'00 36' U320 WTFE ISM450 Fuel Mileage
For over 5 years, at each fuel stop (>130) we have been logging our mileage, gallons into tank, price per gallon, fuel fill-up costs, engine and generator hours.
We fulltime and our no slide coach weighs (full water, fuel, empty waste tanks) in at 31,700 lbs, and our towed Jeep Wrangler 4,800 lbs. Both were Smart Weighed at SKP's in Livingston, TX. We mostly drive 55-58 mph in 5th, or 61 - 64 mph in 6th, always around 1350-1400 RPM with Allison transmission in economy mode 95% of time.
In 2011 (our 1st full year of data), over 10,000 miles, we averaged 7.2 mpg which includes generator and Aqua Hot usage. Allowing .5 gallons per hour for generator the mpg is 7.5. By 2015 our mpg had improved to 7.9 / 8.4. We attribute the improvement to resonator upgrade (2014), valve adjustment (2014), improved driving habits and, maybe, engine break in.
IMO, the metric that makes the most sense, is fuel cost per mile (fcpm). In 2011 the cost was .50 a mile and by 2015 .31 a mile. Like others have said on the blog, these costs/mpg are figured the old fashioned way, by logging the gallons put into tank, odometer reading, and the money paid.
2013 and 2015 are two interesting years. Traveled just over 15,400 miles each year with a fair amount of mountain driving. (see GPS trail screenshots) In 2013 the average cost of fuel was $3.76 per gallon and fcpm .49, including generator/Aqua Hot. Total cost of fuel $7,600! By 2015, with fuel cost dropping and improving fuel mileage, the average fuel cost per gallon was $2.47 and fcpm .31, includes generator/Aqua Hot. Total fuel cost of $4,800. A huge difference! So far, in 2016, 9,000 miles, mpg is 8.1 / 8.6, the fcpm is .25 including generator/Aqua Hot.
We mostly fuel at MurphyUSA, MurphyExpress, WalMart, or Sam's Club fuel stops. We find these stations ,almost always, offer the least expensive fuel in a given area, fairly high turnover of fuel, and offer a 3 cent or more per gallon discount using a Wal-Mart gift card . Using the gift card, the pump will not shut off at a pre-determined CC limit. We fulltime, retired, so don't mind the slight aggravation of finding a fuel spot. We use gasbuddy.com, murphyusa.com and google.maps to plan our re-fuel stops.
This is our results, ymmv, Dave A
Did you seem to notice the power/mpg increase during the driving after the resonator? Like the motor was not seated before?
Exact grades in high gear showed over 30 pounds boost. Did not remember seeing this before. 28? Max.
You would be the poster child to see if my higher temp fan control adds more hp/mpg. 30 hp less power consumption at 180 degrees versus OEM.
One coach buck.
I tow faster and run the motor hard on grades. 8.4 with gen and aquahot.
BUT if yours has more power which I think the ism has versus my m11 I would trade the difference, no problem.
So subjective as far as power.
Howdy Bob,
Definite increase with engine "spooling" up during acceleration. Hard to keep my foot out of it! I noticed a year over year increase of .4 mpg after resonator/valve adjustment. ymmv
Dave A
Valve adjustments seem to have a more positive effect on the M-11 engine,for future reference when we get adjustments have
them tell you which ones and loose or tight.
Same with me. Like the torque pull versus the downshift and rev up formerly
Dave, our coach is about 800 - 1,000 lbs heavier than yours (we have a slide) but our toad weighs only 3,700 lb so not much difference in total weight. Our mpg (total miles/total fuel used) is just a shade under 8.0 after 79,000 miles. We do about 65 mph most of the time in 6th or 58 in 5th. A resonator might help but my guess is that the valve adjustments made more of the difference as well as driving habits.
The resonator definitely gives the impression of more power. We drove up to Mammoth Lakes (8,000' el.) from San Diego and averaged around 7 mpg, but that was with two major grades and Friday afternoon rush hour through San Bernardino (stop and go) which doubled the time it takes to get to 395 & US15. I was disappointed in the overheating going up Sherwin grade between Bishop and Mammoth Lakes - it didn't do much better than my Safari with the 300Hp CAT (860 # torque). I had to pull over twice when the coolant temp reached 220. Ambient temp was 75 and speed was 45-50 mph @ 1800 rpm. I've got the ISM with 450HP and am towing a 4000# Jeep. Before the trip, I replaced the engine oil and coolant.
