Go Back   iRV2 Forums > MOTORHOME FORUMS > Class A Motorhome Discussions
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 08-08-2010, 02:02 AM   #1
Junior Member
 
Join Date: Jul 2010
Posts: 17
40' mh - how large an engine is enough?

i'M LOOKING INTO FULLTIMING IN A 40' MH. TOP ON MY LIST NOW IS THE WINNIE VECTRA 40. I NOTICED THEY COME WITH DIFFERENT ENGINES. THE ONE I LIKE IS THE ISL400. WILL A SMALLER ENGINE BE AS EFFICIENT AND HAVE THE PULLING POWER TO PULL A LOADED COACH AND A TOAD? I'M NOT LOOKING TO DRAG RAG RACE THAT'S WHAT THE CORVETTE IS FOR BUT I WANT ENOUGH POWER TO GO UP HILLS AND IF I WANT TO PASS.
THANKS IN ADVANCE
__________________

__________________
btlabow is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 08-08-2010, 03:32 AM   #2
Community Moderator
 
RV Wizard's Avatar


 
Country Coach Owners Club
Appalachian Campers
Gulf Streamers Club
Join Date: Mar 2000
Location: Chattanooga, Tn.
Posts: 12,062
The ISL will have enough torque to do the job. An ISC might do OK depending on weight. My ISC gets about 9 mpg. Sometimes I wish I had more torque for long steep grades. I am not sure what the ISLs are getting.
__________________

__________________
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7
RV Wizard is offline   Reply With Quote
Old 08-08-2010, 08:14 AM   #3
Senior Member
 
RVThere's Avatar
 
Freightliner Owners Club
Join Date: Aug 2008
Location: Florida Keys
Posts: 2,163
Just drove my 400hp ISL cross country for 6288 miles pulling a Cherokee and got 6.2 mpg. That was about $3000 worth of fuel. If you had a ISC and got the 9 mpg mentioned above, you would have only spent $2000 on fuel.

The power is great but it comes at a price!
__________________
Tom and Katharine
'07 Winnebago Tour 40TD, 400hp Cummins
'17 Winnebago View 24V, '02 R-Vision B+
RVing for 19 years & 150,000+ miles
RVThere is offline   Reply With Quote
Old 08-08-2010, 08:56 AM   #4
Senior Member
 
Join Date: Aug 2006
Posts: 799
I have a 370 hp Cummins ISL with 1200 ft lbs torque. The motorhome is 41' long and weighs 31,000 pounds loaded and tows a 3600 pound CR-V. I have crossed the Rockies several times and crossed the Canadian Rockies two times. It has all the power I need and I'm impressed with the fuel mileage. The last 21,000 miles it has averaged 9.2 mpg figuring with a pencil and paper so that is actual fuel mileage. This one is a keeper.
__________________
Norm4015 is offline   Reply With Quote
Old 08-08-2010, 09:17 AM   #5
Moderator Emeritus
 
Gary RVRoamer's Avatar


 
Join Date: Jan 2000
Location: Silver Springs, FL. USA
Posts: 18,066
100 lbs per hp is the traditional rile of thumb and it applies to motorhomes too. That yields adequate if not blazing, performance. The voluminous low RPM torque & hp of a diesel will get you up the hills nicely. That doesn't mean you won't slow down on a long 6% grade, but you will still get up it fine.

My 2004 ISL (370 hp, 1200 lb-ft torque) gets 8.1 mpg cruising the interstates at 62-65, but falls off to the low 7's on two lane roads. That's with a 33,000 lb coach and 4900 lb toad.

Post 1/1/2007 engines get poorer mileage due to substantially increased emissions controls.
Supposedly the post 1/1/2010 engines buy some of the mpg back with an improved system, but you pay extra cost upfront for the engine and also every mile for something called DEF, which costs about the same as a gallon of diesel and is consumed at the rate of 2% of the fuel used.
__________________
Gary Brinck
Former owner of 2004 American Tradition
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC
Gary RVRoamer is online now   Reply With Quote
Old 08-08-2010, 11:56 AM   #6
Moderator Emeritus
 
RickO's Avatar


 
Join Date: Jan 2007
Location: Litchfield Park, Arizona
Posts: 10,530
That's a very nice coach you're looking at. My Itasca Ellipse 40FD is similar. I have the 400hp ISL w/1200 ft # of torque and power is certainly not a problem. I get 7.1 mpg at 62mph towing a Ford Explorer.

