We've been trying to sort out all of the numbers being tossed around about the Thunder Star 1200 TDI diesel motorcycle. The more we looked, the less sure we were of anything. Close examination of several magazine writeups revealed different numbers within the same article! For instance, Streetfighters magazine had both 180 kilometers per gallon and 180 miles per gallon, an easy slip but quite a difference. The power output numbers are also a bit murky, with kilowatts and horsepower along with newton meters and foot pounds to deal with. The back and forth conversion errors seemed to be rampant everywhere we looked. So, I thought we should ask Star Twin to clear things up and I just received this reponse from the Thunder Star's designer, Jeroen Bernart:
The ThunderStar 1200 TDI fuel consumption varies with the load of the machine. In a race setting the bike produce approx 95 bhp and 220 Nm of torque. When riding on the road (yes, the machine is road legal) it consumes approx. 5 liters every 100 km (race version). In addition, when we reduce the power output (approx 70 bhp, 160 Nm) the fuel economy comes close too 2 liters every 100 km.
It is difficult to provide accurate data, since it is still a prototype. This means we change a lot on the machine and have not done real fuel economy test. As for the power output, we are also experimenting with different mappings. This results in different power outputs so I hope you can imagine we can not give a final power output.
So, according to Jeroen, the output is 95bhp and 162 foot pounds in a race setting with fuel consumption at 85 miles per gallon. Reducing power to 70bhp and 118 foot pounds yields 212 miles per gallon! (Correction, 117 mpg. Thanks, Nick!)
I think we should wait on the final numbers for fuel economy since, as Jeroen said, they're still experimenting and have not done a real test. It's also interesting that he never mentioned the 250 foot pounds we've seen before though he did say 220 newton meters, a similar number though a different unit of measure, which may be the source of those previous numbers.
In all fairness to Star Twin, I think they have built a tremendous motorcycle and some of the numbers quoted probably arose from incorrect conversions of the numbers they gave out, an easy mistake to make with internatonal measures but, as with all things technical, something that should be checked. I am eager to see a controlled test to find out what the numbers turn out to be, however, I believe Star Twin has a real winner here which needs further development. This bike needs to be produced.