Sometime in the next few days, McLaren will freeze the design of its next mid-engined sports car. It matters, as it will be their biggest seller.

This car, codenamed P13, goes into production at the end of 2015. That date means it will physically replace P1’s place in McLaren’s Production Centre in Woking. But it takes less than a third of the man-hours to make than the crazy-complex P1 takes, so McLaren will be able to make a lot more of them and, crucially, sell them for a lot less.



The signs are that the P13 will cost about £125,000, putting it below the top end of the Porsche 911 tree. It’ll have less power than a 911 Turbo S, and is rear-wheel not four-wheel drive, but it does use a carbon fibre structure. So it’s a different kind of car.



McLaren has said many times that all its models will use basically the same carbonfibre tub, dubbed ‘monocell’. This tremendously stiff structure runs from the bulkhead ahead of the driver’s and passenger’s feet, back to the bulkhead behind them. (The P1’s even stronger structure, called ‘monocage’, also embraces a carbonfibre roof frame, but it’s an adapted version of the same thing.)



From that we know that the fundamental layout of the P13 will be the same as the 12C and 650S - a strict two-seater, with the later option of a spider version.



According to Mark Vinnels, McLaren’s engineering director, the final styling sign-off for the P13 is a choice between two models. And as you’d expect from McLaren, selecting between them isn’t just a beauty contest.



It’s about which one can be built to the highest quality. The skin will be aluminium - steel is too heavy - but Vinnels is working with suppliers to investigate what processes can best be used to make the P13’s panels. They’ve looked, for instance, at superforming.



In any case, the P13 will be mostly aluminium on the surface. The new 650S has more carbon fibre, including its doors.



The P13 will also have a similar suspension system to the 12C and 650S. This has a set of fluid pipes linking the top-left and bottom-right, and vice versa, of the dampers at each end of the car. Electronically controlled valves open and close these links. There are no anti-roll bars, and soft springs. It means the car can have a soft ride when the dampers are decoupled on a straight, for ride comfort, but great roll control in corners.



Vinnels implies that although this system is expensive, it gives McLaren such advantages over the competition that it’ll be included on the P13.



He also outlines some of McLaren’s other must-haves: drivability, comfort and great visibility by supercar standards. The company has also said that the new nose design, similar on the 650S to the P1, will be echoed on all future cars. But they want to emphasise it’ll not be a near-identical cookie-cutter theme. The designers want you to be able to tell the cars apart.



Which brings us to a difficult question. If the P13 has the same tub as the 12C and 650S, and the same basic layout, and similar suspension, how is McLaren going to make sure it doesn’t cannibalise those cars? Well, the fact that the 650S has moved up in price and power tells us something. The P13’s power will be a fair bit below that 650bhp level.



How much? Under 500bhp, you can be sure. Some company sources have said it’s about 450bhp. After all, it will be lighter than the competition. But if so, will it need the V8? After all, if it gets a lower-boost version of the 650S’s 3.8-litre engine, and likely the same transmission too, then the differentiation between the P13 and its big brother gets even slimmer.



So I ask Vinnels if a V8 is central to what makes a McLaren. He says no: what matters is getting the necessary performance and drivability. Seems to me a turbo V6 will help reduce the P13’s weight even more, as well as being one of the few things to making it feel truly different (as opposed to just slower) than the 650S.