Good luck.
__________________
Rick, Nancy, Peanut & Lola our Westie Dogs & Bailey the Sheltie.

2007 Itasca Ellipse 40FD
RickO is offline   Reply With Quote
Old 08-09-2010, 01:11 AM   #7
Junior Member
 
Join Date: Jul 2010
Posts: 17
Quote:
Originally Posted by RV Roamer [Gary] View Post
100 lbs per hp is the traditional rile of thumb and it applies to motorhomes too. That yields adequate if not blazing, performance. The voluminous low RPM torque 7 hp of a diesel will get you up the hills nicely..
Gary,
You speak of 100lbs. per hp. 100 lbs. of what? I'm assuming GVW. The sentence about the torque and the 7hp threw me. It seems there can be too much hp which lowers the fuel efficiency of the MH. I also noticed from the replies that while the hp ratings differed the torque ratings seemed to all be around 1200 ft. lbs.. Is the efficiency and or fuel mileage a function of the horsepower or the torque?
__________________
btlabow is offline   Reply With Quote
Old 08-09-2010, 06:44 AM   #8
Registered User


 
Monaco Owners Club
Join Date: May 2009
Posts: 3,198
The 1200 ft-lbs of torque is being limited by the miracle of modern electronics.
That's how much the transmissions can take.
__________________
JimM68 is offline   Reply With Quote
Old 08-09-2010, 07:10 AM   #9
Senior Member
 
HD4Mark's Avatar
 
Winnebago Owners Club
Coastal Campers
Join Date: Oct 2009
Location: Marathon, Florida
Posts: 2,894
Our Vectra has the ISC 350hp and it has plenty enough power for us. Can't comment on the mileage though. Never figured it out 'cause we are going anyway
__________________
Mark & Nancy
2004 Winnebago Vectra 40KD
Shep dog, R.I.P. Kenzie dog Toad 2015 Jeep Wrangler Willys Wheeler
HD4Mark is offline   Reply With Quote
Old 08-09-2010, 09:49 AM   #10
Moderator Emeritus
 
Gary RVRoamer's Avatar


 
Join Date: Jan 2000
Location: Silver Springs, FL. USA
Posts: 18,066
Quote:
You speak of 100lbs. per hp. 100 lbs. of what? I'm assuming GVW. The sentence about the torque and the 7hp threw me. It seems there can be too much hp which lowers the fuel efficiency of the MH.
Typo - that was supposed to be "torque & hp", not "7 hp". All the ISL engines have 8.9L displacement and a max1200 ft lbs of torque, but the hp varies and so does the rpm where that hp is available. The miracle of electronic engine controls. as someone already said. Great peak horsepower does not mean greater fuel consumption unless you actually use that peak hp regularly. If it takes, say, 140 hp to keep a coach rolling at 62 mph, then you use 140 hp worth of fuel, whether it is a max 400 hp or a max 425 hp version of the engine. A physically smaller engine, e.g. the 8.3L ISC, might be more fuel efficient at that same 140 hp, but all the ISLs will be about the same.

Hp = torque*RPMs /550. You need to know the torque actually generated at the RPMs you run at for this to be meaningful. The peak torque (1200 ft lbs) is at a fairly high rpm value that you seldom use, and the peak horsepower RPMs rarely coincides with the peak torque RPMs.

If fuel economy is your major concern, get a smaller displacement engine (the ISC or ISB) and buy one built before 1/1/2007. And keep your foot light on the go-pedal.
__________________
Gary Brinck
Former owner of 2004 American Tradition
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC
Gary RVRoamer is online now   Reply With Quote
Old 08-09-2010, 11:12 AM   #11
Senior Member
 
mythplaced's Avatar
 
Alpine Owners Club
Texas Boomers Club
Join Date: Jan 2009
Location: United States
Posts: 1,282
Quote:
Originally Posted by RV Roamer [Gary] View Post
......

