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Showdown: Porsche’s WEC racer vs Merc’s W06 F1 car | Top Gear

March 10, 2016

Please understand that this is more of a dare than an instruction. Go to the Federation Internationale de l’Automobile website, and, assuming you’re feeling lightly masochistic, download the Formula One technical regulations document. It’s 90 pages long and full of such gems as “3.12 Bodywork facing the ground: fully enclosed holes are only permitted in the surfaces lying on the reference and step planes forward of a line 450mm forward of the rear face of the cockpit entry template…”

Riveting stuff. You can do the same for LMP1, too. 79 pages of equally impenetrable motorsportese. It would be half that number, actually, if it were all in one language, but since Le Mans, the ACO and the FIA are all French, the LMP regulations run in two columns, French on the left, English on the right. So let’s call that 40 pages.

What this surely boils down to is that your average F1 car is twice as technical as your bog-standard Le Mans Prototype. Not so. Just more tightly bordered and organised. Both start with fuel regulation at the core of their policy – the pressure to be more fuel-efficient (and therefore relevant) governs much of the thinking process about the future of motorsport. As for how each formula is set up, think of it this way: Le Mans gives you an energy allowance and tells you to go off and do what you want. F1 gives you an allowance and tells you how to spend it as well.

This feature came about from an idle comment Mark Webber made when I was chatting to him late last year, “You know, at Shanghai, our fastest lap in qualifying was only half a second slower than Lewis’s fastest race lap.” Jeepers. I hadn’t given it much thought, but I’d always assumed there were eons between how long it took, say, a Mercedes F1 W06 Hybrid and Porsche 919 Hybrid to get themselves around a circuit. Turns out that’s the case. Mark wasn’t wrong, but Shanghai was the closest it had ever been. Nevertheless, it got me thinking…

Back in the office some digging occurred, and then some arm-twisting, and finally both Porsche and Mercedes granted us access to their world championship-winning cars for this photoshoot and, perhaps more startlingly, agreed to provide us with comparative telemetry data from one circuit: Spa. You can see more about that and have a go at playing the race engineer by analysing and interpreting the data (at the end of the gallery). But first the technology.

Regulations govern all sport. They are the framework within which each sport operates. The motivation in adopting hybrid technology for both F1 and LMP is fuel efficiency: they want to be seen as relevant, advanced, cutting-edge. But where endurance racing regs leave engineers to decide what tech works best for them, in F1 those decisions have already been made by the regulators. They decide the toys you get to play, meaning less scope for imagination and creativity.

Let’s deal with F1 – and yes, I’m going to have to keep this simple and skip lots of stuff, else we’ll end up with something Tolstoy-esque in length, meaning and complexity. So F1 cars are limited to 100kg of fuel (about 133 litres) per race, and have to use power units comprised of six components, only one of which is the 1.6-litre V6 engine. The others are the turbocharger, the kinetic energy recovery system (MGU-K), the heat energy recovery system (MGU-H), the energy store (battery, supercapacitors or flywheel – it’s the one area teams have some options, although they all use batteries currently) and the control electronics. Power figures are never discussed, but it’s widely accepted the V6 turbo develops about 600–650bhp, while electrical power is restricted to 161bhp. The car, including driver, has to weigh at least 701kg.

Meanwhile, under LMP1 regulations, it’s the rate of fuel flow that’s restricted, but this varies depending on how much electrical energy you want to release per lap: two, four, six or eight megajoules. Just to follow that for a second, a joule is a measure of energy, roughly equivalent to a tennis ball travelling at 13mph, or the power needed to produce one watt for one second. A megajoule is a million joules. Anyway, the more electricity you choose to use, the less fuel you get. The equations are almost constantly being tweaked to keep things competitive, with fuel-tank size and flow rates adjusted, but in essence electrical power is worth fractionally more than petrol/diesel power.

No one in LMP1 uses the same method. Famously, Nissan rocked up at Le Mans last year with a front-wheel-drive machine with a flywheel system in the 2MJ class. Audi opted for the 4MJ class for its 4.0-litre V6 diesel, Toyota 6MJ for its naturally aspirated V8/supercapacitor-equipped TS040, and Porsche? Well, somewhat unusually, Porsche copied F1 technology.

