MPG increase of 15%+

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MPG increase of 15%+

August 19, 2011, 08:13:28 am

Since we have had Ruby, we have averaged about 6 1/2 mpg. On our last trip from Chicago to Northern Michigan, approximately 700 miles, I heeded some advice I read on the forum and on this trip, as much as possible, I drove focusing on the tach, not the speedo. I always tried to keep engine RPM between 1200 and 1400 regardless of speed. I reset the silverleaf before this trip, and upon returning home it indicated 7.7 mpg. My question is - can the transmission be reprogramed to widen the shift points to make driving easier? The way it is now, 62 mph is approximately 1350 rpm, but 59 mph is over 1500. Perhaps with transmission reprogramming, I can hit 8. Are these figures similar to what others are realizing? At $4.00 per gal, it pays to save.

GregoryS
2003 Designer towing 04 Lexus RX 330

Re: MPG increase of 15%+

Reply #1 – August 19, 2011, 08:19:55 am

Gregory,

Very similar situation in our coach.

However, don't make any early assumption based on one trip of 700 miles. There are other factors that can control the spread between 6.5 and 7.7 mpg -- or higher.
We have been known to get 8 and slightly higher on flat ground with no winds in the Economy Mode.

Re: MPG increase of 15%+

Reply #2 – August 19, 2011, 08:38:30 am

Quote from: GregoryS – August 19, 2011, 08:13:28 am

Since we have had Ruby, we have averaged about 6 1/2 mpg. On our last trip from Chicago to Northern Michigan, approximately 700 miles, I heeded some advice I read on the forum and on this trip, as much as possible, I drove focusing on the tach, not the speedo. I always tried to keep engine RPM between 1200 and 1400 regardless of speed. I reset the silverleaf before this trip, and upon returning home it indicated 7.7 mpg. My question is - Are these figures similar to what others are realizing? At $4.00 per gal, it pays to save.

GregoryS
2003 Designer towing 04 Lexus RX 330

Greg,
We have same year coach.
I average 7.3 mpg over 125,000 miles.
Better on some trips but avg 7.3 over life of coach.
I do not think it will ever get any better, traveling the mountains of the west coast.
I have put trip odometers starting when I get on the freeway and one that starts when leaving the RV park. That short drive from the RV park to the freeway kills my average for that leg.
62 mph seems to be worse mpg & 66 mph seems to be better mpg.
Here are some mpg on different legs of my trips.
June 22 2008 RV Trip

June 18 2009 RV Trip

Re: MPG increase of 15%+

Reply #3 – August 19, 2011, 08:52:31 am

Agree with other posts, checking MPG on anything less than a few thousand mile trip is reasonably meaningless. A 2% slope of the pavement at a pump really affects amount of fuel you can put in the tank. Also, tail/head winds, mountains/flat, ambient temperature, etc are all factors reasonably beyond your control.

Can the Allison ECM be re-programmed to lower shift points. Simple answer is YES. Real answer is you need to do some careful checking before doing it. Record the lowers RPM in each gear when accelerating at light throttle. Also record highest RPM in each gear before the upshift. The shift points can be lowered, I believe in 100 RPM increments-- it affects all gears/shifts. This lowers the max RPM in each gear. But, it is quite likely that lowering shift points 100 RPM's will put the engine BELOW PEAK TORQUE RPM in the next higher gear. NOT GOOD. If you are a VERY attentive driver you can do this, but you sure don't want to get in a situation where you are operating the engine below peak torque RPM under heavy load. And lowering the shift points and putting it in "D" could easily cause this to happen.

Brett

Re: MPG increase of 15%+

Reply #4 – August 19, 2011, 09:35:30 am

Total miles - 22,479 = 9.6 MPG avg.
Just return from Upper Peninsula - Total Miles - 1792 = 11 MPG
Avg. cost of fuel = $3.94
Driving speed approx. 58 MPH

Re: MPG increase of 15%+

Reply #5 – August 19, 2011, 12:04:12 pm

Earlier this year we went East to West on the UP and just for the heck of it drove at 40mph. Got 14mpg according to VMS 240 CL. Of course this is only possible because of the low traffic and the ease others could pass us on a 2 lane road - and the lack of a head wind (as near as I could tell we did not have a tail wind)

It's kind of interesting to see how mpg varies based on gear, mph and rpm. I can get in 6th gear and stay there (except for an occasional hill) at 62mph (1350rpm or so) and can pretty much stay in 6th by dialing down cruise control as far as 60mph (1300rpm or so).

At the beginning of this Summer's cross-country trip I decided to try and get the same $/mile as last year's. It's not hard if you are OK with living in 5th gear and slow down - as illustrated by the posting below.

Since we work hard at not being in a hurry and stop as often as we need to exercise our legs to do something every day aimed at avoiding a second blood clot hospital stay experience, going slower is not a big deal with us. (At rest stops we'll typically walk its length back and forth, twice.)

