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 09-01-2013, 10:02 PM   #183
Senior Member
 
Piker's Avatar
 
Join Date: May 2011
Posts: 1,299
Quote:
Originally Posted by CampDaven View Post
Interesting!

I would be interested in details of your rig. It is not in your profile.

I burn diesel and get 10.5 to 12.3 at 23,500 lbs, MH plus toad. I dont check long term mileage.
There is a little information in my signature below...

Our rig runs somewhere between 21,000 and 22,000 lbs when fully loaded. I've never pulled a toad, but hope someday that we can get set up to do that. The engine is a 5.9L Cummins B series. The transmission is a 6-speed Allison MD3060, and the rear axle is a Rockwell (not sure the gear ratio). Of course this is all set up in a pusher configuration. I am told that the Holiday Rambler Endeavor LE's were considered an "entry level" diesel pusher back in the day. For us, almost 20 years after it's construction, it was a used - entry level - entry level diesel pusher.

The old 12-valve Cummins are great engines... nearly bomb proof, pretty efficient, and easy and inexpensive to adjust for increased performance. They lack the sophistication of the newer computer controlled diesel engines, but they don't have all the emissions stuff to contend with either.

I'm probably considered a little bit of a gear-head, and I've made some adjustments to our Cummins for increased power... I machined a new fuel plate for the fuel pump, added a boost regulator, adjusted the AFC (Aneroid Fuel Control), made the exhaust more free flowing (and cooler sounding), and added a DIY 2-stage water injection system specifically to help control high exhaust temperatures that are a product of the increased fuel to the combustion cycle.

Basically, I've changed the fuel pump so that it can deliver more fuel to the engine when I want it... at the same time I've increased the max boost potential from around 22psi to 30 psi. The changes have made a very significant increase in power output, and they haven't decreased fuel economy at all, since the efficiency of the engine hasn't changed. Actually, by increasing boost to handle the additional fuel, you can actually increase the efficiency of the engine a few points under certain circumstances.

The newer computer controlled engines are even easier to adjust for power... but it's a little more costly. An add on chip or a programmer can change the fuel parameters similarly to what I've done with the old 12 valve, but with a much greater degree of sophistication and accuracy. I think you will find that most people who do these types of modifications will see a dramatic increase in HP and Torque, without a negative effect on fuel economy. Of course, that all depends on how radical the changes are. One thing to remember... the more radical the tune, the more reliability you sacrifice. You can only push these things so far past factory specs before the service life of your pieces parts gets reduced exponentially. I figure I've got a pretty mild tune on ours, so we're good for as many miles as we can afford to drive it over the next decade.

From some of the investigation I have done on our particular 230hp cummins, we should be at or around 300 hp at this point. Torque is probably up from 600 lb-ft to maybe 800lb-ft. These are just guestimates based on similar engines with similar mods that have been dynoed before and after the changes. I'm not concerned with exact numbers here... the point I'm making is that the difference is dramatic, and the mileage is acceptable.

When we were looking at used motorhomes, I narrowed the search by the following criteria... 12 valve cummins, 6 speed allison, and around a 20,000lb gvw. I knew that with this combination 10mpg would be possible, and that even with 75,000 or more miles on the rig, the drivetrain should have plenty of life left in it. You can't say that for a 20 year old gas engine motorhome with that many miles on it. By that time, the old gas engines are just about ready for an overhaul... the cummins however, should keep running for a long long time... one of the benefits of the diesel engine. I could never afford to buy a newer coach with a diesel power plant, but I figured I really couldn't afford to buy an older gas powered coach either since engine work would probably be necessary sooner rather than later. Of course, there's no guarantee on anything, but I decided it was worth it to put my money on an older cummins... just my $0.02.

That was probably a pretty long winded explanation, but this stuff is kind of fun for me. I'm not sure if there is anything i could do to get better fuel economy at this point... I've done everything I can afford to do. 10 or 11mpg is acceptable for us, and I'm pretty happy with the performance too. If I had to sacrifice power to get better mileage than what I'm getting, I don't think I would do it. It's just too fun to drive the way it is...

-cheers
__________________

__________________
1994 Holiday Rambler Endeavor LE - Engine Rebuilt and Restoration in Process
Piker 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 09-02-2013, 11:25 AM   #184
Senior Member
 
UsualSuspect's Avatar
 
Fleetwood Owners Club
Join Date: Feb 2008
Location: California
Posts: 611
We have had our rig for a little over a year. After 3,472 miles, the average is 8.37 MPG. Since I have to climb the Grapevine going north, or climb up up and over the same range going east except on a different freeway I am happy with it. I try to stay right around 65 as I have found that 70 and above will cut it down to around 6 or 7 at best.
I did not buy the rig for fuel economy, I bought it to go camping with comfort and convenience. I keep track of it so I have an idea about what I need to budget for upcoming trips.
__________________

