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Old 10-13-2015, 06:28 AM   #15
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I am surprised at the number of people that use partial throttle going up hill in a diesel. Modern diesels since about 2000 or so are all computer controlled. Now days even the throttle linkage is fly by wire. When going up a hill stand on that sucker (unless you end up accelerating)!! The computer will only add fuel that you can actually burn. No excess black smoke, no tearing anything up. A diesel hast the duty cycle to handle those big hill all day long.

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Old 10-13-2015, 07:38 AM   #16
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It isn't the going up too slow that causes problems (except to fragile egos), it is the going down too fast.

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Old 10-13-2015, 07:52 AM   #17
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It seems many folks are talking about climbing hills on Interstate type roads. That's pretty easy and if you like pouring a lot of fuel thru the engine - go for the WOT mode.

When you get to climbing/descending challenging hills/roads (defined as very steep, narrow, lots of sharp corners), WOT simply won't work. As previously noted, it is up to you (the operator) to shift to the appropriate gear and keep the engine RPM in the ideal range (which varies by engine). Speed is not important - don't worry about those cars behind you. When the warning sign for the corner says 25 MPH, you better believe it. I've found my rig will corner at the posted warning speed but it prefers a couple MPH under the warning speed (ok, maybe it is me that prefers that).

Descending is similar - the rule of thumb of using the same gear as you climbed is simply not useful (in the more challenging road scenario). You are typically dealing with a short straight and then a 15-25 MPH sharp corner (and then repeat). It is temping to let the rig speed up on the straight (especially when their is a line of cars around you) but is is often better NOT to do this as you just have to work to get slowed back down for the corner. For every steep descent with corners, find a speed that is comfortable (depends on the road width, number of corners, and corner speeds) and stick to it (using whatever engine brake you have available - not service brakes). If you get in a situation where you are using the service brakes a lot, you may not be doing things correctly but regardless, use the turnouts to stop and let the brakes cool.
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Old 10-13-2015, 08:06 AM   #18
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On steep grades where heavy trucks are doing 30 mph I let the coach slow to around 50 mph and then set the cruise. I release the cruise control before descending and let the exhaust brake do its job. I could cruise faster up hills but im in no rush.
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Old 10-13-2015, 09:16 PM   #19
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If you don't go to WOT, you are not getting all the horsepower you paid for.

It does not hurt a modern diesel to run for long periods at WOT.

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Old 10-13-2015, 09:35 PM   #20
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I'm still trying to figure out the ISX we have. It has so much torque that I really don't need to worry much. 1950 ft lbs from 1100 to 1600 rpm and 1350 is 60 mph. It just PULLS!! But I do wish it had a pyro on it.
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Old 10-14-2015, 12:22 AM   #21
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For those "stab it and steer it" drivers.

Operation in Hilly and Mountainous Terrain
In rolling terrain, use a light throttle and allow momentum to carry the vehicle over short grades
In hilly and mountainous terrain, where possible, use the engine’s entire operating range before gearing down
When cresting steep grades, use gravity to bring the vehicle back to the desired cruise speed

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