[Anchorman]

So - getting the Veyron to a real top speed of 253 mph is truly impressive, in terms of power and aerodynamics.

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[flash]

yes - on so many levels it boggles the mind



having driven 200mph (just 2 runs to say i did it, and won't EVER be doing it again) i can tell you that the level of nerve and control required is nothing short of insane - things change dramatically at that speed - i want no part of that, thank you very much

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[wjk_glynn]

[quote name='flash' post='31774' date='Mar 2 2007, 07:30 AM']i accidentally dug up a formula i found decades ago that dealt with real world horsepower to speed...[/quote]



Can you state the formula (and who derived it)? I'd love to drop it into a spreadsheet and play with it...



Karl.

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[flash]

don't know who derived it - been floating around for 30 years in my notes



the formula is:



new hp = (new speed / old speed)3 * old hp



as i said, this does not take into account anomolies in aerodynamics and the things needed to correct them, so that a car can stay on the ground at the new speed

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[Anchorman]

That formula "does not compute". Did you mean "new hp = (new speed/old speed)^3 * old hp"? or did you mean "new hp = (new speed/old speed) * 3 * old hp"? Since the first version seems to mesh reasonably well with what is stated in the Veyron top speed run, I'm assuming you meant that version of the formula.

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[flash]

new hp equals new speed divided by old speed then cubed then times old horsepower



my computer doesn't have the correct characters to do the formula so it shows up right (that or i'm just too lame)

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[Anchorman]

The "^" (carat) is the symbol that represents "to the power of..." At least, it does in Excel, so it should be good enough for our use. That's what I figured, though.

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[pmcrespo]

Anyone know the "factory quoted" RPMs at top speed (153) for a Tiptronic?

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[Renalicious]

According to that formula, around 5100 to 5300 rpm. Not factory quoted... but was I close? <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[flash]

something is wrong there - it should be a bit over 6200 i think

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[pmcrespo]

Indeed, that is why I was questioning. I have not done a flat out run and have not found any "test" results that quote RPMs at Top Speed for the Tip. Thanks for the input....

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[ds968]

So a couple of weeks ago I discovered that I have a O speedometer variance at 80mph ( one of those mobile electronic boards which flash

" your speed is:___ " . This is a frontage road with very little traffic so if I see it there again, I'll pass by at 100 and see if if the speedo stays

error free at that level as well. Just hoping those things don't also have a camera, or the speedometer is the only thing that will stay FREE <img src="/forum/images/smilies/968/dry.gif" class="smilie" alt="" />



My tires are 265 40 (17s) rear and 235s fronts so that might be some of the the reason for the accuracy.

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[flash]

your 265/40 has a 1.01% increase in diameter - a 235/45 is about the same - a 235/40 would be in the other direction by 2.5% - the larger diameter would help to correct some of the error, so you are indeed closer to the accurate reading than somebody with stock tires



the speedometer error isn't too bad in the 50-90 range - it doesn't start getting nutty until it gets to the upper end of the dial, where it can be off more than 10mph in stock trim - i have 2 different magazine articles where they tested it and showed some pretty goofy error rates



lol - reminds me of an old cable driven speedo i had a long time ago - danged thing would actually start bouncing over 100mph



anyway, i wouldn't trust those stationary radars too much - they are wide band guns that also factor in other traffic, designed as warning mechanisms, and not used for citation purposes - i have "played" with the one near me and had it blip some very interesting numbers - one day i made it show a 30-60 acceleration in 50 ft in the denali - i know the car is quick, but that was pretty funny



lol - must have been the jet-pack i installed

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[saxman]

I've found that my speedo varies it's accuracy quite a bit. At 65 mph, it'll read a few mph off, but at 70, it's spot on. A bit peculiar.



This is based on setting cruise control and comparing the speed to the gps read out on my navi. Always amusing to see my speed to the 100th of an mph.

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