downforce is just negative lift

How a day driving high-downforce cars at VIR taught me I’m OK being slow

We try out a Radical SR and Ligier Formula 4 car at Formula Experiences.

Jonathan M. Gitlin – Sep 11, 2018 7:35 am | 105

Credit: Jonathan Gitlin

Racecars in the pitlane at VIR — Credit: Jonathan Gitlin

When the invitation to try out the new formula and sports prototype cars at Virginia International Raceway arrived in my inbox, I was pretty sure I’d have to politely decline. I could hear the boss’ response immediately: “So, you just want to spend a day at the track doing laps?”

But this invite stayed on my mind longer than I anticipated. The cars I’d be driving—a Radical SR1 and Ligier Formula 4—both offered something I’d yet to really experience: genuine aerodynamic grip. Maybe there actually was something to be gained by saying yes. The powers that be seemed to agree, and so it was I found myself making the five-and-a-bit-hour drive south from DC in the height of summer, all to find out more about the invisible hand that the racing world calls downforce.

A brief history of aerodynamics

Little attention was paid to the concept of aerodynamics during the first few decades of the automobile. This is not surprising; although foundational work by Bernoulli and Euler dated back to the mid-18th century, any practical applications that existed were focused on taking to the skies. When thought was given to the way a car moves through the air, it was in the aid of top speed. If you could lower the amount of drag on a car, you could make it go faster with less horsepower. This practice was exemplified by the streamlined bodies given to Grand Prix cars from Auto Union and Mercedes-Benz in the 1930s, an effort by German industry to boost the precious ego of its Nazi dictator.

The world war that followed taught us much more about aerodynamics, as clever minds on all sides tasked themselves with building better warplanes. Even so, that knowledge took even more time to trickle down to the more frivolous pursuit of making a faster racing car. Malcolm Sayer at Jaguar was a pioneer here, applying his slide rule to the design of the Jaguar C-Type in order to win Le Mans in 1951 and then again in 1953. Still the application of aerodynamic principles at the time was aimed at cutting drag.

As cars got faster and faster, that other aerodynamic force that we call lift began to assert itself (for lift is proportional to speed). That’s great if you’re sitting in an airplane and want to fly, but it’s more of a problem if you’re in a car that’s trying to slip the surly bonds of earth. A car’s tires only have a finite amount of mechanical grip, which has to be split longitudinally (accelerating and braking) and laterally (turning left or right). If you start to exert lift upon the car, that decreases the loading on the tires. As the load decreases, so does the total amount of mechanical grip. At best, this results in slower acceleration, longer braking distances, and less cornering ability; at worst the driver will simply lose control and crash.

With hindsight, the solution was obvious. If an airfoil moving through the air generates lift, then an inverted airfoil moving through air should generate negative lift. Instead of taking to the sky, a car so equipped should find itself pushed down toward the track, which in turn means more traction. A car that generates downforce can therefore corner faster than one that doesn’t. And to make things even better, the faster it goes, the more downforce it generates.

In fact, the first known car fitted with downforce-generating wings was built in 1929, a rocket-powered Opel called the RAK2. But for reasons best known to history, it took 35 years for anyone to follow up on the idea. For that, we have to thank an innovative Texan named Jim Hall. Hall was a racer and co-owner of Chaparral Cars, and he started playing with aerodynamic devices on his cars in the mid-1960s in order to improve their stability at speed. At first these were moveable spoilers, but in 1966 the Chaparral 2E showed up with a honking great wing mounted on pylons high above the rear deck, and the racing world was changed forever.

Hall actually gave racing engineers another tool to generate downforce, exploiting what’s known as the ground effect. Instead of using an inverted wing, the entire body of the car can generate downforce by means of side skirts and a specially shaped floor (called a venturi) that creates an area of negative pressure underneath it. The most extreme examples of ground effect cars are Hall’s 1970 Chaparral 2J and Gordon Murray’s 1978 Brabham BT46B, both of which used fans to further reduce the underbody air pressure. In both cases, uproar from their fellow competitors led to the cars being banned (2J) or voluntarily withdrawn (BT46B).

