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Old 07-12-2013, 09:15 AM   #113
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Originally Posted by Sky_Boss View Post

Ya know...different strokes for different folks. If one doesn't find value in any particular thread, then why say anything at all? Personally, I find questioning the questions of others pointless because it just sounds...well...pointless.

Each of us has questions that are particular to our desire for information. Sometimes the answers to what others might consider are pointless questions are as instructive to to OP in their quest be become informed. Early on I certainly asked what some might have considered as pointless questions. It was through thoughtful answers that I realized that in some cases the answers lead me to the conclusion that it just didn't matter. I, for one, tend to like to pick the fly crap out of the pepper only to find the answer didn't have a major impact on the big picture. Still, I had to explore those questions to ensure I wasn't missing something.

As one that is rather anal-retentive , it is how I explore concepts. YES...it is a curse.

S'okay Don.
I only pondered a wonderment.
A curious RVM will ask just about anything, aye?

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Old 07-12-2013, 03:25 PM   #114
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Originally Posted by hogdriver View Post
My college Mechanical Engineering professor said mpg was only related to mass and velocity.

I had a 95 HR Endeavor 35 FT (26,000lb) with a 230HP 5.9 Cummins pulling a toad and I consistently got 10-12 mpg. The smaller motors work harder but seem to get better mpg.

Same toad, pulled by my 2002 40 ft (30,000lb+) Monaco w 330 HP I got 8-10 mpg.

Same toad, pulled by new 43ft 2013 Entegra (40,000 lb) w 450 HP Cummins I get 7-8 mpg.

I'd be curious to know what the Prevost folks get with a big Detroit Diesel and their weights. My guess is the mileage bottoms out around 6-7 mpg.

Of course winds and hills are big factors but I can edge my mpg up 1-2mpg but just driving slower at 62-65mph.
I talked to the owner of a 45-ft., 2006 Prevost who's here in Homer, AK, at the moment. Driving from Connecticut, he's been getting 6 to 7 mpg, he said.

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Old 07-12-2013, 03:29 PM   #115
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Our 25-ft., 2013 class A Itasca Reyo (T model) averaged 15.1 mpg over the first 10,000 miles and ranges from 13.8 to 20 mpg. This is a light vehicle on a Mercedes Sprinter van chassis, 11 ft. high.

GVWR (gross vehicle weight) 11,030 lb.

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Old 07-12-2013, 07:54 PM   #116
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Originally Posted by Sky_Boss View Post
OH...a detail oriented person like me. LOL My MH isn't terrible and perhaps it shows about 1 MPH less than my GPS when I am running 62 MPH per my GPS. doing the math it means I am actually getting .0162 more MPG than I thought.

However, your case is interesting. Consider that you, too, also targeted 62 MPH (seems like a popular target speed) for fuel efficiency. First, the speedo was not showing you going as fast as you actually were so it would seem to me that it would also show less MPG. Second, on top of that, you were actually going about 65.5 MPH with the added aerodynamic drag which would also push your MPG down further. Finally, you are running a tab bit higher RPM which has a tad bit of an effect on MPG.

Theoretically, that means even after you fix your MPG calculations to your real miles driven, you should see a minor improvement in MPG because you will be going slower. Per the "rule of thumb" (See slide 19 in FMCA presentation FMCA Presentation - Cummins Engines) that 3 MPH costs you about .3 to .4 MPG. That is even before you add the Banks tuner to the equation.

Sorry...got carried away with the math. LOL

I installed a Banks Economind diesel tuner and IQ. One of the features on the IQ is you can calibrate your speed using GPS. I found I was running 5.7% faster than what my speedometer was showing. I also checked using the mile markers for 5 miles at 60 mph. The gps speed and mile markers are close enough. I checked my mileage and on one leg it went from 8.6364 to 9.1286 after correcting the mileage. I wonder how accurate the different speedometers out there and how the differences affect the reported mileage.
We have just arrived at Cherry Hill Park from Texas. Went 30 to 40 then 81 to 64 then 95 to DC. Not the best route to get great mileage but I did an average of 9.1137 mpg. I have been running 60 to 65 where I could. I was getting 8.2446. I donít know how much the Banks setup helps but I have been running in level 2 and getting an average of .8691 improvements traveling the back bone of Tennessee. That doesnít sound like much but itís about $50.00 so far on this trip.
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Old 07-12-2013, 09:56 PM   #117
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'06 Mandalay 40E with the Cummins ISL, 400 HP. Coach weighs just over 34,000 pounds. No dinghy.

We ran about 3,500 miles in the last 3 weeks, running I-75 from Ohio to Florida and back, then a second trip to Tennessee via I-71, I-65 and the Western Kentucky Parkway.

