Darby Barber’s Turbocharged Miata: A Time Attack Special

While finishing her studies at College for Creative Studies six years ago, Darby Barber started searching for a fun vehicle to use on the weekends. Like many of us, she saw the potential in a Mazda Miata. Bought with the earnings from Motor City Masters, a car-design-focused reality TV show she partook in, her NB Miata was meant to be nothing but a toy. However, we all know how quickly goals change when the racing infection sets in.

Darby didn’t come from a racing family, and she didn’t start as a teenager in a go-kart. Instead, her career aspirations, though not exactly motorsport-oriented, led her to get behind the wheel. Darby works as an automotive designer, and her competence in exterior design landed her a job in that department at General Motors. The natural development from shaping cars, to working on them, to wanting to race them, is easy to understand.

With a stock NB in her garage and good weather to enjoy it, she booked her first track day at the fast and flowing Waterford Hills. It couldn’t be described as a huge success — a couple of spins and a black flag might’ve put a damper on some people’s first track day — but Darby was unfazed. More importantly, she was completely hooked.

She began by performing the typical track day tweaks. A rollbar and a Sparco F200 seat with a four-point harness kept her safe and secure. For more grip, she added 15 by 8-inch Konig Helix wheels and 225-section Toyo R888 tires. At the rear, she chose the safe and stabilizing Hawk DTC-30 brake pads, while a more aggressive DTC-60 compound is up front. With a set of questionable-aged HKS shocks in place, she started autocrossing regularly and ran into her first challenge.

Off to a strong start.

Addressing Shortcomings

“Maybe because it was hitting the bump stops, though I’m not sure, but the car would understeer terminally then snap oversteer,” she mentioned. While she learned to drive around this flaw, her interest in setup pushed her towards a set of supple and widely adjustable Xida coilovers — some of the best for the Miata. This quelled some of the Miata’s vices and encouraged her to push harder and harder. Confident and in search of more speed, she turned away from autocross and started making track days her favorite distraction.

No longer confined by a cramped cone course, the Miata’s lack of power was apparent. She toyed with the idea of supercharging the motor, but something about that form of induction didn’t stoke her creative fires much.

Around that time, she hitched a ride with Brian Spears and sampled what 550-turbocharged horsepower felt like in a featherweight Miata. This, combined with her appreciation for the excess of Group B rally cars, pushed her towards finding the perfect turbo.

Hilariously, Darby took out additional student loan money to finance the turbo kit she’d been eyeing. “I’m still paying 8-percent interest on it, and I still don’t regret the purchase one bit,” she laughs. The cost of the Borg-Warner EFR 6758 is pretty impressive, even without interest, but it is arguably one of the best for the road course. Not only is it hyper-responsive and the best in terms of transient response, but it’s also very robust. “I’ve been through four motors in the last few years, but the turbo has never failed me,” she notes.

This responsive snail brings humor out of Darby. When I asked why she opted for an external wastegate, she replied, “For the noises!” Clearly, though this car is intended to be fast and functional, her ebullient personality shows itself in the parts she’s chosen.

The Borg-Warner turbo’s lightweight aluminide turbine wheel gives Darby the ability to modulate the throttle like she would with an N/A motor.

While Darby wasn’t a natural wrench, she taught herself how to work on cars and became quite handy; a testament to how far love for a vehicle can push a person. She learned to assemble an engine, swap out several transmissions and a differential, paint and vinyl wrap, and even fabricate her own intercooler piping.

Tuned on AEM EMS4 with a Fab 9 downpipe and manifold, the once-anemic BP motor was suddenly generating 250 horsepower at the rear wheels. With assistance from the factory six-speed gearbox and a 4.10 rear, acceleration was no longer an issue.

Having little interior in the 2,350-pound Miata only helped acceleration.

Not only did the newfound shove give her plenty of triple-digit thrills at Gingerman, Waterford Hills, M1 Concourse, and Grattan, but it also allowed her to drift the Miata at higher speeds. With a welded differential and an accessible 200 lb-ft of torque, she could lay black stripes along the banking at Auto City Speedway, as we see below:

Getting Serious

Three years of casual drifting and track days gave her plenty of confidence, but eventually, she sought something more competitive. Her first stab at a time attack took place at the Speed Ring in 2017, where she dueled with Cody Miles and his 600-horsepower Subaru WRX. After experiencing the stark difference in performance between the two machines, she found the spark needed to focus on the development of the Miata and the strength needed to continually open her wallet.

To compete at the sharp end in Gridlife, she knew she had to make her Miata faster, stiffer, and stickier — and so she quit drifting on the weekends. She tossed the welded differential aside, reinstalled the Torsen, and hung up her two-colored drifting gloves. That said, she still indulges in a little corner-exit oversteer on hot laps, but from then on, the Miata was shaped to get around corners as quickly as possible.

