From Denmark With Love

Ken Kurtz’s extensive background in IMSA GTP not only gave him something on which he could hang his helmet, but it also set the stage for a midlife return to motorsports. The incomparable thrills of being a young pro stayed with him long after he left the pro leagues, as did his considerable talent.

Kurtz got another chance after a friend ushered him back into club racing in the early 2000s, and his dominance in Spec 7 and Spec Miata rapidly expanded his network. After a short while, the multiple champion was getting offers for seats in faster vehicles — a 900-horsepower Trans Am being the most powerful car he would drive in that period.

After many years of fun in slower machinery, he faced the prospect of driving something with the performance that could transport him back to his halcyon years in some of the wildest prototypes ever built. In the early teens, his racing friend offered him the chance to move into a prototype, though this patron-pal wasn’t sure which way to go.

Back in the High Life

Aly Bruner turned to Kurtz for his racing expertise and asked which prototypes were worth considering. For a moment, the two pondered some of the old IMSA GTP and their European contemporaries from WSC, and Kurtz couldn’t deny he wanted another shot at riding one of these low-flying rockets.

When the glow of reminiscing the good old days faded, it became clear they’d only be signing up for an expensive headache. The costs of running a 30-year-old car with limited support and the need for specialized tools were too steep to be anything more than a painful trip down memory lane. Nostalgia can be costly.

They recognized that buying something newer, simpler, and normally-aspirated was the most painless and economical option available to them. When a brochure for a Ligier JS P3 passed over Bruner’s desk, they had to consider it. The Ligier was already well developed and supported by a number of major teams, but the cost to get into one, even a second-hand example, was astronomical. They had to look elsewhere.

Not long after, Kurtz got wind of the Aquila CR1 through a local sports car dealership. That this prototype was unlike most of their inventory seemed strange, but the specs were motivating and so was the price. The Danish-built prototype presented a cheaper alternative to the Ligier — and this particular car was even cheaper because its first owner was trying to get rid of it in a hurry. Apparently, he claimed the car had tried to kill him.

Kurtz and Bruner took that as a sign, though they still had their doubts. Those just about evaporated when they learned that the CR1 had spent the last 16 years competing in a number of European series including Swedish GT, Britcar, Dutch Special Saloon, and the British Supercar Challenge Series. The subsequent conversations with Aquila Founder and CEO Dan Suenson was the clincher. It was clear that they would be in good hands.

Saving sixty large over a contemporary LMP3 was in large part due to the Aquila’s simplicity. It comes with forced air driver cooling, an FIA-spec electrical fire extinguisher system, an FIA FT3 safety cell, an adjustable pedal box, a front crash box, air jacks, and a simple traction control system. However, it lacks the ABS, lockup indicator, and rear-view camera that are de rigueur with such cars nowadays.

More than the absence of amenities, which make long stints easier, the main cost saver is the chassis. Like the GTP cars Kurtz drove in the late 80s, the Aquila uses an aluminum monocoque which isn’t as light as the Ligier’s carbon monocoque, but still remarkably stiff and resilient. It still weighs in at 2,300 pounds with fuel and driver, so it’s not exactly hefty, either.

At the price of a little additional weight, they save themselves the hassle of certain regular rebuilds, carrying extra spares, and being able to fix local areas of the chassis without a complete refresh. These things delay service intervals and bring costs down considerably.

Maintenance is simplified by the symmetry left to right and fore to aft. Brake discs, Top hats, calipers, pads, and uprights are identical front and rear, as are hubs, wheel bearings, and hub carriers. All suspension members are genuinely non-handed, meaning the same part is used left and right, and all spare suspension arms are jigged and delivered complete with pressed-in spherical bearings so that no adjustment is required when one is replaced.

Teething Problems

A simpler construction promised fewer headaches, but it wasn’t totally without them. The Hewland’s NLT transmission’s paddle shifters weren’t working properly upon arrival, so Kurtz learned to rely on the push-pull lever in the interim, which didn’t last long. “By working with Aquila’s Chief Engineer Johan Rauchfuss, we realized a broken line in the steering wheel was shorting something in the ECU. We’d been seeing the appropriate voltage drop with every pull of the paddle, but nothing was happening at the gearbox.”

Customer support to the rescue. With the Aquila top brass on the other end of the call guiding them, they were able to determine that an internal ground had been destroyed in the ECU. With a new ECU and new steering wheel in place, their shifting issues were resolved. “The Zoom calls with Rauchfuss and Suenson helped us get out on track quickly.”

After that, the air conditioning system became their bugbear. It kept burning up compressors, which would seize and throw a belt, sometimes filling the cabin with smoke in the process. More than just the driver running hot, the cooling system proved itself insufficient in California summer heat, and so they installed a different pumping system and added a PWR oil cooler.

And with those fixes, the car was ready to rumble.

Serviceable Stump Puller

The Aquila can be optioned with a variety of engines, gearboxes, fuel tanks, and other accoutrements to suit the owner’s needs and budget. This example’s Chevrolet LS7 is not exactly exotic by modern prototype standards, but it is a refined pushrod motor that is light, powerful, easily serviced, and reliable. As optioned from the factory, its stock LS7 made somewhere around 420 horsepower at the wheels, but the car’s first owner sent the motor off to Huffaker for a rebuild complete with forged internals and an approximate 650 horsepower.

The 7.0-liter engine now produces a manageable, flat, and predictable wall of grunt that, spread between the sequential’s six gears, makes it faster than anything Kurtz had ever driven. Better yet, it was easier to drive and more reliable than the old force-fed prototypes he remembered so fondly.

