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Author Topic: MPG doubled on manual over automatic???  (Read 3215 times)
ilyafish
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« on: June 21, 2009, 03:09:55 PM »

So I have been browsing around and seeing what is on the market right now, and alot of guys with coaches that have a manual transmission are claming they get roughly 10-11 mpg on a coach that gets roughly 5-6 mpg with an automatic.  I know if you drive it right, it makes a difference....but I have a hard time believing that it nearly doubles the fuel mileage.  If that is the case, I am in the market for a manual.  Just wanted everyones professional opinion as i originally thought this was a sales pitch but I see the same numbers coming up from different people selling their coach.

Also....if i find a coach i love but it is an automatic....what is the overhaul process we are talking about to make it a manual (and is it even worth it?)
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« Reply #1 on: June 21, 2009, 03:17:30 PM »

Hi Ilya,

I think the airplanes outside your hotel are stirring up pixy dust from Disney World and clowding up your mind.. Grin

Seriously, get some sleep! Didn't you just drive 22 hrs?  Cheesy Cheesy

Nick- LMAO
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« Reply #2 on: June 21, 2009, 03:22:55 PM »

Not going to happen with the same coach and engine driving the same speed you do lose 1 to 2 mpg with a automatic       good luck
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WEC4104
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« Reply #3 on: June 21, 2009, 03:25:14 PM »

Here's the hidden story behind the story... Many of the manual transmission coaches (mine included) are set up with their original engine configuration with quite modest horsepower figures.  The automatics tend to be either later models with bigger engines, or older coaches that had an engine swap performed along with the change to an automatic transmission. Also, because of the age situation, the manual transmissions tend to be in coaches having shorter length and less frontal height.  Not really an apples to apples comparison.

With the engine and coach factors the same, the manual transmissions do tend to yield higher fuel mileage, but not even close to doubling it.
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« Reply #4 on: June 21, 2009, 03:27:31 PM »

I have an auto and get 5.8 to 7.5 mostly 6.5 . I have two friends that I have traveled with , they have manuals. neither one gets very much better if any better. both wished they had automatics.
 FWIW, I say buy a bus for the condition it is in and priced in your range.
It all depends on how you drive it. I have got 8.2 doing 50 to 52mph. It was a trip when I had more time than money.    Hope you get what you want, Tom
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« Reply #5 on: June 21, 2009, 03:30:39 PM »

IM,

I haven't a clue on conversion costs either way.  But, like you, I have been watching and listening.  Here is my take:  In all the time I have been reading here I have only found one Knut that said a stick was better.  That was "Bob of the North".  His comment to me was that "you are only really shifting the thing when you are off the highway".  Close quote, as I remember.  Bob has a 9 speed Road Ranger but I am fuzzy on details.  Now Bob is a man whose opinion I will take to the bank on any given day but there is a problem.....Bob recently thought he needed an engine replacement and he was going to go with an 8V92 coupled to a 740 auto.  Now, everyone I have noted that expressed an opinion has been for the automatic over the manual.  That has included a "highly respected" Knut that up graded to a "Auto Shift' 13 speed manual.  And he doesn't use the clutch except to start ONCE.   So, as I count the votes, it is 100% for the auto with one iffy renege.  The renege, learning that his engine is OK, isn't going for a auto conversion, I note.  So, I guess the consensus is not "perfect".  The ultimate config seems to be running the engine thru a 6 speed Alyson....NERVANA!  Even the truckers vote for the auto and are often the most adamant of the lot.  I started out thinking a stick would be my preference and I have changed my mind.  I don't want to be the "I'll do it my way Pioneer" with a decision so irrevocable as trans choice, let alone one so contradicted.  For me now!

