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

™

treadle, output voltage

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

™

treadle. This is the state of least

potentiometer resistance. The ET-2

™

treadle returns the

maximum percentage of supply voltage to the engine control

unit (see Figure 2).

SD-15-4106

Engine Idle Throttle Full Throttle

Manufacturer (Closed) (Open)

CAT 13 - 21% 79 - 89%

Cummins 8 - 18% 70 - 80%

Detroit Diesel 6 - 14% 86 - 94%

Mack 10 - 20% 70 - 85%

FIGURE 2 - ET-2

™

TREADLE OUTPUT VOLTAGE, AS A

PERCENTAGE OF SUPPLY VOLTAGE

FIGURE 3 - ET-2

™

TREADLE OUTPUT VOLTAGE

CLOSED THROTTLE OPEN THROTTLE

ET-2

™

TREADLE

OUTPUT

VOLTAGE

CUMMINS

Bendix

ET-2

™

Electronic Treadle

CONNECTOR

FIGURE 1 - ET-2

™

ELECTRONIC TREADLE

TREADLE

COVER

CABLE ASSEMBLY

ROLLER

MOUNTING BASE

DOUBLE RETURN

SPRING

PIVOT SPRING

POTENTIOMETER

Summary of content (8 pages)

PAGE 1
SD-15-4106 ® Bendix® ET-2™ Electronic Treadle TREADLE COVER POTENTIOMETER DOUBLE RETURN SPRING 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).
PAGE 2
Figure 3 illustrates the relationship between throttle position and engine RPM. Potentiometer performance will vary for each engine application, therefore potentiometers must not be interchanged. WARNING! PLEASE READ AND FOLLOW THESE INSTRUCTIONS TO AVOID PERSONAL INJURY OR DEATH: When working on or around a vehicle, the following general precautions should be observed at all times. 1. Park the vehicle on a level surface, apply the parking brakes, and always block the wheels. Always wear safety glasses. 2.
PAGE 3
POWER SUPPLY (9-16 VDC) A DIGITAL VOLT/ OHM METER B C PACKARD ELECTRIC CONNECTOR 12010717 (CONNECTOR X) PIN C GROUND RESISTOR TEST LOAD (47,000 OHM FOR DETROIT DIESEL, 300,000 OHM FOR MACK) INPUT PIN 3 PIN B VOUT (OUTPUT) OUTPUT PIN 2 PIN A VREF (INPUT) GROUND PIN 1 POTENTIOMETER POTENTIOMETER PC. NO. ON THIS SURFACE FIGURE 5 - ET-2™ TREADLE ELECTRICAL TEST SCHEMATIC FOR THE DETROIT DIESEL CONNECTOR C wear, or physical damage. Check end-to-end electrical continuity at terminals.
PAGE 4
6. Record the output voltage when the pedal is in the idle position (V1). Then slowly depress the pedal. When the ohm meter shows that the resistance has changed from “overload” to about .003 ohms (or from .003 ohms to “overload”), stop depressing the pedal. Record the voltage (Vx) registered with the pedal in this position. Then press the pedal to the full throttle position and record the output voltage (V2). 7. Calculate the “switch point percentage” using the formula below.
PAGE 5
Closed Throttle (open) Range: 10-20% Open Throttle (full) Range: 75-90% PIN A VREF (INPUT) -8V 2000 OHM ±5% RESISTOR PEDAL POSITION SENSOR (PWM) .001µF PIN B VOUT (OUTPUT) RED (CABLE) 47,000 OHM ±5% RESISTOR PIN C GROUND BLACK POTENTIOMETER VOLTMETER (V => %) Caterpillar output voltage is Pulse Width Modulated FIGURE 8 - ET-S™ TREADLE ELECTRICAL TEST SCHEMATIC FOR THE CATERPILLAR CONNECTOR potentiometer until the ohmmeter reads the same resistance as shown on the label within ±10 Ohms.
PAGE 6
Closed Throttle (open) Range: 5-17% DIODES IDLE VALIDATION SWITCH IVS PIN 6 TEST LOAD 470 OHM TEST LOAD 470 OHM Open Throttle (full) Range: 70-81% LOCK TAB V3 (LOGIC HIGH AT IDLE) PIN 2 POTENTIOMETER SET VOLTAGE AND PC. NO. SHOWN HERE V2 (LOGIC LOW AT IDLE) PIN 1 IVS GROUND Vs SUPPLY VOLTAGE PIN 5 PEDAL POSITION SENSOR Vs SUPPLY VOLTAGE PIN 3 .
PAGE 7
5. The installation of the remaining components is much easier if the inner and outer springs (12 & 13) are compressed and caged. This can be done with a short piece of wire, or even a paper clip. The springs should be compressed so that their ends are approximately one inch apart. 6. Place the spring support (14) inside the caged spring assembly. Then insert the springs into the roller assembly (15). The curved ends of the springs fit over the small bar directly behind the roller. 7.