View Full Version : Diesel Engine Size
07-01-2010, 11:42 PM
I am researching Class A Diesel motorhomes for a purchase. I have spent numerous hours on the net looking at different models, at dealers lots looking over, inside and out, different models and have come to the conclusion that it doesn't matter what you buy you will have what you pay for.
So my questions come down to this: looking at all the motorhomes I see CAT, Cummings, etc., diesel engines from 245, 265, 275, 300, 500 hp. For a diesel pusher that is say over 34 feet long with say 2 slides which size engine would you recommend? The driving area would be the total USA.
07-02-2010, 12:50 AM
IMO i would go with the biggest cummins they have to offer ,, but that is just me ,, the bigger the engine the less u will be passed on long hills ,, but one thing the bigger the eng ,, the less gas milage u will get ,, i know when i had my Alegro Bus ,, i was lucky to get about 6mpg ,, if i had left it stock i might have able to get about 9 or maybe 10 outta it ,, :o :) :)
But for DL ,, man that black smoke sure looked and smelled good :laugh: :laugh: :laugh: :clown:
07-02-2010, 09:11 AM
Hi there Okie 143,
Before I bought mine I test drove a Cummings 265 34 feet with one slide and it was okay on flat land with no hills or wind but I had trouble staying in the top gear pushing a bit of wind and when I went down a valley I thought I was going to have to get out and help push it up the other side, so that told me right there not to buy it. I did buy a 38 ft Beaver which has a gvw of 32000 lbs, no slides, 330 Cat and it is perfect, the wind won't bother it at all, going through a valley will maintain 50 mph up the other side. So IMO I think you need to have a minimum of 300 hp unless you are doing mountains a lot then you need more. Hope this helps, have a good day.
07-04-2010, 05:20 PM
I have a 38' with 300HP Cummins, I have been very pleased with the power and milage. We just returned from a trip to the Smokie mountains, I was able to maintain 55MPH on most hills and average 10MPG while towing a Jeep Grand Cherokee.
great that yours is doing so great. :laugh: :laugh: :laugh:
07-04-2010, 06:23 PM
Darwin the hills in the smokey's are just little roller coasters. :laugh: Come out to the west and give that Cummins a real work out. ;) :laugh: :clown:
07-04-2010, 07:39 PM
We are planning a trip out west soon. Do you think I would have a problem in the high elevations out west? I could only give my experience where I have been and my small cummings performed very well. I appreciate your comments.
Torque is more important than HP but you do need enough HP to. I would say minimum of 300HP and 800-900 on the torque side. C-7 and up Cat and ISC and up cummins. I have the CAT 3126 330HP 880 ftp torque a 38' double slide towing 7500 lbs and it does OK but could use the C-9 or the ISL. And yes the 9000ft pass's do test the motors.
07-05-2010, 07:41 AM
I think Len hit it on the head. Torque is a key factor. Knowing your M/H engines torque band and staying in it is a major factor in all aspects climbing hills/mountains, mileage etc. Driving a M/H is a perishable skill if it sits for long lengths of time in my opinion. Once you get the hang of it, climbing is not a huge deal irregardless of engine size. You don't want to lug the engine, don't be afraid of your transmission down shift if need be.
My first M/H was a 38' single slide with an ISC 315 and I had no problems climbing anything east or west coast. Some made it to the top faster but it sure didn't bother me. Got great mileage and loved the coach. Present M/H has a ISX 525 in it and have no problems climbing. Do suffer a bit in mileage in mountainous or hilly areas. Not much of a difference in mileage on flat land. I'm never in a hurry to go anywhere and run along at 58-65 mph right in my engines sweet spot.
The CAT Cummins argument will go on forever. Both make a great engine. You may here CAT is going out or is out of the M/H market. Don't worry those engines had numerous applications and support will not be and issue. I've read never seen one that Mercedes was in the market for a while but they had some issues. I can't speak for those never met anyone that had that engine in their M/H.
I don't think any of the engines you mentioned would be a big problem in the size of the M/H you are talking about. Course it your preference. I do like Lens comment on ISC for Cummunis engines can't speak for CAT. I read somewhere on one of the other forums that some of the early ISB engines had a problem with something they called "Killer Dowel Pin" which could ruin your whole day engine wise. There is a fix that Cummins has/had for that engine if your M/H selection has that engine in it I'd scour the maintenace records to see if that fix had been completed.
Now concerning a 34' M/H I think I would really look at the wheelbase. I would not want to sacrifice my ride (porposing) in a shorter wheelbase if I did not need to. Test drive the M/H on all road conditions especially on highways with some hefty expansion joints.
07-05-2010, 10:38 PM
Forgot this one in the above balloon juice. Some of those smaller hp engines in your original post may be married up to a 5 speed transmission vice a 6 speed. My preference would be a 6 speed.
07-28-2010, 06:37 PM
Hey! That 300 HP Cummins is just fine! Our 32' Meridian, pulling a Honda Pilot, WITH a tandem axle ATV trailer w/three Polaris 500's does just FINE out here in the Rockies! Sure it only goes UP Vail pass at 45mph, but it still get a very respectable 8-9 mpg. We love it. Have over 60K on it.
Size DOES matter, but not that much! :cool:
07-28-2010, 07:15 PM
325HP to 360HP range will do just fine at 38' or less. Mosty mountains and pulling a larger toad, go bigger.
Choosing Horsepower and Torque
Higher torque ratings are more important than high horsepower ratings if you pull a trailer, haul heavy loads or drive on roads with long, steep grades.
If you like to see how fast you can get from stoplight to stoplight -- or if you do a lot of other quick acceleration driving -- horsepower is more important.
09-28-2010, 03:21 PM
This summer we took our Horizon 40' Diesel from Maryland to the Candian Rockies and back. We went through many high 8,000 foot plus passes and the engine and trans were superb. This is what we have
Cummins® 425 HP ISL Engine with Allison® 3000 MH 6-Speed World Transmission and Electronic Shifter
Torque: 1,200 lbs./ft., Max. Net at 1,300 RPM ...that torque let me pass trucks going up steep grades. It is not a sports car, but it pulls with a full load. We did not tow a toad, but I don't think it would make that much diffence. Our toad would be out Toyota Prius and tow dolly, about 3,500 lbs together.
10-03-2010, 10:37 AM
Just thought I would throw in my 2 cents here because I pondered that same question for a long time before I bought my 39 ft , 2 slides, 2001 dutchstar. It has the 300hp cat with 870 ft lbs of torque. I would call it adequate. I sure would not want to go any smaller & at times thought the 330 would be better. I do get 10 miles per gallon which is better then I thought I would get. I drive between 60 & 70 where the speed limit allows. :laugh: :cool:
10-16-2010, 05:41 PM
We have a 2002 Winnebago Journey 33 ft with 2 slides, Cummins ISB @275 HP 660 Foot Lbs torque with 5 speed Allison traney towing a Suzuki Vitara 4 door. I looked into taking the engine to 300 HP but the local cummins dealer said the Allison 5 speed is rated at 600 foot lbs torque and is already maxed out. He said he would do it for me but he didn't recommend it. I wish our rig had the six speed 3000 but we will have to live with what we have I guess. I'm an old diesel mechanic and I think I could take care of it but where I would worry about it is pulling the long hills.
Powered by vBulletin® Version 4.2.0 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.