Deep Dive: Ken Thwaits’ Optima Ultimate Street 670-HP Lancer Evo IX

A former Pro Mazda champion and muscle car fanatic, Ken Thwaits might’ve taken a couple decades off to raise a family but he never truly hung up his helmet. Six years ago, his love for motorsport brought him back into a highly competitive category that brings a wide array of cars into heated competition. One strange little car, a Lancer Evo, caught his eye.

When he first returned to racing, he immediately set his sights on the Optima Ultimate Street Car Invitational with his fifth-gen Camaro. Thwaits won the 2014 GT3K Class Championship in the series, but a fifteenth-place finish at the 2014 OUSCI was less than stellar in his eyes. At least he was able to glean some useful information from the disappointing result. Thwaits noticed four plucky Mitsubishi Lancer Evolutions finished ahead of his Camaro, and, recognizing the pattern before him, he decided to take a trip down an entirely new path.

A resourceful man, Thwaits went ahead and contacted the company that had prepped several of the aforementioned Evos: RS Motors. If you can’t beat ’em, join ’em. Or, as in Thwaits’ case, commission ’em. The decision to run the understated little import was first met with confusion from his peers, then validated shortly after witnessing another Evo give then-champion Danny Popp and his Corvette a hard time. No other car even came close.

Since then, he’s proven his competitiveness and ability to develop a car. In addition to winning the 2017 Optima Ultimate Street Car Invitational title, he took third overall and second in class (to the overall winner) last November. In the sumptuously upholstered cabin of his wildly-modified Mitsubishi Evo IX, Thwaits finds a competitive side to him that allows him to push further than he knew possible.

A Svelte Start

Picking one of the lightest Lancer Evolutions sold stateside marked an auspicious start to Thwaits’ monster Evo IX. The RS variant uses a revised 5-speed, an aluminum roof, and roll-down windows. It even lacks a radio. Thwaits is a man with exacting standards, so he replaced the trunk and driveshaft with carbon fiber pieces. While at it, his team at Showtime Motorsports tore the car down to the unibody, then tossed on a set of Wilwood brakes, bolted on a widened bodykit of their own design, and installed a set of stunning Forgeline wheels under the understated fender flares. Then came in several specialists to address the suspension and engine.

Underneath subtle fender flares, Forgeline GS1R wheels are backed by a set of Wilwood brakes.

His first attempt at a custom suspension setup was frustrating; a broken control arm sidelined his early efforts, and the weight transfer wasn’t ideal. Unfortunately, the Mitsubishi Evo is limited somewhat by its MacPherson strut design; specifically, the roll center drops at a rate of 3:1 with ride height. Lowering the ride height to reduce total weight transfer causes greater roll moment and requires more roll stiffness, and more stiffness means more total weight transfer forward. To get the lowest possible ride height without sacrificing weight transfer characteristics, he had to go with a custom set of uprights and arms. 

To ensure he had the strongest suspension and the best geometry, Thwaits turned to Dallas Cutler of SSB Designs. Their arms correct geometry, reduce cost, reduce weight, add bump-steer correction, and exceed the factory unit’s strength. “After he had the other guys’ control arm break, we decided to send him down a set of my uprights, arms, and caliper mount brackets,” Cutler said. How considerate.

Its trick suspension gave the Evo greater agility without lowering it past the mandated minimum ride height of 3.5 inches.

These arms had been tested with several professional teams and had been vetted, so once they arrived at Thwaits’ doorstep, he decided to have his mechanics immediately swap them on. Along with JRi coilovers, this new setup allowed Thwaits to make good use of the outrageous power he was anticipating.

The Evo’s Mighty Powerplant

Thwaits hired engine guru Bob McCann to put together the 4G63. “This year, we scrapped the cast iron motor in favor of the new billet piece, though we’ve held onto their ported cylinder head with 1mm oversized valves and Kelford camshafts optimized for the MIVEC system. While the old block worked well, we kept running into the typical problems people face with this motor: popping headgaskets on high boost,” McCann began.

Now, they use a Bullet Racing billet aluminum block, which helps with heat exchange. To address some of the headgasket-related problems, they added bigger head bolts and a thicker deck.

Inside, the full rotating assembly is all Manley. “We retained the oil squirters to keep the piston crown a little cooler. We also mounted a custom double-pass radiator, mounted at 30° for better airflow, as well as a massive Garrett intercooler from STM,” McCann continues. These touches, in addition to a vented carbon hood, cooler-burning C85 fuel, and an inconel exhaust help keep everything as cool as possible. With the massive turbocharger shoehorned between the motor and the radiator, keeping temperatures manageable was no mean feat.

