Turbocharging A Voodoo-Powered S550 Mustang for Road Racing

Long before this S550 build began, the groundwork had already been laid. Paul and Brian Faessler had rigorously tested and perfected their AIX-winning ’65 notchback and its force-fed V8. Through years of trial and error, they learned what a turbocharged engine required to perform in a road course setting, and how an old pony’s antiquated suspension design needed to be modernized.

Ten years after the development of their notchback began, they turned their attention to the newest S550 Mustang and its independent rear suspension. If they could improve the car’s aero and make their turbocharged engine package as tractable as possible, the modern Mustang could be shaped into something that would stun a seasoned vet and give Radicals a run for their money. At the very least, it would garner some attention for their Cincinnati-based speed shop, Paul’s Automotive Engineering.

Ford Motor Company had been supporting the father-son duo over the years, but this particular project had to start entirely on their own dime, and because there were no body-in-whites available to them, the Faesslers picked up the cheapest 2017 Mustang they could: an automatic base model powered by a V6. That was fine since they would have to replace most of the factory componentry, anyway.

They immediately chopped the roof, pulling 65 pounds from the top of the car and granting themselves easy access to the cabin where they could place and assemble their roll cage. From the outset, they looked to remove as much weight as was practical, and move the remaining weight to where it ought to be.

After cutting a few hundred pounds of excess metal, they installed their own set of carbon doors and a carbon decklid skin. “The handle mechanisms and hinges weigh as much as the doors!” Brian Faessler exclaimed.

Some of their budget had to be allocated to maximizing the rather large contact patches. In went their own short/long-arm double-wishbone setup K-member for the desired tire width and suspension geometry. Basically, the front roll center is far more stable, and this design enjoys better negative camber gain as the body rolls, keeping the tires flatter to the pavement for less tire wear and more grip.

Following that, they designed their own coilover setup using four-way JRi dampers from Ultimate Performance with the right spring rates and valving to suit the tall, pliable tires needed to put the power to the pavement. At the rear, their custom DOCOL cradle setup raises the entire rear suspension into the body by two inches to maintain driveshaft angles and suspension geometry.

Clearly, traction had been prioritized from the start. The independent rear suspension allowed for more camber gain, but they remained conservative when it came to setting their static values because they needed to prioritize power-down over peak lateral grip. More than 2 degrees of negative camber is adequate for a front-engine, rear-drive car with this kind of straight-line potential.

They tried the Coyote V8, but eventually switched to the flat-plane version of the 5.2-liter Voodoo engine because it promised a little more robustness than the cross-plane Coyote. Big midrange power was the aim, and with the turbo torque available, there is never much reason to run much higher than 7,000 rpm, anyway.

The improved cylinder head efficiency allows them to make power with less boost than before, thereby helping the turbocharger and engine last. Being a small shop with limited funds, they had to prioritize durability.

This block has been stuffed with Wiseco pistons as well as K1 connecting rods, and the stock head uses Ferrea valvetrain components. Onto this proven combination they’ve bolted several TiAL Sport turbochargers that, in a decade of running this package, have never failed. “The engine and induction system are both proven quantities,” Paul Faessler said.

The combination of displacement, a responsive midframe turbo, and a MoTeC M150 controlling everything has made the motor surprisingly tractable. “We have traction control, too – but that hasn’t worked for the last two years,” Paul Faessler said with a laugh.

A Quaife QBE69G pneumatic sequential six-speed has made a seamless power delivery possible and does away with most issues related to transient lag. The greatest challenge is turning that power into propulsion, though having 365-720-18 Hoosier Circuit S2 slicks to administer that power helps. Even more, it’s Brian Faessler’s deft touch that makes this car generate such good propulsion at corner exit. “I’ve got a lot of experience in turbo cars —11 years in this car — and I know how not to overwork them.”