The way we look at it is we all have the same destination in the end. It's the journey that's interesting and we experience more of it by slowing down.

1999 40ft U320 towing Honda Element

best, paul

Quote

Total miles - 22,479 = 9.6 MPG
Just return from Upper Peninsula - Total Miles - 1792 = 11 MPG
Driving speed approx. 58 MPH

Re: MPG increase of 15%+

Reply #6 – August 19, 2011, 12:23:19 pm

Previous MPG anecdotes and suggestions are also discussed here:

MPG

Re: MPG increase of 15%+

Reply #7 – August 19, 2011, 12:39:57 pm

It sure would be nice to be able to coast along in 4th just a little slower than 48 mph. A lot of times we are sightseeing where we are not loading the engine but 3rd is really annoying. Have spent thousands of miles with a Detroit 2-cycle and a 5 speed manual so figure I can decide when to shift down and when not to.

We tried the downhill run to San Francisco from our house at 2000 feet, about 140 miles. At just over 50 mph in 4th, we could get 13 mpg with a slight tailwind. Heading to campgrounds here in the mountains, we get in the 5 mpg range.

Sorry, but just another reason to hate automatics along with their excess weight, premium diet for ATF, relative inefficiency and the devil that lives inside all of them.

Re: MPG increase of 15%+

Reply #8 – August 19, 2011, 03:27:03 pm

Pierce, 48 MPH is where your MODE button comes in handy, with MODE ON tranny will wait to downshift later than in regular mode. I sometimes do this in heavy traffic, engage mode, downshift to 4th or even 3rd and let tranny do the work.
Gary B

Re: MPG increase of 15%+

Reply #9 – August 19, 2011, 03:57:15 pm

Quote from: Gary Bouland – August 19, 2011, 03:27:03 pm

Pierce, 48 MPH is where your MODE button comes in handy, with MODE ON tranny will wait to downshift later than in regular mode. I sometimes do this in heavy traffic, engage mode, downshift to 4th or even 3rd and let tranny do the work.
Gary B

Hi Gary,

Where is your mode button? On my selector panel I have spots for 8 push buttons but the top two on the right side are blanked out. Perhaps is something your later coach has? Sure would like to have something like that. On the other hand, it would not be the first time I missed something. I must have a dozen glasses but never can find a pair when I want to read something.

I case I don't have one, wonder if a switch could be fitted?

Pierce

Re: MPG increase of 15%+

Reply #10 – August 19, 2011, 03:59:22 pm

Gary,

Forgot to ask if you have a 4 or 6 speed in your U280?

Re: MPG increase of 15%+

Reply #11 – August 19, 2011, 05:08:45 pm

Pierce, Mine is a 3060R, 6 speed with retarder. Mode Button is marked and is to right of panel. I'll see if I can find a photo.
Gary B

Re: MPG increase of 15%+

Reply #12 – August 19, 2011, 05:12:01 pm

Pierce, Follow this link.
www.rvtechstop.com/articles/allson2.pdf
If yours is not a six speed this will probably not be of any help.
Gary B

Re: MPG increase of 15%+

Reply #13 – August 19, 2011, 05:33:51 pm

Gary,

Another dream dashed. 4 speed here but thanks, good reading for those with the six speed.

Re: MPG increase of 15%+

Reply #14 – August 19, 2011, 06:12:04 pm

For those with the Allison 6 speed 3000 or 4000 series from an article I wrote a long time ago:

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 RECOMMENDATION 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 thermostatically controlled temperature, if 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 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.

Brett

Re: MPG increase of 15%+

Reply #15 – August 19, 2011, 06:31:17 pm

Brett,

Excellent post, real world conditions well explained in everyday language. I just need the 6 speed now. My 4 speed hunts so much on long grades it must be a NRA member. I just punch in third and sit back and relax until reaching the top.

Re: MPG increase of 15%+

Reply #16 – August 19, 2011, 07:01:12 pm

Quote from: Pierce & Gaylie Stewart – August 19, 2011, 06:31:17 pm

Brett,

Excellent post, real world conditions well explained in everyday language. I just need the 6 speed now. My 4 speed hunts so much on long grades it must be a NRA member. I just punch in third and sit back and relax until reaching the top.

Right answer. Hunting between gears is really hard on any transmission.

Brett

Re: MPG increase of 15%+

Reply #17 – August 19, 2011, 10:23:20 pm

Lately I have been driving alone. Out of boredom I have started a new game. I crank the rearview mirror down a bit so that I can see the exhaust. I watch for black smoke.... My thinking is black smoke means unburned fuel, or incomplete fuel. Is that correct. Driving with a softer pedal seems to make no difference in time as I go from one unsechronized (sp?) stoplight to another in towns and cities such as Santa Fe and Taos. It may not be saving me fuel but I don't get as irritated at other drivers. andy1

Great note Brett....

