Rolls Royce Phantom

[robert carter]

I have now read 2 reports that the new RR Phantom has a dial on the dashboard that indicates how much power is available in reserve. My problem is, that these reports go on to say that at 100MPH the driver still has 90% of the available power in reserve from the 453BHP engine. What miracle of engineering allows only 45.3 BHP to propel this Massive Brick of a car at 100MPH????

[okgo]

Is it because its holding it at a cruise which is not as intesive as using more of the engines power to haul the thing to 100 from a standstill?

Edited by okgo on Saturday 28th June 16:50

[robert carter]

You would need a 50MPH tail-wind or at least 100BHP to maintain 100MPH surely. There is an awful lot of air to push out of the way at that speed.

[shalmaneser]

My 54bhp Nissan Micra can hit an indicated 100mph!!!(with no tailwind!)

[robert carter]

Your Micra doesn't weigh over 2.5 tons and is probably a lot more aerodynamic, with a frontal crossection aprox. 30% less than that of the Phantom.

[Dracoro]

Work it out for your own car.

at 100mph, you're doing X revs. look at a power graph to see how much power is being used at X revs.

I suspect the RR is running 2000rpm at that speed?? I'd be guessing around 100bhp.

Need to know how their power reserve works. it is a rev counter that sweeps right to left? I'm guessing it hits 100% at peak power. Bugatti Veryron has similar thing too doesn't it, instead of %age it states bhp.

[MaestroDave]

Simple aerodynamics (for a guy with a degree in maths and engineering):

Power = (Rolling Resistance x V^3 x CdA)/(76716 + Rolling Resistance)

So Power to do 100mph (=160kmh) = (1.7(guestimate for low roll resist tyres) x 160^3 x 0.36)/(76716 + 1.7)

= 32kW = 43bhp

43bhp from 453bhp = about 10% ie 90% power remains...

No sculduggery what so ever - infact, they're being generous.

Dave

[Balmoral Green]

I thought that, but couldn't do all that mathematics.

[cardigankid]

This was all shown on the Top Gear review of the Phantom, currently being repeated on Dave for the benefit of those of us holidaying in Scotland in a downpour. There was also quite an interesting review of the car in an old Top Gear magazine (July 05 I think), in the form of an interview with Simon Cowell (who at that time owned two) which was highly complimentary. The TG people separately rated it the best car in the world. For that reason I suspect the comparison with bricks is superficial.

By the way, thanks for the mathematics. I couldn't have done that, but it bears out my point. Adequate. More than adequate.

Edited by cardigankid on Monday 7th July 18:36