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Old 05-20-2013, 05:04 AM   #15
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Freightliner RV chasis manual says climb at 2000. What goes up must come down. What is the proper downhill rpm? Does using an engine brake change the desired rpm range?
Nothing directly to do with rpm on the way down, but one of getting the speed and revs and gear at the right point such that the auxiliary brake does most of the work and all you need to do is use the foot brake moderately-firmly for a few seconds every twenty seconds or so to keep things under control.

Search for "snub braking" here and on the www and read up on the safe way to go downhill.

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Old 05-20-2013, 07:27 PM   #16
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Ok here we go again. Torque is what accelerates you from a standstill especially with a heavy mh. It is horsepower that gets you up a steep grade. If you climb a steep grade at max torque rpm then you will overheat. If you are not then it is not a very steep grade. You need to be at your peak horsepower rpm to climb steep grades and not overheat lug the motor. I have 1700 ft lbs of torque and 515 hp and there is no way I can climb at peak torque even with all my torque. I have to go to 1800 rpm where my horsepower is. If I let it drop to my peak torque it will never recover. If you are climbing a steep grade then forget a out mpg. Your motor is software protected and it will not be hurt at peak hp rpm and max boost. Obviously some people have never driven a eighteen wheeler up a steep grade. You are not going to make it at peak torque believe me. When I say steep grade I am talking 6% or greater. Try driving on I-5 from California into Oregon which is 8% for 12 miles. It will show you real fast where your rpm should be.

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Old 05-21-2013, 09:05 PM   #17
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cleaning out your radiator in all those hard to get places helps to keep it cool. It's real easy on a pusher with a side mount radiator to have the bottom 3" plugged up after awhile.
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Old 05-21-2013, 09:47 PM   #18
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Op, yes there is a rpm range you should try to stay in when climbing long steep grades. That rpm range depends greatly on what engine you have. If you could find a dyno printout of your engine it would show you a torque curve and horsepower curve, as a rule of thumb your hill climbing should be done at the rpm where these two lines meet. In big diesels 13L and up this usually falls around 1500 rpm on these newer Diesel engines. On the smaller 8L diesels the rpms will have to be held higher.
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Old 05-21-2013, 09:56 PM   #19
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I should clarify what I meant by where the horse power and torque meet. The point at which your torque begins to drop and your horsepower is close to max.
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Old 05-22-2013, 08:19 AM   #20
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If you keep your radiator clean and your "slobber-tube" feeding into a container, you shouldn't have any cooling problems. These diesels are made to take the long grades without overheating, even in the hottest summer weather. The problems arise when you don't pay attention to your cooling system. There are plenty of threads on here about cleaning your radiator and making sure your overflow tank is not cracked.

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