DETROIT Engines: Throttle Control Digital Input - VSG Inhibit (Throttle Nominate)

VSG Inhibit

Figure 1.1 - EEC and Throttle Nominate (for Main Panel)

Variable Speed Governor
The Variable Speed Governor (VSG) is an optional governor. VSG converts its throttle input (analog voltage or frequency) to a VSG set speed between Idle and Rated Speed. VSG determines the Engine speed error and varies Engine fueling to maintain the desired set speed. VSG may override the EEC if it is requesting greater power then the EEC. To prevent this, VSG Inhibit must be used.

#EEC Wiring for One EEC and Hand Throttle (Two Independent Stations)
Figure 1.2 - DDEC III/IV EEC and Hand Throttle Harness

#Throttle Control Digital Input - VSG Inhibit
Digital Input functions are activated when the Digital Input wire is switched to Battery ground (circuit #953). The Digital Input can be controlled by either a switch or an OEM interlock depending on the function.

VSG Inhibit must be configured for use with EEC. Read More: ECM I/O Configuration on Detroit Diesel Diagnostic Link (DDDL) Software.
Figure 1.4 - ECM I/O Configuration
H2 - VSG Inhibit (wire #524)
This option disables the analog VSG from Hand Throttle (wire #510) and ALT MIN VSG whenever the VSG Digital Input is grounded. Grounding the VSG Inhibit Digital Input will reduce Engine speed to Idle. When the ground is removed from the input, the throttle must be reset to zero before Engine speed can be increased from Idle. Frequency input and J1939 commands are not affected. The Engine speed will remain unchanged as long as the Digital Input is grounded regardless of VSG request.

#VSG Station Change and VSG Station Change Complement
Figure 1.3 - EDM and Hand Throttle (for Remote Panel)
The dual throttle Variable Speed Governor (VSG) feature provides the capability of having VSG throttles at two locations, with only one throttle active at any time. The dual throttle feature requires two Digital Inputs.

DDEC monitors the switch inputs and maintains the current Engine RPM when a station switch occurs until the newly selected station is qualified by reducing the station position to Idle and then increasing it to the current Engine speed position. After qualification, the Engine speed is controlled by the new station. If qualification does not occur within 30 seconds, the Engine speed will be ramped down from its current value to VSG minimum speed. If the new station becomes qualified, the ramp-down process will be stopped and the new station will have control. Read More: Detroit Diesel Electronic Engine Commander for Engine Speed Cruise Control.

#Monitoring Digital Inputs Functions on DDDL
→Starts the Engine (Detroit Series 60).
1). Connecting to DDDL Software, and select the Diagnostic Instrumentation menu. Read More: Diagnostic Instrumentation using Detroit Diesel Diagnostic Link (DDDL).
→Select to List ^5 - Input/Output display.
→Monitoring din-G2 CRUZ ENABLE (value: Gnd)
→Monitoring din-H2 VSG Inhibit (value: Gnd)
Figure 1.4 - din-H2 VSG Inhibit (value: Gnd)
In this condition, the Engine RPM will control by Cruise Control EEC (refer to Figure 1.1 above), and disables the Hand Throttle from Remote Panel (refer to Figure 1.3 above).
THROTTLE READY and RPM lights are illuminated. 

2). Press the Throttle Nominate button.
→Monitoring din-G2 CRUZ ENABLE (value: Open)
→Monitoring din-H2 VSG Inhibit (value: Open)
Figure 1.5 - din-H2 VSG Inhibit (value: Open)
In this condition, the Engine RPM switched control to Hand Throttle from Remote Panel, and disables the Cruise Control EEC from Main Panel.
THROTTLE READY and RPM lights are OFF. 

Read More:


Subscribe to receive free email updates:

1 Response to "DETROIT Engines: Throttle Control Digital Input - VSG Inhibit (Throttle Nominate)"

  1. Thanks for your experienced on this post, I learned how it works, to switching VSG throttle using EEC or Remote throttle. We have problems same like this before, I was sent you detailed problems on your contact. Thanks.