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Posted by john copeman ontario can. on Thursday, April 17, 2008 at 20:11:03 :
In Reply to: fuel consumption rant posted by Ephraim on Thursday, April 17, 2008 at 17:59:44 :
let you in on a big secret when a truck is doing 65 miles an hour you are pushing about 50,ooo pounds of air out of your way > back in the senentys before aireodynamics, a flat face cab over engine tractor with a trailer at 70 mph was puhing 150 000 pounds of air resistance as well as pulling 110 000 gvw so the work effort in the 70s was, 260 000 pounds of "work applied" >so i know nobodys going to agree with me and start trashing me, but on a diesil engine on the road THEY ARE only speed limiting govenors not load limiting >so you ask where the fuel goes? it the the number of revolutions per minute that counts> ie when loaded ,you are using the LOWER gears for a greater amount of time hence MORE revolutions > the pumps pop opens a injector, re more fuel used >that theroy is based on a lever the longer the lever the greater the mechanical advantage> BUT it takes more time to do the work savvy! >or better put take a hand crank winch, you can lift a good deal of weight but you have crank the handle many times to lift the load ,same your engine turns more times when loaded > when your empty your engine has LESS work to do hence fewer revolutions LESS fuel>in TRUUCK news fleets, when speced out correctly, are over 7 ,8 mpg (IMPERIAL GALLONS)>thats why some one get 5 mpg and someone gets 8 mpg >its all math and physics and HOW the truck is spected out !! when PETERBUILT truck (Paccar)came to canada i was asked to manage the sevice department my biggest concern was that salesmen were selling lots of chrome and colour BUT were not putting the pencils to the truck , and what a mess> i left after having to change over the trucks in the shop and fight with the management over rear end switches and transmission swaps it was a lack of knowledge in the sales dept issue nothing wrong with the trucks J