I cruised at 65 mph on the interstates and the parkway. According to Silverleaf, I averaged 7.9 mpg over those miles. I am very happy with that.
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Old 07-13-2013, 08:34 AM   #118
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Originally Posted by Razzman View Post
I have no clue what my mileage is, nor do I care to know. It's just like my boat, I accept that it is what it is. If I knew what it was then I'd just dwell on it, and that takes the fun out of it IMO.
Then why even read the thread...?
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Old 07-13-2013, 08:49 AM   #119
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Originally Posted by Ramzfan View Post

Then why even read the thread...?
Just like you I'm offering my opinion, does it matter? Who cares anyway?
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Old 07-21-2013, 12:17 PM   #120
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Originally Posted by Razzman View Post
I have no clue what my mileage is, nor do I care to know. It's just like my boat, I accept that it is what it is. If I knew what it was then I'd just dwell on it, and that takes the fun out of it IMO.
Correct. I want my wife and I to arrive safely, enjoy our resort campground, and eat great food. If I was obsessed with mpg we would be on a motor scooter not motorhome. Just saying.
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Old 07-21-2013, 05:54 PM   #121
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Call me crazy, but I for one enjoy reading stats on RV performance and function. That Silverleaf thingy would have me on cloud 9. If I had one of those, I'd never leave the Motorhome...

We just finished our very first RV vacation in our old '94 Endeavor... a round trip of just over 6200 miles from western PA out to Yellowstone, down to Tucson, and then home again.

I started out taking meticulous notes on fuel economy, but about 2 days into the trip I couldn't get cooperation from the crew so I said the heck with it. I knew that in the grand scheme of things, it didn't really matter anyways cause we were having fun.

Though I didn't keep a running tally of the entire trip, I did hand calculate the fuel economy at every refueling:

Without generator use, the best we saw was 11.21, the worst was 10.60.

With generator use for air conditioning, the best we saw was 10.56, and the worst was 9.98.

There were a few times when the RV wasn't sitting level at the refueling station, and the average was way high, like almost 13... I didn't count those numbers and simply waited until the next fuel stop to get an average between the two.

Our motorhome is a little overweight when fully loaded... around 21,000 or so. Surprisingly, speed didn't seem to make all that much difference in fuel economy. We drove through the mountains sometimes at 25 and 30 mph... and on the interstate upwards of 75mph... and at every fill up we stayed between 10 and 11 mpg. I suppose that is about a 10% difference... that could be considered significant I guess...

The cummins B5.9 engine in our Endeavor is no longer in it's stock configuration. As an avid tinkerer, I was able to change the fuel plate in the injector pump, adjust the AFC a little richer, and increase the max boost level from about 22psi to 30 psi. Based on some of the articles I've read on this engine, these mods probably put it up close to the 300hp mark, and perhaps 800 ft-lb. I did not modify the pump to change the usable rpm range of the engine... it still defuels rapidly at 2500rpm.

The engine is also equipped with a water injection system... And while I can't make any claims on increased mpg due to the water injection, it did do the trick for keeping EGT in check... which was necessary with all the mods to the fuel pump. I suspect that the cooling effect of the water mist injection on the air charge had some positive effect on fuel economy, but I just can't say how much if any...

all for now.

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Old 08-18-2013, 02:10 PM   #122
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I wonder why class A manufacturers don't make more aerodynamic coaches that look more like large Sprinters or Damon Avantis? What happened to the aerodynamic coaches of yesteryear, why doesn't anyone care any more? Did focus groups or buyers decide they preferred the brick shape, or did someone decide the bus was the shape to emulate?

Incidentally, seems Bobio's greatest mpg secret was drafting behind semis... anyone else try that?

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Old 08-18-2013, 05:18 PM   #123
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I find the biggest impact on my MPG is actually side-winds , not so much my speed. Probably because to counter the wind I need to turn my tires in to it, which causes the front tires to scrub a bit... Aerodynamics would do nothing for this ...
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Old 08-18-2013, 05:55 PM   #124
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Alaska trip 2013

We returned home 2 weeks ago tomorrow from our trip.

Driving our 40' 2011 Coachmen Sportscoach pulling a HHR Chevy we averaged 9.95 miles per gallon. The coach has a 340 hp Cummins with 6 gear Allison tranny.

Seemed that flats, hills, mountains, curves, genny use didn't seem to make much difference. In the 11,261 miles we saw a lot of mountains and hills. Twenty-five mph quartering winds cut it to 7.7 in Nebraska on I 80.

The "sweet spot" seemed to be at 62-63 mph so the tach was at 17-18k. I tried to limit the use of the "jake break" since the tach reaches 30-35k when engaged. AM I RIGHT? High jake brake rpm's will cut into mpg. My theory anyway?
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Old 08-18-2013, 06:16 PM   #125
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7.5 mpg with a 40' Monaco Knight DP (Cummins ISC 330 HP) towing a Ford Fiesta on a 8,800 miles trip to the Yukon and NWT last month.
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w/Dawson, our mini aussie, in a 2007 Monaco Knight 40DFT, towing a 24" Pace garage.
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Old 08-18-2013, 07:02 PM   #126
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8.8 mpg over last 6600 miles towing a Saturn. 330 HP cat. Deserts , mountains , off interstate roads and interstates. Generator running some of the time. Did the real math and 8.8 is my number. 62 mph is max speed.

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.
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