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Author Topic: MPG and Generator Use  (Read 1830 times)

UK-RV

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MPG and Generator Use
« on: November 19, 2006, 08:18:07 AM »
Hi Guys

Im still trying to get a correct MPG reading for the RV - the display tells us we get 7.8 mpg on average, which seems slightly low - I was expecting around 9 miles per US gallon (which will give nearly 11 miles per UK gallon).

How is the mpg figure calculated ?

Is the fuel rate recorded as and when the vehicle is being driven or is it taken from what is in the fuel tank ?

In other words, if we use the generator the fuel level will drop in the tank, but would it affect the overall mpg given.

In case it makes a difference, the RV is Fleetwood Expedition on Freightliner with Cat C7.

Thanks
Paul
« Last Edit: November 19, 2006, 08:19:43 AM by UK-RV »

Tom

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Re: MPG and Generator Use
« Reply #1 on: November 19, 2006, 08:26:12 AM »
Paul,

It's highly unlikely that your generator usage will be included in the calculation of fuel consumption. Various things will affect how the actual consumption deviates from expected, including how heavy your foot is, terrain, weight of all your stuff, weight of your tow, etc. Have you tried keeping a manual record of fuel fills and mileage? One easy way to do that is with the Rolling Stock software that you'll find a link to here.
« Last Edit: November 19, 2006, 08:34:37 AM by Tom »
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Shayne

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Re: MPG and Generator Use
« Reply #2 on: November 19, 2006, 08:46:41 AM »
Wow   Wish I got that kind of mileage but then I really and truly don't care  cause if I can't afford it  I stay home.   Yet  my 6.8 MPH might hot be that bad considering I run the genset about 60% of the time on the road.  If I'd want better mileage I guess I'd have to slow down or  unload something.  Wonder if the wife wants to be left in Amarillo again  LOL    NOT  Beside not sure the head can stand it   Too many knots.
Old, Stubborn, Opinionated, Set in my Ways, and Independent,  IMHO

UK-RV

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Re: MPG and Generator Use
« Reply #3 on: November 19, 2006, 08:51:15 AM »
Hi Tom

Given that we've now done 24,000 miles we should have a pretty good average over that distance - which should even out the weights, terrain etc.

It is, after all, showing our average MPG, as opposed to the instant mpg option which will show as low as 5mpg uphill and 85mpg downhill.

I did look at Neds program - only about 20 minutes ago actually  ::) - and I did think of asking if he could adapt a version for UK use (£ sign, 4.54 litre per gallon, etc).

I think there could be a (small but with potential) market for it in the UK.

I must admit though, Ive only recently (last 5,000 miles or so) started using the cruise control regularly - it does take a while getting used to as I like to feel "in control" of the pedal.

Having said that, we rarely go above 60mph and try to travel at a steady 55mph whenever possible.

Paul

Tom

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Re: MPG and Generator Use
« Reply #4 on: November 19, 2006, 09:00:40 AM »
Paul,
 
My driver often insists she's taking it easy but, since I'm looking at the GPS and engine/transmission parameters while she's driving, I know when she's driving with a heavy foot. Depending on who's driving, the navigator in your coach could do the same. I use the (free) VMSpc software from Silverleaf Electronics. It does require you to buy a pigtail from them with a plug that will fit the diagnostic connector on your coach. It will also give you instantaneous, trip and cumulative MPG. FYI Silverleaf is used by some of the OEM coach builders.

FWIW keeping track of my fuel consumption manually was a nightmare because of the design of Monaco's fuel tanks and fuel fill. The actual fuel pumped at each fuel stop would vary by as much as 10-15 gallons from my calculated consumption. VMSpc took away all the variability/error.
« Last Edit: November 19, 2006, 09:05:07 AM by Tom »
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Shayne

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Re: MPG and Generator Use
« Reply #5 on: November 19, 2006, 09:19:23 AM »
Paul   It sounds as if you should only go downhill.  Seems as if you get better mileage that way.  Just remember when heading to Fl from Canada is all down hill.  You'll have a long way uphill on the return.
Old, Stubborn, Opinionated, Set in my Ways, and Independent,  IMHO

UK-RV

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Re: MPG and Generator Use
« Reply #6 on: November 19, 2006, 09:31:54 AM »
"......will show as low as 5mpg uphill and 85mpg downhill."

28 MINUTES !!!! - I am disappointed with you guys.

It took someone 28 minutes to reply to my above comment and recommend only driving downhill.

LMAO

Paul

Ned

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Re: MPG and Generator Use
« Reply #7 on: November 19, 2006, 09:36:39 AM »
Paul, Rolling Stock has options to work with US Gallons, Liters, or Imperial Gallons.  If using liters, then fuel economy is shown in liters/100km.  Sorry, it won't change the currency symbol for you, but if you change the locale in Windows, it might work.
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

Tom

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Re: MPG and Generator Use
« Reply #8 on: November 19, 2006, 09:39:36 AM »
Ned, I either didn't know or had forgotten that RS has metric options  :-[
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Tom

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Re: MPG and Generator Use
« Reply #9 on: November 19, 2006, 09:41:42 AM »
But Paul, it took only 8 minutes and 5 seconds for the first reply. I wasn't going to suggest you keep going downhill, but Shayne says it the way he sees it  ;D
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BernieD

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Re: MPG and Generator Use
« Reply #10 on: November 19, 2006, 09:44:46 AM »
Paul

The instant MPG figure displayed on your Driver Information Display is based on the metered fuel going thru the engine. The Engine Control Module is programmed to calculate your mileage based on your metered fuel and tire circumference, all of which affect the MPG calculation. If your tires are new, your mileage driven is actually more than what is shown on your odometer, which would show less than your true MPG. As the tires wear, that variance decreases. Have you ever compared your distance driven based on mileposts or GPS programs to the mileage recorded on your odometer? I have about a 5% variance between my speedometer and my GPS.