But even without turbo lag or the H-pattern-concerns of old, the big-bore motor requires some care from the driver. Most of its 560-odd pound-feet of torque is available from 2,700 rpm. The flat curve makes a small step toward redline, but the distinguishing characteristic of the curve is its near-horizontal mesa shape all the way to 6,900.

The brakes and the steering are unassisted, but the drive-by-wire system helps make throttle control a little easier. To help prevent the driver from making an unintended throttle application after hitting a bump, for example, the ECU offers the ability to manipulate the parameters of the throttle dead zone. This programming cannot be adjusted inside the car and must be done beforehand.

Essentially, this determines the range of values outside of a given throttle position that will not be responded to, so the throttle application remains fairly progressive and predictable, despite what the vertical loading would force a motor controlled by a cable to do. With such a torquey motor and a stiffly-sprung car, this form of assistance is invaluable.

Squatting and Squirming

Of course, the driver is still responsible for turning power into propulsion. “You have to modulate the throttle pretty carefully and use your foot like a potentiometer,” Kurtz elaborates. This is part of the car’s unique charm; that immense torque matched to a rear tire with a tall sidewall (roughly twice as tall as the front sidewall) allows the driver to treat it like an old GTP car.

“There’s some room to slide the car in slower corners, but when the rear starts to go, you feel the hair on the back of your neck stand up. There’s just not a lot of leeway. If the tires are cold and it starts to slide, forget about it. There’s no saving the car then.

“It’s all different once they’re warm. After you rotate it, you try to get back to throttle as early as you can. The fun part is setting the rear with the throttle. The sidewall acts as part of the suspension. Once you feel the tire lean over a little, you feed in the power, sense it squat, and fire it toward the next corner. That traction is something you don’t get to experience in many front-engine GT cars, and it reminds me a lot of the good old days,” he adds.

The two times Kurtz has spun the car have been at corner exit, but only once was the spin caused by a careless throttle application. The other time, he broke the cardinal rule of driving a stiffly sprung prototype: avoid the curbs. Nuzzling the inside curb at Sonoma’s Turn 3A unsettled the rear long enough to turn a pretty cautious throttle application into a full 360-degree spin.

This no-no is just a fact of life. The Aquila is a prototype with a flat floor and a stiff setup intended to keep the airflow under the car, known as the aero platform, as constant as possible. Therefore, it’s not only the hopping that helped induce the aforementioned spin, but the fact that taking a trip over the curbs momentarily robs the car of considerable downforce.

Its aerodynamic requirements and the attendant and unavoidable suspension compromises make the car a little less than flexible when it comes to setup. Its operational window is quite narrow. “The biggest difference between this and a production car is that the balance must be dead on,” Kurtz emphasizes.

Set up incorrectly, the Aquila is a lethal car. Set up properly, it’s much more forgiving than its shape and specs would suggest. Its single-element rear wing and flat underbody develop enough downforce at speed to plant the car in a reassuring way. It hops over bumps and dashes over cambers, but its rear remains glued and seldom snaps unpredictably.

To help fine-tune its balance as the race wears on, the driver can adjust the front sway bar from inside the car. The rear blade-style bar cannot be changed. Thankfully, the centrally-mounted fuel tank, which sits on the other side of the bulkhead behind the cockpit is positioned so that burning off fuel doesn’t affect balance much. “Mainly, I shift the brake bias forward as the car gets lighter,” Kurtz adds. Beyond those two adjustments and the two fuel maps selected with a rotary knob on the steering wheel, there’s very little fiddling that Kurtz has to busy himself with during a race. Simplicity is key.

Squinting and Sussing

When practicing a little restraint around the curbs and during throttle application, Kurtz finds the car reasonably reassuring. Actually, his typical concerns revolve around those around him, who struggle to see the low-slung Aquila at the most crucial of times. “When I drive alongside an E46, I know they won’t see me unless they look down. The roof is only 38” tall — about 40” with the tow lift in place. Some people say the GT40 is low, but this is something else.”

Between the small wing mirrors, which vibrate too much to do much good, and the solid bulkhead behind the driver, getting a sense of those around the car is always tricky.

“I’ve learned to look way farther down the road to try to assess how quickly I’ll catch the cars ahead,” Kurtz begins, “because the closing speeds vary so much from car to car. Is it a Spec Miata or another momentum car? Then I won’t try to dive-bomb them. It takes a general understanding of the other cars out there and what their limitations are, but more than that, it takes a retraining of my vision to get a sense of when and where I’ll make the pass.”

VIDEO FROM SONOMA RACEWAY

To make their lives easier, Kurtz and Bruner recently installed a Wolfbox digital rear-view camera, which made it much easier to dice in close quarters. “Before the Wolfbox, I usually held my line after an overtake to avoid contact, which wasn’t ideal. Now, I can defend down the inside much more confidently than I could before.”

Very little modification has been necessary to get this car into fighting shape, but the aforementioned teething issues have been mostly solved. With the aim of keeping the car as un-custom as can be, they’ve been careful in the parts they’ve chosen. “The aim is still getting more seat time, which hasn’t been as easy to find as we hoped.”

With a couple NASA Super Unlimited wins and a few United States Touring Car Championship race wins under their belts, they’re looking to continue fine-tuning the Aquila. In the meantime, Kurtz will get a chance to grapple with a machine that not only tests his fitness in ways most production cars don’t, but has the wonderful effect of transporting him back to his glory days.

It’s only truly over when you (or your doctor) decide it is.