Posted by MoparNorm on Monday, March 13, 2006 at 1:13AM :
In Reply to: Re: O.T.- Dodge CTD - good mileage towing and ex brake use posted by Andy (in MI) on Sunday, March 12, 2006 at 6:27PM :
Questions on Jacobs Exhaust Brakes?
Q: How does the Jacobs Exhaust Brake work and why do only diesel engines use them? A: A diesel engine, unlike a gasoline engine, has no intake throttle plate. When the truck is coasting and there is no fueling in the cylinders, a diesel engine with no exhaust brake produces less retarding (slowing) power than does a gasoline engine. By adding a Jacobs Exhaust Brake, restriction is created in the exhaust system during the coasting condition. This increases pressure in the exhaust manifold, slowing the pistons during the exhaust cycle when the exhaust valves are open. This produces improved retarding power that helps slow the vehicle. The Jacobs Exhaust Brake is actually superior in performance to an intake throttle in a gasoline engine. An intake throttle produces vacuum in the cylinder during the intake stroke, which can reach a maximum level of about 14 psi. The Jacobs Exhaust Brake produces a backpressure somewhere in the neighborhood of 60 psi, resulting in enhanced retarding power. Q: What is the part number for ? A: Comprehensive parts manuals for all model years are available on the Jacobs Dodge Ram service webpage at http://www.jakebrake.com/content.php4?doc_uid=73 Q: Is the 48RE Automatic Transmission approved for use with the exhaust brake? A: The 48RE transmission is a Dodge component and is covered by the Dodge warranty. Consult Dodge / DaimlerChrysler for official status. Unofficially, testing late in the 48RE development process identified an incompatibility with exhaust brakes. Design changes to both the transmission hardware and the control software are still in process as of February, 2004 and current validation is not expected to complete before at least August, 2004. If validation tests are completed successfully, this answer will be updated with specifics about which vehicles have the necessary transmission hardware and what is required to receive the necessary software/calibration reflash. The part number for the exhaust brake will be unchanged if / when warranty-approval is given by Dodge / DaimlerChrysler to install the Jacobs Exhaust brake on 48RE transmission vehicles. Q: What is the warranty of the Jacobs Exhaust Brake? A: The Jacobs Exhaust Brake, available through authorized Cummins and Mopar dealers, is the only exhaust brake that is factory-approved by Dodge. Warranty manuals for all model years are available on the Jacobs Dodge Ram service webpage at http://www.jakebrake.com/content.php4?doc_uid=73 Q: Does the Jacobs Exhaust Brake help with engine warm-up at idle? A: Yes, activating your Jacobs Exhaust Brake will enable the engine to reach normal coolant operating temperatures twice as quickly at idle. By closing the Exhaust Brake at idle, backpressure is increased and the result in a higher load on the engine. This creates more heat to more quickly increase coolant temperature. In very cold climates, such as in Alaska, coolant temperatures may not typically be high enough to open the coolant system thermostat. Under these conditions, using the Jacobs Exhaust Brake for idle warm-up will result in higher idle coolant temperatures than are possible without the Exhaust Brake. Q: What is Exhaust Brake Cruise Control and how does it work? A: Exhaust Brake Cruise Control is a feature on 2003 and later vehicles that activates the exhaust brake when vehicle cruise control is active and vehicle speed goes above the cruise control set point. When climbing a hill, the standard cruise control will increase fueling to try to prevent a loss in vehicle speed. Similarly, when descending a hill, the standard vehicle cruise control will decrease fueling to try to prevent an increase in vehicle speed. For steeper downhill descents and/or heavier vehicle loads, decreasing fueling alone may not prevent an increase in vehicle speed. Exhaust Brake Cruise Control will turn the exhaust brake on and off to attempt to prevent an increase in vehicle speed beyond the cruise control set point. For steeper downhill descents, use of the vehicle service/foundation brakes in addition to the exhaust brake is required. Q: The Jacobs Exhaust Brake on my 2003 or later truck is sometimes on at idle and sometimes it turns off. Is this normal operation? A: Starting with MY2003, a feature was added to turn off the brake at idle to conserve fuel after the coolant temperature reaches a certain level. The exact coolant temperature at which the brake is deactivated at idle has changed between model years. As of January, 2004, all production calibrations and service flash calibrations have the brake shutoff temperature set at 182 degree F, just below the 190 degree F thermostat opening temperature. Q: Why is there a delay before the brake is activated after releasing the accelerator pedal? A: For 1998.5 and later vehicles with 24 valve engines, the Engine Control Module delays the activation of the Jacobs Exhaust Brake after lifting the accelerator pedal to prevent the brake from engaging during transmission shifts. The delay also allows the turbocharger to slow down, preventing an abrupt decrease in impeller speed when the exhaust brake is activated. For these reasons, no other exhaust brake control method is recommended. Additionally, for 2003 and later vehicles, the Exhaust Brake Cruise Control feature will only work when the exhaust brake is controlled by the Engine Control Module. Q: After using cruise control on my 2001.5 or 2002 truck with manual transmission, the exhaust brake will not activate. If I cycle the key switch, the brake will start to function again. Does the brake need to be replaced? A: The APPS/Throttle Position Sensor could be the cause of this condition. When vehicle cruise control is activated, the foot pedal is in the released (idle) position. Vibration at the foot pedal when it is the idle position can cause the sensor position to drift. The result could be that the exhaust brake is not activated after cruise control is deactivated. A new version of the APPS/Throttle Position Sensor was released to address this condition. Last updated 16-Feb-04
Does Ford own Cummins?
No, Ford does not own any part of Cummins Inc.
Do you have any advice on truck options?
Can an exhaust brake be used on the 24-valve engine? What about with an automatic transmission? Yes, the new manual transmission 24-valve engine was designed with the exhaust brake in mind. Replacement of the exhaust valve springs will not be required as it was on some models of the previous style engine. Exhaust brakes are not recommended for automatic transmission engines. Please note: Current 12-valve-compatible E Brakes designed for '89-'98 model Dodge Rams should not be installed on '98 and later 24-valve electronic engines. Doing so can cause serious damage to the engine.
NOTE: From the Jacobs web site. the Jacobs brake is now APPROVED for use with the 48RE automatic transmission.
MN