Author Topic: ALLISON MODE BUTTON  (Read 15747 times)

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Offline Brett Wolfe

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ALLISON MODE BUTTON
« on: September 23, 2011, 06:30:46 AM »
ALLISON MODE BUTTON

There are TWO TOTALLY DIFFERENT "LET THE TRANSMISSION CHOOSE THE CORRECT GEAR" MODES/PROGRAMS in the Allison ECU which is the "electronic brain" controlling shifting and other functions.

In ECONOMY MODE, the transmission will not downshift even at WOT (Wide Open Throttle) until the engine pulls down to peak torque RPM in some application and 200 RPM lower that "regular mode" in others.

In REGULAR 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 difference (except accelerating from a stop IF you are at or close to wide open throttle).

It can make a BIG difference in rolling hills. If you are in rolling hills and regular mode (particularly with the cruise control on), it is common for the transmission to shift down to 5th on the uphill and back to 6th on the downhill. Repeat this process hundreds of times. In economy mode, you will stay in 6th gear unless the hill is so steep or so long that the engine can not pull it without dropping below peak torque RPM. If you can pull a hill in a higher gear (lower engine RPM) AND the engine does not overheat, THAT IS WHAT ALL ENGINE MANUFACTURERS RECOMMEND FOR THE MOST ECONOMICAL WAY TO CLIMB A HILL with a modern turbo, after-cooled diesel engine.

If you know you will need a lower gear because of the steepness of the grade and/or are engine temperature is rising higher than the thermostatically controlled temperature, while driving in economy mode, 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 (or shift up) when past the steep section, or agree to pump extra fuel at the next fill-up.

IF your engine begins to overheat, your HP/weight ratio is low OR if it irritates you to loose a few mph on a hill in the name of saving fuel, in the hills, by all means drive in regular mode.

It confuses me to hear people advocate driving in economy mode only on flat ground, as there is not 1% difference in shift RPM's between regular and economy mode on flat ground, excepting accelerating from a stop if you use WOT.

Every time you start the coach, the transmission is in regular 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" on how much difference in fuel economy driving in economy mode will have. On flat ground where you will be in 6th gear irrespective of what mode you are in, there will be ZERO difference. The MOST difference in mileage will be in rolling hills, where in regular mode, particularly if on cruise control you will start up a hill in 6th gear, go to WOT in 6th gear, downshift of 5th gear still at WOT (WHERE IT IS USING A LOT MORE FUEL). After the hill is crested, the transmission will up-shift to 6th, then likely coast a little in 6th gear (unless you are driving with the exhaust brake on-- if you are it then applies the exhaust brake AND downshifts TOWARD the pre-select gear which is generally either 2nd or 4th).And so on 6-5-6-5-6-5-6-5.......

A modern turbo inter-cooled diesel is much more efficient at low RPM high throttle settings.

Note: In either mode, you are free (and welcome) to use the up and down arrows to PRO-ACTIVELY choose the correct gear. You can not screw anything up-- even if you down-arrow to 1st gear at 70mph, the transmission understands that you meant "please downshift to the next lower gear as soon as the engine RPM will not exceed the pre-set amount. Then downshift again when safe....."

By the same token, you can shift between regular and economy mode as often as you want with the transmission in any gear when you make the change.

OPINION: I drive in economy mode 99% of the time, including in REAL mountains, but use the up and down arrows to choose the proper gear. I use regular mode ONLY when I am willing to say, "I am willing to throw a lot of fuel away to gain a little performance." When passing on 2 lane roads, THIS IS the case.
« Last Edit: November 15, 2011, 08:05:51 AM by Brett Wolfe »

Offline LyleFikse

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Re: ALLISON MODE BUTTON
« Reply #1 on: March 07, 2012, 07:02:12 PM »
Thank You, Thank You.  This advice alone has paid my Chapter Fee for several years.  We were just returning to Iowa from Southern Calif when I read this information.  We have a C7 350 in a 40 foot 2007 Damon Tuscany.  I had asked in the regular forum about a chip to increase mileage.  No more.  Slowing down to 55-57 mph from 65 mph and using the economy mode on the Allison have improved our mileage from 7.5 to around 10 mph.  (Thats like 200+ free miles per tank.)  One tank was almost 10.6 until we ran into a head wind.  As a new RV driver this information really helps.  Brett, you're great.
Lyle Fikse
2007 Damon Tuscany  Cat C-7
2013 Lincoln MKS

