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      11-12-2012, 06:01 PM   #35
NISFAN
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Drives: The best kind of F30 :)
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Quote:
Originally Posted by MaestroAl View Post
You're kinda missing the point with this whole Torque Vs Power argument.

Soooo.... a couple of facts from the world of physics to help straighten things out Power (bhp/kW) is only a factor when it comes to ultimate, out-and-out top speed. That is all. End of. It has literally NO bearing on acceleration. None. Zip. Nada. Torque is the ability of the engine to turn the wheels and accelerate the car. Power is there to overcome overall friction - in this case in the form of tyre, air and mechanical friction.

Now you understand that, you'll understand why torque is all that matters in the real world. The reason that an M3 will accelerate faster than a 330D or any other high torque/low rpm car for that matter, is the way in which it delivers its power. The critical factor in this is the gearbox. A gearbox ... get this ... is a torque multiplier. That's all it is. Simples.

So take a 330D at 3000rpm giving out 400 ftlbs of torque (I'm making these numbers up for the sake of our little experiment here) and then take an M3 [i]at the same speed but in a different gear ratio so that it's at 6000 rpm and giving out 300ftlbs of torque. Since the M3 is at twice the engine speed of the 330D here, it is running twice the gear ratio and so its torque, relative to the 330D, is doubled. I'm not saying it's putting out 600ftlbs here, just that the final torque to the drivetrain will be double that of the 330D at the same speed in this instance. that's why an F1 car with a tiny 2.4l V8, putting out a miserly 200ftlbs of torque can move like the clappers. That 200ftlbs of torque is developed from 17k to 18k rpm so you get huge multiplication from the gearbox. Same goes for bikes.

However, and here's the killer, who drives like that on a normal day? Nobody for long anyway To get that "fast feeling" (which is simply forward acceleration for most people), one simply needs to put one's foot down in any gear at any speed in a car with tonnes of torque and you're off. A normal overtake from 60-80mph in top gear ... the 30D will hand the M3's ass back to it Most driving, done between 1500 and 4000 rpm is right in the 30D's sweet spot where maximum torque is available whereas the M3 isn't even on cam by then. Same goes for the 335i. And I know I've said this a million times (especially over in the American forum 'cause it's soooo rewarding) but the 335i and, to a lesser extent the M3, is only quicker than the 30D when you wind the nuts off it. Under all other circumstances, it's slower.

So next time you look at a car's performance figures, look a little closer and see the bigger picture. I honestly have no idea why the automotive world still goes on about bhp in 90% of cars. it only matters in hypercars where going over 200mph is an issue. What's your maximum torque and at what rpm is it developed. Only then can you compare like for like in the real world. And forget Top Gear lap times, they're only of use for entertainment (which they surely are) and are the TV equivalent of a bedroom poster. Torquey cars just feel quicker for 90% of driving. It's only a matter of physics and it's all about torque.

Simples
Nice write up ......but wrong Power is the real engine performance indicator
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