YMMV,

John
« Last Edit: June 21, 2009, 03:36:54 PM by JohnEd » Logged

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junkman42
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« Reply #6 on: June 21, 2009, 04:07:23 PM »

I average 6.2 with an HT70 which is a true 6 speed automatic and a 8v71.  I can not see any advantage fighting a clutch and shifting in traffic for no gain.  Modern automatics once locked up are no different than a standard transmission.  Just My take.  John
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« Reply #7 on: June 21, 2009, 05:43:13 PM »

The only people getting 10 MPG are driving older, 35 foot, light weight coaches with a stick in the flats.  If you are driving a 45 foot, 20 ton bus, the mileage is not even a part of your vocabulary.
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« Reply #8 on: June 21, 2009, 05:52:05 PM »

Do all the listings claim "New clutch" also?  Wink You'll hear it all from the seller. If anyone of them had converted their bus to an auto it would have that listed in bold type.
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« Reply #9 on: June 21, 2009, 06:27:08 PM »

The real choice is whether you want to drive with BOTH hands and Feet or one foot and a hand. As you get older that multitasking will cost you more.

One foot on the clutch, one on a go pedal, one hand on the shifter and one hand on the steering wheel, while looking left, right, ahead and to the rear and watching the backup camera, tachometer, water temp & oild pressure gauges...

Hmmmm....

Then to make things worse is having a gabby co-pilot trying to steal what little brain power you have left...

I like automatics.

The trade off is worth saving all the extra effort especially in traffic or when you are tired ( arm weary ).... Oh.. Don't forget that brand new left knee replacement that you will need ( maybe? )....

Nuts... Dave..
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« Reply #10 on: June 21, 2009, 06:36:43 PM »

With my H3 45'  I average 7.2 to 7.8 mpg  and that's with the B500 and near 550HP Series 60..    8.1 mpg was my best coming across the midwest plains last year.
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RJ
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« Reply #11 on: June 21, 2009, 07:45:22 PM »


So I have been browsing around and seeing what is on the market right now, and alot of guys with coaches that have a manual transmission are claiming they get roughly 10-11 mpg on a coach that gets roughly 5-6 mpg with an automatic. 




Iminaccess -

What these guys aren't telling you is how they came up with that 11 mpg figure for their bus.

It's all in the math: 5 mpg around town, and 6 mpg on the highway equals 11 mpg.

See, wasn't that easy??   Cheesy Cheesy Cheesy


Seriously, here's my take on this, after spending 25+ years in the bus industry:

35 foot coaches w/ six cylinder engines: 8 - 11 mpg

35 foot coaches w/ eight cylinder engines: 7 - 9 mpg

40 foot coaches w/ 8V71 or 6V92: 5.5 - 6.5 mpg

40 foot coach w/ 8V92: 5.5 - 7 mpg

40 foot coach w/ electronic S-60: 6.5 - 8 mpg

45 foot coach w/ electronic engine: 6.5 - 8 mpg

40 foot transit bus w/ diesel engine in revenue service: 3.5 - 4 mpg

40 foot transit bus w/ CNG: equivalent of 1.5 - 2.5 mpg (but it's clean air, folk!!)


These are overall averages, with so many variables it's hard to point to one specific and tell you "that's what you're going to get."   

HOWEVER -

Notice that the smaller and lighter the coach, the better the mileage.  Also note that the newer, heavier 45 foot coaches, with the more powerful engines and overdrive transmissions, are getting approximately the same or slightly better mileage than the older 40 footers.

IMHO, it's not worth the expense to convert an automatic back to a manual box for the (generally) 1 - 3 mpg difference in fuel economy.  And the ease of driving an auto, especially in congested urban areas and for most RV folk, far outweigh the slight mileage penalty.

Clear as mud?