Offline Tom Bernardi

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Re: ALLISON MODE BUTTON
« Reply #2 on: March 07, 2012, 08:02:34 PM »
Lyle,

Unless you drive two lane hilly roads, chances are real good that most of that savings came from dropping your average speed to 55-57. I experience the same thing when I consistently lay off the pedal in the right hand lane. Keeping it in the economy mode certainly helps, and I do that also.

You will also be happy to know that you will also experience better tire tread life - according to the Goodyear RV tire guide you experience a 15% penalty when you drive at 65 compared to 55.

Safe travels,
Tom

Tom (and Sally & Valentine) Bernardi '07 National RV TropiCal LX 35'/Freightliner/350HP CAT/'06 Honda CRV Our travelogues and life at www.bernardihome.com, no Google ads, no books to sell, just fun stuff!
Tom
2017 Newmar Dutch Star 4054 / Freightliner 450HP Cummins ISL / Blue Ox Avail / '17 Jeep Wrangler Sahara / Brake Buddy /
Silverleaf VMSpc w/Pressure Pro TPMS

Offline Doug Bohman

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Re: ALLISON MODE BUTTON
« Reply #3 on: March 08, 2012, 11:59:13 AM »
A modern turbo inter-cooled diesel is much more efficient at low RPM high throttle settings.

Brett, not sure I understand this sentence. Low RPM and High Trottle seem contradictory.

Thanks.

Offline Brett Wolfe

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Re: ALLISON MODE BUTTON
« Reply #4 on: March 08, 2012, 01:54:42 PM »
A modern turbo inter-cooled diesel is much more efficient at low RPM high throttle settings.

Brett, not sure I understand this sentence. Low RPM and High Trottle seem contradictory.

Thanks.

Doug,

YES, a modern turbo inter-cooled diesel is more efficient at low RPM high throttle settings than high RPM, lighter throttle settings. The statement is correct.

So if you have a choice of producing XX HP to climb a grade and can do it in 6th gear in economy mode at WOT (Wide Open Throttle), that is more efficient than gearing down to 5th gear (power mode or down arrow) and running at higher RPM at lighter throttle settings.

Said another way, there are more HP/gal produced at low RPM's than high. Just more efficient-- less friction loss. If you look at the amount of energy needed to just move the pistons up and down at higher RPM's it is significant.  Heck, try to turn one of these engines over by hand!  Then consider the amount needed to do, say 1,440 RPM and then look at it again at 2,300 RPM. 

You will hear 18 wheelers pulling grades at these lower RPM with the throttle on the floor for mile after mile-- just above peak torque RPM if they are buying their own fuel for the same reason.  This AIN'T a Detroit Diesel 2 stroke!  Same goes for Caterpillar, Cummins, Detroit Diesel 4 stroke engines such as the Series 60, etc.

Lugging (running at peak torque RPM at high throttle positions is JUST FINE for these modern engines and is what each of the engine manufacturers recommends in writing for most economic operation.  And yes, this would KILL an old Detroit Diesel 2 stroke.  But that "tribal knowledge" went out more than two decades ago.

Offline kenbuck2

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Re: ALLISON MODE BUTTON
« Reply #5 on: March 09, 2012, 07:25:09 AM »
That tribal knowledge (great phrase I haven't heard before) is still alive on many MH forums. There are those who will argue for days that high rpm is "better" for the engine. Often cooling is thown in to confuse the issue, with the "gear down and raise the rpm for best efficiency and cooling" advice. High rpm might be good for direct drive cooling, but not efficiency and with hydraulic fans I'm not sure that makes any sense at all.