The radiator, which is large enough to cool a Corvette, can be spotted from behind the massive intercooler.

The team alternates between two variants of the BorgWarner EFR. The twin-scroll turbocharger uses a low-inertia titanium aluminide impeller and a Full Race manifold for incredible response without much compromise to the top end. Its boost threshold is impressive, but it’s the transient response which makes it outstanding. This characteristic isn’t seen on the dyno, but it transforms the behavior of the motor in mid-corner situations when Thwaits needs to feather the throttle; the sort of situations where a heavier impeller might delay power delivery long enough to prevent him from balancing the car perfectly.

The larger turbocharger, an EFR 8374, provides as much as 670 horsepower to all four wheels, while the smaller 7664 makes as much as 550. The larger 8374 reaches full boost at an accessible 3,500 rpm, which is perfectly responsive for the circumstances, but the problem is its violent delivery. “The 8374 comes on like a light switch at 3,700 rpm,” Thwaits added with a chuckle. With 30 pounds of boost available from so low in the rev range, it’s capable of roasting rubber effortlessly.

The EFR comes with an integrated wastegate, which simplifies plumbing and makes it possible to squeeze the snail in the narrow valley between the radiator and engine.

Of course, this isn’t much of an issue at higher speeds, which makes the 8374 it ideal for the road course. For tight autocross events with an abundance of hairpins, the team use the smaller turbocharger for a softer delivery and a more manageable rush of torque, even with the full 30 pounds of boost available in every gear. To maximize its manageability, they opted for a trick Motec 150 ECU with a wild array of features to make the motor more tractable. “Anti-lag, drive-by-wire, and a number of other features allow us to do anything and everything to achieve a certain mount of boost by a certain engine speed. This ECU is the icing on the cake, and makes everything much more predictable,” McCann said giddily.

Despite the linear delivery from the smaller snail, even such an agreeable engine must be driven skillfully to get the most from it. “In autocrossing, you have to anticipate the power and lag—and try to have the car straight by the time the turbo spools,” Thwaits mentioned. This helps minimize wheelspin and capitalize on the drivetrain advantages. In case he needs to dial in any countersteer, Thwaits can do so swiftly—thanks to a KMP paddle-shift system controlling the a Drenth sequential gearbox—by keeping both hands on the wheel at all times. Fortunately, the power is put to the pavement pretty well, since it’s administered through a Wavetrac center differential and a Cusco 1.5-way in the rear, then onto the fully-forged, monoblock 18″ Forgelines GS1R open-lug wheels, each of which are wrapped in 315-section BFG Rival S tires. Capitalizing on its traction advantage was one of their greater aims.


Focused yet Flexible

The Evo’s grip and thrust available are wonderful traits, but if they’re not suited to each of the varied challenges of OUSCI, they’re not worth much. The hotly contested event gets more and more challenging as the year goes on, with the final event only featuring the best entrants from the various regional races. Far from a standard autocross, drivers need to find a competitive setup to suit the situation they find themselves.

On some of the faster courses, the Evo can’t quite match the big-bored V8 competition on the straighter sections, but a combination of traction, predictability, and good aerodynamics helps Thwaits and his Mitsubishi remain in contention. A custom carbon splitter, carbon sideskirts, tusk-like canards, a flat underbody, a rear diffuser, and an Evo VII wing at the rear give Thwaits the stability he needs. “We trim the wing out as much as we can at places like Road America,” he elaborated; this helps them stay in contention with the 1,000-horsepower ‘Vettes. However, even that’s pushing the limits of what’s allowed aerodynamically. “We’re not supposed to have huge billboards on the back of our cars—they’re supposed to look stock!”

“We immediately went two seconds faster at some courses with the addition of the diffuser,” Thwaits mentioned proudly.

On faster courses, managing the corner exit is relatively simple. The four-wheel drive Evo, further stabilized by 7° of caster, rewards a rough touch. “You really need to hustle the car; brake late, throw it into the corner, and mat the throttle early. Most of the time, the four-wheel drive will sort you out,” Thwaits said.