Since only engine fuel usage is used in the calculation, your generator fuel usage is not part of the formula. Many of us use an estimate of 1/2 gallon of diesel fuel per hour of generator usage. When you refuel you do have to take generator usage into consideration. If you have a Hydro/Aqua Hot system, that also has to be taken into consideration.

Finally your MPG is strongly affected by your driving habits. I have heard that there is somewhere around a 1 MPG drop for each 5 mile increase over 60 MPH. Hilly country will yield lower MPG figures. I have seen about a 1 MPG difference between eastbound (tailwind) travel and westbound (headwind) travel over the same route. Low tire pressure also has a negative effect on MPG. Using the cruise control improves your MPG since you keep your engine running at a more constant speed.

My coach, with a 400hp engine, has a travel weight around 30,000#s and tows a 4,500# truck. Since delivery, using Ned's program for tracking, I have averaged 8.75 MPG over 68,000 miles, adjusted for generator but not for odometer error. I usually drive between 62-65 MPH and have the cruise control on most of the time. Now that my engine is finally broken in, I think  :D, and I've dropped my highway speed a bit, I've gotten over 9 MPG on a number of tankfuls.
Bernie & Marlene Dobrin
Home is Goodyear, AZ
Missing our Travel Supreme

UK-RV

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Re: MPG and Generator Use
« Reply #11 on: November 19, 2006, 09:51:34 AM »
Bernie,

Thanks for all that info - Im still trying to digest it.

Ned,

If the RS prgram is set to imperial gallons, will it show results as miles per gallon - ie does it only show km if litres are selected ?

I will download a copy and see what happens to the $/£ signs and will report back this evening (about to hit the road shortly)

Paul

PS If I reversed for the remainder of our tour and took a few miles off the odometer, would that improve the mpg shown ??  ;D ;D

If so, could I ask them to put it on the container ship backwards for our return to the UK - that should take a few thousand miles off  ;D

(sorry, getting silly now)

Karl

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Re: MPG and Generator Use
« Reply #12 on: November 19, 2006, 09:53:59 AM »
Bernie,

Unlike you, I rarely use cruise control, except on flat roads,  because it tends to downshift more than necessary. I find that letting the rig slow down 5-10 mph has increased my overall mileage slightly over 1.2 mpg. I would welcome the use of cruise if it would allow that kind of loss of speed, but it can't anticipate the height or length of a hill as well as my eyes can.
Karl (Cheesehead) Kolbus   Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting "...holy cow ...what a ride!"

Jeff

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Re: MPG and Generator Use
« Reply #13 on: November 19, 2006, 10:43:09 AM »
Bernie,

Unlike you, I rarely use cruise control, except on flat roads,  because it tends to downshift more than necessary. I find that letting the rig slow down 5-10 mph has increased my overall mileage slightly over 1.2 mpg. I would welcome the use of cruise if it would allow that kind of loss of speed, but it can't anticipate the height or length of a hill as well as my eyes can.

Karl:

When we first had our 460 Pace it downshifted going over an overpass. I took it to Ford for service and complained about the cruise trying to maintain speed and they made some kind of adjustment that let the cruise lag about 4-5 mph before adding enough power to  downshift. Sorry but I have no idea what they did but they did not charge me specifically  for it so it must have been simple. (I was doing a major service plus replacing wheel seals so the bill was pretty good sized already.

BernieD

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Re: MPG and Generator Use
« Reply #14 on: November 19, 2006, 10:52:47 AM »

Unlike you, I rarely use cruise control, except on flat roads,  because it tends to downshift more than necessary. I find that letting the rig slow down 5-10 mph has increased my overall mileage slightly over 1.2 mpg. I would welcome the use of cruise if it would allow that kind of loss of speed, but it can't anticipate the height or length of a hill as well as my eyes can.

Karl

Like Jeff, my engine manufacturer also adjusted the cruise tolerance to reduce the excess shifting. I also have the advantage of a diesel engine, where the torque is highest at below normal travel rpm, reducing the need to downshift.
Bernie & Marlene Dobrin
Home is Goodyear, AZ
Missing our Travel Supreme

Ned

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Re: MPG and Generator Use
« Reply #15 on: November 19, 2006, 10:56:37 AM »
Paul, RS will show MPG when either Gallons or Imp. Gallons is selected.  If you choose Liters, then it will show (and you must enter) all distances in KM.  You can switch between units at any time.  When we are in Canada, I switch to Liters for entering fuel fills, then switch back to Gallons to show MPG and enter the mileage from the odometer in miles.
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

Ned

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Re: MPG and Generator Use
« Reply #16 on: November 19, 2006, 10:57:51 AM »
Also, with the Allison transmissions, the Economy mode will drop the shift points (200 RPM?) and reduce the down shifting in rolling terrain.
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

Shayne

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Re: MPG and Generator Use
« Reply #17 on: November 19, 2006, 12:35:39 PM »
Paul   I don;t understand how it ony took 28 minutes   usually takes me 35 to  say Hi   with this old hunt and peck  one finger operation.  Man you got speedy results.
Old, Stubborn, Opinionated, Set in my Ways, and Independent,  IMHO

Karl

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Re: MPG and Generator Use
« Reply #18 on: November 19, 2006, 12:43:46 PM »
Jeff and Bernie,

Thanks for the info. I'll look into it! :)
Karl (Cheesehead) Kolbus   Life's journey is not to arrive at the grave safely in a well preserved body, but rather to skid in sideways, totally worn out, shouting "...holy cow ...what a ride!"

 

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