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Big Bottoms: The Massive Rear Diffusers of GT Cars

This year’s GTE rules open up valuable aero developments for many manufacturers including Ford, Aston Martin, and Chevrolet. Noticeably left out, however, was Porsche with their rear-engined 911 RSR anchored by the traditional position of the flat-six power plant.

Confirmed by recently released footage of the new German GTE competitor testing at Sebring, Porsche’s making a point to catch up to its competitors by moving the engine forward and slapping a larger diffuser on the naughty end of next year’s RSR. How do the new Porsche aero developments stack up against the competition? We’ll have to wait and see who can perform better on track, but for now we can contrast and compare these large pieces of carbon adhesion.

Photo: Fansofthe12hours
Photo: Fansofthe12hours

Our first subject is the newly revealed diffuser on the 2017 911 RSR. It’s larger than before and certainly takes aim at the others with a completely redesigned rear fascia. Three main sections are separated by four dividers, designed to greatly improve downforce numbers. Of course, this is made possible by moving the engine forward.

Photo: Adrenal Media - AdrenalMedia.com
Photo: Adrenal Media – AdrenalMedia.com

One of the first to flaunt a bodacious rear diffuser was the current spec Ford GT. Designed to the GTE rulebook, the Ford GT took every advantage of the rules and then some (with a waiver to allow the car to race before production models were available). With a look that said, “Ahem, my headlights are up here!” the GT features a diffuser that protrudes beyond the rear of the car, making it a critical piece of hardware almost directly in harms way.

Utilizing the already strong foundation planted by the first generation C7.R, Pratt and Miller elected evolutionary development on the Corvette that debuted in 2014. It may not look too menacing from this angle, but the rear diffuser on the 2016 C7.R was effective enough to help deliver Corvette Racing’s 100th win this year. The ground clearance at the back of the current-spec Corvette is large enough to hide a family in.

The new BMW M6 GTLM is largely based on the GT3 car, which is why we’re expecting a new true to spec GTE car upon BMW’s debut in the WEC come 2018. It will be interesting to see where BMW takes the aerodynamic developments of their new GTE competitor, but an even larger rear diffuser would not be out of question. This year’s GTLM car features a whopping piece of kit at the back along with a fancy paint scheme.

Photo: Adrenal Media - AdrenalMedia.com
Photo: Adrenal Media – AdrenalMedia.com

The new Ferrari 488 GTE takes the prancing horse in a new direction with twin turbos feeding the hungry V8 ahead of the rear axle. This leaves enough room for plenty of trickery at the hind quarters of this colt. From this shot alone of the No. 71 GTE Pro AF Corse Ferrari, it’s easy to see just how tall the tunnels are. As opposed to Ford’s flowing and curvaceous diffuser, the Italians decided to follow suit with BMW and Corvette with very clean, straight lines; in stark contrast the front splitter looks like an organic structure grown instead of manufactured.

Photo: Adrenal Media - AdrenalMedia.com
Photo: Adrenal Media – AdrenalMedia.com

The final specimen in this piece is the beautiful Aston Martin Vantage V8. This aerodynamic wonder features an almost gurney flap-like vertical strip at the exit. Following a more round shape similar to the Ford GT, the Vantage’s diffuser is fitted beneath the hiked-up rear fascia. Also like the Ford, the Aston’s diffuser protrudes beyond the back of the car and is accented by fluorescent green making the already large piece of carbon look even more pronounced.

So who’s got the most egregious looking rear diffuser? Beauty is in the eye of the beholder, and thus, fans and engineers alike will decide on their favorites based on looks and performance. One thing is true, current GTE race cars are featuring the perfect balance between form and function from front splitter to rear spoiler. The eye candy we can expect to see with next year’s models may not stray too far from the norm, but should still leaving us feeling a flushed at letting it all hang out.

Dusty Michael

As a mechanical engineer, Dusty’s passion is for sports cars and endurance racing. In his opinion, there’s nothing better than a race car closely based on a model that you can go out and buy from the manufacturer showroom. He’s very particular about his writing utensils and appreciates a great, cruelty free pomade.