Currently reading: Our best group tests - McLaren 675LT vs Porsche 911 GT3 RS
What happens when you take two hardcore supercars on a 400-mile road trip? We line up a Porsche 911 GT3 RS and a McLaren 675LT to find out

Thursday, 9.23am: MIRA Proving Ground, nuneaton, west midlands - Thunderbolts are the least you’d expect. A scorched sky, some localised banshee wailing, perhaps – a pathetic fallacy worthy of an ancient Greek myth.

But the weather is anticlimactically calm and clear now as the very low, very loud and very angry-looking McLaren 675LT rolls to a stop in the car park at the MIRA Proving Ground.

Waiting in the same line of marked bays is the car I’ve driven here: one of only a handful of 2015’s other new model introductions with the potential to deny the McLaren the status that Woking would claim for it.

A nemesis? Maybe not – but a rival, a kindred immortal. Something equally special, too, if not more so. Because if this McLaren isn’t the most exciting driver’s car of the year, the new Porsche 911 GT3 RS may very well be.

Both of these cars were outstanding athletes before their latest performance makeovers. Both, as I’m banking you’ll already have read, have since been endowed with the kind of performance and handling superpowers that are normally reserved for cars with racing liveries. And right now, both are here at the start of a very special 400-mile, 36-hour UK road trip.

Read the full McLaren 675LT review

This won’t be the average comparison test. Extraordinary cars call for an equally extraordinary opportunity to reveal themselves – and that’s what these two are getting. And yet it’s already too late for a typical head-to-head verdict on the 675LT and GT3 RS. They’re sold out. So, much as we like to imagine there’s a throng of wealthy individuals waiting with bated breath for Autocar’s endorsement before ordering a new car, we can leave the final arguing and justifying aside.

Instead, we will simply find out what life on road and track is like in the company of not one but two of the most hardcore, most wanted sporting machines that this year, or any year, has to offer.

Thursday, 10.49am: MIRA’s mile straights

Our reason for starting at our favourite Midlands proving ground is simple: the Porsche will feature in a full Autocar road test in the weeks to come, and MIRA is where our road test performance benchmarking magic happens. So a morning of flat-out testing lies ahead, followed by an afternoon of photography.

Then it’ll be an early evening blast north-east, onto little-visited moorland roads once used by this magazine’s road testers to become acquainted with one of the McLaren’s legendary forebears.

Standing-start and in-gear acceleration first. I watch the GT3 RS put in a few runs with colleague Matt Prior at the wheel before hopping in myself.

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Perhaps the aforementioned banshees have turned up after all. The howl that Porsche’s flat six makes is sabre-sharp and supremely characterful. Porsche’s launch control system makes it sound all the more frenzied, governing it at high revs until the car’s gigantic 325-section rear tyres can transmit 493bhp all on their own.

From inside, the car certainly feels fast – even on a wide, empty, mile-long stretch of perfectly flat asphalt – but, like the GT3, only supercar-fast once it’s revving beyond 5000rpm.

The higher reaches of the Porsche’s rev range feel so special, though, suffused with incredible pedal response and with a visceral power delivery still building until beyond 8000rpm, that you want to stay among them whenever you can. The whipcrack changes of the excellent seven-speed PDK dual-clutch automatic gearbox make it possible to do just that.

Although it’s close on swept volume, the 675LT’s engine might as well be from a different planet. This is a compression ratio of 8.7:1 versus the Porsche’s 12.9:1, twin turbocharging versus Stuttgart’s atmospheric aspiration and 175bhp per litre compared with the GT3 RS’s 123bhp per litre.

Porsche 911 GT3 RS

Price £131,296; 0-62mph 3.3sec; Top speed 193mph; Economy 22.2mpg; CO2 emissions 296g/km; Kerb weight 1495kg; Engine 6 cyls horizontally opposed, 399cc, petrol; Power 493bhp at 8250rpm; Torque 339b ft at 6250rpm; Gearbox 7-spd dual-clutch automatic

McLaren 675LT

Price £259,500; 0-62mph 2.9sec; Top speed 205mph; Economy 24.2mpg; CO2 emissions 275g/km; Kerb weight 1403kg; Engine V8, 3799cc, twin-turbo, petrol; Power 666bhp at 7100rpm; Torque 516b ft at 5500-6500rpm; Gearbox 7-spd dual-clutch automatic

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Mr£4worth 11 October 2015

And the best engine?

You have to hand to those Germans -
Price £131,296; 0-62mph 3.3sec; Top speed 193mph; Economy 22.2mpg; CO2 emissions 296g/km; Kerb weight 1495kg; Engine 6 cyls horizontally opposed, 399cc, petrol; Power 493bhp at 8250rpm; Torque 339b ft at 6250rpm; Gearbox 7-spd dual-clutch automatic

That's amazing performance from a 399cc engine!

fadyady 15 August 2015

'go hard or go home'

This pretty much sums up this incomparable comparison review. Riveting read though. Porsche is a one-trick pony, McLaren a fully rounded car.
gigglebug 16 August 2015

fadyady wrote: This pretty

fadyady wrote:

This pretty much sums up this incomparable comparison review. Riveting read though. Porsche is a one-trick pony, McLaren a fully rounded car.

If the Porsche is a one trick pony as you describe it then isn't that kinda the whole point of it anyway?? It's not trying to be every car for every occasion is it, Porsche has plenty of alternatives in their line up if that is what is required and if it's only trick is to be one of the most rewarding car's to pilot available for the dedicated driver regardless of price point then hasn't it met it's brief?? The fact it's half the price of the LT surely makes it good value? Love the LT by the way, by far the most resolved car in their range if you discount P1

fadyady 17 August 2015

My bad

gigglebug wrote:

If the Porsche is a one trick pony as you describe it then isn't that kinda the whole point of it anyway?? It's not trying to be every car for every occasion is it, Porsche has plenty of alternatives in their line up if that is what is required and if it's only trick is to be one of the most rewarding car's to pilot available for the dedicated driver regardless of price point then hasn't it met it's brief?? The fact it's half the price of the LT surely makes it good value? Love the LT by the way, by far the most resolved car in their range if you discount P1

My bad. I should've said that this Porsche or this variant of the 911 is a one-trick pony compared to this McLaren which is an infinitely more complete car. And with 4-pots on the way, Porsches would soon be as innocuous, unexciting and safe as the Volkswagen Golf.

Ofir 15 August 2015

675LT

The NA engine of the Porsche has to be a huge factor in terms of driving excitement but probably not enough to make it more attractive than the Mclaren which is a truly extraordinary machine as it should be for twice the price.

Now, if the 911 had a manual gearbox to go along with that engine I think the table would have turned. It would have cost another tenth to the GT RS which is slower anyway, but that wouldnt have mattered at all.