10-12 mpg MC9!

[luvrbus]

I have some hound records from Dallas that show the 5A and 5B getting 9.4 mpg  some 8's doing the same tons of 4106 GM in 10 mpg range all 240 hp` fwiw

[buswarrior]

Let's take a look at the proportions of change in this post.

5 mpg to 10 mpg to 15mpgis a DOUBLING and a TRIPLING or a HALVING or a THIRDING, depending on your current position.

What can you do with the daily driver to double/triple/halve/third your fuel economy?

You can ruin it pretty easily, but can you raise it? The laws of physics can only be stretched so far.

Are we making assumptions about the current set-up that there is something wrong?
Did not the original purpose of the coach have cost of operation as a consideration?

Google the heavy trade press. It is popularly accepted that the driver, best to worst, can fool with fuel consumption by 30%. That is where the encouragement for driver training in fuel economy and being sure the drivers know about fuel, as per RJ's post, where the drivers actually fueled the coach and had the opportunity for that feedback and comparisons.

If you make too much energy consumption available to the driver, it will get used.
If you limit the energy consumption available to the driver, it can't get used.

Witness the detail in the post by luvrbus:

240HP settings.

Cheapest parts change on your 2 stroke Detroit equipped coach?
Put the smallest injectors into it that you can find and see what you get?

As for the data collection methods...
The precision of the measuring is a huge variable.

The method and calibration of the distance measurement.
How far out does the odometer need to be off to damage the calculation?

The methods employed to fill the tank and over the calculation period, ensure that the tank is at the same level beginning and ending? You aren't trusting that every pump is accurately measuring the fuel are you?

How much fuel is in a 1/2 inch in your tank? How much fuel can be held in each degree of lean of the coach at the fuel island? Using inches, volume in US gallons is (length x width x height) divided by 231.

happy coaching!
buswarrior

[bevans6]

Last time I was in Texas it seemed to me to be mostly flat...  Not all, but mostly.  I can see 9 or 10 mpg with a 240 hp setting in a country with no hills to speak of...  My run through New Brunswick when I go to my other home has a 1,000 foot elevation change - but it does it about 10 or 15 times, on 6% grades or better, and I can't get 10 mpg in my pickup truck towing my car trailer!

Brian

[artvonne]

  To be completely fair, mileage is always going to be less climbing grades all the time no matter who the throttle jockey is. If you can pull off 9 MPG in the mountains climbing grades all day long, its gotta do better in the flats if you keep the speed down.

 Speed is the single greatest fuel robber next to continuous speed changes. If your constantly giving it throttle to pick up a few mph, then coasting back down a few and throttling it up again, you will NEVER see good mileage. Bus, car, airplane, locomotive, it doesn't make any difference.

 Regardless of its shape, a Bus has the aerodynamics of a barn door. Once the Bus is over 30 mph, air drag starts to become the greatest load the engine has to propel after parasitic losses. By 60 MPH the HP required to push it through the air is well over 100 HP. Its quite easy to find fuel burn charts on various Detroit diesels, which clearly show the fuel burn rate in gallons per HP per hour. Air drag also increases with the square of speed. Double the speed, you quadruple the drag HP. Whatever HP was needed to push the Bus through the air at 40 MPH, 80 MPH will require 4 times the HP. Or you could look at it as a 400% increase in power consumption. So then, to increase from 60 MPH to 80 MPH, which increases speed 25%, would require double the HP. There is no way your going to get the same fuel burn at 80 over 60, youll get 1/2 that or less.

 Slow down, dont chase your speed with the throttle, use hills to your advantage whenever possible and safe, and do all the things ever told or written about maintenance regarding fuel economy. Then be precise in how you fill your tank, keep scrupulous records to track fuel economy, and lie through your teeth.

 The only other thing that can be done, is to locate the sweet spot and keep it there as much as possible

[wg4t50]

Oh What fun we have reading these gossip wannabee hopeful maybe mpg numbers.
For me, the 12V-71/MCI7 W/10Sped direct & 3.73  with 11X24.5 got 5.9mpg always on flat land, who cares about running the hills, swaped over to the 8V-92@580hp 10spd OD, could get 7.5mpg, but more fun playing with traffic, fuel burn is the cheapest part of playing bus games, so why all the hot air ?  WHO CARES, seems it is about like women lying about their weight.

[RoyJ]

Speaking of aero drag, I don't know why coaches in North America don't focus more on drag. Take the Neoplan Starliner for example:



This thing has a drag coefficient of 0.36!!! That's better than some sedans!

Having a modern power train, I don't doubt for a second these can crack 10 mpg on the hwy, driven conservatively. Mercedes achieved over 12 mpg in a 82,000 lbs euro semi.

[Iceni John]

Last year my friend was driving his Crown ten-wheeler with a 270 HP 6-71T and ten-speed non-overdrive Roadranger back from Sacramento to SoCal, and at a steady 55 MPH it got a shade over 10 MPG, including up and over Tehachapi.   That was with all the seats out, but it still weighed in the mid-20s.   The only reason he was driving so slowly was because his tach wasn't trustworthy, and he didn't want to risk over-revving the engine  -  he's used to a big Cummins 855 in his Gillig.   Interestingly, I was following him in his Dodge Hemi pickup and got only 20 MPG, but he says that's the best it's ever done!   (55 MPH all the way down 99 through California's Central Valley is really tedious!)

Aerodynamics and Cd numbers are largely unknown to most drivers here.   Try asking a car salesman what the Cd is for a new car (or how much CO2 it produces), and you'll probably get a blank frog-like expression.   Where gasoline is $8 a gallon, or more, those factors are of major importance.   Some years ago one of the old Crowns got up to 102 MPH (on a racetrack!), but their aerodynamics are less brick-like than modern buses.   My bus is far less aerodynamic than them, but the old adage of 6 MPG at 70 MPH and 7 at 60 pretty much applies to it.   Older Crowns can sometimes get 11 or 12 MPG, either with Detroits or Cummins, but I'm guessing they would have the overdrive ten-speeds.

