[changzuki]

Originally Posted by sheepdog 44

In my opinion, it's two things. 1, is BSFC as Sendler already mentioned. Which is ideal for the centurion; being at the optimal engine loading in an underpowered diesel at a very aero efficient speed. When a motorcycle can be overpowered in many instances.

Where does the underpowered fit in? Was it the passing on the uphills part?
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My opinion is a bit different and I feel it is very "appropriately powered". RQ Riley did a wonderful job choosing the small Kubota for Centurion whose intended purpose was an urban commuter, not a drag car, and not a tow truck. And for the urban commuter application it's darn near perfect I'd say!
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Going one step further, it has roughly 17 horsepower per 1340lbs (weight on raceday)... The horsepower is just fine, it's not underpowered folks; it's way too heavy! A better way to look at it is: comparatively Centurion competed at a weight disadvantage when hp/wt is considered - and THAT is the drive behind lightening it up - it's a pig! Unlike sendler's experience with his motorcycle, everytime I lightened Centurion, the mpg increased. So for the GGP I ran with that and the numbers hit an all-time high - to include the trips to and from on the Interstate.
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Running with the adding-weight theory:
Sheepdog 44 - your Insight outporks Alfred State's by a longshot - but on the GGP track, do you really think you could at least "tie" with their best mpg? By this adding weight theory, surely you have a distinct weight advantage.
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Sendler - you've still missed the part of the passage "gap filled and boat-tailed" so to simply say that 1300 lbs is the sole reason for a stark improvement in mpg is lop-sided and ignores a couple of very important pieces. But let's run with it anyway... Bring the weight of your bike up to that of Centurion and at least tie my numbers on the Green Grand Prix track. You'll have every advantage of the weight you speak of for pulse-n-glide (which I did not do) and you have the advantage of the overpowered engine you mentioned.
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Also, for both Sheepdog 44 and sendler, the recent focus of the mpg discussion in this thread has been the Green Grand Prix, mostly because it mimics real world driving and a target mph, and not a specific scenario of say an exceptionally long downgrade to take advantage of coasting with the engine shut-off, etc, etc. But I see the conversation drifting to these very specific scenarios. So, yes, a point is proved by tipping the scale to those scenarios, but the real world is very different from those. Look at all the top mpg results from the past GGP (and elsewhere). I see a recurring theme: Aerodynamics, and, lightweight. Did they all miss the mark??
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~CrazyJerry