My C9 engine booklet says in no fewer than 4 places that low rpm is the most efficient. I do have the argument in my head every now and again. When I started driving diesels 33 years ago, the Cummins 210 was to be kept between 1700 and 2100 rpm, and never lugged. Back then I had a choice of 20 forward and 4 reverse gears to use.
Ken Buck
2007 Beaver, C-9 Cat, Allison 3000MH

Offline Doug Bohman

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Re: ALLISON MODE BUTTON
« Reply #6 on: March 09, 2012, 11:34:14 AM »
Thanks for the explanation Brett. Now I understand your original sentence. I think another way of stating this is to simply use the highest gear (6) possible when climbing hills and downshift (using the down arrow) only when necessary?

I guess your sentence just did not click with me when first read. Now it makes obvious sense.

Offline Dieselguy

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Re: ALLISON MODE BUTTON
« Reply #7 on: March 12, 2012, 11:32:00 PM »
Hello I am new member just bought a Beaver Patroit Thunder with a 525 HP Cat and being a 35 year Detroit Diesel Mechanic you are so right on, loved them old 2 cycles but as we age I know  the greatness of a 4 stroker torque torque torque. There was a old saying with the old 2 cycles was slam you hand in the door be4 you drove a detroit  cause now your mad lol.Cause you couldn't lug them Detroits the four cycles are great at the bottom end just like like you explained was a very good topic explained very well.

Offline jbrosecity

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Re: ALLISON MODE BUTTON
« Reply #8 on: December 08, 2012, 04:28:34 PM »
pardon me if this is off topic but I didn't see a similar topic for the Caterpillar CX-28 Transmission mode button.  I am wondering if it works on the same principle, toggling on/off economy mode?   It doesn't tell me anything about it in the country coach manual... I am going to have to go digging in the supplied Caterpillar manual, but thought I might just get a quick yes or no here.  I attached a screenshot of the shifter keypad from the manual
Joseph Burkle
2008 Country Coach Inspire 360 43' Founders Edition
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Offline Warren Hoye

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Re: ALLISON MODE BUTTON
« Reply #9 on: January 23, 2013, 07:04:09 AM »
Brett
I am new to the club & diesel pusher operation as well. This information is very usefull and answers many of the questions I have about my CAT 330HP diesel engine and Allison 3000 transmission operation You have my thanks!

Warren Hoye

Offline LJ2654

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Re: ALLISON MODE BUTTON
« Reply #10 on: January 24, 2013, 06:27:44 AM »
Kudo's to Brett for the great explanation as how to properly use the Allison economy mode and regular mode.

Since I bought my Beaver Contessa a year ago I have played with the buttons to see what seemed like the best way.

Now I know what to do to get the mileage that is the best for this Cat 3126B....thank you for explaining it in laymans terms....

Offline djnosnow

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Re: ALLISON MODE BUTTON
« Reply #11 on: February 09, 2013, 03:22:33 PM »
I hope I'm not off line on this topic, BUT.. the documentation in my motor home equipment list shows my transmission as an Allison MD3000HH.  I am interested in getting it reprogrammed (and I am wondering who might be able to do this for me?)  My thoughts are to: drop the shift points down 200 rpms and change the ECON mode to become the default.  What with most western freeways having 65 mph and up for a motor home pulling a trailer or toad, except for CA & OR, I seem to get the better mileage around 62MPH trying to keep below 1700 rpm.  Problem is the very sight grades and rolling hills usually cause the downshifting to 5th.  And, to stay near the CA and OR speed limits, I am almost always in 5th.  I would prefer 6th.
Thanks for any help    PS: my engine numbers read: DFE/3126  330hp
Tony Monson

Offline Brett Wolfe

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Re: ALLISON MODE BUTTON
« Reply #12 on: February 09, 2013, 05:18:32 PM »
Tony,

Any Allison dealer can re-program your ECM.

Changes I would make (not necessarily what I would recommend for everyone):

Default to economy.
5th gear pre-select for engine brake.

Before considering dropping 100 or 200 RPM for the shift points, you need to look at the minimum RPM in each gear.  NOT a good idea to allow any diesel engine to run at below peak torque RPM (1440 RPM for your engine).