Hp = torque*RPMs /550. You need to know the torque actually generated at the RPMs you run at for this to be meaningful. The peak torque (1200 ft lbs) is at a fairly high rpm value that you seldom use, and the peak horsepower RPMs rarely coincides with the peak torque RPMs.....
????



Per cummins, http://cumminsengines.com/assets/pdf/4971107.pdf

My ISL 400 puts out max hp at 2100 rpm & max torque at 1300 rpm...and I see 1300 rpm all the time..

Do you know something I don't know??
__________________
Michael (Home base Northern CO)
USED TO HAVE; 03 Alpine 40MDTS Now RVless
http://www.tripadvisor.com/MemberPro...AA11052EA9DBB0
mythplaced is offline   Reply With Quote
Old 08-09-2010, 11:49 AM   #12
Senior Member
 
Jerry J's Avatar


 
Winnebago Owners Club
Freightliner Owners Club
Join Date: Dec 2000
Location: N Id
Posts: 587
Fairly high rpm? 1300? At a seminar a Cummins rep said the sweet spot is 1400 to 1600 rpm. More rpm will get you up the hill faster but use more fuel. I seem to drive in this range while driving down the highway.
1200 lbs. at 1300 rpm, 425 hp at 2100 rpm.

>>>>>>>>>>>>>>>>
The peak torque (1200 ft lbs) is at a fairly high rpm value that you seldom use, and the peak horsepower RPMs rarely coincides with the peak torque RPMs.
<<<<<<<<<<<<<<<<
__________________
Jerry J.
2008 Winnebago Vectra 40TD
2007 Honda CRV
Jerry J is offline   Reply With Quote
Old 08-09-2010, 12:19 PM   #13
Senior Member
 
Always-RVing's Avatar
 
Fleetwood Owners Club
Join Date: Aug 2009
Posts: 959
The 8.3 ISC does fine for flat to moderate hilly, rolling terrain cruising (31,000 lbs-35,000 lbs). When climbing more serious mountains, I really need more power. The engine lags and overheats easily. There is of course a cost trade-off with cost. The next size up (400-425 ISL can run $20-30,000 more) in coach cost plus you'll pay more at the pump with less MPG. Both engines are great. The ISL is a higher end motor and used in larger, higher end motorhomes.

Just to mention. The ISL is often trimmed back on torque so not to over power the tranny. One more thing... ISL's require a side radiator. Side radiators use hydraulic to power the fan which can take 25-75 horsepower. It's the requied size of the radiator that forces a side mount instead of rear. There is not enough room across the rear for it.

The motors are widely used commercially and often get 600-800,000 miles. They are both very durable, powerful and long-lasting engines. Bullet Proof
__________________
Fleetwood Providence 2008 40e
Ford F-350 4x4 Diesel 6.0L 2006
Honda CR-V 2006
Always-RVing is offline   Reply With Quote
Old 08-09-2010, 02:33 PM   #14
Senior Member
 
Jerry J's Avatar


 
Winnebago Owners Club
Freightliner Owners Club
Join Date: Dec 2000
Location: N Id
Posts: 587
My Vectra has a rear radiator (425hp,ISL).
One of the best motorhomes I have driven was a 08 or 07 Alpine 36' with a 425 and active air. That was an enjoyable driver. I don't think there ever is too much power for hills or passing. I think weight to power ratio is what really makes the different.
__________________

__________________
Jerry J.
2008 Winnebago Vectra 40TD
2007 Honda CRV
Jerry J is offline   Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Slides, Leveling, Engine - Puzzled Rookie? Injun Joe Monaco Owner's Forum 60 09-04-2010 09:10 PM
Dirty Engine. Good ideas to clean safely... leedowney Winnebago Industries Owner's Forum 10 03-01-2010 06:35 PM
Check Engine Light On in my Cummings 275 Turbo Diesel. Oil Level too high??? leedowney Cummins Engines 37 03-01-2010 03:18 PM
Engine cutout Rich Pratt Workhorse and Chevrolet Chassis Motorhome Forum 45 02-08-2010 09:11 PM
Dutch Star engine starts with key removed Triton Newmar Owner's Forum 27 02-15-2008 06:28 PM

» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 03:50 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.