bazzee said:

the horizontal axis is labelled as mph not rpm. If this is the case I can't see the two graphs as being directly comparable seeing as ...

ok, ok. if we are to let a few facts spoil a good story, i concede Bazzee is correct, and the comparison of HP at a given MPH (road speed) is just a tad misleading due to the variation in crank RPM.

so in the interest of correctness, the data file was exported into a spreadsheet and the data series of run 8 and run 6 were aligned to the same RPM.

to redeem my storytelling ways, i slightly biased the alignment to favour run 6, as can be seen by a detailed eye.

so now, i reckon the graph shows the HP at around 7,000 RPM is close to

45 HP for run 8, and

39 HP for run 6. or +15% ?? ???

& i think i just worked out why Fred's printouts are always 1 or 2 HP more than what i get plotted.

the default for the graph software appears to have the correction factor set to 'SAE', and i've just noticed Fred's printouts have the correction factor set to 'STD'.

therefore with the CF = 'STD', Ian's Monty racer actually pulled 53 HP at the rear-wheel. (thumbup)