To get the best results for the Jacobs Exhaust Brake, it is necessary to observe several simple operating procedures. The Jacobs Exhaust Brake is activiated when the following conditions are met:
1. The system ON/OFF switch is in the ON position
2. The engine is not being fueled.
There will be a one or two second delay between the time when the accelerator pedal is released and the Jacobs Exhaust Brake is commanded closed by the Engine Control Module. This delay is programmed into the Engine Control Module and is not adjustable. The purpose of this delay is to prevent unintended activation of the exhaust brake during gear change events.

Driving with the Jacobs Exhaust Brake
To obtain the optimum braking performance from the Jacobs Exhaust Brake, it is necessary to keep engine speeds as high as possible, but NOT TO EXCEED 3200 RPM. As can be seen in Figure 1, more braking power is available at higher engine speeds.

When decelerating the vehicle, select a gear that will cause the engine to operate near to, but still below, the 3200 RPM redline speed. Only change gears as driving conditions permit. Once the desired vehicle speed is reached, no further downshifts are required. If the vehicle speed becomes lower than desired, either depress the accelerator pedal to increase engine speed or shift up into a higher gear.

Manual Transmissions
Manual gear selection will be necessary to operate the engine at the levels producing maximum braking power. This occurs approximately between engine speeds of 1900 and 3200 RPM. If more braking power is desired, manually downshift to the next lowest gear from the present gear when engine RPM decreases to approximately 1900 RPM.

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