Little change, big difference

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We’re in somewhat of a McLaren product onslaught right now. I was recently back in the 625ps 12C – the original darling of the new McLaren Automotive – then soon after out at Dunsfold on the Stig’s stomping ground with the 915ps P1 hypercar with Formula One-style e-boost when desired. And just now I’ve been in the tight optional racing seat of a 650ps 650S on the 5.4km (3.4 mile) Ascari race resort in southern Spain. And, if that’s not enough, in 2015 comes the 911 Turbo-fighting entry model currently called P13 and rumored to pack something just north of 505ps.

There is no doubt, first off, that McLaren has been learning the feet-to-fire series production game like few other companies have had to these days. Making this ambitious product cycle at least a little easier for the smallish Woking, UK, shop are: the use of the same essential aluminum-carbon fiber chassis and the same 3.8-liter M838T biturbo V8 by Ricardo for every model, not to mention the same Graziano seven-speed DCT.

The evident unflappable power range of M838T cannot be underscored enough. Within a year, this compact and relatively lightweight dry-sump V8 will be in five models, providing between 499ps in the 12C GT3 racecar and 737ps in the P1 with its larger turbo housings. How did McLaren tweak the motor from the 12C’s 625ps up to the 650S’s 650ps, and the torque from 600Nm up to 680Nm? Many would simply say that they probably switched out the turbos and fiddled with the software.

Indeed, the software was altered, though they are using the two same MHI turbos maxing at 21.8psi of

boost pressure each. What has been changed in hardware is the header, pistons and exhaust valves, while function alterations include improved heat dissipation, more effective air-fuel mix and combustion in the chambers, plus the latest form of inertia push and a change in the cam timings.

Thermodynamics increasingly reigns here as new ways are found to send the heat generated in an IC engine packing. Engine cooling is improved not only via better coolant circulation around the combustion chambers, but also by a more diffused spray mixture of air and fuel together, with a better combustion and exhaust path for the spent mixture. New pistons in the chambers create less friction between parts while also being instrumental in the better combustion. On the 12C, the two engine radiators at the edgier side intakes are parallel with the sides of the car. On 650S, the side intakes are larger and more rounded to take in more outside air, while the radiators within are now angled toward the incoming air path by 11°.

Pretty simple equation, really: greater and cooler intake and charge air, plus improved heat dissipation after combustion, creates performance benefits from the same engine block.

Finally, in conjunction with the Speed Shift Gearbox, inertia push uses flywheel spin to keep the torque surge climbing when at or over 5,000rpm in track mode of the powertrain dial. With each upshift, revs actually blip up a bit to further eliminate any hint of biturbo lag.

I really appreciate all this added character to the M838T by McLaren and Ricardo. My only quandary is whether McLaren will, even just for the thrill of it, soon provide us with a second chassis with a different footprint, and a second engine. It’s approaching that time in the next two years.

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