FWIW & HTH. . .
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RJ Long
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« Reply #12 on: June 21, 2009, 11:35:44 PM »

If you drove an automatic bus chasing a manual transmission bus and kept to the same acceleration rate as the manual bus, you'd find the fuel mileages to be very close to each other.  In fact (and this has been proven over and over), a poorly driven manual transmission bus will get worse mileage then an automatic bus.  The main reason Allison transmission buses gets much worse mileage then the manual transmission bus is that punching the Allison from the light is so much fun-and it burns more fuel. 
The pure truth is-the only difference in efficiency between the manual and Allison is in the first few yards up to about 20 mph-where the Allison's transmission's torque converter will lockup and be as straight through as the manual transmission.  What most don't know (and this is straight from Allison), is that the Allison transmission takes an additional 20hp over the manual transmission to just turn it over to over come the frictional losses caused by the clutch packs dragging through the transmission fluid.  So you do pay a penalty-but properly driven, should only be maybe as much as one gallon more in a hard day of driving.  Personally-I'll take my Allison everytime-so much so, I just had my truck's 13spd overdrive replaced with the Allison HT740 without overdrive.  But with my gearing, I'll have a comfortable cruise at 65mph at 1800rpm-which is just right for my older Caterpillar 3406B mechanical 400hp engine.  Good Luck, TomC
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« Reply #13 on: June 22, 2009, 06:07:51 AM »

a lot of guys with coaches that have a manual transmission are claiming they get roughly 10-11 mpg on a coach that gets roughly 5-6 mpg with an automatic.

Hey, We get 11 with our automatic (6 on the highway & 5 in town) 5+6=11.  I don't think anyone can change mileage more than by 1-1.5 MPG by simply changing from auto to manual. Driving style, weight, terrain, etc. will also affect MPG.  Jack
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« Reply #14 on: June 22, 2009, 07:34:00 AM »


FUZZY MATH....  I Love It!

 Cheesy Cheesy Grin Cheesy Cheesy Grin Cheesy Cheesy Grin
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« Reply #15 on: June 22, 2009, 08:41:02 AM »

I agree with Jack that you will probably only see a 1-1.5 mpg gain based solely on the transmission.

 Most agree that the biggest factor is your right foot.

It has been discussed here many times by different posters on the gains seen based on speed driven.

I think for most, the automatic with a lite foot is the way to go.

Though I personally enjoy shifting.


Cliff
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« Reply #16 on: June 22, 2009, 08:57:02 AM »

Our old Eagle 05 (40' x 8V71N x 4spd manual) got about 5.5-6.5 MPG, empty at 30K lbs and a smidge less towing fully loaded at over 37K lbs. This was about 30-40% less than my 35' GMC Fishbowl with a 2spd auto and 6cyl.

The 'new' MCI challenger (35' x 8V71N x 4 spd manual) has a log book showing high 7's to low 9's. Same owner for over 30yrs, same trip every year, same trailer.

Hopefully by not towing, and the addition of synthetic engine oil, running 60-65MPG, she'll provide a consistent 8.0+MPG or better, unless running the hills alot. The gearing is a bit short for highway blasting but works well for hills.

I broke my promise that the "next" bus would have an auto and turbo engine, at least it has power steering-- which makes shifting and turning MUCH easier.

In a round about way this might help.....
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« Reply #17 on: June 22, 2009, 10:36:56 PM »


. . . and the addition of synthetic engine oil, running 60-65MPG, she'll provide a consistent 8.0+MPG or better. . .
 


Gary -

Be careful here.  Detroit doesn't recommend running multi-weight oil in the two-stroke diesels, and the vast majority of synthetics on the market are multi-weight - how many of them are CF-2 or even CF-4 rated???

The ONLY straight 40wt synthetic that I'm aware of that comes close to meeting DDA's 2-stroke specs is made by Royal Purple.

You might want to compare the price of seven gallons of synthetic vs seven gallons of dino, and pencil out whether or not a slight increase in fuel economy can/will justify the difference in cost between the two oil types over the life of a single DDA-recommended oil change period.  Oh, and don't forget to factor in the additional oil you might need to keep the level correct between changes, too.

If you decide to stick to dino oil, remember DDA recommends using just straight 40wt, CF-2 oil with a 1% or less sulfated ash content in the two-stroke engine.

FWIW & HTH. . .

 Wink


Now back to our regularly-scheduled fuel mileage discussion. . .

