Number crunching the epic Porsche GT3 RS vs GT4 RS fight

Here’s a head to head battle for you. Porsche 911 GT3 RS versus Cayman GT4 RS. If you haven’t, I’d urge you to read the feature or watch the film first. Not least because we had fun filming this one – yes, some of those passes were as close and fast as they looked. 

As part of the film we did a quarter-mile drag race, which the GT3 RS won, but I thought you might enjoy a bit of a deep dive into the data. Not least because of Jack Rix’s confident declaration that if the race had carried on over half a mile, the GT4 RS would have clawed it back and actually won. More on that anon. Or just skip on to the table at the bottom if you must. 

Power to weight ratio is central to any drag race. It’s the simplest guide to a potential result, although of course it leaves a whole bunch of stuff out, from traction and aerodynamic resistance to gearchange speed, gearing itself, torque delivery, tyres and tyre pressures and so on. With 493bhp pushing 1,415kg, the GT4 RS has 348bhp to push each tonne along. For the 518bhp, 1,450kg GT3 RS, the figure is 357bhp per tonne. In other words there’s very little in it, but the slight advantage is with the GT3 RS. 

Both cars are managing traction (ie having to control or limit wheelspin through their launch control systems) until at least 50mph. The GT3 RS has the initial advantage for two main reasons: it has wider rear tyres, and more weight over them due to the rear-mounted engine. And that’s enough to give it a car’s length advantage off the line which it then carries on extending to 60mph, 70mph and beyond. A 0.06secs advantage at 30mph is 0.12secs at 60mph and 0.16secs at 80mph. Small margins indeed. And from there everything pretty much level pegs all the way to 140mph where the GT4 RS is still 0.10secs behind. There’s been nothing in it. 

That changes over the next few seconds. The GT3 RS takes 2.82secs to go from 140 to 150mph, the GT4 RS takes 2.53secs. From 150 to 160mph the gaps are huge: 4.04secs plays 3.17secs. And in that increment, the GT4 RS catches and passes the GT3 RS on the ground. The GT4 RS reaches the half mile marker after 17.62secs doing 154.7mph, 0.06secs ahead of the GT3 RS that is doing 152.1mph. Aerodynamics have caught up with the GT3. A rear wing capable of generating 409kg of downforce at just 124mph is a liability as speeds climb, even if the DRS flap is open. 

So yeah, given enough tarmac, the GT4 is – eventually – faster than the GT3 RS. It’s a fairly colourless measure of performance though. And not nearly as marked as what happens when you nail the brakes. All Porsches have stellar stoppers, none more than the RS versions. The GT3 RS records the third best stopping distance we’ve ever recorded from 100mph – 74.60 metres, bettered only by another Porsche, the 918 Spyder (71.1 metres) and McLaren’s 720S (74.5 metres). It pulls a peak of over 2g. The GT4 RS still stops from 100mph in under 80 metres, which is stonking, enough for sixth overall on the braking leaderboard, pipped by the McLaren P1 and Ferrari SF90. 

That’s enough from me, all the figures are below. Digest to your heart's content.