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Old 03-16-2016, 05:39 PM   #1
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Should choosing the right Cummins on its HP/Torque Rating?

We've been looking at preowned Class A motorhomes as of late, and there seems to be a host of different engines. Most show a horsepower rating, and of course each will also have different torque ratings.
I thought I'd see if those of you that bought 'preowned' if the engine was a large consideration when you chose the rig you did? I'll be towing, either an enclosed trailer, or toad for the majority of the time, and I'm not one to like holding up traffic on the long mountainous byways, there again, like everyone else, I'll work at trying to get the best fuel milage possible as well, as I look at it as a challenge more than anything.

I do realize the larger Cummin's engines, tend to be in the longer wheelbase Class A's (usually over 40') but not always. Was there a specific year where different HP rated Class A's changed their specs? Another consideration I suppose for some, is where the EPA emissions systems where put on, perhaps lowering HP ratings somewhat?
Would like to learn as much as I can, with regard to the engine's, if you've come to the conclusion that a specific HP is really not adequate for when towing (I'll often be in mountain regions)?
Just by what we've looked at in the Tiffin/Nemar line, 2006 is the lowest year of unit we'd drop to, and possibly up to 2010.
Have to get out and head to our local dealer and test drive different lengths. I'm told the 37' is different than the 40'..and 40+ w/tag is different again, and the sales person we talked to was more than willing to get out and try different units.

Thanks in advance, on anything you can suggest/advise or comment on!
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Old 03-16-2016, 05:50 PM   #2
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ISB is the smaller engine. Others such as ISC and ISL, etc. are larger engine. When recently searching for a used DP I did not want a ISB.
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Old 03-16-2016, 06:05 PM   #3
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Most of the large Cummins engines will have both a higher HP and higher torque as it's hard to have one without the other.

On some of the posts regarding engines a good rule of thumb is 1 HP per 100 lbs of total weight. So if you have a 36K rig you would need 360 HP, if the ratio is greater then that you good to go.
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Old 03-16-2016, 06:45 PM   #4
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HP/TQ would not have been my consideration before I owned my first MH. It is now. 505 HP with 1550 TQ is nice. More could only be nicer!
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Old 03-16-2016, 06:53 PM   #5
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floor plan was the first consideration since I assumed the ISL's 425 hp and 1250 lbft torque would do what I needed... and it has.

Even with a bad fuel filter going through the Appalachians it still did fine as long as it wasn't coughing from the fuel filter, got it changed and "more better" !

And many of them can be tuned for better performance too...
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Old 03-16-2016, 09:00 PM   #6
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I have a 31,000lb motorhome eith a CAT 330 (330hp and 850ft/lbs torque) it is OK but we absolutely slow down (too much for my taste) climbing grades and it is worse when towing our 4500lb Jeep. It may meet minimum criteria of 1hp/100lbs but I would look for more. In a used MH for me to consider purchase, condition and maintenace are #1, Floor plan is probably #2 but HP and Torque are now how I decide which Coaches to decide to investigate condition, maintenance and Floorplan now that I have experience.
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Old 03-16-2016, 09:37 PM   #7
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I am not a class A or a Cummins owner, but I just wanted to chime in and agree with others that you are on the right track. I think it is smart to move hp and torque to the top or near the top of the list. Especially when you plan to tow and plan to visit some mountainous areas.

The big 600hp Cummins would be a nice engine to have, but I don't know if they were up to that rating in the year range you are considering.

When shopping, be sure to check the engine specs yourself. When I was shopping previously owned rigs, I ran across a few sellers who guessed at the engine specs instead of confirming them.

I don't think anyone comes to regret purchasing too much power. Best of luck with your search.
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Old 03-16-2016, 10:11 PM   #8
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Yes, yes and yes. Based on your user name, you are familiar with light duty diesels (power stroke). I had a 7.3, 6.0, and 6.4. When looking for my DP I targeted mid range coaches with 400HP+ and pre 2007 EPA emissions.

I understand the positives of cleaner technology in EPA 2007 and 2010 requirements, however after seeing the impact of both stages of EPA emissions requirements on LDT diesels, and where my budget limited me - my decision led me to the 400ISL Cummins. Cummins went to a 425HP with the 2007 EPA, and I believe the extra 25HP was lost in EGR and DPF (IMHO).

I ended up with a 2007 37 foot tag axle, with 2006 Cummins 400ISL (Engine build date Dec 2006), no EGR, SCR, or DPF, or DEF (2010).

It works for me...

I tow a 2007 Jeep, 4,600 lbs. I do slow down up long grades, but I downshift and drive it in the power band.

Engine was important to me; second only to manufacturer (Country Coach, Travel Supreme, higher model Monaco).

