With 25% different components on the car, the McLaren 650S is obviously very much like its 12C sibling (the 12C continues as McLaren’s entry model), but the new parts confer a distinctly different, more aggressive attitude on the 650S.

The new car’s name comes from its 650 PS or 641 hp (478 kW) power rating, a 25 hp (19 kW) increase from its twin-turbo 3.8-L V8 engine. Naturally, it was no simple matter to find more power in the already strong engine. McLaren’s effort focused on improving the engine’s cooling so that it can run additional ignition advance, reported Executive Director of Product Development Mark Vinnels.

That doesn’t just mean larger radiators, though they are part of the package. Inside the engine the combustion chambers and pistons are reshaped, and most significantly, smaller exhaust valves permit more coolant flow between them to whisk away heat from the hottest part of the combustion chamber, he said.

Changes to the phasing of the exhaust cam improve efficiency slightly, trimming the 650S’s CO2 score to 275 g/km from the 12C’s 279. Fuel economy is 24.2 mpg on the EU combined driving cycle.

These tweaks have fattened and flattened the 650S’s torque curve, which peaks at 678 N·m (500 lb·ft) at 6000 rpm, but is mostly flat between 2500 and 6500 rpm, Vinnels said.

The result is performance of 3.0 s for 0-100 km/h (0-62 mph), 8.4 s for 0-200 km/h (0-124 mph), a 10.6-s quarter-mile, with a top speed of 207 mph (333 km/h) for the coupe. The retractable hardtop Spyder adds 0.2 s to its 0-200 km/h acceleration time and loses 3 mph of top speed.

According to McLaren, both versions of the car weigh the same 3020 lb (1370 kg), which is 13 lb (5.9 kg) lighter than the 12C even though its larger radiators add mass.  “We’re never going to go to market with a car that’s heavier,” Vinnels declared.

The savings were accomplished through the use of lighter forged aluminum wheels and carbon ceramic brakes that are now standard equipment on the 650S.

Performance was never considered a shortcoming in the 12C, but fierce competition in the super-sports-car segment demands continuous improvement. But a shortage of character was a common complaint about the 12C, which McLaren has addressed in the 650S. The most obvious change is to the swoopy, sexy new bodywork that is clearly intended to be more eye-catching than before. It is also functionally better, as the enlarged scoops flow more air to the bigger radiators that contribute to the increased engine power.

The 650S bears a family resemblance to McLaren’s flagship P1, which was designer Frank Stephenson’s goal. “These cars are dramatic to drive,” he said. “I want to reflect that in the new design.”

Simultaneously, the new bodywork increases downforce, which improves the 650S’s high-speed handling response. A new front splitter contributes to downforce that is 40% higher on the 650S than on the 12C, which significantly improves the car’s turn-in response, Vinnels said. “You really notice it on corner entries,” Vinnels explained. LED light technology let McLaren make the 650S’s headlights smaller, giving more flexibility in shaping the front bodywork.

The boosted front grip is balanced by increased use of the deployable rear wing and air brake on the back of the 650S, Vinnels added.

Handling response and feel is additionally improved by the fitment of new Pirelli P Zero Corsa tires that were specifically developed by the Italian tire maker for the 650S. The tires contribute a large portion of the improvement in the 650S’s handling, reported Vinnels.

With their increased grip comes the need for stiffer spring rates, which have increased by 22% front and 36% rear. This doesn’t mean that McLaren has dismissed its previous approach to the market, which is to provide civilized cars that owners can drive daily without suffering. Softer damper mounts and the returned shock absorbers improve on the 12C’s already comfortable ride in conjunction with the track-ready handling.

“If your only target is a faster lap time, then you simply make a good racing car,” said Vinnels. “To make a car that can produce good lap times and has a great breadth of usability—a car that rides well, is refined, is every day usable—that’s a much harder challenge.”

While many of the improvements to the 650S are visible physical changes, many more upgrades are in the virtual arena, where McLaren’s computer coders have adjusted the car’s programming to both improve performance and driver engagement.

McLaren brought the programming in house for its various vehicle control systems, such as the electronic stability control, antilock brakes, and for control of the car’s transmission and clutch, giving drivers more ability to control the car at its limits, Vinnels said.

“We’ve maintained safety with greater yaw angles, for a longer time, before it corrects,” he said. And when hammering the brakes, the ABS computer is not only slower to intervene, it will also relinquish control if the driver eases off the pedal. “It is more progressive in application and it is easier to back out of,” so when triggered, the ABS doesn’t clamp down so aggressively and will return control to drivers more seamlessly than before.

Software controlling the Bosch engine management computer and the Oerlikon Graziano seven-speed dual-clutch gearbox has been revised to include some technically unnecessary but viscerally entertaining actions such as engine “flares” on upshifts.

An ignition cut on shifts gives the impression of action, while the throttle mapping is now more linear so drivers feel immediate power rather than turbo lag followed by a hit of power. As before, exact mapping is driver-selectable by choosing among the normal, sport, and track modes available.