Hi,
In my Lister FR manual is a set of graphs showing consumption curves at various outputs and speeds, the graphs cover the engines from FR 1 through to FR 6, I know they are a bit different to the CS range but do employ a very similar combustion chamber design.
The FR 1 figures ( this is as close a number as possible from the graph ) show 1000 Rpm 4.9 Hp and 0.75 Imp galls per hour and at 1500 Rpm 7.5 Hp 0.9 Imp galls per hour. The fuel consumption in pounds of fuel used per B.H.P. hour as a percentage of load at 1500 Rpm show 100% loading to be the most fuel efficient, the actual numbers being 0.47 lbs Bhp hr @ 100% load with a fairly even convex curve to 0.62 lbs Bhp hr @ 45% load.
What is interesting is the difference in specific fuel consumption between an FR 1 and an FR 6, 0.47 lbs Bhp hr and 0.425 lbs Bhp hr respectively at 100% loading, this would indicate the better mechanical efficiency of multi cylinder engines.
My thoughts are that our actual usage of engines will always be a compromise between many factors and the manufacturers figures are no more than a starting point for most.
Mark.
