Fuel Mileage

[TomC]

I have an AMGeneral Transit 10240B (much like a GMC new look transit) that still has the destination board. At 1800rpm, I'm cruising at 58mph. I finally had the chance coming back from the Bay area to run the bus without the car and without the generator running (was cool enough) to get a fuel mileage check. I got 7.3mpg. Not bad for a 31,000lb bus that is 41 years old (that'd be like a medium sized car getting over 70mpg). Good Luck, TomC

[PP]

So Tom, if I'm reading this right, you're going to let the DW follow in the toad (with AC  ) and sweat your butt off in the bus the next time you take it out? 

[neoneddy]

I've posted a few times beating around the bush on MPG.  I'm averaging in the 5's lately pulling a 5,000 van with a 31,000 lb MC9. I was doing some digging again last night on it,  I think I might be too light on the pedal.    I've added a boost gauge, working on the tack.   the last 500 miles I put on it, I tried to keep it around 3-7lbs boost even while accelerating, like getting flipped off slow (sometimes), sure I can hammer down and be up to 65 pretty quick, but I don't need to get there quick and I enjoy the drive.

I've got the 6v92 , HT740.  It runs 55 at the governor in 3rd gear.  I don't know what RPM that is yet.   I was looking at this and other resources recently https://www.powerlinecomponents.com/literature/detroit_diesel/brochures/6v92ta-tta_automotive.pdf .

My conclusion that I'm too light on the pedal is, it seems the more careful I am, the worse it gets.  I've been cruising more at 60 than 65..  last year or even this spring (it was lighter then too) I drove it 65-70 and got well into the 7's .   I'm thinking my engine likes to be in higher RPM ranges, sitting at 60,61,62 in 4th is not making it happy.   

At this point I need to try something different.  So I've added to my trip log spreadsheet a column for "target speed" where I put what speed I'm trying to stay at.  I'm going to go more 65-70 our next trip and see what happens. 

[buswarrior]

Apples and Oranges... if you changed the weight, trail or toad or not.

Pushing wind is huge, dragging weight is significant, stop and go is killer.

Boost gauge is good, tach is a waste of time on an auto 4 speed, there are no decisions to make, you have no choice what gear to be in, you are speed limited to gear choices.

Your 55 mph in 3rd is going to be a little over 2150 rpm or so, with a 3.7 differntial.

Auto box, once you're in top gear, faster burns more fuel.

Nothing wrong with 5 mpg with a gross of 36 000 lbs!

happy coaching!
buswarrior

[neoneddy]

@buswarrior Well my thought is, these engines are not as efficient at all RPM ranges, So I'm going to experiment with it more.   

Or I'm going to install one of these http://www.greenshieldsproject.com/about

[windtrader]

Seems like a very basic model of bus with various aerodynamic shapes could be simulated in any ordinary software these days. one up with a rough difference in Cd for estimating mileage change. Same thing with pulling tow vehicles of different weights.

[neoneddy]

@windtrader One step ahead of you, except so far I haven't been able to find such software excpt here https://software.nasa.gov/software/ARC-14275-1   .  I inquired about it, but it requires a government contract.

[RJ]

Ed -

I've shared this before, but will share again:

In 45,000 miles over 3.75 years on our MC-5C (28,000 lbs), we have an overall average of 6.48 mpg.  Uphill, downhill, headwinds, tailwinds, rain, snow, towing (3100 lb VW), not towing, genset running, genset not running, Interstate, rural highways, around town, you name it.

Coach is anemically-powered with a 6V71N mated to an MT-644 automatic, geared so that 60 mph is 2100 rpm, thus basically running on the governor all the time.

Also (and I've found this to be true in the car as well), it doesn't seem to matter if I drive 60, 65, 70 or 75, the overall trip average speed works out to be 50 mph, start to finish.  So we use that for planning purposes: Today's trip is 285 miles?  That equals 5.7 hrs, regardless of what Google Maps, MapQuest, or the Garmin says it should be.

Buswarrior -

I like the tach - helps me keep my speed more consistent since I don't have a cruise control.

FWIW & HTH. . .

[Geoff]

Believe it or not, the new Michelin XZA-2 ENERGY tires I put on a year or two ago actually increased the fuel mileage on my bus.  I don't have any hard data since I haven't been able to drive it in over a year due to my back injury, but I am thinking it made 1/2 to 1 mpg difference.

[luvrbus]

Oh the world of technology like it or not a 50,000 lb bus,pulling a 20,000 lb trailer, 500+ hp and 2000 ft lbs of torque getting 7 to 8 mpg just leveling the hills out at 65 mph @ 1200 rpm with no smoke

[sledhead]

Oh the world of technology like it or not a 50,000 lb bus,pulling a 20,000 lb trailer, 500+ hp and 2000 ft lbs of torque getting 7 to 8 mpg just leveling the hills out at 65 mph @ 1200 rpm with no smoke

yup

550 hp and 1875 lbs of torque 7-8.4 mpg and on cruise up and down the hills at 63 mph

happy happy !

dave

[richard5933]

My 1974 GMC 4108 gets between 7-8 mpg. Oddly, it gets around the same mileage as my first car which also was a 1974 model, a Pontiac Grand Safari station wagon. Guess I haven't gotten that far in life.

[luvrbus]

My 1974 GMC 4108 gets between 7-8 mpg. Oddly, it gets around the same mileage as my first car which also was a 1974 model, a Pontiac Grand Safari station wagon. Guess I haven't gotten that far in life.

The old 2 strokes do ok if you are not pushing a lot of weight ,if it was pushing a 45 ft,50,000 lbs bus ,102 wide and towing you would be down in 4's with a 8v71 @ 50mph   

[lostagain]

Years ago, we had a 1 ton Chevy pick up with a 454 towing a big bumper pull travel trailer that got 7 to 8 miles to the gallon. Now with the bus we get about as much, but the bus is MUCH nicer and bigger.

JC

[chessie4905]

If you only got that kind of mileage from a grand safari sw., somethings wrong.