In adopting a small-capacity petrol engine (here a 2.0-litre V4 turbo rather than a 1.6-litre V6), and two hybrid systems, it followed the template laid out by Mercedes. Again, power figures aren’t openly acknowledged, but it’s believed the V4 puts out over 500bhp, while the two recovery systems – kinetic from brakes and heat from the exhaust gases – help deliver a massive hit of e-power. How much? Well, Porsche states over 400bhp, but rival teams believe it could be much, much higher than that, perhaps as much as 750bhp. The 919 weighs 950kg including the driver.

This means F1 and LMP1 cars have similar power-to-weight ratios. Around 1,140 bhp per tonne for the W06, plays a potential 1,310bhp per tonne for the 919. Of course that’s by no means the end of the story – both are designed for very different disciplines: a two-hour sprint versus a 24-hour, well, sprint. Don’t go thinking that these days endurance racing is about measured consistency, staying out of trouble and metronomic reliability. As Mark Webber says (see slide 11), Le Mans is now an all-out, no quarter given, dash for the flag.

Strip away the bodywork and underneath, the 919’s carbon tub looks much like an open-wheeler, and, by all accounts the two have similar downforce levels (about 700kg at 80mph, it’s believed). However, due to its faired-in wheels and closed cockpit the LMP1 car has much lower drag.

So why, with all that power, isn’t it faster on the straights? Because it uses its electricity differently. An F1 car is allowed to deploy 4MJ per lap, but only through a nozzle 161bhp wide, if you see what I mean. The Porsche has twice the electric reserves, but squirts it out through a 700bhp hose. Its reservoir is depleted sooner. So rather than use it at high speed, where electrical consumption is massive, Porsche uses it for the first phase of acceleration. Yep, the 919 accelerates faster than the W06.

But weighing 250kg more, it doesn’t have the braking and speed through fast corners of the Mercedes. Overall, in qualifying at Spa, the W06 was 7.57 seconds faster. The margin was smaller in the race, but that’s still a big gap: the LMP1 car would have been last on the F1 grid. The same story plays out across other circuits the two have visited: Silverstone, Shanghai, Bahrain and Austin.

Will LMP1 cars ever be faster than F1 cars? Doubtful. F1 cars now are slower than they were 10 years ago, and if LMP1 lap times start to genuinely rival them, doubtless F1 regulations will be altered to maintain the advantage. The question is whether this will improve the racing, which, at the end of the day, is what it’s all about. Despite the restrictions, racing isn’t close in F1 at the moment. But in LMP1, where the teams make their own technology and hardware choices, the margins are small and the cars more distinctive. If nothing else, there are lessons to be learned there.

Mark Webber

“Compared to an F1 car, the first things you notice about an LMP1 car are the extra weight and the higher centre of gravity. It tests the driver and is perhaps a wee bit more challenging to drive. Certainly at Spa, Eau Rouge in an F1 car is easy flat, but you have to hold on to the 919 a bit more and our speeds are about 20-30kph down through the quick stuff.

“Where we have advantage is in the slow corners. An F1 car stops better, and the line and trajectory aren’t much different, but we maybe want to get the car turned in sooner, so we can get back on the power. And then what we have in our favour is 4WD and fantastic Michelin tyres – we can really lean them, they’re so much better than the tissue paper we had in F1. So out of La Source, we can really give an F1 car a run.

“It would be really interesting to take the 919 somewhere like Barcelona, which is mostly slow-speed corners, because I reckon we’d be pretty competitive against an F1 car there.

“The biggest thing to get used to when I moved from F1, besides the weight of the car, was the traffic and range of conditions in a WEC race. You know, low sun, the rain, the dark and, most of all, the other cars, which maybe don’t have such experienced drivers and might be travelling much slower. So you need the car to give you confidence, be really consistent and predictable.

“And where you see F1 cars backing off and having to manage fuel reserves, we never have to do that – we’re flat out, all the way. And the 919 is just awesome, the most advanced car I’ve driven, without a shadow of a doubt.”

Spa-Francorchamps

Broadly speaking, the lighter, nimbler F1 car is quicker through the speed traps and into corners, but the 4WD Porsche can get on the power earlier, so exits the medium- and slow-speed corners faster. Through fast curves the W06’s downforce and lighter weight give it the advantage.

KEY

Merc speed/gear: green
Porsche speed/gear: black

Source: Showdown: Porsche’s WEC racer vs Merc’s W06 F1 car | Top Gear

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