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RJ Long
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« Reply #18 on: June 23, 2009, 12:57:33 AM »

RJ-

While I appreciate the good intentions of looking out for a fellow bus nut, in lieu of another thorough explanation of "why", feel free to spend a little time getting acquainted with the answer (it does a much better job than I at this time of night):

https://www.amsoil.com/storefront/ame.aspx



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« Reply #19 on: June 23, 2009, 06:53:58 AM »

http://www.axlealliance.com/pdf/vocations/Lube-Oil-Fuel-Requirements.pdf

This has a ton of useful tech info about oil and fuel for Detroit Diesel.

....now back to the real subject at hand.....
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« Reply #20 on: June 23, 2009, 07:42:39 AM »

Gary,

Great link on oil as per Detroit Diesel.  It's good to have info from the manufacturer and their say on additives.  Although, I know Lucas oil is a commonly used additive by busnuts and truckers.  Does it help or hurt is a subject I think will never be settled. 

The 40wt oil can be purchased from Napa and others but I've never seen 50wt anywhere.  Might be good to boost the 40wt with some 50wt after a couple thousand miles. 

Rick
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« Reply #21 on: June 23, 2009, 08:30:18 AM »

Gary -

I don't want to hijack this thread any more than it already has been, so please take a look at the new thread I will be posting later on tonight.

FWIW & HTH. . .

 Wink
« Last Edit: June 23, 2009, 08:32:44 AM by RJ » Logged

RJ Long
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« Reply #22 on: June 24, 2009, 06:18:14 PM »

 i cant speak for any other bus, ours is a 4106, we drove it from lexington NC to california and back again, towed a car and i drive fast when traffic conditions allow, i had the 4 speed manuel transmission, the bus got 10+ mpg on every check both directions. wife wanted a automatic so she could drive, had it put in , did not change anything else v 730  shifts great never had any trouble, but the truth is the bus now gets 7 mpg and you have to keep a close eye on the engine temp , never got over 180 on the calif trip even on long climbs, i am now hesitant to climb long climbs. also the top speed is reduced to 76 mph as opposed to better than 80, i dont mind that because i dont care to drive that fast but thats one reason for the reduced mpg. the transmission final gear is not the same. This is the experience i had, i would never change over a 4106 if i had to do it again.
Frank Allen
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« Reply #23 on: June 24, 2009, 11:27:07 PM »

i cant speak for any other bus, ours is a 4106, we drove it from lexington NC to california and back again, towed a car and i drive fast when traffic conditions allow, i had the 4 speed manuel transmission, the bus got 10+ mpg on every check both directions. wife wanted a automatic so she could drive, had it put in , did not change anything else v 730  shifts great never had any trouble, but the truth is the bus now gets 7 mpg and you have to keep a close eye on the engine temp , never got over 180 on the calif trip even on long climbs, i am now hesitant to climb long climbs. also the top speed is reduced to 76 mph as opposed to better than 80, i dont mind that because i dont care to drive that fast but thats one reason for the reduced mpg. the transmission final gear is not the same. This is the experience i had, i would never change over a 4106 if i had to do it again.
Frank Allen

Frank,

I think your story is the most concrete and semi-scientific for comparing the two transmissions and effects on MPG. FWIW, sorry to hear of the huge drop in MPG; diesel isn't a $1.35 anymore (sniff).  It might be worth replacing the ATF with full synthetic to help internal effeciency and lower the heat exchanger (oil/coolant) temperature. Naturally it'd last longer, too. I'd also put in a good word for something like Redline Water Wetter to help reduce coolant temps. Lastly, the trans should be locked up in direct or over-drive. Not doing so would drastically lower MPG and raise RPM some when throttling on.

I'm a big fan of both Redline and Amsoil products. Not cheap, but well worth it IMHO.

No doubt the reduced gearing makes some difference. If she's good on the hills one could decrease the axle ratio, if something was available and appropriate for your needs.

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Cheers,
Gary

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