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Topic: ISM450 Fuel Mileage (Read 3054 times) previous topic - next topic

Re: ISM450 Fuel Mileage

Reply #25 –
We travel @ 60-65 mph
Our overall weight is 36320
The screen shot highlighted area is current trip from New Hampshire to Colorado
The selected media item is not currently available.Bob & Faith Rozek
1997 U320 40'
Xtreme Remodel
2010 Scion XD

Re: ISM450 Fuel Mileage

Reply #26 –
Quote from: DavidS –
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)
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.

Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: ISM450 Fuel Mileage

Reply #27 –
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?
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: ISM450 Fuel Mileage

Reply #28 –
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
The selected media item is not currently available.Bob & Faith Rozek
1997 U320 40'
Xtreme Remodel
2010 Scion XD

Re: ISM450 Fuel Mileage

Reply #29 –
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.
Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: ISM450 Fuel Mileage

Reply #30 –
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? 
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS

Re: ISM450 Fuel Mileage

Reply #31 –
Quote from: Chuck Pearson –
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
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: ISM450 Fuel Mileage

Reply #32 –
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.

"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4

Re: ISM450 Fuel Mileage

Reply #33 –
Quote from: Caflashbob –
Good info,  what speed do you try to tow at?  Sounds like low 60's?
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. 
The selected media item is not currently available.Richard & Susan Peck
____________________
1999 40' U320 "Bob Patrick"
(2000 4010 U320 WTFE Floor Plan, Single Slide)
Build #5567  |  MC #17522

Re: ISM450 Fuel Mileage

Reply #34 –
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.
Jim C.
coachfree, previous 1997, 1999, 2000, and 2003 Foretravels.

Re: ISM450 Fuel Mileage

Reply #35 –
Hdff,
Here you go.
John M.
John & Carm Morales

"We travel not to go anywhere, but to just go.  We travel for travel's sake.  Our great desire is to move."
 

Re: ISM450 Fuel Mileage

Reply #37 –
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
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4