Community Forums

Ourrvtrip · 08-10-2015, 12:06 PM

That's a difficult one to determine. If you go off your Spartan computer, it may read from 7.2 to 8. However, I just made a run from Houston to Branson and ran through East Texas with temp reading 104 to 105. So gen was burning some fuel keeping the 3 A/C's up and running (and gen fuel burn is not factored in to Spartan computer coach mpg) . Dash A/C was also on. And to top it off, then I hit the mountains in northern Arkansas that required mashing the throttle just to make it up them before sundown. So there are A LOT of factors that play in to mpg. Cool flat terrain will yield surprisingly decent mileage while hot hilly terrain will suck the tank dry. Tommy

Mr_D · 08-10-2015, 12:27 PM

Our rig gets an overall average of 7.6 after 45,000 miles.

60 mph = 1350 rpm

Going by the best rpm calculation I should be running 1750 rpm
HP x 33,000 = A
Torque x 6.283 = B
A/B = Sweet spot

650 X 33,000 = 21,450,000
1950 X 6.283 = 12,251.85
21,450,000/12,251.85 = 1750 rpm

Guess I need to speed up to get the best mileage.

waterboy10 · 08-10-2015, 03:34 PM

8.6 is the lifetime average. When the coach was delivered to Florida it showed 6.2 mpg as I recall. I bet the delivery driver was petal to the metal all the way (about 1300 miles). I do not believe that when the generator is running that it is in the coaches mpg calculation as it is a independent circuit and the computer measures fuel to the engine only (per Ted Cook). We rarely use the house ac's when driving as the dash air cools us just fine. 1850 rpm feels like a good spot for the engine and tranny setup IMHO.

Kitz · 08-10-2015, 04:52 PM

We have about 15,000 miles under our belt on our 2014 Aspire and I track every fill up. Across the board average is 7.7mpg. I usually run between 62 and 65 mpg using cruise as much as possible. I see little difference whether I'm towing my Jeep or not, running A/C or not and so forth. The terrain is the biggest cause for variation. I've been over 9 here in the South and under 6 when running in the mountains.

wmpbauer · 08-10-2015, 06:31 PM

I disagree...in my experience, WIND can be a much bigger factor than terrain....excluding the bigger mountains......they screw everything up. Also, I get a little better mileage when I control the throttle, rather than using the cruise.

Still, I do better going @ 67-8 mph....1850 rpm.

Pat Bauer, President
Entegra Coach Owners Association
2013 Aspire DEQ
Ford Edge

Ann n Gene · 08-10-2015, 06:33 PM

I absolutely agree on the wind. Makes a huge difference on my coach. JMHO

2016 Cornerstone 45B on order
Formerly 2011 & 2013 Anthems
2014 Lincoln MKT towed

dave&ginny · 08-11-2015, 07:45 AM

Quote:

Originally Posted by waterboy10

8.6 lifetime of the coach. I drive about 65 at 1850 RPM's. All types of driving out west to Florida to New England, etc. 25,000 miles on the coach. It is a Aspire DEQ but same drive train as a Antehm. It is fully loaded with typical RV stuff. If I move up to 70MPH I notice a drop in mileage. 1850 seems to be a sweet spot for economy and performance.

I have found the same

757driver · 08-11-2015, 08:03 AM

Over 90 sq. ft. of frontal area, wind is a huge factor in mileage.

waterboy10 · 08-11-2015, 03:42 PM

I like the wind behind me but it hardly ever happens. When we went from Michigan to Door County via Chicago the wind was very bad. Makes for a tense drive. Had to have a beer right away on arrival (any excuse).

FreshAir · 08-11-2015, 08:46 PM

Yea, wind can be your friend or your enemy. Direction.

Did some fun quick, basic, basic, wind force calculations. Assumptions, 90 sq. ft flat surface motor home front cap. .00256 [std. quick estimator] x wind speed squared x sq. ft. surface.

65 mph plus 0 mph head wind = 973 lbs of force on front cap.
65 mph plus 15 mph head wind = 1,474 lbs of force on front cap.

65 mph plus 30 mph head wind = 2,079 lbs of force on front cap.
65 mph plus 30 mph tail wind = 282 lbs of force on front cap.. I'm kinda winging it here.

How does the 450 Cummins react to this? I don't have a clue. FWIW.

Pat

LVUS101 · 08-12-2015, 12:06 AM

8000 miles on our 2015 Anthem 44B. 2300 of those are from the transportation company. Best mileage according to the gauge has been 8.8. My math shows the gauge is off by almost one mile per gallon. My own calculations don't take into account the generator use and we use it quite often this summer. I drive between 55 and 65 mph and use cruise control as often as I can.

Steve Ownby · 08-12-2015, 06:49 AM

Quote:

Originally Posted by DGBPokes

I assume....(you know what that means )

HP x 33,000 ( weight?)
Torques x6.283 (what is 6.283) where does that number come from and what does it mean?

The 33,000 is a constant as is the 6.283.
I picked this calculator up on a diesel forum at some point & don't have any clue as to its origin.

I'm also guessing, since HP is calculated from torque and rpm that this formula is an attempt to approximate the rpm where the HP and torque curves cross.

It doesn't relate to economy as diesel engineers all agree that the lowest RPM that will maintain top gear without dropping below max torque is best for mpg.

If I were climbing a long 6% or greater grade, I would consider this sweet spot to be the low end of my desired rpm range.

Steve Ownby
Full time since '07

CampDaven · 08-12-2015, 09:03 AM

That's a lot of calculating and science that does not mean a lot to the bottom line!
If I get 7 or 8 over 1000 miles, at $2.50/gallon, is about 45 bucks. Chump change compared to the luxury and lifestyle we enjoy, eh?

I drive easy, downshift and lose the race up or downhill, and never split hairs.
Works well enough!
Happy Trails!

Gary.Jones · 08-12-2015, 10:47 AM

Steve

But, at low revs and at bottom of rev range in a higher gear, you are heating up the engine maximally. I have found that I climb long steep hills much better and with much cooler engine temp near the top revs at a lower gear. If my Allison will not downshift to a lower gear at higher revs, I force the downshift and climb the grade easier and cooler..... Right?

Gary