Brett

Offline djnosnow

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Re: ALLISON MODE BUTTON
« Reply #13 on: August 20, 2013, 08:08:59 AM »
Brett
sorry for getting back so late,
Please explain you comment on 5th gear pre-select for engine brake.  Just how does this affect the shifting point?
Tony

Offline Brett Wolfe

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Re: ALLISON MODE BUTTON
« Reply #14 on: August 20, 2013, 09:26:49 AM »
Tony,

The pre-select gear for the engine brake is the gear towards which the transmission downshifts when the engine brake is applied.  With a 5th gear pre-select, when the engine brake is activated (switch on and throttle closed) it will downshift to 5th. It will not downshift further at high RPM-- it will only downshift at "regular" or non- engine brake RPM.  To select a lower gear you must use the down arrow. If a lower pre-select gear is programmed, the transmission will continue to downshift towards that gear as soon as it will not over-speed the engine in that next lower gear.

As stated earlier, the best pre-select gear for coming to a stop is 2nd.  The pre-select gear that gives you, the driver, the most control in terms of mountain driving is 5th.  If you are a "put it in drive and go" driver, a lower pre-select gear is probably better.  If you don't mind manually determining gear selection, a higher pre-select gear is probably better.

Bret

Offline Five

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Re: ALLISON MODE BUTTON
« Reply #15 on: December 30, 2013, 01:27:11 PM »
A modern turbo inter-cooled diesel is much more efficient at low RPM high throttle settings.

Brett, not sure I understand this sentence. Low RPM and High Trottle seem contradictory.

Thanks.

Doug,

YES, a modern turbo inter-cooled diesel is more efficient at low RPM high throttle settings than high RPM, lighter throttle settings. The statement is correct.

So if you have a choice of producing XX HP to climb a grade and can do it in 6th gear in economy mode at WOT (Wide Open Throttle), that is more efficient than gearing down to 5th gear (power mode or down arrow) and running at higher RPM at lighter throttle settings.

Said another way, there are more HP/gal produced at low RPM's than high. Just more efficient-- less friction loss. If you look at the amount of energy needed to just move the pistons up and down at higher RPM's it is significant.  Heck, try to turn one of these engines over by hand!  Then consider the amount needed to do, say 1,440 RPM and then look at it again at 2,300 RPM. 

You will hear 18 wheelers pulling grades at these lower RPM with the throttle on the floor for mile after mile-- just above peak torque RPM if they are buying their own fuel for the same reason.  This AIN'T a Detroit Diesel 2 stroke!  Same goes for Caterpillar, Cummins, Detroit Diesel 4 stroke engines such as the Series 60, etc.

Lugging (running at peak torque RPM at high throttle positions is JUST FINE for these modern engines and is what each of the engine manufacturers recommends in writing for most economic operation.  And yes, this would KILL an old Detroit Diesel 2 stroke.  But that "tribal knowledge" went out more than two decades ago.

I was reviewing this thread and came across this statement regarding the most efficient way to operate a turbo diesel is at low RPM and a high throttle setting.  The only way I can envision this working is with the transmission in the manual mode.  If not in the manual mode it would upshift if at wide open throttle.  Is this thinking correct?
American Coach Allegiance
400 HP ISL, 3,000MH Allison
Spartan Chassis

Offline Brett Wolfe

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Re: ALLISON MODE BUTTON
« Reply #16 on: December 30, 2013, 03:35:44 PM »
Five,

I am not aware of any "manual" mode in the Allision.

What "Economy Mode" allows you to do is operate at lower RPM AND higher throttle positions without downshifting.  In fact, the only time economy mode makes a difference IS at higher throttle positions.  At lighter throttle positions, just like in your car, the transmission upshifts at low RPM and doesn't downshift unless you get on the throttle.  Economy mode just allows you to "get your foot into it" without downshifting as soon.

And, yes, both Caterpillar and Cummins both suggest this is the most fuel efficent way to climb a grade.  No question, if a few more MPH is important, run in a lower gear at higher RPM with more fuel consumption.

Offline Five

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Re: ALLISON MODE BUTTON
« Reply #17 on: December 31, 2013, 07:43:59 AM »
By "manual" I meant using the up/down arrows.  If you down shift using the arrows, will the transmission up shift automatically once it reaches the appropriate speed for the next gear?

So if I'm getting this right, the low RPM, high throttle setting is used in the Economy mode, and since it is in that mode, the transmission will not up shift as soon as it would in the normal mode.

