ISM450 Fuel Mileage

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ISM450 Fuel Mileage

October 07, 2016, 03:49:25 pm

'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

Re: ISM450 Fuel Mileage

Reply #1 – October 07, 2016, 06:42:00 pm

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.

Re: ISM450 Fuel Mileage

Reply #2 – October 07, 2016, 07:21:52 pm

Quote from: Caflashbob – October 07, 2016, 06:42:00 pm

Did you seem to notice the power/mpg increase during the driving after the resonator?

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

Re: ISM450 Fuel Mileage

Reply #3 – October 07, 2016, 08:04:24 pm

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.

Re: ISM450 Fuel Mileage

Reply #4 – October 07, 2016, 08:55:05 pm

Same with me. Like the torque pull versus the downshift and rev up formerly

Re: ISM450 Fuel Mileage

Reply #5 – October 07, 2016, 09:46:41 pm

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.

Re: ISM450 Fuel Mileage

Reply #6 – October 09, 2016, 01:00:41 pm

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.

Re: ISM450 Fuel Mileage

Reply #7 – October 09, 2016, 01:37:08 pm

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.

Re: ISM450 Fuel Mileage

Reply #8 – October 09, 2016, 01:55:53 pm

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.

Re: ISM450 Fuel Mileage

Reply #9 – October 09, 2016, 02:37:06 pm

Quote from: wolfe10 – October 09, 2016, 01:55:53 pm

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.

Re: ISM450 Fuel Mileage

Reply #10 – October 09, 2016, 03:33:09 pm

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.

Re: ISM450 Fuel Mileage

Reply #11 – October 10, 2016, 01:22:15 pm

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.

Re: ISM450 Fuel Mileage

Reply #12 – October 10, 2016, 01:47:02 pm

Quote from: speedbird1 – October 10, 2016, 01:22:15 pm

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

Re: ISM450 Fuel Mileage

Reply #13 – October 10, 2016, 02:10:16 pm

Mine was due at 120,000, which was performed by Bernd. He advocates for more often

Re: ISM450 Fuel Mileage

Reply #14 – October 10, 2016, 03:25:31 pm

Speeds used when towing would be helpful in the mpg quoted.

Re: ISM450 Fuel Mileage

Reply #15 – October 10, 2016, 04:10:45 pm

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.

Re: ISM450 Fuel Mileage

Reply #16 – September 26, 2017, 03:26:34 pm

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), 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

Re: ISM450 Fuel Mileage

Reply #17 – September 27, 2017, 10:01:35 pm

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)

Toad is roughly 4,400

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. :-)

Re: ISM450 Fuel Mileage

Reply #18 – September 28, 2017, 12:36:25 am

Good info, what speed do you try to tow at? Sounds like low 60's?

Re: ISM450 Fuel Mileage

Reply #19 – September 28, 2017, 12:56:12 am

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.

Re: ISM450 Fuel Mileage

Reply #20 – September 28, 2017, 12:55:18 pm

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.

Re: ISM450 Fuel Mileage

Reply #21 – September 28, 2017, 04:13:52 pm

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.

Re: ISM450 Fuel Mileage

Reply #22 – September 28, 2017, 04:34:12 pm

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.

Re: ISM450 Fuel Mileage

Reply #23 – September 30, 2017, 09:29:20 pm

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?

Re: ISM450 Fuel Mileage

Reply #24 – September 30, 2017, 09:39:15 pm

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)

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