I'll have better mpg figures as we head up to Idaho.
Sven, looks like 4th gear. You were probably close to 100% engine load and max boost. Try 40-45 mph in 4th. Maybe a bit less load and heat.
Sven,
What RPM were you running when the 220 temp was reached?
Just like your last coach, if coolant temperature is rising, gear down, raise RPM and back out of throttle.
Basically, if flooring the throttle does not gain you anything, you are in too high a gear.
Higher RPM, turns the water pump and fan faster.
I kept in mind what you had posted earlier, Brett. I went as high as 2200 rpm at one point. When I push the down shift arrow, the transmission doesn't always drop down and I lose momentum if I back off the throttle. Many years driving a fire truck have shown me that increasing the throttle without a corresponding increase in RPM is lugging. If anything, it dumps more fuel into the cylinders (at least on the older pumpers) that can't be burnt, creating a lot of black smoke. I never floor the throttle, since I can see that I'm already running at 100% power. I will continue to experiment, as I'm sure I will have many opportunities.
Sven are you using a VPMS setup for your coolant numbers?
My dash gauge reads 220 as it's pickup is separate from the engines more accurate ECU.
VPMS was 208-210 at the same time.
The m11 and ISM as far as I know do not engage their manual engine cooling fans until 210.
Obviously you are an experienced operator so please excuse my personal observations over the same time you have about the engine temps issues.
I have ran our coach this month over countless steep passes at altitude and the VPMS never got over 225 with the resonator installed.
Floored. Manual downshifting.
225-230 and still climbing on the VPMS is the only time I would get concerned myself.
Had a zillion similar demoes and conversations with concerned owners over the 30 years.
Zero issues. Zero failures.
Yes I have run 6v's the same way as have my customers.
In other words after verifying the engines temp with the VPMS I would not and have not pulled over on the same grade.
Now IF your ISM produces more power than my m11 it well may run hotter so excuse me if we are comparing apples and oranges.
Bet it stops at 220-225 on a VPMS up the grade.
But you cannot be wrong pulling over. I did not like the safety issues sometimes generated pulling over myself.
Too many hills in the Rockies in my opinion to pull over unnecessarily.
Scary I know but.......
Easiest thing is I say nothing.
As per Roger & Susans response, my coach is almost the same as theirs and similar weight and mileage. My coach has averaged 7.8mpg since birth and it is a standard version with no engine mods. My last trip was 8.2mpg over 770mls with the toad. It was owned previously by folks in Washington state so has been in the mountains all of its life.
What is the current feeling as to when the valves need adjusting?? My servicing bunch say that Cummins require it at 100,000mls??
Speedbird 1.
Howdy Speedbird1,
We had ours adjusted at 115,000. It seems like it was due at 120,000, but I'm not sure where I got that figure. Bernyd's in Coach Buck City, adjusted ours also installed resonator at that time.
Dave A
Mine was due at 120,000, which was performed by Bernd. He advocates for more often
Speeds used when towing would be helpful in the mpg quoted.
During my ownership I usually tow at 56-70mph to get the mileage I quoted.
I guess I can wait a little longer for the valve adjustment, thanks.
Speedbiord 1.
2016 update to our fuel Mileage:
Total miles; a little over 11,400 with some Mountain driving (see GPS trail screenshot) in Colorado (includes Grand Mesa, CO65 Grand Mesa Scenic and Historic Byway - Wikipedia (https://en.wikipedia.org/wiki/Grand_Mesa_Scenic_and_Historic_Byway)), Wyoming, and Montana.
Average PPG of fuel was $2.08, the lowest of my six years of tracking fuel costs. MPG was 8.1 / 8.6. The FCPM was .26, which includes AquaHot usage and 157 hours of generator time. MPG steadily increasing and the fcpm decreasing Yr ovr Yr. Hopefully, these trends continue.
ymmv, Dave A
Just additional datapoints, for whatever they are worth. We only have 2 years operating history and the numbers from watching VMSpc. We've put about 30,000 miles on the coach in 2 years.
- 1999 450hp U320 with slide at near GVWR 34,880 (we're full time; nowhere else we can keep/store things)
- MPG varies from 7.2 to 8.2, depending on speed, terrain, and how much city driving
- We did our valve adjustment at 133,000 (Cummins, Coburg, OR). At that mileage we were possibly overdue, although I have a friend who works for Cummins Southeast and said between 120-150K. I'll add the engine sounded and ran better after the adjustment, so I'd have done it earlier if I'd known.
