8.3 md 3060 mpgquestion

[Brewerbob]

From the OH side of WV to MD (over the Appalachian Mtns) the Blue Bird got 7.9 mpg with an AT643 and 4.44 rear.

[superdave]

Originally Posted by Brewerbob

From the OH side of WV to MD (over the Appalachian Mtns) the Blue Bird got 7.9 mpg with an AT643 and 4.44 rear.

yep 7.3 in the mountains, 8 in florida. I wish I knew how all these busses are getting 12 mpg, lol

[EastCoastCB]

Originally Posted by superdave

yep 7.3 in the mountains, 8 in florida. I wish I knew how all these busses are getting 12 mpg, lol

My big bus does around 8-10 with a 466, 643, and 4.44 rear.
My shorty does like 12 or so with 444, 545, and 4.10 rear.
We obviously don't have mountains here, so that may be part of it.
Maybe those big Cummins just use more?

[superdave]

yes mountains make a difference. I was quoting b b who has the same motor/ tranny and in most cases a big heavy bus.

[cadillackid]

alot depends on RPM and how much you are loading the engine.. I dont profess to know all the science behind the diesel engine,

but I do know that even unloaded at higher RPM the T-444E. and from what ive observed, the DT-466E get much worse mileage when they are run at higher RPM even with a low engine load factor...

the variance in MPG on a lot of these busses I believe is partially attributed to driving style and of course terrain, but a lot on the gears.. and the gears Vary greatly..

my DEV bus is a mechanical DT-360 and is completely dependent on vehicle speed and a bit terrain when it comes to its MPGs.. my engine can be running under a pretty heavy load (I can actually hear the turbo in that one so i can tell when its under load).. and the MPGs dont go down a lot.. run the bus fast and even a seemingly lighter engine load and lower RPMs dont seem to net me that much more...

my T-444E, dropping my vehicle speed just a LITTLE.. which with a 545 drops my RPMs down results in a significant gain in MPG's.. I have measured mechanically my MPGs and have now gotten my compouter display calibrated to be pretty spot on so I can drive it for MPGs if I choose..

the drivers of powerstrokes typically have fairly tall rear gears and the Overdrive transmissions.. so they see their RPMs drop and MPG's go way up.. (im sure most here know that the T-444E and the Powerstroke 7.3 are very much similar.. both built by Navistar, one sold to ford and slightly modified, the other used in Navistar medium duty trucks and busses)..

Ultimately Diesels would rather Lug not Rev for the best economy it seems..

-Christopher