When testing out a McLaren supercar out in the wild, expect attention. Lots of it. People ask what you do for a living, middle school students stop in their tracks to stare and take video, and fellow motorists wave on the highway. The British company’s latest achievement is the 750S, and it’s no t only a piece of artwork on wheels in either the coupe or open-top body style, it’s a mechanical beast that zooms from zero to 60 in a blistering 2.3 seconds. The 750S is rear-wheel drive and equipped with a 4.0-liter twin-turbo V8, situated longitudinally behind the seats and topping out at 206 mph. It’s a sleek car that begs for a joyride—within reason, of course, because no one wants attention in the form of a speeding ticket. And the spider version (in convertible form) is especially gratifying. All the better to hear the snarl, bark, and howl of all eight cylinders. The 750S is rear-wheel drive and equipped with a 4.0-liter twin-turbo V8 capable of reaching 60 mph in 2.3 seconds. Images: Kristin Shaw / Popular Science A symphony of engine and exhaust sounds in the 750S At the helm of the 750S’s impressive mechanical prowess is Sandy Holford, a 16-year McLaren veteran. As the chief engineer, his job is to bring together all the different experts at McLaren to get the best overall mix, or recipe, he says. Along with that mix is a distinct soundtrack, a specific roar that only McLaren can make. Every car has a “voice” and the McLaren’s is a crisp mid-level growl that sounds to my untrained ear as though it’s not quite as low as a Lamborghini and not as high as the clipped staccato notes of a Pagani. Once you learn the notes of the McLaren symphony, it’s unmistakable. “We don’t focus on just exterior sounds; we review and score the exterior and interior sounds separately,” he says. “You want the car to sound fantastic when it goes past, but as a driver, you also want it to sound fantastic when you’re inside the cabin. Both are equally important to us.” The engineers don’t target a specific decibel range for the 750S. Instead, they focus on acoustic quality, linearity, and crescendo. As the driver engages the accelerator, the sound builds like an orchestra pit in a powerful section of music, boosting engagement and connection to the car. Part of the sound comes from powertrain development, and McLaren did deliver increased performance with the 750S, but Holford states the primary goal for the vehicle overall was driver engagement. “That building crescendo is a direct response proportionally to your foot on the pedal, bringing that cognitive connection with the vehicle,” he says. “We tuned it acoustically to give the 750S a sharp and distinctive, clear tone.” The noise, vibration, and harshness engineers in Holford’s department would explain they “reduced the second and sixth order sounds and allowed the fourth order acoustics to dominate, then pushed the eighth order sound to get that higher crescendo at higher engine speeds.” In non-engineering terms, they balanced specific sound frequencies to achieve a big, clear sound, rather than just big volume that doesn’t necessarily represent the quality of the car. Picture a cheap stereo setup with a giant woofer, for instance. It can belt out the sound but it’s going to be a different kind of noise than if the same song was played on a high-end audio system. When I left the house in the morning to take my son to baseball practice at 6:30 am, I wasn’t so sure how the neighbors felt about that crescendo. But to me, it’s literally music to my ears. The building crescendo of sound is a direct response proportionally to the acceleration. Image: McLaren More combustion, more pressure, more layers, more power The 750S emits thrilling pops and crackles to accompany the music, like a drumbeat. That’s the combustion of fuel at play, entering the exhaust manifold and coming down the full exhaust system, Holford explained to me. Importantly, when in track mode that’s a whole different story. “It’s a combination of ignition timing versus fuel injection, so you end up with a little bit of excess fuel that then combusts as it heats through the engine cycle,” he says. “When you get to track mode, you don’t want any excess fuel. You want every single piece to have been used optimally for that performance element.” The secret to the 750S’s insane acceleration is decreased vehicle weight and the additional power squeezed from the same engine used in the supercar’s predecessor, the 720S. Key factors are a combination of revised internal components and bespoke calibration, Holford says. That includes increased turbocharged booster pressure working together with twin fuel pumps that deliver more fuel and air. As a result, the 750S can combust more with greater power. McLaren also upgraded from a dual layer to a triple layer head gasket to cope with that additional combustion within the engine. “When there is more pressure in the cylinder, because we have more fuel and more air, it needs more compression and more resistance to keep that pressure within the cylinder,” Holford says. “We have to go for a more robust ceiling interface from a dual layer to a triple layer to manage it.” All in, the 750S is a poster car, the kind of vehicle that’s often affixed to walls around the world as inspiration.   “That’s the thing for me, when I see kids with their Hot Wheels McLaren car, or their [McLaren] T-shirt or whatever else, that’s just fantastic,” Holford says. “Because it shows what we’ve done and how people are really appreciating and enjoying the products we make.” The post The symphonic sounds of the McLaren 750S are a feat of engineering appeared first on Popular Science. ...read more read less