And now I finally have a fitting opportunity to say what we've all heard in television commercials: "Your mileage may vary." ;-) These numbers, however, were not achieved by "a professional driver on a closed course" and no "don't try this at home" warning is needed. :-)
Good info, what speed do you try to tow at? Sounds like low 60's?
7.9 mpg over 85,000 miles. Changed toad from a Wrangler to a Cherokee, about the same weight (3,500 lbs). MPG seems to have gone up .1-.2 over the last 5,000 miles since the change.
Not a ism but my m11 VPMS shows 8.2 for the last 11,000 Miles. That's at 36,000 pounds combined weight.
Long term engine computer showed 7.7 mpg for the coaches first 100k Miles.
I and bob Rosen changed our hydraulic fan controllers to correct the fan speed.
The 11k mileage is since the change and I tow at 70 mph normally and run the uphills hard.
Flatter roads like la to Vegas and back I get 9.0 mpg.
Still at 70.
More than 1 mpg better if I go 60.
Michelins helped as coach coasts much better since the new tires were installed.
Resonator helped also.
It's a system. Everything contributes.
Across Nebraska I posted 11 mpg photos here for a long slow stretch with no wind and a very slight downhill.
Versus better mpg I just go faster. Bad bob.
My over heating issues are mostly resolved now, since I replaced my radiator and transmission coolers. On our last trip to Washington, we averaged 7.8, but that included driving down the coast 101 and a lot of stop and go traffic due to road work. I would like to hear more about the upgraded fan controller.
As we have discussed before, the ideal setup for the fan is that it NOT go to high speed (or highER speed if variable speed fan) until coolant temperature has risen to where the thermostat is fully open and coolant temperature rises an additional 5-7 degrees F.
Said another way, you do not want to give up HP and MPG to turn the fan faster than is necessary. A big waste to have the fan taking additional HP while the thermostat is still fully capable of managing coolant temperature all by itself.
Note: the fan will always need to be running, though low speed is fine to keep air moving over the CAC. If not, intake manifold temperatures would rise.
Ok now a dumb question from the new guy on the forum. I put my transmission in D a 6 displays and I go, how do I shift gears manually or go to economy mode?
Shifter pad will or should have up and down arrows.. those will manually change gear. Should also be a button for eco mode. ( at least on mine there is)
We travel @ 60-65 mph
Our overall weight is 36320
The screen shot highlighted area is current trip from New Hampshire to Colorado
Correct.
And, this from an article I wrote many years ago for the FMCA magazine on use of the economy mode:
ALLISON TRANSMISSION MODE BUTTON
BY BRETT WOLFE, F252125
The Allison transmission control module (TCM), which is the "electronic brain" that controls shifting and other functions of the transmission, has two different automatic gear-selection modes/programs.
In Economy Mode, the transmission will not downshift even at wide-open throttle until the engine pulls down to peak torque rpm in some applications and 200 rpm lower than Performance Mode in others. In Performance Mode, the transmission will downshift much earlier to maintain higher engine rpm.
Only at higher throttle positions is there any difference, so on flat ground you will not notice any variation between the two modes, except when accelerating from a stop if you are at or close to wide-open throttle.
However, mode selection can make a big difference when traveling over rolling hills. If you drive in such areas while in Performance Mode (particularly with the cruise control on), it is common for the transmission to shift down to fifth gear on the uphill and back to sixth gear on the downhill, repeating this process hundreds of times. In Economy Mode, the transmission will stay in sixth gear unless the hill is so steep or so long that the engine cannot pull it without dropping below peak torque rpm. According to engine manufacturers, the most economical way to climb a hill with a modern turbocharged diesel engine is in a higher gear (lower engine rpm), provided the engine doesn't overheat.
If, while driving in Economy Mode, you know you will need a lower gear because of the steepness of the grade and/or the engine temperature is rising higher than the thermostatically controlled temperature, use the down arrow to drop a gear (this is what I do) or switch out of Economy Mode. Be sure to switch back into Economy Mode when past the steep section or you will be stopping at a service station for fuel sooner than you expected.
While you are driving in hilly terrain, if your engine begins to overheat, the engine's horsepower-to-weight ratio is low, or it irritates you to lose a few mph in the name of saving fuel, by all means drive in Performance Mode.