“I knew to make the car as fast as it could be, it had to be a single-purpose machine,” Darby recalled. Photo credit: @midwestmediacollective

She started by buying the aerodynamic elements she needed and crafting the ones she couldn’t find. After purchasing the 9 Lives Racing Wing, which stretches 66-inches wide, she fashioned her own endplates for the wing from Alupanel. Darby used the same material to balance the front with canards. She even fabbed a birchwood splitter. The love one feels for a car can motivate them to craft some interesting pieces, especially when they’re naturally creative.

An OMP Halo seat gives her somewhere to rest her head when g-forces begin to turn her neck into a noodle.

To complement the aero gains, Darby installed a set of Jongbloed 15 by 10-inch wheels and wrapped them in 245-section Hankook RS4 tires. This grip and cornering speeds called for greater braking performance, so she wisely upgraded to Stoptech STR trophy kit. Lightweight billet floating rotors helped trim a little unsprung weight, and they gave her plenty of confidence with repeated heavy stopping.

As we can see in the footage below from the tight and technical M1 Concourse, the grip and stability are there. Though it’s fast and somewhat friendly, the short wheelbase and instantaneous torque of the EFR turbo make it dance a bit under throttle:

With more grip and stopping power, it only made sense to increase the boost pressure and stretch the BP motor a little more. The resulting 320 hp and 250 lb-ft at the rear wheels were enough to spar with Corvettes and M3s. No longer limited by a lack of power, she could start planning a serious attempt at a Gridlife podium.

Over the next few Gridlife events that year, she cut her lap times at Gingerman down by several seconds. She could walk tall knowing she’d covered the 2.21-mile course in 1:41. That confidence, bolstered by the supportive network of friends she made there, would come in handy when she squared up to one particularly heavy hitter.

The trial-and-error in learning a new form of competition was made easier by her new friends.

Fighting with the Best

Jackie Ding’s exploits have been covered many times in these pages, and his presence in the time attack scene has grown wildly in the last few years. He was one of the big names on the marquee at Speed Ring 2018, which meant Darby was shocked when she learned she’d be battling him.

When Jackie’s fidgety S2000 gridded up in front of her, she had to begin planning her approach to this nose-to-tail battle — arguably the most challenging one she’d been in yet. The Speed Ring goes by touge-style rules: if the gap between the two grows, the lead car wins. If it shortens, it’s the following car which takes the win. While there’s no passing allowed in this format, having a competitor trailing closely behind increases the pressure quite a bit.

Though relatively inexperienced, Darby remained sanguine on the starting line. “My thought process during the battle was to focus on the track,” Darby begins, “not on him.” Sometimes the best defense is a potent offense. Jackie had the same mindset. “We didn’t do anything to psych each other out, but I did notice he had his mirrors folded completely in,” she laughed.

Battling with an ex-formula racer was always going to be tough. Photo credit: JN Garage

With 100-horsepower more than Jackie and enough torque to spin her wheels through slower corners, Darby was definitely the quicker of the two in a straight. However, with so many fast corners and heavy braking zones, the disparity in power didn’t make too much difference. She still had to duel with the experienced and relentless Ding, whose high entry speeds and tail-out style are hard for anyone to match.

Darby’s silky smooth driving helped her snag the first victory by a little less than a tenth. “Looking back at the footage, I couldn’t believe I won one of the rounds!” she recalled joyfully. The following round, with Darby leading, she fell prey to her habit of over-charging the entry phase. A big lockup (3:34 in the footage above) brought Ding back into contention.

Despite Jackie’s dirt-dropping moments, his car control, experience, and gutsy style helped him win the final round with a time of 1:13.4, but Darby wasn’t dismayed. Considering it was her second attempt at Speed Ring, and that she was only a half-second behind one of the best around, that result is worth a tip of the hat. Clearly, there is plenty of racing success in store for this promising young woman.

It’s been a constant challenge for Darby, but she revels in it. Her powerful Miata inspired her to learn how to drive, how to work on vehicles, how to find the right mindset for competition, and how to find that regular inspiration needed to move forward. With 400-plus horsepower on the horizon — possibly involving a K24 engine — and an OS Giken differential to put said power to the pavement, she might soon be the owner of one of the most powerful Miatas gracing North American road courses.

That grunt should be enough to run with most big-bore cars on the straights of Road America, Road Atlanta, and Mid-Ohio — all tracks she wants to try in the coming year. She’s already dropped into the 1:38-range at Gingerman, and she’s made quite a name for herself in the Midwestern time attack scene. A little more tinkering and seat time, and this intrepid young racer will be a regular sight atop the Gridlife Street Mod podium.

 

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About the author

Tommy Parry

Tommy Parry has been racing and writing about racing cars for the past seven years. As an automotive enthusiast from a young age, he worked jobs revolving around cars throughout high school, and tried his hand on the race track on his 20th birthday. After winning his first outdoor kart race, Tommy began working as an apprentice mechanic to amateur racers in the Bay Area to sharpen his mechanical understanding. He has worked as a track day instructor and automotive writer since 2012, and continues to race karts, formula cars, sedans, and rally cars in the San Francisco region.
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