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Old 09-28-2011, 07:38 PM   #1
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Which Diesel for pulling power?

Don't want to start a war here, but interested in a MH that will pull a full size toad up long steep hills without bogging down. I'm looking at a 35 foot MH with a 300hp cummins. Is that enough power for this MH?
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Old 09-28-2011, 07:45 PM   #2
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that is a real good eng. you should'nt have any trouble
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Old 09-28-2011, 08:43 PM   #3
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As I understand it, its all about torque. We have a Cummins ISC, 1050 ftlbs of torque. Pulls our 5K lb pickup through the passes of SW Oregon pretty well.
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Old 09-28-2011, 08:52 PM   #4
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Quote:
Originally Posted by krhyde1945 View Post
Don't want to start a war here, but interested in a MH that will pull a full size toad up long steep hills without bogging down. I'm looking at a 35 foot MH with a 300hp cummins. Is that enough power for this MH?
All depends on torque. IE. a 330 hp Cat and a 350 hp Cat have the same torque at 860 ft lbs.
In my 34 ft Motorhome I can pass just about anything going through through the mountains towing a 3,200 lb Honda CR-V.
They also use that same engine in 40 ft Coaches. I doubt that they would have the same preformance with all that extra weight.
It really depends with what you will be happy with. Good luck.
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Old 09-28-2011, 08:55 PM   #5
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Welcome to the forum!

I think that's a fine motor for that size coach but you need to clarify what you mean by "bogging down". Anything short of a 650hp, million dollar rig is going to slow down when pulling a heavy toad up long, steep grades.

We have a 400hp 1200ft lbs ISL Cummins in our 40DP with a Ford Explorer (4500#) and I make sure to keep up momentum when hitting a grade and still spend a good bit of time at 45 mph by the time we crest.

Good luck...

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Old 09-28-2011, 09:29 PM   #6
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Quote:
Originally Posted by krhyde1945 View Post
Don't want to start a war here, but interested in a MH that will pull a full size toad up long steep hills without bogging down. I'm looking at a 35 foot MH with a 300hp cummins. Is that enough power for this MH?
You need to know if it's an ISB (5.9l) or an ISC (8.3l) 300 hp engine both were used in MHs of that length, but there is about a 400 ftlb difference in torque. MHO. you WANT the bigger motor . You also need the weight of the unit you plan to tow and the chassis tow rating of the coach.
And as Rick O says, if you can't tolerate slowing down at all , you need .$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$.
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Old 09-28-2011, 11:06 PM   #7
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I have the Cummings 300 in my Discovery. I think it is around 600 to 650 #'s of torque. I tow a Tahoe. This summer we cruised from Chattanooga to Myrtle Beach in Tow. We averaged 9.5 mpg towing. The difference between the Cummings 300 and Cat 330 is hp and torque but you lose the MPG with the Cat. We visit Fall Creek Falls several times a year we have to pull 2 mountains to get there. I have towed the Tahoe up 7-8% grade at 30-40 mph for several miles without any problems multiple times. Like all have posted before me.....you may not get there fast but you will get there. Just have to keep the RPMS high.
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Old 10-01-2011, 08:22 PM   #8
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The rul;e of thumb is 1 horspeower per 100 lbs of weight, so your 300 hp should be able to move 30,000 lbs of coach and toad with reasonable performance. But if you don't want to slow down even 1 mph on long grades, then you probably need more than 1 hp per 100 lbs. Maybe more like 1/85. You may have a hard time finding that much power in a 35 foot coach.
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Old 10-01-2011, 08:37 PM   #9
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As several people have already said "it's all about torque." Manufacturers like to advertise HP because people know what it means but also because they can do inexpensive things to make a 300 HP engine into one they can advertise as having 350 HP.

However, nothing they can do will change the torque which in diesels is pretty much a function of engine size. So that MH you are looking at could have any of several engines, some of which may not have the performance you are looking for.

By any measure our MH is grossly over-powered and I absolutely love it! We have just spent the past two months in Wyoming, Montana and Idaho going up and down numerous mountains and it was a great experience because I honestly never had to worry about how it was going to perform. Today, going east out of Salt Lake I-80 climbs 3,000 feet in a rather short distance; we were able to pass the smaller economy cars and most of the trucks. Is that really important? Of course not, but it does take a lot of the stress out of driving.

The other thing that usually comes with a large diesel (Cummins ISL or larger), is a true compression brake (a Jake brake). Don't confuse a compression brake with an exhaust brake, they are not equal. Going west through Lookout Pass on I-90 from Montana into Idaho I had my Jake on full and my transmission in 3rd gear and was able to follow an 18-wheeler down the mountain at 45 mph with virtually no use of the brake pedal. Talk about reducing stress--this is really it. Going down mountains can be a lot more challenging than going up them!
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Old 10-01-2011, 08:51 PM   #10
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Back to real life....
As Skip said, there are 2 300HP cummins engines.
The 5.9 dodge pickup motor (ISB) and the ISC, an 8.3 liter truck engine with over a thousand ft-lbs of torque.

A motorhome with a 33,000 lb GVRW with less thasn an ISC is underpowered.
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Old 10-01-2011, 09:02 PM   #11
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Back to real life....
As Skip said, there are 2 300HP cummins engines.
The 5.9 dodge pickup motor (ISB) and the ISC, an 8.3 liter truck engine with over a thousand ft-lbs of torque.

A motorhome with a 33,000 lb GVRW with less thasn an ISC is underpowered.
I'm not sure what exactly wasn't real life about the previous posts; I apologize if I was too verbose.

What I would recommend in a 33,000 MH (the same weight as ours) is nothing less than an ISL engine (or the CAT C9 equivalent). If you are approaching the issue by asking about performance then you are someone to whom this matters. Some people are content as long as their MH climbs the hills (which they all will); some are not. I would be content with a MH less powerful than what I own, but only slightly so.
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Old 10-01-2011, 09:36 PM   #12
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Sorry Joel.
A Patriot Thunder, even 10 years old, is beyond real life for most. With a C12... heck, that bad boy could give my Camaro a run.
OP doesn't seem to be shopping in that ballpark.
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Old 10-02-2011, 04:29 PM   #13
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Since there is a fixed relationship between torque and horsepower, I don't think it is any more one than the other when it comes to performance. Horsepower = Torque x RPMS/5252, so if you have more torque at a given RPM, you also have more horsepower. A larger engine usually has more torque (and therefore more horsepower) at lower RPMs, so can climb steep grades without straining at higher RPMs. But the smaller engine producing less torque but revving to higher RPMs can still do the job, cause when the day is done it's horsepower that gets work done.
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Old 10-02-2011, 11:39 PM   #14
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Since there is a fixed relationship between torque and horsepower, I don't think it is any more one than the other when it comes to performance. Horsepower = Torque x RPMS/5252, so if you have more torque at a given RPM, you also have more horsepower. A larger engine usually has more torque (and therefore more horsepower) at lower RPMs, so can climb steep grades without straining at higher RPMs. But the smaller engine producing less torque but revving to higher RPMs can still do the job, cause when the day is done it's horsepower that gets work done.
JMHO, There is a key word in you statment ,Gary , and I am glad you didn't leave it out " straining". Given the limited gear ratios avalible in MH transmissions and differentials, there are huge obstacles for the lower torque engines to overcome before they get to their horsepower band. Then were back to the OP's "bogged down".
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