Downsize HP's

D16 · Sep 1, 2007

scania580 said: ↑

My boss when I was driving in England would pull our bonus if we ran less than 9 mpg, I could normally average about 9.6 the truck at the time was a scania R 420 cab over hauling a reefer trailer. max gross weight 44 metric tonnes.

I would have to do this on regional multi drop delveries in and arround major cities including London.

In my experience more hp does not allways mean less mpg, using a bigger engine you can shift at lower revs, skip change and use the additional tourqe to your advantage. I think another thing that helps with the economy is speed. UK trucks are limited by law and an electronic limiter to 56 mph. this is suposed to be the optimum speed. Because drag is directley proportionate to speed. each time you increase speed, drag increase 4 fold. ie double your speed and you multiply the drag by 4. this means more fuel is used to overcome drag the faster you go.

so with this in mind tuck manufacturers in Europe normaly design the torque curve of an engine to be long and flat. IE it produces max torque over a wide low rev band with out peaking. this enables up shifts to be completed at about 1100-1390 rpm ( normaly marked with a green band ) and the truck is geared to run at 56 mph in top gear within the green band. see tourque and power chart

so I gues what Im saying is its not the engine size that matters most, its the way you drive it. and big power does not allways mean less mpg.

I also believe that the UK imperial galon is slightly larger than a US Galon ( one thing that not bigger and better in America ) so that would have an influence on Uk trucks average of 9 + mpg. but not to much. its mostly down to the driver and speed.

The trick is to maintain you rpm between in the scania's case 1100 and 1390 the flat band of max torque on the graph, this is the rev band marked in green on the scanias rev counter. " stay in the green keep it lean "
Click to expand...

Convert to metric Imp. gallon is 4.6 liter,US gallon 3.785 liter.So now You live in flat Oklahoma and what is yours MPG in US?

woolybear · Sep 1, 2007

My imperial Mpg is about 6/mpig pulling 64 metric tonnes.

woolybear · Sep 1, 2007

Apples and oranges.

D16 · Sep 1, 2007

woolybear said: ↑

My imperial Mpg is about 6/mpig pulling 64 metric tonnes.
Click to expand...

BTW do You have any troubles with "Active pressure cooling System"i.e. overheating?Cause mine is already shotdown by dealership(computer always send messages"check active pressure cooling system").

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