It confuses me to hear people advocate driving in Economy Mode only on flat ground, as there is not 1 percent difference in shift rpm between Performance and Economy modes on flat ground, except when accelerating from a stop if you use wide-open throttle.
Every time you start the motorhome, the transmission is in Performance Mode. This is the default setting. If you push the mode button, it goes to Economy Mode and the light illuminates.
There is no absolute number that can be given to illustrate the difference in fuel economy that will result when driving in Economy Mode. On flat ground where you will be in sixth gear no matter what mode you are in, there will be zero difference. The most significant difference in mileage will occur in rolling hills, where in Performance Mode, particularly if on cruise control, you will start up a hill in sixth gear, go to wide-open throttle in that gear, and downshift to fifth gear still at wide-open throttle, where it is using a lot more fuel. After the hill is crested, the transmission will upshift to sixth, then likely coast a little in that gear unless you are driving with the exhaust brake on. If you are, the exhaust brake will be applied and the transmission will downshift toward the preselected gear, which is generally either second gear or fourth gear. And so the process will continue, with the transmission shifting up to sixth gear on the downhill, back down to fifth gear on the uphill, etc. The problem with this is that a modern turbocharged diesel engine is much more efficient at low rpm with high throttle settings.
Note: In either mode, you are free to use the up and down arrows to proactively choose the correct gear. You cannot screw anything up, even if you downshift to first gear at 70 mph. The transmission circuitry understands that you want to downshift to the next lower gear as soon as the engine rpm will not exceed the preset amount. Then it will downshift again when safe.
By the same token, you can shift between Performance and Economy modes as often as you want with the transmission in any gear when you make the change.
I drive in Economy Mode 99 percent of the time, including in the mountains. I use the up and down shifting arrows to choose the proper gear. I use Performance Mode only to pass another vehicle on a two-lane road, when I am willing to sacrifice a little fuel economy to gain a short-term burst of speed.
Flite2010 I looked at the chart without looking to see whose post it was.
Looking at the10 mpg and the previous 300+ mile 11.8 stretch I thought wow that's like mine.
But at low to mid 60's mph versus 69-70....
Wonder if the ism done the same way as us will get similar numbers?
Bob,
I can't see why an ISM would not see an improvement.
My mileage is based on real driving conditions. At the end of the trip everything is considered such as traffic, road work mountains, idling, etc. I like to roll an entire trip into a single average. The current trip I am on has seen a daily range from 8.5 to 12.5 mpg. The 11.8 mpg was a day trip, all highway.
Bob
I think the only way to really state MPG is for the last year or five years or the life of the coach. We had a 700 mile run from Denver to HWH in Iowa @ 11.5 mpg. Basically downhill all the way with a good tail wind. Nice for bragging but the 7 mpg days balance it out. Everything has an impact on MPG especially the driver and where you drive. This year, almost 11,000 miles, lots of mountains, just at 8 MPG. I am fine with that.
Any way you slice it, these are good numbers, doubt that my 8.3 does much better. What year did the ISM start going in the 320's? That's the red top, right?
My '99 has it, I don't know about '98
M11 was 95-99. ISM 99 on up?
Different injection system and variable turbo on ISM.
Bottom of both engines are similar or the same as far as I can find.
Bigger engine spinning slower can get better mpg than the reverse.
Sorry to be so slow replying. The last 2-3 weeks have been busy!
We tow at 65 mph, which is the limit for our toad (2012 Ford Edge). To pass, I'll exceed that, but don't run sustained miles at 70+ any longer.
I have mileage envy. Bob, think the ism's went to variable turbos in 04, mine is standard without wastegate.
But I am 39300 lbs without toad and dw thinks I drive too fast.
Hdff,
Here you go.
John M.
Nice presentation — well done!
Jcus i lost my hydraulic pdf showing a controllers ramp up in speed versus temps.
Universal chart showed idle speed to 185 degrees then a ramp up to full speed at 199F.
The one Foretravel speced was idle at 165 and full high speed at 180.
50-60 hp draw on full speed. 20 at Idle.
If you have the same valve in your radiator piping with two hoses running to it you probably have the 180 unit.
It's so far off I wonder how Foretravel ended up with it?
My coaches temp seems unchanged after the fan controller change.
Versus Foretravels radiator was too small so they turned the fan on high on purpose.
Does not seem to be an issue as filte2010 and I have tested these hard in the desert under load at high speeds up grades in the summer.
Only difference was more power and better mpg by far.
Did change to a blue tech Donaldson and a resonator