I'm an old airplane/helicopter driver and have a difficult time grasping the low RPM/high throttle concept. ;D
American Coach Allegiance
400 HP ISL, 3,000MH Allison
Spartan Chassis

Offline Brett Wolfe

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Re: ALLISON MODE BUTTON
« Reply #18 on: December 31, 2013, 09:31:56 AM »
REPLY IN SOLID LETTER CAPS

By "manual" I meant using the up/down arrows.  If you down shift using the arrows, will the transmission up shift automatically once it reaches the appropriate speed for the next gear? YES AND NO.  THE DOWN ARROW WILL LOCK THE TRANSMISSION IN THE GEAR SELECTED, BUT BETWEEN THE ENGINE COMPUTER AND ALLISON COMPUTER, THEY WILL NOT ALLOW THE ENGINE TO OVER-SPEED.  IF ON FLAT GROUND, THE ENGINE COMPUTER WILL SHUT OFF FUEL AT GOVERNED RPM.  ON DOWNGRADE, THE ALLISON WILL UPSHIFT TO PREVENT OVER-SPEED.

So if I'm getting this right, the low RPM, high throttle setting is used in the Economy mode, and since it is in that mode, the transmission will not up shift as soon as it would in the normal mode. CORRECT

I'm an old airplane/helicopter driver and have a difficult time grasping the low RPM/high throttle concept. ACTUALLY, THIS IS NOTHING NEW.  GENERATING THE SAME HP WITH LESS FEET OF PISTON TRAVEL REDUCES HP LOSS TO FRICTION.  THIS IS ALSO TRUE WITH GASOLINE ENGINES. I CAN REMEMBER BACK IN THE 1980'S WHEN BMW INTRODUCED THE "e" SERIES VEHICLES.  THE OBJECTIVE WAS TO RUN LOW RPM/HIGH THROTTLE POSITION FOR BEST ECONOMY. ON A GASOLINE ENGINE THERE ARE TWO THINGS THAT COST FUEL AT HIGH RPM/LOW THROTTLE POSITIONS:  FRICTION AND THE WORK THE ENGINE HAS TO DO TO PULL PISTONS DOWN AGAINST THE VACUUM AT LIGHT THROTTLE POSITIONS.

THIS DOCUMENT FROM CATERPILLAR CORP COVERS A LOT OF THIS: http://forum.dieselrvclub.org/index.php/topic,6594.0.html 

BRETT

 ;D

Offline Five

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Re: ALLISON MODE BUTTON
« Reply #19 on: December 31, 2013, 12:28:03 PM »
Got it...thanks for your help.
American Coach Allegiance
400 HP ISL, 3,000MH Allison
Spartan Chassis

Offline JJT-NC

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Re: ALLISON MODE BUTTON
« Reply #20 on: January 29, 2018, 11:24:30 AM »
Great information in this topic. Now that I have the knowledge I just need to turn it into skill!  ;-)

I am a new motorhome owner (Cummins 6.7l ISB and Allison 3000).  I've been trying to use cruise control (and econ mode) on highways to optimize efficiency - with the thought that steady speed is the best policy.

I learned from this topic that manual oversight on downshifting is needed, especially on inclines.  Is it the experience of this team that managing these inclines is best done with cruise control set and manual gear selection if needed?   I guess I am wondering how well the cruise control programming works with the engine and transmission programs.

Thanks!

Offline Brett Wolfe

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Re: ALLISON MODE BUTTON
« Reply #21 on: January 29, 2018, 01:28:16 PM »
JJT-NC,

Welcome to the Diesel RV Club.

Not sure you won't get a wide variety of answers to the "cruise or no cruise on grades".

Here is my take on it:  I want to know what is happening when we get into long grades, so I take it off cruise.  That way, once I go to WOT (Wide Open Throttle) I know to keep an eye on coolant temperature and downshift (I do it with the down arrow, but others just let Mr Allison do it) as soon as temperature starts going above thermostatic control/or on most engines when coolant temperature reaches 200 degrees F.


But, I am more proactive than most-- heck, I still prefer a manual transmission if my cars.