The McLaren 600LT’s top-mounted exhaust isn’t just for show

McLaren is not a company known for fickle design follies, and even though the top-exit exhausts that pierce the engine cover of the company’s 600LT look like the stuff of concept fantasy, they make as much engineering sense as they do street theatre.

In the case of the Longtail’s sibling, the 570S, dumping waste gases at road level requires a complex exhaust system that hurdles the rear axle, involving restrictive angles all the way, but the 600LT gases take a short cut and that has numerous advantages.

Not only does the shorter system reduce back pressure, allowing the 3.8-litre turbo V8 to find even more power and noise, a significant chunk of weight is left on the parts shelf. Eight kilos is saved in tubing and a further 4.6kg spared in heat shields and the cooling fans that would be required to vent heat from the engine bay.

McLaren’s trademark aerodynamics are also improved. Without conventional low-exit pipes, the wall-to-wall rear diffuser is an aerodynamicist’s dream, allowing greater air management at the rear of the car. The result? Boosted downforce and improved stability.

There’s little aerodynamic upset where the exhausts spit hot gas centrally over the large rear spoiler, with a majority of the hard work performed at the outside edges of the wing. A coating of matte black Ceracoat prevents heat damage to the carbonfibre surface and structure. However, no, there’s no happy by-product such as extra downforce, with only a few grams of thrust generated by even the most hardcore turbo-car exhaust, but you might be able to toast a marshmallow. Sweet.

But don’t expect to see the next Kia Cerato blowing exhaust through its top. Despite the advantages, top-exit exhausts generally only work for cars which have the engine located behind the driver, and which have high horsepower expectations.

Before McLaren, Porsche brought the race-car-derived feature to the road on the back of its V8-powered 918 Spyder hyper hybrid, and you can bet the 600LT won’t be the only car to follow the high-performance German’s lead.