__________________
2007 Fleetwood Excursion 40E
2007 Chev Classic CC LB D/A - Toad
2013 Jeep Sahara Unlimited - Backup Toad
UsualSuspect is offline   Reply With Quote
Old 09-02-2013, 12:22 PM   #185
Senior Member
 
ChallengerRN's Avatar
 
Join Date: Dec 2012
Posts: 2,079
Quote:
Originally Posted by UsualSuspect View Post
We have had our rig for a little over a year. After 3,472 miles, the average is 8.37 MPG. Since I have to climb the Grapevine going north, or climb up up and over the same range going east except on a different freeway I am happy with it. I try to stay right around 65 as I have found that 70 and above will cut it down to around 6 or 7 at best.
I did not buy the rig for fuel economy, I bought it to go camping with comfort and convenience. I keep track of it so I have an idea about what I need to budget for upcoming trips.
I budget in reverse I guess. Put fuel on the card then worry about it when we get back. LOL
__________________
ChallengerRN is offline   Reply With Quote
Old 09-02-2013, 12:30 PM   #186
Senior Member
 
calhyatt's Avatar


 
Newmar Owners Club
Freightliner Owners Club
Join Date: Mar 2012
Location: Weston, Fl.
Posts: 914
Quote:
Originally Posted by ChallengerRN View Post

I budget in reverse I guess. Put fuel on the card then worry about it when we get back. LOL
X2. Only control I have on diesel cost is the pressure I supply to the throttle!
__________________
2003 Newmar Kountry Star 3905, Freightliner XC chassis with CAT 330. Winnie the black lab, pretty Airbus captain wife, retired airline pilot with 11 grandkids. UH-1 pilot (Huey) U.S. Army 1967-1983. RVN 68-69. Northern Idaho my summer home.
calhyatt is offline   Reply With Quote
Old 09-03-2013, 06:56 AM   #187
Member
 
Join Date: Aug 2009
Posts: 31
Cummins

Here is my everyday full to full mileage performance on my ISL 400 hp; 7000 miles 9.1 miles to a Canadian gallon not taking generator fuel into consideration. Next time I'll calculate gen hrs for a truer reading. I figure 9.1 isn't all that bad , it's like a lot of folks have said it is what it is a lifestyle.

40 ft Travel Supreme approx. 30,000 lbs GVW
__________________
pub1898 is offline   Reply With Quote
Old 09-03-2013, 08:23 AM   #188
Senior Member
 
vraines's Avatar
 
Join Date: Feb 2012
Posts: 695
I remember year back when I was a young man I ride-shared with three gentlemen and the conversation regularly drifted to how great their gas mileage was with their own cars. Mine was a high hp V8 and not much to brag about in that department. One day I tired of the bragging, so I stopped the car and got out and went back to the filler tube for a minute, fiddled around for a bit and returned and started the car and continued on our way. Shortly, one of the braggers asked what I had just done and I responded that I had to let some fuel out as I had just added the latest fuel saving device and it was causing a problem. That ended the conversations on fuel mileage. I later spent a career as a pilot and one fact about fuel consumption is that words alone do not extend the flight range and burn-out-time.
__________________
2007 Dutch Star 4320
2010 Mazda Miata 6 speed
Roadmaster tow
vraines is offline   Reply With Quote
Old 09-03-2013, 11:45 AM   #189
Senior Member
 
ChallengerRN's Avatar
 
Join Date: Dec 2012
Posts: 2,079
Quote:
Originally Posted by vraines View Post
I remember year back when I was a young man I ride-shared with three gentlemen and the conversation regularly drifted to how great their gas mileage was with their own cars. Mine was a high hp V8 and not much to brag about in that department. One day I tired of the bragging, so I stopped the car and got out and went back to the filler tube for a minute, fiddled around for a bit and returned and started the car and continued on our way. Shortly, one of the braggers asked what I had just done and I responded that I had to let some fuel out as I had just added the latest fuel saving device and it was causing a problem. That ended the conversations on fuel mileage. I later spent a career as a pilot and one fact about fuel consumption is that words alone do not extend the flight range and burn-out-time.
What your saying is that some reported milages we hear people talk about might make them glide home. Lol
__________________
ChallengerRN is offline   Reply With Quote
Old 09-03-2013, 11:53 AM   #190
Senior Member
 
Okrver's Avatar
 
Monaco Owners Club
Join Date: Sep 2006
Location: Tulsa,Oklahoma
Posts: 199
Toadless 11
Towing 8-9
__________________
OKrver 2002 HR Ambassador
2003 Dodge Dakota 4X4
2012 Polaris ESP 850 Tour
Okrver is offline   Reply With Quote
Old 09-03-2013, 02:07 PM   #191
Senior Member
 
WesinRockies's Avatar
 
Fleetwood Owners Club
Join Date: Oct 2012
Location: Colorado
Posts: 581
Almost done waxing her up then off to Chattanooga in Oct see what I get then!
__________________
Sally, Hailey (Shih Tzu) and Me!
08 Revolution LE 40E
12 Jeep Wrangler,10 FLHX
WesinRockies is offline   Reply With Quote
Old 09-04-2013, 06:24 PM   #192
Member
 
Join Date: Nov 2011
Location: On the road when we can
Posts: 47
How much is transmission a factor?