Even without the trick fans, passive ground effect cars were able to generate huge levels of downforce. In Formula 1, Colin Chapman’s Lotus team was the first to really crack it, and the 1977 Lotus 78 generated about 40 percent more downforce than any other car on the grid. Ground effect cars quickly became the thing to have, and lap times tumbled as a result.

Generating downforce with ground effects rather than wings had some other benefits. A ground effect design will create fewer kilograms of drag per kg of downforce than a wing. And it isn’t as affected by the turbulent wake of air behind another car, which means the racing can be closer. But there was a downside: if something happened to disrupt the seal that separated the underbody airflow—hitting a bump in the track or damaging a side skirt—the effect vanished immediately. There were severe consequences should that happen in a corner. F1 banned the practice in 1983, although the prototypes that raced at Le Mans and in IMSA continued to use ground effects until the early 1990s.

At this point, it would be remiss of me not to note that the advent of downforce in racing hasn’t been entirely positive. Cornering speeds have gone up and lap times have gone down, but many believe this has happened at a cost to the actual racing. This year’s IndyCar generates significantly less downforce than it did a year ago, which has made the cars harder to drive but added to the spectacle. And the rule makers of Formula 1 are in a constant battle with the teams to limit the amount of downforce those cars generate. But for now, downforce remains a feature in most of the racing world—including a few laps for some journalist at Virginia International Raceway.

A Radical SR1 racecar — Credit: Formula Experiences

America’s Nürburgring?

I have a confession to make. While you may imagine I’d bite off your arm for the chance to drive a fast racing car on track, I was actually of two minds regarding the invitation from Formula Experiences. I haven’t raced in anger since 2016, and the past couple of years’ travel schedule has not been conducive to getting much track time. It’s safe to say the cobwebs had set in.

Track map for the South Course at Virginia International Raceway — Credit: Virginia International Raceway

Truth be told, at the age of 42, I’ve sort of made peace with the fact that I’m not really that fast any more. Plus, Southern Virginia in the middle of summer is HOT, and that’s without wearing layers of fireproof nomex.

Nevertheless, it would be daft to turn this opportunity down, particularly since the track is such a gem. VIR—everyone calls it VIR—might not have quite the same history as Road America or Watkins Glen, but it’s still one of the country’s best. Set just across the border from North Carolina, it’s a highly challenging but very rewarding racetrack that some think of as America’s Nürburgring.

I even have some history with VIR. Back in 2013, some friends and I finished second (out of 106 cars) in a 24 hour endurance race at the circuit, held on the 24-turn 4.1-mile (6.76km) Grand Course. Formula Experiences (thankfully) doesn’t use that massive configuration. Instead, it runs the South Course, a 1.65-mile (2.66km) ribbon that features a decent straight, the awkward hairpin called the Bitch, part of the Climbing Esses, and South Bend, a fast, blind, left-hander that would showcase what all this downforce stuff is all about.

The cars

The majority of the cars at Formula Experience are Radicals, open-topped sports prototypes from the UK that are adored by track day addicts the world over. That is not too surprising—Peter Heffring, the man behind the operation, is an accomplished racer in the cars. Despite these vehicles’ extreme looks, they’re actually relatively friendly to drive. The stable is a mix of single-seat Radical SR1s and two-seat Radical SR3s, plus Heffring’s faster, more powerful SR8.

Even the entry-level SR1 is a seriously competent machine. Under the fiberglass skin it’s actually a relatively simple tube frame chassis with some stiffening panels along the sides and underneath. The suspension is Radical’s proprietary “Nik-link” design, with front and rear unequal-length wishbones and adjustable dampers. The aerodynamics come from the front splitter, the shape of the bodywork, and a pretty big rear wing. The car is powered by a 1.3L, four-cylinder Suzuki bike engine that loves to rev up to the 10,000rpm redline. While 175hp (130kW) might not sound like much, the car weighs a mere 1,080lbs (490kg), so the power-to-weight ratio is more than adequate even with a slightly overweight journalist onboard.