Where the Evo truly excels is on the tight and technical autocrosses, and the OUSCI has no shortage of them. By running 3.5° of negative camber to help with turn-in and rotation, he’s able to flick the Evo into certain hairpins for a speedy and efficient exit. Sometimes, Thwaits dials a little extra brake bias to the rear to facilitate some rotation, though that was not as easily achieved as turning a knob in the cockpit. “The factory ABS system wasn’t too happy with much rearward bias, and it would lock the rears too much,” he added. To ameliorate this condition, Thwaits opted for a Bosch ABS system, which allows for more slip and less intervention. Despite him still pressing through the factory pedalbox, the new ABS system means Thwaits is much better equipped to accurately bend the Evo around hairpins.

Getting the Evo to pivot on its nose without much rear lockup required a trick Bosch ABS system.

One variation of the autocross, known as the Speed Stop, requires the driver make a standing start, followed by a handbrake turn, then a short slalom, before finally stopping in a 40′ box. Predictably, the Evo’s drivetrain, wide footprint, and short wheelbase give it a great edge over its rivals. Simply put, none of the domestics can put their power to the pavement as well as the tech-heavy rally-based car can.

The secret ingredient is having an experienced setup engineer on hand. JRi’s JJ Furillo tweaks the Evo as track conditions change, and that makes the a massive difference. “Parking lots change drastically throughout the day,” Thwaits mused, “so we had to make sure our setup changes were strong; we learned they were worth a second easily.” That exploitable power at any speed, maximized by an experienced team and a capable chassis make the Evo the all-weather, all-situation weapon it is.

Swift and Successful Eye Candy

Though optimized for road racing, the Evo is also a show car. Perhaps not the most outrageous, but its clean, simple, and thoughtful presentation is striking. The interior is not stripped, nor is it chock-full of garish racing bits. Instead, a set of Sparco seats, trimmed in custom black and red leather, replace the factory Recaros. The rest of the interior is upholstered in the same leather scheme, and the carbon dash accents, carbon instrument cluster, and carbon handbrake accent the cabin.

Reupholstered in beautiful leather, the cabin blends focus and comfort like few can. Photo credit Forgeline

A Motec electronic dash relays all the pertinent data to Thwaits without turning the cabin into a stress-inducing nerve center. “For a car that spends most of its life on the track, it’s got a pretty swanky interior,” McCann added. Despite all the leather and glitz, it’s still relatively light—weighing just 3,250 pounds.

In the engine bay, the red valve cover and the black titanium hardware continue on the Evo’s color scheme. So do the massive intercooler, radiator, catch can, and oil cooler—all of which are anodized black. Though it looks near-factory, a bit of tweaking was needed to squeeze it all in; the front frame rails were modified to accommodate the new cooling ancillaries. Simple, clean, and yet very high-quality—all valuable traits when a car needs to be as impressive standing still as it is turning laps.

Not hard to see how this black beauty stole the show. In the OUSCI, aesthetics are important.

A Rocky Path to Victory

And impress it did. Though those clean lines and striking black paint won the Lingenfelter Design & Engineering Challenge, mechanical issues dogged the Evo in the final road course events that year. Wisely, Thwaits decided to turn the boost down slightly towards the end of the following season, which left him with just 550 horsepower. Though this was disconcerting, since some of his competitors were making nearly twice that figure, his reassuring performance from the previous year proved he was able to make better use of the power than his rivals, and that reliability was the deciding factor. It proved to be the right decision.

Despite a surprising third-place finish in the Lingenfelter Design & Engineering Challenge, Thwaits’ Evo won the Detroit Speed Autocross and the PowerStop SpeedStop Challenge, which left little room for anyone else to take the title provided he could retain his reliability through Falken Tire Road Course Time Trial. Thwaits ended up finishing 11th overall, which was good enough for 90 points; bringing his total at the event to 488 points. Austin Barnes and his ACR Viper took the fastest time on the big track, but still fell just short of Thwaits’ overall score at 485 points. After years of coming close, Thwaits enjoyed victory after the tightest finish in OUSCI history.

Not ready to rest on his laurels, Thwaits has some intriguing plans for the Evo. He’ll continue battling in the OUSCI and other local time trial events, as well as making appearances at several shows along the way. Additionally, the development of the car hasn’t slowed; the ABS and ECU still haven’t been fully tuned. They also plan on using the newer EFR Black Series turbochargers, which flow even more. Some aerodynamic adjustments, a revised rear brake setup, and more boost are other items on the list. You’d think this Evo couldn’t get much quicker with all its road car compromises, but Thwaits and company are determined extract every iota of performance lurking underneath its midnight hide.




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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