The next day, Matt Saunders, Cook and photographer Luc Lacey are in a car park on the B4560 above Crickhowell. It’s a bit miserable with showers coming and going. Saunders has brought with him the MX-5. We’ve chosen a 1.5-litre version because its 130bhp will better illustrate the point we’re making.
We plan to make three different runs. The first is the run up from Llangattock (a small village just outside Crickhowell) up to a T-junction where it meets the B4560. Once you’re out of the village, it’s national speed limit the rest of the way. We reckoned that the best plan was to drive up in a pair with the lead car setting the pace and the one behind it being the one whose data was being captured. For consistency, Saunders is to drive the McLaren on all the runs and me the MX-5. Cook will ride shotgun in whichever car is being ‘data captured’.
The second and third runs we will make along the B4560 in each direction. Our first run is between fields and trees but the others are much less hemmed in and across open moorland. The first run is entirely uphill, the others mostly so. No point using long stretches of downhill because both cars will spend time coasting with closed throttles.
So here we go. Saunders in the 720S on run one with me following in the Mazda with Cook. He’s not even using a laptop, just his mobile phone, which receives the data via Bluetooth from a widget that he’s plugged into the car’s OBD port. It’s that simple.
On these damp roads, it’s amazing how much effort I have to put into keeping up with the McLaren. Also, it’s much easier to keep myself from going over 60mph than I expected it to be. Mostly I’m in third and fourth gear, only briefly into fifth.
With the run done, Cook slips into the 720S and it’s their turn to follow me as I drive as near as possible at the same speed as before. I suspect Saunders is having less trouble keeping up with me than I did following him. Now to what we call the top road. Our first run on this route works perfectly and we later discover that we’ve managed to keep within two seconds of each other over a run that took 140 seconds. Unfortunately, on the run in the opposite direction we’re baulked by traffic, but no matter because the results from our first run up from the village and then our first across the open moorland are excellent.
Saunders reports that he’s been using hardly any throttle but I can’t wait to see what the data says. Cook produces a graph that tells the story perfectly. For long stretches, the MX-5 used about 93% throttle (actually, the maximum opening possible), while in contrast the 720S only for one brief instant used 70% but averaged nearer 25%. Our speeds, as you can also see from the graph, were very similar – and more or less within the limit.