The transmission is a sequential six-speed ‘box with a chain-driven Quaife limited-slip differential. Although the car has three pedals, you only need to use the clutch when leaving the pitlane. On the move it’s just a case of watch for the shift lights and flick the right-hand paddle to grab the next gear; the electronics will momentarily cut ignition so you needn’t lift. Downshifts come with automatic throttle blipping, and the gearbox will override you if you call for a lower gear too early to prevent you over-revving it and destroying the clutch or punching some piston straight into the valves. Zero to sixty is despatched in 3.5 seconds, and it should hit almost 140mph with a long-enough straight. More impressive is the cornering potential—up to 1.9 lateral Gs in a fast-enough sweeping corner even on (barely) treaded tires.

The Ligier Formula 4 car is even more uncompromising, even though it’s meant as the most junior rung on the single-seat ladder that, with enough skill and, perhaps more importantly, enough money, may eventually lead to Formula 1. It’s a fully carbon fiber affair, something that’s easy to appreciate here as Formula Experiences’ car has plenty of unpainted panels boasting “pre-preg” weave. Suspension is double wishbones all around, and onboard there are adjustable pushrod dampers, as found in the higher formulae. The front and rear wings are actually aluminum, not carbon—presumably to keep costs down and make them a bit tougher.

The F4 car also gets a four-cylinder engine, but this time it’s a 2.0L Honda K20 C1 engine that makes 160hp (119kW). The transmission in this case is a Sadev six-speed sequential, with a pneumatic paddle shift system. Like the Radical, it has a clutch pedal that you’ll only use to get it moving from a standstill. Since the F4 car weighs 570kg, its performance shouldn’t be quite as good as the SR1, although it runs fully slick tires so has a bit more to give when you come to a corner.

The experience

Our event actually kicked off the night before, when Heffring took each of the attendees for a few quick SR8 passenger laps around the South Course in the dark. VIR has no floodlights (although the SR8 is fitted with headlamps and a lightbar) and even if you have a pretty good idea of the track layout, it’s a frenetic, disorienting exposure as a passenger. You definitely felt the Gs as Heffring swept through South Bend, and I’d be surprised if we were doing less than 140mph before braking for the Bitch. Even two-thirds of the way up the straight, the air was doing its best to pull my helmet off, proving there’s a reason that people who race open-cockpit cars buy helmets with some aerodynamic shaping to them.

It’s a clever move on Heffring’s part: given the very mixed experience levels of his customers, putting the fear of god into them the night before letting them loose in his race cars probably does a lot to keep everyone sober and sensible on track.

A Formula 4 at Virginia International Raceway — Credit: Jonathan Gitlin

The next day started bright and early in the classroom as Heffring gave me and the other five attendees a condensed course on what to expect. This covered stuff like what the different marshals flags mean, fundamental concepts like a tire’s circle of friction and weight transfer, as well as the racing line around the South Course. It’s not as in-depth as you’d get at a race school, but even the most expensive Formula Experience ($2,695) is less than half as much as you’d pay for one of those multi-day courses. The point is not to leave with a race license but is instead to experience what these cars can do.

After about an hour in the classroom, we moved to the simulators (running iRacing) to get familiar with the layout. A few laps was sufficient to remind me which way the corners strung themselves together, and from there it was finally time to get in the Radicals. (Heffring and his team sent me and the other experienced driver out first.) Achieving a good fit in the cars is vital—you want to be strapped in as tight as possible, and you have to be able to see where you’re going. Someone racing a Radical or F4 car would have a custom molded seat prepared, but for us it was good old foam pads and a bit of trial and error.

A Radical SR3 at Virginia International Raceway — It gets hot in southern Virginia in the summer, and these race cars do not have air conditioning or any form of driver cooling. But an umbrella keeps the worst of the sun at bay while waiting to get back out on track. Credit: Jonathan Gitlin

Once suitably situated, we were sent out into the paddock to warm the cars up. The trickiest thing about the Radical was getting away cleanly. Flick a toggle switch to turn on the ignition, then nudge the red start button to fire it up. Next you clutch in, press the Neutral button on the steering wheel, and flick the downshift paddle. (Yes, downshift, because the powertrain is from a motorbike and that’s what they do.) Another quirk of the powertrain is the importance of remembering that, should you spin, you have to remember to put the clutch in. Fail to do that and you’re almost guaranteed to burn out the starter motor. That will put the car out of commission for rest of the day and earn you an $800 repair bill for a new one, although you do get to take the broken starter home as a trophy. (This happened to one unfortunate attendee at turn 7, the Fishhook.)