I wonder how much drag is caused by the flat backs of most buses, compared to the rounded rumps of older buses like Crowns and Flxibles?   Maybe that's why they slip through the air better, because they have smoother airflow at their rears?

John      

[RnMAdventures]

When you compare it to other vehicles that are considered fuel efficient, these old buses are VERY fuel efficient. My motorcycle averages 36-42 MPG. The average weight with me and my stuff is probably 1100 lbs. The average being 39 MPG, that is 28.2 lbs per MPG. My 4106 if the loaded weight is 26000, that is 3714 lbs per MPG.

I am not sure I did that comparison right, but the most fuel efficient motorcycle on the planet can't touch that.

[Jeremy]

When you compare it to other vehicles that are considered fuel efficient, these old buses are VERY fuel efficient. My motorcycle averages 36-42 MPG. The average weight with me and my stuff is probably 1100 lbs. The average being 39 MPG, that is 28.2 lbs per MPG. My 4106 if the loaded weight is 26000, that is 3714 lbs per MPG.

That's true - and it continues up the scale - trains are more efficient than buses, and ships are more efficient than trains.

I share Iceni John's curiosity about whether the streamlined rear-ends on old Flxibles and similar were aerodynamically better than today's buses. I suspect they must be, because it's certainly true that most of the aerodynamic drag on a bus is from air vortices around the square back end.

Of course having a long, tapered back-end is impractical, so it seems that most effort on buses (as with trucks) is going into shaping the roof. How much of this is science and how much is styling I don't really know.

Jeremy

[Tikvah]

I have a theory about hills and mountains, I'd like to know what you think.  I've proven this with my Chevy Suburban and can only assume it could apply to my coach.

When I'm driving my Suburban I get an average of about 18mpg.  However, when I drive the mountains, I do better.  My theory is that going up the mountain I probably drop to 10, 12, maybe 14 depending on how hard the grade.  However, when I go down, I'm probably getting 30 or 35 or more.  Engine is not working at all.  So, all things being equal.. the drive up the mountain is equal to the drive down.  So, if I take an average, doing the math that puts me well over 20mpg.

I took a trip through the eastern mountains a couple years ago, with four adults, and full load of luggage and got a trip average of 22mpg.  Normally I would say a Chevy Suburban doing 22mpg is impossible... but the numbers work.

Am I out to lunch?  Would the same physics apply to my coach?

Dave

[kyle4501]

When pulling my camper behind my suburban, if I use cruise control, I'll be lucky to average 8 mpg.
If traffic is light & I can vary my speed from 5 over (down the hills) to 10 under (up the hills), then I have averaged over 11 mpg. But, it requires a lot of effort to maintain the optimum pace.  

I had a '93 suburban that averaged 10 @ 55 to 65 mph, but averaged 13.5 @ 85 mph. Weirdest thing I ever saw. Everyone who drove it long enough had the same results.

I haven't driven my bus much, but the few tanks I have run thru, I got much, much closer to 10 than 5 mpg.
(I didn't get in too big a hurry with the old tires under the back. . . . )  
The ole GM's don't have square corners, so that's got to make some difference.


Maybe that ebay bus has a bunch of air tabs on it . . . .

[Barn Owl]

Paul, there are many ways to prove it, but it is not necessary because it simply is not true. Surly with your knowledge and experience you know that and this is an exercise of fun only. With that being said, I am willing to volunteer my vacation, and at the owners expense, take his bus on my next road trip leaving little Wheezy Bus sitting. I will cornstarch my feet, and powder my underwear with Gold Bond Medicated Baby Powder (because I don't want to get itchy down there on those long missions to rewrite the laws of physics) and head west on another cross country trip. Thus setting to rest, once and for all, these braggadocious 40' bus owner's mpg claims.

[Barn Owl]

For BCM posterity long after the ebay ad is gone:

1982 MCI Bus Conversion

Buy it now: $25,000

This MCI has the following.Detroit 8v71, Five speed ,Manual transmission,2 brand new tires in front with mercury  tire balancer.Tires on back 95%.New drums and brakes all around bus.Has new radiators.Two 150 gallon fuel tanks long range bus.10 to 12 miles per gallon.On top two low profile air 5 carrier air conditioners. maxx air power vents.Winegard in motion digital satellite mobile antenna for two receivers you supply your own receivers.12kw Isuzu diesel engine generator.100 gallons of fresh water,and 75 gallons of black and grey water tanks,In side of bus, flat screen tv,radio and cd player,1000 watt amplifier , Bose 161 speakers,,cb radio,hookup  for satellite radio, Atwood distribution panel for house 12 volt and charger for house batteries,Alloc maple flooring,Berklinedoulble recliner leather,Custom cabnets with telescoping glides,Sensor convection and microwave oven,Whirlpool refrigerator,tile shower,bathroom has Sealand fine china toilet,Bedroom has extra sink ,A closet and storage under bed,All windows are double pain,The front one have dual window shades day and night, Back ones have mini blines,This bus is smoke free,Runs great  drives great. You are bitting and buying a used vechicle there is no warranty.

[kyle4501]

A hired bus driver will have different motivation than a retired owner/ operator.
I'd imagine a hired driver wouldn't place fuel economy as their top priority when they had a schedule to keep & early arrivals = happy passangers & late arrivals = a bad day at the office.

[Lin]

Yes it is totally possible to get above 10 mpg on a tank, but to claim that that is what that bus averages just is not so.  He probably decided that the tanks that got 6 mpg should not be averaged in for some reason.