Re: MPG increase of 15%+

Reply #18 – August 19, 2011, 11:20:12 pm

Quote from: Lewis Anderson – August 19, 2011, 10:23:20 pm

Lately I have been driving alone. Out of boredom I have started a new game. I crank the rearview mirror down a bit so that I can see the exhaust. I watch for black smoke.... My thinking is black smoke means unburned fuel, or incomplete fuel. Is that correct. Driving with a softer pedal seems to make no difference in time as I go from one unsechronized (sp?) stoplight to another in towns and cities such as Santa Fe and Taos. It may not be saving me fuel but I don't get as irritated at other drivers. andy1

Great note Brett....

Yes, at high altitude, even with computer controls, you can get a bit of black smoke. Usually an indication of more fuel than the engine can burn. This produces the particulates the EPA complains about. You can see this in a lot of pickups that have been "chipped". Gives diesels a really bad name. With the mechanical engines, heading up a grade, we had to back out of the throttle until the black smoke cut way back so always kept an eye in the mirror. Black smoke can also come from dirty injectors that are not breaking the fuel up into fine enough droplets. Our old engines had about 3000 psi at the injector but the new electronic injection engines can have 30,000 psi at the injectors. Instead of a spray, these put out more of a fog with much finer droplets that are much more completely burned. The new systems also can time the injection over several degrees lowering emissions and cutting the diesel "knock" way down. That's why the new Cummins 5.9s make only about 20% of the noise compared to the original PUs.

At 7700', any engine, turbo (unless wastegated) or normally aspirated will only produce 75% of the horsepower they produce at sea level. Thinner air means less oxygen molecules in a given space and also lower temperature from compression heating in the combustion chamber to burn (explode) the fuel. Especially true coming off a stop sign when the turbo has not "spooled up" yet. Manual transmission vehicles usually give a pretty good puff coming off the line at high altitude while the torque converter in automatics allows the engine to increase RPM quicker with less "turbo lag" resulting in less smoke.

Re: MPG increase of 15%+

Reply #19 – August 20, 2011, 07:36:05 am

Brett, I had a "Bluebird" with a 3208 Cat engine w/ a Allison 4 speed before I got my Foretravel. That unit had a "Mode" switch for the transmission similar to the one being described for the 6 speed. Do you know if something like that could be retrofitted into the Foretravel system?

or anyone out there have that information?

Re: MPG increase of 15%+

Reply #20 – August 20, 2011, 09:09:34 am

Gerry,

Sorry, I don't know. Might give Allison a call on Monday with your transmission model and serial number:

Allison help line 800 252 5283

Brett

Re: MPG increase of 15%+

Reply #21 – August 23, 2011, 01:55:31 am

Fascinating subject. On a recent trip a FT owner-friend told me about this mode button that I have not noticed or used. He thought it very good for mountains. I called my FT dealer and was told it best to not use the economy mode. First reason, it no different of flat/level terrain. Second reason was something to the effect that it would teach the transmission (I do not know how it does this) a different driving style and in time cause hard shifts. I do not understand that. But I will add this. On some fairly steep and long grades, if I had the coach in the regular mode and cruise, at about 62 mph it did not down shift and the rpm stayed right at 1500. If however I had the speed around 55, then for some reason if would frequently drop down a gear. Hmmm. And, when I leave the house I have a neighborhood small hill. At times going up that small hill slowly, in a neighborhood, it will make a hard, jerking, sort of downshift to boost the rpm. I do not like that but perhaps it is not harmful. The way to avoid that is a slightly faster speed but I do not like that in neighborhood. Thanks for this topic. Mike

Re: MPG increase of 15%+

Reply #22 – August 23, 2011, 04:46:09 am

Nutravlr, I also had been advised the same story by a respected source, had to do with the teaching the computer new and unwanted happenings. Have not used the Econ mode since and I get good mpg. MPG is still the result of your right foot.
Everyone has an opinion, me too.
Cheers

Re: MPG increase of 15%+

Reply #23 – August 23, 2011, 08:34:27 am

Mike, I learn something everyday. In my neighborhood I have to slow to make a right turn up a slope and if I am not careful to keep my speed up to stay in 2nd It will make a harsh downshift into 1st. The first time it did it I thought that I had probably torn out the driveshaft. I would never have equated it with the LEARN feature of the Allison in MODE. I'll have to change my habits for a while and see what happens.
Gary B

Re: MPG increase of 15%+

Reply #24 – August 23, 2011, 09:27:07 am

Quote from: Gary Bouland – August 23, 2011, 08:34:27 am

... In my neighborhood I have to slow to make a right turn up a slope and if I am not careful to keep my speed up to stay in 2nd It will make a harsh downshift into 1st. ...
Gary B

Our coach often shudders on a downshift while making an uphill right hand turn. There is a specific turn into a local city park that evokes a less than smooth downshift. I experience the shudder other times as well, but it is very predictable there. My solution has been to slow a bit more and go very easy on the throttle. If I do that, the transmission will make a smoother shift to first. I have just assumed that it was the nature of the beast in those conditions.

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