On track, Heffring uses the tried and tested lead-and-follow method, building up speed successively on each lap and each session. Nothing is being timed, and there is nothing at stake, so it really is a case of only pushing as hard as you feel comfortable doing. My goal for the day was pretty simple: get a feel for the downforce and see if I could left-foot brake. The latter comes naturally to me in a simulator, but I’d never really tried it on track before. As it turned out, in the Radical and later the F4 car just as in the sim, it was utterly natural thanks to unservoed race brakes.

A Radical SR3 race car at Virginia International Raceway — Heffring leads the way in this SR3. The SR1 is parked behind it. You can see that the SR3 has more complex front aero—note the carbon fiber “dive planes” ahead of the front wheels and above the front splitter. Credit: Jonathan Gitlin

As we built up speed through South Bend, it was clear that the invisible hand was helping out, keeping the car glued to the track at velocities that would have seen a non-downforce car understeering off into the grass. The Radical was a joy to drive, and I’ll admit I was dying to know what it would be like to try it on the 3.3-mile (5.3km) Full Course.

Even with the somewhat shorter straight of the South Course, I was able to reach about 127mph before braking for the Bitch, more than fast enough for the airflow to again exert some lift on my helmet. Perhaps with a little more familiarity, you’d nudge 130 before hitting the brakes, but these weren’t my cars, and I wasn’t sure Ars would appreciate the repair bill were the very worst to happen. Running up through the gears before braking and turning down through turns 5 and 6 was a lot of fun, as was the blast out of Fishhook and through South Bend into turn 11. Free from the pressure of worrying about lap times or fighting for position on track, getting a feel for the Radical was highly enjoyable, and I’d recommend it to anyone with a modicum of octane in their veins.

After lunch I switched to the F4 car, an experience I actually didn’t enjoy nearly as much. Partly this came down to comfort in the car. I forgot to put in earplugs, and, as the Honda engine revved high enough to illuminate the shift lights in the steering wheel, it really did get painfully loud. Plus, I didn’t really get a good fit in the car. You sit in a very reclined position, but, even with the foam pads on hand, I wasn’t really situated the way I wanted to be.

Partly, this was also down to fatigue on my part—even though I’d been going to the gym as preparation for my visit to the Multimatic racing simulator in Canada a couple of weeks earlier, I’m in far from tip-top condition. Driving any car on track is a physical experience, and that’s particularly true of these ones, especially through South Bend, which both strains your body and demands some effort in the steering.

A Formula 4 car leads a Radical SR1 at Virginia International Raceway — Credit: Jonathan Gitlin

Worth the trip?

While it’s not exactly cheap, Formula Experiences will certainly qualify as a bucket list thing for some. As I mentioned, you’re not going to leave with a racing license, but the road to one of those will definitely cost a lot more in both time and money. But Heffring and his team have put together a rather good package, one that fulfills the aim of giving you the thrill of experiencing lightweight, high-downforce racing cars in a safe manner. And for those who do get the bug to do more, there are some packages that let you come along to other VIR track days and use their cars.

As for me, between my aforementioned time in the Multimatic sim alongside some professionals and my day at VIR, I think I’m actually quite content racing the slower stuff in the future. I can see how one would get properly competitive in the fast stuff; it just requires more time, money, and focus than I’m prepared to invest. I’d say call me Captain Slow, but someone else already took that one. So with my afternoon feeling true downforce suctioning everything to the ground complete, perhaps staying below 130mph can be a new sweet spot.

Jonathan M. Gitlin Automotive Editor

Jonathan is the Automotive Editor at Ars Technica. He has a BSc and PhD in Pharmacology. In 2014 he decided to indulge his lifelong passion for the car by leaving the National Human Genome Research Institute and launching Ars Technica's automotive coverage. He lives in Washington, DC.

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