Mechanical sympathy plays a large part there, but his care for the car wouldn’t mean much if the right parts hadn’t been picked. The motor’s cooling system is surprisingly simple and effective. With the help of a Bell air-to-air intercooler, an external Setrab oil cooler, and C&R radiator with a built-in oil cooler, the package remains cool for entire races. The radiator is shockingly small; measuring just 16-inches by 8-inches by 3-inches, and yet it works exceptionally well. Some of that has to do with the long process of massaging of the “waterfall” ducting system built into the hood, and the wider inlets in the GT350 front clip — a late-stage upgrade — that optimize airflow.

With such a dependable and tractable powerplant, he can use as much or as little boost as is needed and still run commandingly. Sometimes, Faessler cranks up the boost over the first few laps to stretch a commanding lead with an estimated 800-plus horsepower, then, having earned a cushion between him and his competitors, reduces boost to save fuel.

At low boost, the engine produces more than 600 horsepower and 600 pound-feet of torque, a moderate amount that puts the powertrain through relatively little strain. “We use each motor for about three seasons before we swap motors. The Quaife ‘box lasts about as long, too!” Paul Faessler added.

Though dialing back the boost might hamper his straight-line speeds, Brian Faessler still manages to set his fastest laps toward the end of the race. Chalk that up to reduced fuel load, a nicely balanced car, and Brian knowing how to manage the tires over a full race.

The motor’s been able to remain cool quite easily, but it’s been tougher keeping the brakes and the drivetrain in their operational temperature windows, which is hardly surprising considering the Mustang’s weight and power. The Brembo one-off four-piston calipers clamp 380mm front rotors and Hawk Performance DTC-70 pads kept cool with a pair of 5-inch ducts, and at the rear, the 328mm rotors and DTC-70 pads are cooled by 3-inch ducts.

Spring rates have changed, tire compounds have changed, and a few suspension settings have been tweaked to suit Brian Faessler’s preferences, but, fundamentally, the car has largely remained the same as it began in 2016. Again, the stage had been set with the old notchback before this build even began.

Where the father-son duo have done most of their fiddling in recent years has been in the aerodynamic department. Andrew Brilliant from AMB Aero has helped devise a new setup that has been hugely beneficial. “We had to increase spring rate, but it’s still a neutral car,” Brian Faessler added.

Playing with the APR Performance GT2000 rear wing has been beneficial not only in high-speed stability, but in power-down as well. After holding the SU record at Pitt Race for several years, the team returned with the new aero and set a lap time 4.6 seconds faster than their previous best.

The car currently weighs in at 3,450 pounds – not light, but being a race car, they’ve opted to retain weight and instead focus on safety and reliability. “It’s a race car first and a Time Trial car second,” Paul Faessler added. That’s fine, said Brian Faessler, who admits to being more of a racer than a qualifier.

That weight has some performance advantages, though. “I have no trouble getting the tires up to temperature on the out laps for SU/GT/TT,” Brian noted. That came in handy, as NASA Time Trial sessions aren’t particularly long and he normally has just one or two laps before he’s reached the rest of the pack.

All this careful preparation culminated in a sensational performance that everyone at the 2019 Nationals raved about. There, Brian Faessler started fifth in that Super Unlimited race, but he charged to the lead on the first turn and proceeded to gap the field by 23 seconds on the way to the first-ever class win by a unibody car. After years and years of cleverly innovating and working diligently on a tight budget, they received the undeniable confirmation that their approach was the right one.

The two make up half of a small team who, most weekends, sleep in their 28’ trailer on air mattresses, but limited resources have not stopped them from developing this car into a series-leading standard by focusing on the right things.

Though one would think that a production car’s limitations aren’t able to be circumvented, the expertise of this small and passionate team has made it possible to set times once only achievable by a tube-framed car or a monocoque prototype. In fact, the only car that finished ahead of Faessler at the 2023 Nationals in SU and TTU was Jonathan Finstrom in his 1,000-pound Staudacher S12.

Not too shabby for a big pony.