editorial

The evolution of performance

Many performance benchmarks are used for comparing the performance of cars in order to decide who is best (at something at least). Top speed and acceleration numbers (longitudinal and lateral), top speed are the most used ones. While these numbers are useful for comparing contemporary competitors, this time they will be used for comparing the evolution of record car performance.

The number with the largest halo-effect is still the top-speed. By using the fastest production cars as the selection criterion for this showing the evolution, the progress made can become clear. Turns out top speed itself has increased almost
linearly
over time, from 201km/h in 1949 (Jaguar XK120) to 435km/h in 2014 (Hennessey Venom GT). Since the power required to overcome the aerodynamic drag has a cubic relation (3) to the velocity, the increase in propulsion power required to achieve this would have to increase by a factor of 10,3. The maximum propulsion power increased from 162PS to 1244PS, which is a factor of only 7,7. Considering that new vehicles have higher output powertrains with absolutely (though most likely not relatively) bigger losses and also have downforce rather than lift, the aerodynamic drag coefficient must have gone down by at least 25% to make that possible.

Another standard figure used to compare the performance of cars is the 0-100km/h acceleration. Since power is the product of force and speed and force is the product of mass and acceleration, the power required for acceleration of a car is proportional to the mass, but inversely proportional to the acceleration time (assuming constant acceleration during this acceleration time). The power-to-mass ratio (which everyone somehow keeps calling power-to-weight) should therefore have a proportional relation to the acceleration time (if all other parameters remain constant).

The acceleration time has dropped from 9,8s (Jaguar XK120) to 2,8s (Hennessey Venom GT) for the same selection of vehicles as before. The power-to-mass ratio has increased to 818% between these vehicles (XK120 = 100%), while the acceleration time difference would suggest only 329% would be necessary. Somehow it seems that increasing the power-to-mass ratio does not help improving acceleration beyond a certain point. Drag racers will obviously disagree, but they tend to change the circumstances as well as the vehicle.

It would seem that with Rear-Wheel-Drive only the maximum achievable acceleration is 1,01g (and 0-100km/h in 2,8s), no matter how high the power-to-mass ratio is (0,85PS/kg is the estimated sweet spot). With All-Wheel-Drive 1,13g the limit seems (0-100km/h in 2,5s), since there is no real difference between the 1001PS (0,53PS/kg) and 1200PS versions. Time will no doubt proof these numbers wrong.

When comparing the power-to-mass of these record cars to their acceleration, it also becomes clear that the AWD cars achieve the same acceleration figures with up to 50% lower power-to-mass ratios as their contemporary RWD rivals. Traction therefore makes a bigger difference than power-to-mass. Drag racers would agree this time.

Traction has been improved by better tires and suspension systems, as well as optimised torque delivery via advanced transmissions and traction control systems for both RWD and AWD. The real improvement though is in the fact that mere mortals can achieve the record numbers and not just driving gods (or other people who consider themselves immortal).

The dry vehicle mass of the RWD record cars fluctuates between 1093kg and 1330kg. The AWDs remain between 1450kg and 1915kg. Progress can not be found in the mass of the vehicles, but in the power-to-mass which rises exponentially for every new record vehicle. Unless a revolution happens in the field of traction, not much progress should be expected in acceleration figures. Top speed figures on the other hand are still open. The sky is the limit. Especially if you mess up your aerodynamics. ¤

This article first appeared on my now defunct website www.autoweekly.info on 2014-05-09.

Definition of fast cars?

Sportscars, supercars, hypercars, megacars... Currently there are some debates going on about the moniker to use for fast cars. The designation only has relevance for pub- or street-credibility, but nonetheless the discussions can become as volatile as YouTube comment threads.

Since cars have been around, there was a race for the same credibility going on between manufacturers and the argument was simple: top speed = testicle dimensions (male only market back then). A completely irrelevant figure for the actual performance, but this was the one that really separated the expensive cars from mainstream products and was therefore used to justify it.

300km/h and soon after that 200mph were the numbers which teased the imagination. As soon as one brand achieved one, the others had to beat it, if only by one or two km/h. The fact that these claimed numbers were usually recorded at completely incomparible circumstances and without neutral verification did not seem to matter. It is still interesting to see the graph of this progress.

This friendly fight continued until the McLaren F1 came along. This car was developed for maximum performance and a side effect of low drag, high power in a lightweight and extremely stiff chassis was a top speed so high that the status quo simply stated that top speed actually was irrelevant.

All of a sudden it was more important to have 'a race car for the road', a racing heritage or other non-road car infuences like aerospace technology. Having at least a V10, carbon tub and six speed gearbox driving large wheels with extremely low profile tires only good for drag strips or smooth race tracks was what mattered.

Untill the Koenigsegg CCR came along. The race for top speed and engine power output was back. Bugatti countered well and all of a sudden 1000hp was no longer an imaginative figure, but the actual denominator. Being the only manufacturer having access to tires rated for over 400km/h, they had this number bagged as well.

When Michelin released their high performance tires, Koenigsegg and others such as SSC and Hennessey took their chance and beat all the performance figures which regarding acceleration, braking and top speed. Bugatti came back with the Veyron SuperSport and set the new benchmarks at 1200hp and 417km/h.

Currently the Koenigsegg One:1 is considered to be the ruler, though this is not a road legal car. The Hennessey is, but they did not manage to get the official Guiness record due to not being able to do the record run in both directions.

Does it matter at all who is the fastest or has the most power? If you are an adolescent or someone else who believes that identifying or being identified with something like this does bring a better life, then for sure. To those who appreciate progress in technology a bit. To the rest of the world not the slightest bit. To new small manufacturers who want to give their products a fighting chance, it does a lot.

What is actually remarkable about all this, are not the silly numbers, but that the vehicles are actually still drivable. That is where the real progress has been made.

Now there seems to be a new trend for hybridisation and even electrification. These products match or exceed the benchmark performance figures, but provide a completely different driving and user experience.

Are they better? They bring something new and that seems to be enough to justify them as being better. They seem to be the future that everyone seems to want. Hardly anyone is happy about it though, like with the V6 turbos in F1. Regulations and brainwashing about what should be done seems to have blurred our needs and desires.

It seems that we do need some new definitions to define exiting cars after all. It is just not the one everyone is talking about. By the time everyone will be, we know that we have reached the next phase in performance cars. Can't wait. ¤

This post first appeared on my now defunct www.autoweekly.info website on 2014-05-02.

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