The key to understanding the old McLaren P1’s hybrid system is the phrase “torque fill.” It’s a simple concept; use two turbochargers to boost the hell out of a V-8 and combat the resulting lag and high boost threshold with the instant, low-rpm torque of an electric motor. McLaren used torque fill to wonderful effect, with 903 horsepower and 664 pound-feet from the P1’s hybrid powertrain.
A decade after the P1 comes the W1, McLaren’s new hybrid hypercar, and with it, a new hybrid system with a new philosophy for how to blend electric power and internal combustion. In fact, the W1’s hybrid system is entirely different from anything McLaren has done before.
Richard Jackson, McLaren’s chief engineer for powertrain, says that the older torque-fill approach works the hybrid system too hard. With the W1, the idea is to have an engine that, despite enormous turbocharged power, still has good transient response and a hybrid system that provides a monster boost when you want it.
Photo by: McLaren
The other goal with the W1’s hybrid system was to increase power over the P1’s while decreasing weight. McLaren claims an 88-pound weight savings and an output that is 90 percent greater, at 342 hp and 324 lb-ft. As an engineer pointed out in a Wednesday media presentation on the W1’s powertrain, that’s hot-hatch power on its own.
Admittedly, the W1’s battery has much less energy content than the P1’s, 1.4 kilowatt-hours vs 4.7 kilowatt-hours. It weighs 110 lbs to the P1 battery’s 234 lbs—though McLaren does offer a P1 battery upgrade that cuts the original weight figure in half—and all-electric driving range falls from nearly 8 miles to just 1.6 miles. But, McLaren says W1 customers aren’t really concerned about all-electric driving, so the emphasis here is on creating a lightweight hybrid system that prioritizes performance. And that means a battery that can discharge and recharge quickly.
McLaren says the battery is inspired by that in the Speedtail, and it too uses cylindrical cells. Despite the Speedtail’s battery having slightly more capacity—1.6 kWh—only the W1 has an all-electric driving mode. The W1’s battery is also five pounds lighter. For reference, the Artura has a 7.4-kWh battery that weighs closer to 200 lbs.
Photo by: McLaren
Both the W1’s electric motor and its control unit live in a single unit McLaren calls an “E-Module” that weighs just 44 lbs. It’s mounted to the side of the eight-speed dual-clutch transmission and drives the wheels downstream of the main clutches. This allows for a higher torque output without putting undue stress on the friction material. It’s a different approach from all McLaren’s current and previous hybrid systems.
Of course, the hybrid system is nothing without an engine. The W1 debuts a new 4.0-liter V-8, the MHP-8, to succeed the engine that powered every modern McLaren bar the Artura. It has the same displacement as the old 4.0-liter, but McLaren decreased the bore slightly and lengthened the stroke. Despite that, it’s still massively oversquare with a 92-millimeter bore and 75-millimeter stroke—and it revs even higher, with redline at 9,200 rpm.
Power output on its own is 916 hp and 664 lb-ft of torque, which perhaps not coincidentally is more power and the same torque as the P1’s V-8 plus hybrid system. There’s lots of neat engineering in the engine, too. It’s McLaren’s first dual-fuel engine with both port and direct injection, and the first with hollow, sodium-filled intake valves. A smaller bore spacing, plasma-spray cylinder liners, and a shorter chain drive allowed McLaren to shrink the length of the engine overall. McLaren also wanted to keep the height and center of gravity low, so rather than go for a hot-vee layout, with turbos between the cylinder banks, they’re mounted in the traditional position outside the engine.
Photo by: McLaren
Those turbos are twin-scroll for better response, and larger than those in the old 4.0-liter. McLaren didn’t go for electric turbochargers as used by Porsche, Mercedes-AMG, and notably by Ferrari with the F80, as the extra weight they bring wasn’t worthwhile. The engineers would rather use the battery energy to power the electric motor.
McLaren also put a lot of work into using the engine to boost driver engagement. The engineers optimized component stiffnesses, fit longer exhaust manifolds, and even moved the timing system to the back to give just the right amount of noise and vibration.
Other neat details worth mentioning; the MHP-8 has hollow camshafts, finger followers in the valvetrain, and 3D-printed cores in the water jackets. Overall, this engine is 22 pounds lighter than its predecessor while providing a 15-percent performance increase.
The MHP-8 will go in more than just the W1. So, expect to see this engine in the successor to the 750S, whenever that arrives. The engine was designed to meet the incredibly strict Euro7 emissions standards, and McLaren has no plans of doing a non-hybrid variant.
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