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Old 03-17-2016, 08:55 AM   #9
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I'm in the "more is better" school of motorhome horsepower/torque, but it has never been a big factor in in our buying criteria. Our requirement is that it has to be "enough", which is about 100 lbs/hp. Anything better than that (less weight/hp) we would consider a small plus, but no more important than dozens of other factors. Our main criteria involve livability and reliability, not highway performance.
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Old 03-17-2016, 09:25 AM   #10
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Quote:
Originally Posted by Powerstroke2000 View Post
We've been looking at preowned Class A motorhomes as of late, and there seems to be a host of different engines. Most show a horsepower rating, and of course each will also have different torque ratings.
I thought I'd see if those of you that bought 'preowned' if the engine was a large consideration when you chose the rig you did? I'll be towing, either an enclosed trailer, or toad for the majority of the time, and I'm not one to like holding up traffic on the long mountainous byways, there again, like everyone else, I'll work at trying to get the best fuel milage possible as well, as I look at it as a challenge more than anything.

I do realize the larger Cummin's engines, tend to be in the longer wheelbase Class A's (usually over 40') but not always. Was there a specific year where different HP rated Class A's changed their specs? Another consideration I suppose for some, is where the EPA emissions systems where put on, perhaps lowering HP ratings somewhat?
Would like to learn as much as I can, with regard to the engine's, if you've come to the conclusion that a specific HP is really not adequate for when towing (I'll often be in mountain regions)?
Just by what we've looked at in the Tiffin/Nemar line, 2006 is the lowest year of unit we'd drop to, and possibly up to 2010.
Have to get out and head to our local dealer and test drive different lengths. I'm told the 37' is different than the 40'..and 40+ w/tag is different again, and the sales person we talked to was more than willing to get out and try different units.

Thanks in advance, on anything you can suggest/advise or comment on!
We bought floorplan, basement storage, Freightliner, Cummins, Alison and Winnebago. Because this floorplan was everything we wanted and the Winne products seem to have a good reputation we bought. I thought loosing 20hp would be noticed but this is not the case. This 380hp ISC is all that the old 400hp ISC was and more. The drivetrain is set up better from the factory. The DEF system increased the engine output from 360 to 380 for some reason. We do 6% grades very well, passing many commercial truckers along the way.

Not to sound like a jerk, just a point of truth, are you buying a racer or a vacation home? I agree. Having a reliable, adequate powertrain is essential. But, what you consider adequate may be overkill for some folks.

We came up I-5 from California to Oregon through 2 6% grade passes up to 7 miles long. I never considered that we had a problem with speed. We couldn't do 55mph (towing limit) but we weren't far below it. And, on the open road we get 9 to 11 mpg with not much trouble. With all the mountain climbs on I-5 and running the generator on our overnight truckstop, we used about 68 gal in ~485 miles of mixed driving.

Keep us posted on your progress. Happy trails.

Rick Y
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Old 03-17-2016, 05:09 PM   #11
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Normally the manufacturer mates an appropriate engine to an appropriate coach. The only exception might be on entry level units, or smaller units trying to hold down expenses, that might have the small Cummins. You'll find most mid and higher lever MHs will have enough engine to do the job.
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Old 03-17-2016, 05:36 PM   #12
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Quote:
Originally Posted by jerichorick View Post
We bought floorplan, basement storage, Freightliner, Cummins, Alison and Winnebago. Because this floorplan was everything we wanted and the Winne products seem to have a good reputation we bought. I thought loosing 20hp would be noticed but this is not the case. This 380hp ISC is all that the old 400hp ISC was and more. The drivetrain is set up better from the factory. The DEF system increased the engine output from 360 to 380 for some reason. We do 6% grades very well, passing many commercial truckers along the way.

Not to sound like a jerk, just a point of truth, are you buying a racer or a vacation home? I agree. Having a reliable, adequate powertrain is essential. But, what you consider adequate may be overkill for some folks.

We came up I-5 from California to Oregon through 2 6% grade passes up to 7 miles long. I never considered that we had a problem with speed. We couldn't do 55mph (towing limit) but we weren't far below it. And, on the open road we get 9 to 11 mpg with not much trouble. With all the mountain climbs on I-5 and running the generator on our overnight truckstop, we used about 68 gal in ~485 miles of mixed driving.

Keep us posted on your progress. Happy trails.

Rick Y

Never saw a Cummins ISC with a 400 ho rating. What coach was it in?
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Old 03-17-2016, 07:01 PM   #13
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HP is overrated. Go for the bigger torque. There are 400 HP w 800 FP and there are 400 HP with 1250 FP.
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Old 03-17-2016, 07:08 PM   #14
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Originally Posted by gemert View Post
HP/TQ would not have been my consideration before I owned my first MH. It is now. 505 HP with 1550 TQ is nice. More could only be nicer!
Or maybe not if the engine manufacturer didn't do due diligence when designing/testing their engine!
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