I am considering large (42k GVWR) coaches, some with Allison 3000 series transmissions, others with 4000 transmissions. As a general rule and with every thing else being equal, which of the Allison transmissions would provide the most efficient engine operation and therefore the best fuel mileage? I think that the weight-to-horsepower ratio has a great deal to do with fuel mileage.

Opinions, experiences?
__________________
Just DW & me, the driver
2001 Foretravel U320 42 ft, ISM450
Toad: 2010 Honda CR-V
2InAlabama is offline   Reply With Quote
Old 09-04-2013, 06:27 PM   #193
Senior Member
 
Country Coach Owners Club
Join Date: Jan 2006
Location: Redding
Posts: 3,412
Considering the costs you are considering incurring with Large 42K lb coaches, the transmission's fuel costs or savings would miniscule in the greater scheme of things.
__________________
Dean
1995 CC Magna #5280
C8.3L 300hp Cummins, 31,000lbs
deandec is offline   Reply With Quote
Old 09-04-2013, 06:54 PM   #194
Member
 
Join Date: Nov 2011
Location: On the road when we can
Posts: 47
Dean said: Considering the costs you are considering incurring with Large 42K lb coaches, the transmission's fuel costs or savings would miniscule in the greater scheme of things.

That may be true, but since we are going to be traveling mostly in the western US, I want the best fuel mileage that I can get. If the 4000 will give me the best performance and the best fuel mileage in the mountains with no cost difference, why not?

I looked at the Allison website for a comparison, but found no answers.
__________________
Just DW & me, the driver
2001 Foretravel U320 42 ft, ISM450
Toad: 2010 Honda CR-V
2InAlabama is offline   Reply With Quote
Old 09-04-2013, 07:24 PM   #195
Senior Member
 
Steve Ownby's Avatar
 
Join Date: Nov 2008
Location: Cosby, Tn
Posts: 6,396
Quote:
Originally Posted by 2InAlabama View Post
Dean said: Considering the costs you are considering incurring with Large 42K lb coaches, the transmission's fuel costs or savings would miniscule in the greater scheme of things.

That may be true, but since we are going to be traveling mostly in the western US, I want the best fuel mileage that I can get. If the 4000 will give me the best performance and the best fuel mileage in the mountains with no cost difference, why not?

I looked at the Allison website for a comparison, but found no answers.
Chassis builders use the 4000 with engines with a higher output than the 3000 is rated for. The 4000 weighs about 300 pounds more dry than the 3000 and requires approx double the fluid. The ratios in each gear are slightly different. The Cummins ISL represents the upper limit for the 3000. The Cummins ISM, ISX, the Cats above the C9 and the Detroit are all paired with the 4000.

My current coach which I have full timed in for going on 7 years is an ISM/4000 combo. My coach and towed combo weight about 44k. In rolling to flat driving at a target speed of 62 on Interstate travel I get 8 - 8.2 mpg. In the eastern mountains is 7.6 - 7.8. Out west it's 7.2 - 7.6. These numbers have been pretty constant over the last 50 k miles.
__________________
Steve Ownby
Full time since 2007
2003 Monaco Signature
Steve Ownby is online now   Reply With Quote
Old 09-05-2013, 11:29 PM   #196
Senior Member
 
mvpmich's Avatar
 
Freightliner Owners Club
Join Date: Jan 2012
Location: SE Michigan & Central Florida
Posts: 199
Quote:
Originally Posted by dajudge View Post
If you get 10 or more mpg, you must be travelling downhill all the way, possiby with the engine not running.
Dajudge, don't be so quick to judge. I have the same basic rig as Maladjusted and just returned from a 5,000 mile trip to/from California via the Grand Canyon (going) and Route 66 (returning). Our OA average mpg was +9.5 towing a Saturn Vue. During the Nebraska/Colorado leg we averaged over 11 mpg. Only once did our speed drop below 45 on a +6.5% grade and we were still passing the truckers. We probably would have had better mpg if we didn't make all the stops and side trips along Route 66.

Can't say enough about the Freightliner/ Cummins setup.
__________________

__________________
mvpmich
2012 Sportscoach Cross Country 385 DS Freightliner XCR w/ Cummins ISB 6.7L 340 hp
2009 Saturn Vue, Blue Ox Alpha, RVi Brake 2
mvpmich is offline   Reply With Quote
Reply

Tags
diesel



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


» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 08:52 AM.


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