Bro, Do You Even Lift?
Last week, our own Doug DeMuro asked the B&B for their opinion on the stupidest automotive feature. He then gave his personal opinion as to what that feature might be. I’m here to tell you why he’s completely wrong, and why he’s probably also completely right.
Let’s review Doug’s suggestion for “stupidest automotive feature” right quick:
I’ve never really understood the purpose of this retractable spoiler. Ninety-nine percent of the time, when you see it sticking out on a Porsche 911, the driver is just cruising down the interstate. That’s because the spoiler is designed to deploy based on speed, not driving style, apparently in some bizarre effort to keep your car on the road should you begin to experience the effects of a massive windstorm.
The funny thing is these spoilers are never adequately sized to actually do anything. They’re just there to be spoilers, so you can tell your friends you have a cool spoiler that extends out at speed as if you’re in a race car, when in reality the spoiler is the size of a license plate and it wouldn’t have any effect on any vehicle larger than a Hot Wheels.
Obviously Doug’s aiming for humor here, but as TTAC’s resident owner of a Porsche with a retractable spoiler, I feel compelled to defend the indefensible for a moment and to explain just why the retractable spoiler was such a brilliant idea at one time. And then I’ll have to admit why it’s not such a great idea now.
Let’s start with why you would want a spoiler at all. Consider, if you will, the airplane wing. You all remember how that works, right?
The air moving over the top of the wing has a longer path to travel. It therefore moves faster and creates a zone of low pressure above the wing. Since the pressure beneath the wing, on the flat surface, stays the same, the net effect is to lift the wing.
Having looked at the side profile of a wing, let’s look at the side profile of a proper 911.
You can clearly see how a 911, or any vehicle that approximates the shape of a wing, generates aerodynamic lift at speed. This aerodynamic lift reduces the pressure on the tires and reduces their ability to grip the road. Moreover, for reasons that it would take more than a paragraph to explain, the lift tends to be strongest at the back of the “wing”. For that reason, the original 911 tended to be difficult to control as high speed, because not only was it suffering a grip problem as speeds increased, it was also experiencing a change in the ratio of grip between the front and rear wheels. Today’s 911 GT3 has 245-width tires in front and 305-width tires in back, but the original 911 had 165-width tires both front and rear, leading to some genuinely troubling behavior once you got much above 80mph or so.
Porsche addressed this with the fastest early 911, the Carrera RS 2.7, by adding a “ducktail”.
The ducktail disrupted, or “spoiled”, the wing-like airflow and caused an area of high pressure over the back wheels that helped reduce the overall wing effect. Note that a ducktail or any similar spoiler can’t really create measurable downforce. Its purpose is just to remove some of the lift. The first-generation Audi TT, for example, had a 911-style tapering rear. That shape reportedly generated about 140 pounds of lift over the rear wheels at 125 mph. After five people died in accidents that might have been related to high-speed handling issues, Audi installed a small lip spoiler to reduce that rear lift by about two-thirds.
Now let’s look at a 911 with a wing, as opposed to a spoiler:
That’s a wing, you see. It creates measurable aerodynamic downforce on the rear of the car, increasing grip as your speed increases. Very few street cars have wings that increase downforce, although the Viper ACR sure as hell does; most street cars have spoilers that reduce lift somewhat. The difference between a spoiler and a wing is that cars with wings grip better at 150 mph than 50, whereas cars with spoilers do not grip as well at higher speeds. They’re just less troublesome.
Porsche’s justification for restricting the use of spoilers to the Carrera RS and, a few years later, the Turbo Carrera was simple: Spoilers are aesthetically impure and unpleasant, so they should be limited to very fast road cars. A 1970 911T was many things, but with only 125 or so horses it wasn’t fast.
The arrival of the 964-generation 911, with its 250-horsepower 3.6-liter engine, put the company in a bit of a pickle. It was pretty much as fast as a ’77 Turbo Carrera, if not a bit faster, so shouldn’t it have a spoiler out back? The obvious answer from an engineering and safety perspective was “yes”, but the aesthetic and marketing issue wasn’t as clear cut. While American buyers were big fans of “whale tails” and the like, making cars like the paper-tiger Carrera 3.2 “Turbo-Look” big sellers, Europeans supposedly preferred the clean look of a slick-tail 911. The largely mythical high-powered German businessman, using his 911 or S-Class or BMW as an alternative to high-speed rail across West Germany, was still a powerful enough archetype to swing product-planning decisions in the pre-tech-boom, pre-Russian-capitalism market.
So Porsche came up with a solution. The 964 looked like a standard 911 at rest, but at freeway speeds it would deploy just enough spoiler to bring rear-end lift within safe parameters. It’s really a brilliant idea. Doug’s note that the spoilers deploy at odd speeds is, I believe, an effort on the part of Porsche to prevent the deployment of a spoiler from being evidence that the driver was speeding. You really only need the spoiler at 80 mph or above, but in a country with a 65 mph speed limit, that’s problematic to have it deploy at illegal velocities.
Having driven a variety of Porsches at relatively high speeds, I can personally attest to the effectiveness of the retractable spoiler. The photo at the top of this article shows me and my son doing about 100 mph on the back straight of Mid-Ohio. He was only three years old at the time so I was anxious not to kill him. The rear spoiler makes the handling of the 993 very predictable and safe — from a perspective of rear-engined sports cars, anyway.
Why doesn’t every car have a retractable spoiler? Well, most cars are designed in a wind tunnel to minimize lift nowadays, something that didn’t happen as much in 1963 when the original 911 bodyshell made its debut. And most cars are far more wedge-shaped than a 911. Still, it’s worth noting that non-Porsche cars with the same sort of boat-tail rear, like the current AMG GT-S, often feature an active rear spoiler. The VW Corrado, another car that pioneered this feature in the late Eighties, almost certainly didn’t need it, being wedge-shaped and already featuring a small lip at the end of the tailgate — but what the hell, it was fun. It’s not uncommon to see NASA Time Trial Corvettes with a “Gurney flap” bolted on to the rear deck. The Gurney flap is a more aggressive kind of spoiler. The current Corvette, when ordered in Z51 form, comes standard with a Gurney flap.
Like Doug DeMuro, I have little patience for people who use the button to keep the spoiler deployed. But I’ve found a justification for having the button around: When there’s a cute girl working the drive-through at Wendy’s, you can deploy the spoiler while talking to her as a conversation device. If you think this has never gotten a Porsche driver laid, you’d be wrong, although it makes enemies more often than it makes friends.
As to why current Porsches, which are wind-tunneled to a fare-thee-well, feature the retractable spoiler, I think I covered the reasons for that a few weeks ago. The “base” 911 is now associated with a retractable spoiler, so that’s why the Panamera has one and why the Cayman has a tiny one. But we’ve long since abandoned the idea that the 911 is purchased by steely-eyed German company directors who like to do 250 km/h in a rainstorm. It’s safe to say that pretty much everybody who buys a 911 today would like to have actual racing wings on the thing. The only reason they don’t all have wings is because that’s how they get you to pay more money for the car. There’s no way the fixed wings on the GT3 cost more to make than the retractable arrangement on a base Carrera 2, but we’re talking about a company that charges you more to not have a convertible top on your Boxster.
So the retractable spoiler is technically sound, but it’s socially stupid — which makes Doug wrong, and right. But as for me and my 911, we will continue to prefer it. Perhaps the best comment I ever heard about the feature, however, came from a female friend of mine, a former stripper and escort, who was driving behind me on the freeway years ago and said to me afterwards, “Well, that car’s just like a girl: when you want to hustle, you got to stick your ass up.” Now that’s smart, right?
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