(Top Gear): The Stig's flying hybrids

Near as I can tell, the only conclusion you can take away from this article is, never buy ex-road test loaners.

 

This might be the first time ever that someone has worn a racing suit in a Prius.

 

Top Gear's Jeramy Clarkson ... what a tool



One era he's peddling plush toys ... the next era he's machine gunning a Prius. What next

.

 

I hope not.
Got Hybrid? - Sport - Auto Reviews - Car and Driver

 

I've been puzzling about Stig's multiple laps and I think it may be his confusion at the MPG at high speed. During the BMW vs Prius 'test,' Stig drove drove the Prius like a formula I. Maximum acceleration and maximum brake. He achieved 17 MPG and was expecting the same result this time ... but it didn't happen.

There is a mistaken impression in some automotive technical circles that the Prius transaxle is especially inefficient at high power settings. I'd seen some indirect references but the best source is SAE 2009-01-1321, "An Analytic Foundation for the Two-Mode Hybrid-Electric Powertrain with a Comparison to the Single-Mode Toyota Prius THS-II Powertrain," Jerome Meisel. I suspect the Stig thought the earlier 17 MPG was due to transaxle inefficiency and he was trying to figure out why he didn't get even worse results at maximum speed.

Now some of us have realized that ~1/3d of the power 'recirculates' and this is subject to an approximate 0.96*0.96 efficiency or ~8% loss of 1/3d power, ~3%, not counting the gears. Stig was expecting a higher energy loss with the transaxle heating and poorer mileage. I suspect he couldn't believe what was going on ... and ran extra laps.

Stig was expecting the Insight, running at maximum throttle, to achieve higher MPG. Yet he didn't count on cooled, exhaust gas recirculation and higher than expected ICE efficiency. The Prius protected the catalytic converter by diluting the intake air with cooled exhaust. He also might have missed the muffler, high-power, shunt valve. So the Prius kept running and the MPG wouldn't go down.

I can imagine the debriefing.

Bob Wilson

 

Heh, hear hear

 

Over 100mph in a Prius, I would say it's a wise decision.

 

Not only Stigs fly.... So does a Prius

 

This is what I got with full throttle in my NHW11:

Just as our NHW11 reached 100 mph, the fuel economy (green line) plateaued at ~22 MPG. It might be interesting to measure the MPG of the NHW20 at maximum throttle.

Bob Wilson