Specific fuel consumption

Honest John Back Room » Technical matters
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Tue 22 May 2007 23:04
Specific fuel consumption - nb857
I was watching Top Gear on Sunday and they had the Merc SLR on. JC said that it could empty it's 21 gallon tank in 19 minutes, that's 66.3 gallons/hr under full load for a 626 hp motor.

At work we have a machine with a 360 hp Cat C9 (8.8 litre) and it works at between 94-100% for 12 hours at a time and consumes about 10 gallons each hour at this loading. So it has just over half the power and uses a 6th of the fuel. What gives?

So why does the Merc SLR use so much fuel (assuming my maths is correct and JC's figure are accurate)?

What is the specific fuel consumption of a typical car? 210g/kw/hr ish?

How much does unleaded weigh?

Is it just heavey duty engine that are at peak effiency (sp) under full load/torque?

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Tue 22 May 2007 23:26
Specific fuel consumption - Screwloose

That equates to roughly 3-4 mpg. Not unexpected for that much power fighting that much drag.

An industrial diesel is designed to minimise it's fuel consumption; 10g/ph is about right for a constant revs engine of that power.
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Real MPG enables you to register the fuel economy you are actually getting against your make and model of car, its engine and type of transmission.

Every time you enter an average consumption figure against your car, the overall average automatically adjusts to reflect it.

Real MPG