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Old 02-26-2013, 12:53 PM   #15
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Join Date: Apr 2011
Location: Powell River, B.C.
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Just pulled out an old Cat download, with a HP-weight -speed on a 6% grade chart.
At 34,000 lbs , RV and toad 330 hp should get you around 45 mph
A 40,000 lbs a 330 hp unit will only do about 38 mph.
Since Cat , went out of the on highway engine market this download is no longer on their web site.
Too bad , JMHO, it was a must read for all DPMH owners.

99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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Old 02-26-2013, 01:02 PM   #16
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Based upon that chart at 300 hp and 36,000 lbs he is right in the ball park.


2005 Sportscoach Elite 40' C-7 350 Cat w/MP-8
Suzuki Samurai toad w/VW 1.6 turbo diesel
800w solar system
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Old 02-26-2013, 04:02 PM   #17
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Originally Posted by jauguston View Post

What RPM is your tach reading at that speed. 36,000 lbs and 300 HP is not going to be real speedy.


Well, when it is 95 degrees outside, I run at about 2100 rpm to help it cool via the side radiator.

When it is cooler, like yesterday, I held it at 1700 rpm which is closer to maximum torque. No difference in power performance but maybe less fuel consumed.
1995 CC Magna #5280
C8.3L 300hp Cummins, 31,000lbs
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Old 02-26-2013, 05:36 PM   #18
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Originally Posted by chuck49 View Post
...on that motor say max torque of 1250lbs at around 1400 RPM... I like to keep the RPM a little higher than that on a long pull...We always kept the RPM between 1800 and 2200. Now that is too high. Depending on the grade (or not) I like to keep mine between 1400 and 2000. Climbing a long steep grade maybe around 1500 to 1700 to keep the torque more in the peak range. But keep and eye on that temp gauge especially in hot weather.
Contrary to popular opinion, it is NOT "torque" that gets you up a hill. It is HORSEPOWER. Your diesel engine - Cat or Cummins - does not develop maximum HORSEPOWER at only 1,400 rpm. Max HP will be up around 2,000 to 2,200 rpm. Both manufacturers also recommend running at 2,000 or more to assist in cooling. The water pump runs faster, the fan runs faster and both help to keep the engine cool on a long grade.

Lugging up a grade in 6th gear at 1,400 - 1,600 RPM is not good for the engine. Manually shift down to 5th or 4th as needed to keep your RPM near the 2,000 mark and you will pull the grade at the highest speed your coach is capable of, all the while keeping the engine as cool as it can be in that situation.

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