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Old 02-06-2013, 07:43 AM   #1
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Diesel HP--how much is enough?

Now considering Diesel pusher-1990-2000 year range. Note most are 34 to 40 feet long. HP starts at 230HP on up to 300hp in the later models. Live in Florida, relatively flat land and much of the year would be traveling in the Southeast. Would like to tow a Honda Oddesey van at least 65 mph. Assume the 6 speed Allison a must. Don't think the 230HP will do it. How about the 250HP Cummins? Or do I have to go on up to the 300HP Cummins? I know weight is a big factor. Are all DP constructed such that longer is always heavier or are there some models, say in the 37 foot range, that aren't as heavy as the heaviest model in the 34 foot range MH.? Don't really want to go long, but want pusher.Would a 250HP Cummins do the job as described in a 35 to 36 foot range? Thanks.
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Old 02-06-2013, 07:45 AM   #2
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They'll all "do the job", just slower than some others. My DP has the 300HP Cummins. Perfectly adequate in my 40 footer.
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Old 02-06-2013, 08:10 AM   #3
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Quote:
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They'll all "do the job", just slower than some others. My DP has the 300HP Cummins. Perfectly adequate in my 40 footer.
I agree. For your application, horsepower might not be a big issue.

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Old 02-06-2013, 08:14 AM   #4
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It's about power to weight. The rule of thumb, is one hp per 100 pounds of weight. For real world performance torque is important too. I would be looking for a Cummins 8.3 liter which will be called the "C" engine or "ISC" in electronic engines. The "B" engine will have similar hp ratings to the "C" engines but significantly less torque. Owners of "B" engines will be quick to defend their engine and I'm not putting it down but the old saying from the 50s and 60s " there is no substitute for cubic inches" is still true when getting heavy weights rolling. The Cat 3126 or C7 will also perform well.

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Old 02-06-2013, 08:17 AM   #5
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A rule of thumb that gets tossed around is at least 1 BHP for every 100 lbs of total weight (MH + toad). Not being a motorhome person, I don't know how valid that is, but I've seen it here enough to throw it into the discussion to either be substantiated or shot down.

As an aside, that would only require 250 BHP for my rig's 25,000 GCW - quite a bit less than the newer diesel trucks actually have available.

(I guess Steve beat me to the punch.)

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Old 02-06-2013, 08:25 AM   #6
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I have a 275hp Cummins "C" 8.3. Works fine even in the mountains of West Virginia.
BTW according to the latest FMCA towing guide, Honda no longer approve the Oddysey for towing 4 down so you will lose your warranty if you buy a new one.
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Old 02-06-2013, 08:30 AM   #7
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Agree with Ricko. How fast do you want drive, what are you pulling, are driving flat lands, etc. Like flying speed costs money. I typically run 55-57 mph travelling on flat and hilly terrain amd my ISB is fine although, I do not tow a toad. Look at your needs.

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Old 02-06-2013, 08:30 AM   #8
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My 36' with the 275HP works really good for me especially in the southeast. When I travel in the mountains it sometimes slows on 6% grades to 45 to 50 MPH but that's not a big deal to me. Fuel economy is also a little better with the smaller engine.
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Old 02-06-2013, 09:29 AM   #9
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We have a 37-1/2 with a 300 Cat and Allison 6 speed. Usually run abot 62 mph in economy mode. Tow a Hyundai Elantra on a tow dolly. The Cat has plenty of power and pretty much holds 55 mph on normal grades without down shifting. Gets 8.5 -10 mpg but usually to the lower side due to wind resistance.

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Old 02-06-2013, 09:46 AM   #10
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Steve's formula is most likely spot on. In my early searches those in the know stated" 10 HP for every foot of coach length ". Most likely a bit less accurate, however close enough. Ie, 40 ft. Coach, 400 HP diesel. All that said, my first coach was a 39'6" Fleetwood Excursion, sorry I cannot remember the gross vehicle weight, this coach had plenty of power pulling a 4700 lb. toad, 330 cat diesel. Even if its flat land many times you will need power to enter interstates or bridge climbing. As suggested test drive and find the sweet spot in mph. We run at 63,mph interstate and get 8.1 mpg pulling a Ford Edge. Best of luck in your search!
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Old 02-06-2013, 09:50 AM   #11
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Quote:
Originally Posted by Steve Ownby View Post
It's about power to weight. The rule of thumb, is one hp per 100 pounds of weight. For real world performance torque is important too. I would be looking for a Cummins 8.3 liter which will be called the "C" engine or "ISC" in electronic engines. The "B" engine will have similar hp ratings to the "C" engines but significantly less torque. Owners of "B" engines will be quick to defend their engine and I'm not putting it down but the old saying from the 50s and 60s " there is no substitute for cubic inches" is still true when getting heavy weights rolling. The Cat 3126 or C7 will also perform well.

Get out & test drive everything you can and enjoy yourself.
Further to Steve's comment about torque, it is the broad peak torque vs. rpm range of the "C" engines versus that of the "B" engines that makes the difference.
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Old 02-06-2013, 09:58 AM   #12
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Hi fighterpilot,
The 1 hp per 100 pounds of weight is a minimum for me. I have a Cummins ISC 330 hp, 950 Ft lbs of torque. The coach and toad combined are a bit over 37K lbs. The combination requires patience when in the mountains. It will haul, if momentum is not lost and the "pedal is to the metal". However, once in the slow lane (with the trucks) one will remain there for the balance of the ascent.
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Old 02-06-2013, 10:24 AM   #13
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I have the 350HP 8.3 Cummin, my BL has the 300HP 8.3. We both have 40'ers. He does not keep up with me in the Mtns. I pull an 02 Odyssey and he pulls a PT Cruiser on a dolly.
I have heard "Bigger is Better" but I am happy with what I got.
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Old 02-06-2013, 10:27 AM   #14
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We have the Cummins ISC 350 and a 31k pound 40 footer and can keep up with any traffic. We might not be the first one up one of these mountains out West, but we'll be right behind you. The 8.3 liter Cummins is a solid performer. Only downside is that it cannot be equipped with an internal engine brake like a Jake brake. An exhaust brake helps slowing you down but lacks the true performance of the Jake.
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