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0-60 mph Calculator
Calculating the 0-60 times for sports cars
We're often asked whether we can produce a simple 0-60 mph calculator to determine a car's theoretical 0-60 time based on a few simple criteria such as its weight and power (bhp or brake horse power).
Our answer's always been a fairly emphatic no; at least in theory. There are simply too many factors that can affect a car's acceleration:-
BHP - Brake Horse Power
Car performance figures are normally quoted as their maximum power and this isn't always available to the driver as at any given road speed, in a given gear the engine won't be achieving maximum power except for a brief period, normally just before the gear change. However, in practice, during a fast 0-60 test the driver is able to achieve pretty close to the theoretical maximum power by a) slipping the clutch, b) spinning the tyres, and c) leaving the gear change (where necessary) until the last possible moment so that when second is taken at a speed that puts the car close to its maximum power.
Tyre Adhesion
At the start of a timed run the driver will spin the wheels to get maximum power from the car, and the ability of the tyres to turn the power delivered to them into forward motion is paramount. The more powerful the car, the more difficult a job the wheels and tyres have to deliver that power to the road. Their work is significantly affected by the layout of the car, with rear wheel drive cars putting down the power quite well, and four wheel drive cars doing an even better job of converting the engine's power into forward motion. On the whole though, car designers do of course take all these factors into account, with the more powerful cars tending to have designs that do a good job of putting down the power available. So the variation caused by this factor is significant, it doesn't make it impossible to calculate a car's theoretical acceleration.
Driver Skill
This one of course is a major factor, unless you're driving a BMW M3 with launch control. Dump the clutch too fast and the engine looses revs, or else the tyres just spin. And if a gear change is required it has to be executed at the right time, with speed and accuracy. However, we can assume for the purposes of this calculation that the driver is reasonably skilled so this factor can all but be eliminated for manual cars.
External Resistance
At lower speeds, the rolling resistance and air resistance have little effect, but towards the sixty miles per hour point both start to play a part. However, if we confine our analysis to sports cars, we find that they tend to have similar cDs (Co-efficients of Drag) for this not to be a major factor.
Internal Resistance
Again, we find that in general these cars are similar to each other in terms of the resistance of their internal components that this doesn't make a major difference. However, if we include true automatics in the equation the situation is very different, and it's hard to factor this in.
Gearbox Technology
Some 'automatic manuals' such as the latest BMW systems can be just as efficient as a manual, and the DSG systems being developed by manufacturers such as Audi should be every bit as efficient as a manual, and should also change gear faster than any human using a conventional box. So for now, we're going to assume we're talking about regular manual sports cars. Gearbox ratios also play a part in making it possible to keep the car in its power band during the trial.
But can you calculate 0-60 times based on horsepower and weight
Well, having decided that in theory it's not possible we're reminded of the engineer's adage - In theory, practice and theory are the same thing, but in practice they're not.
We analysed the manufacturer's 0-60 times for a range of popular sports cars and found that in practice the quoted 0-60 times are easily and quickly calculated to the nearest second by dividing the weight of the car in Kg (Kilogrammes) by the cars' maximum brake horse power. Further analysis revealed that the more precise formula for most cars is:-
weight of car in kilogrammes
0-60 time
=
---------------------------
maximum bhp of car * 0.9
OK, it's not a precise science, but it does work (most of the time),
So for example, take the current Toyota MR2 which weighs in at 975Kg and has a maximum power of 138bhp. Using our formula we calculate the car's 0-60 time to be 7.9 seconds, and the quoted figure is 8.0.
Further analysis suggested that this tended to be true across quite a wide range of cars, and where it wasn't true, it was possible to explain why the car was achieving better than, or worse than figures.
Using this theory, we accurately predicted the figures for many cars to within 1/10th of a second.
For example:-
TVR Tuscan S (Manufacturer's quoted
0-60 time 4 seconds)
weight 1100Kg, Max Power 310bhp, Calculated 0-60 time 3.9 seconds.
Porsche Carrera 4 (Manufacturer's quoted
0-60 time 5 seconds)
weight 1405Kg, Max Power 316bhp, Calculated 0-60 time 4.9 seconds.
Porsche Boxster S (Manufacturer's quoted
0-60 time 5.7 seconds)
weight 1320Kg, Max Power 260bhp, Calculated 0-60 time 5.6 seconds.
BMW M3 CSL (Our test 0-60 time 4.3 seconds).
weight 1385Kg, Max Power 355bhp, Calculated 0-60 time 4.3 seconds.
Porsche Carrera 4s (Manufacturer's quoted
0-60 time 5.1 seconds)
weight 1470Kg, Max Power 316bhp, Calculated 0-60 time 5.2 seconds
See more information on the results we calculated, compared to the manufacturer's own 0-60 times, and the times resulting from our tests - zero to sixty times.
(Please note - manufacturers' specifications can change - please check any manufacturers' details for yourself before basing a purchasing decision on any data on Cars-Cars-Cars.Org
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