How a Neglected MX-5 Became a 320-HP Time Trial Weapon

Until 2023, Zak Rustigian’s only motorized vehicle was a van. However, his background in competitive mountain biking and his mechanical aptitude had already set the stage for a rapid ascent into Time Trial success.

Rustigian, a Ford technician, bought a neglected Miata from a co-worker with the aim of making it a fun daily until a buddy encouraged him to try one track day —and that was game over. Within a year, Rustigian had his NASA license.

Just as boldly, he decided to turbocharge the Miata in focus, which proved to be hasty. Its 270 horsepower was enough to shred two Mazda six-speeds, and the stouter BMW ZF6 replacement couldn’t be balanced correctly.

Vibrations be damned. With that car, Rustigian took the leap into TT4 and TT3, but was running in the back of the pack because he had never optimized it for those classes. “I wasn’t bothered – I was just happy that I had a racing license,” he recounted, enthusiastically as someone coming back from their first lapping day.

However, his enthusiasm started to wane after a motor rebuild. With his newly acquired appreciation for a simple, atmospheric motor, he decided to part out the Miata and find a naturally-aspirated successor. “Corvette, M3 – I couldn’t decide. Then I thought about the third-gen Miata with the 2.5-liter swap. Cheaper, more familiar, and a little bit of an underdog, it seemed right,” he explained.

“I’d been following Andy Boss, Mitchell Yardley, and Frankie Ho – all of them had swapped their cars and proved the potential of that combination. I mean, their times were similar to my personal bests, and they were down a hundred horsepower!” he recounted.

After four days without a car, Rustigian rolled a rougher NC with some trackday modifications up his driveway. “Rollbar, hardtop, Tein coilovers, stripped interior, and 17×8” wheels. There were 163,000 miles on the motor – a perfect candidate for an engine swap,” he continued.

The first order of business involved a few items from the Mazda Motorsports catalog: sturdier RX-8 front hubs, rear Mazda Motorsports hubs from the Spec MX-5, as well as 12.7” front rotors from an RX-8 with Wilwood Superlite calipers.

Taking a page from his last car, he didn’t skimp on cooling and installed an oil cooler, hood vents, and radiator ducting. Along with those changes, he threw on a set of 17×10” Konig Hypergrams, even though they’d be overkill for the stock 2.0-liter. He had made up his mind and wanted to make sure the car could support the 2.5-liter Duratec.

“Lo and behold, the car was already pretty quick its first weekend out. Apparently, NCs aren’t allowed in TT6, so after winning on Saturday, the race director stripped me of my win and bumped me into TT5, where I finished fourth out of eight. I thought, ‘Crap – maybe this thing is legit!’”

Spurred on by that auspicious weekend, he acquired the 2.5-liter Duratec for little less than $500 from LKQ Online. Another $1,500 would cover the other parts needed.

“I grabbed a stock motor out of a 2017 Ford Fusion and fitted it with Esslinger Stage 2 camshafts, ARP camshaft bolts, Brian Crower valve springs, a Fluidampr, and a set of Chikara oil pan baffles. It made a 181 horsepower at 7,200 rpm – about 200 revs higher than most regard as safe.

Installation hurdles were minor. “You need to plug the balance shafts that come with it and use the oil pan from the Miata because it won’t clear the subframe otherwise. You also have to transfer over the intake manifold and valve cover, then find a solution for a PCV plate (Motorcraft Pt. No. 4L5Z-6A785-AA). The PCV valve is part of an assembly that bolts onto the block, not the intake manifold,” he explained.

Transitioning to the new power only took a few laps, and by the end of 2025, Rustigian took the TT5 class win several times. “After running lower-midpack in different classes through 2023 and 2024, I couldn’t ask for a more satisfying 2025 season,” he exclaimed.

In case the current motor blew, he picked up a replacement for a little over $300 – a precaution after sixteen successful weekends on said engine. With the chance to build a new motor, he started pining for his boost days. Maybe, if he did things sensibly, this second stab at turbocharging might be more enjoyable.

From Tip to Tail

“Three things I learned to prep for boost: regap the rings a couple thousandths if you’re running boost, fortify the head bolts with the 2.3-liter Ecoboost head bolts, and go for a milder cam,” he stated. This time, a milder set of Fab9 Stage 1 would work best for midrange.

When it came to picking a turbo kit, he decided on Kraken, a small Bulgarian company known for its free-flowing manifolds.

Taking advantage of a promotional sale, Rustigian picked up a full top-mount turbo kit for a mere $3,200 after tariffs – saving about $2,000 over the competition’s products. This included a Pulsar G25-660 turbo, a front-mounted intercooler and piping, oil lines, piping, oil, exhaust manifold, and full exhaust – everything but the blow-off valve. All in all, the kit added another fifty pounds to the total – bringing competition weight to 2,660 pounds.

For fueling, he added a Deatschworks 300 (340lph/hr) pump, ID 1050 injectors, and E85, exclusively – he’s heard horror stories about the Flexfuel capabilities of the few budget options available.

“The stock ECU is more sophisticated than you might think – it compensates for manifold pressure. The cost-effective tuning solution is the $400 ECUTek platform that allows the user to create tunes for the stock ECU. “The software just allows for tweaking any table included in the stock maps. It’s not as powerful as a full standalone ECU, but it’s much easier to dial in for beginners/intermediates,” he added.

Rustigian keeps an eye on traditional oil and temperature gauges, an Innovate standalone wideband sensor, and the ECUTek app on his iPhone. The last conveys coolant temperature, AIT, MAF readings, and another AFR for extra safety.

Yes, Sweat It

Rustigian’s heat-related worries weren’t unjustified – he’d done his homework. “I’d heard about people frying everything in the vicinity of the turbo with top-mount kits since the ABS module, brake lines, and the alternator are all next door,” he said.

To avoid any issues, he wrapped the ABS module and brake lines in aluminum head shielding, added a turbo blanket, then moved the second alternator from exhaust side to intake side after the first one fried. Thankfully, removing the air conditioning unit allowed for a Mazda5 alternator to be installed where the A/C was on the opposite side of the block.

He takes responsibility for melting the oil drain tube. “I decided to drill into the block right near the motor mount, which I thought offered a lot of space, but I did it before I bought the kit.”

These teething problems were dealt with easily. What wasn’t was the regular failure at the turbo v-band. “The manifold features a set of short runners and is connected to the turbo with a 2.5” v-band. Normally, I tighten the v-band bolts every few sessions because they back themselves out. After the third event, I noticed a rattling noise; the v-band had split in half and the turbo was hanging on by a thread.”

Thinking it was a fluke, Rustigian replaced it and continued on as usual, but the second v-band broke after two more track days. Since then, he’s relied on a homebuilt brace that’s bolted into one of the transmission bellhousing bolts and bolts into the very bottom of the downpipe with a clamp.

“I can’t call myself a trailblazer. The turbo kits for this motor have been documented well enough to where I could go online and buy all the parts I needed. What I didn’t have a guide for was cooling; not many actually track their turbocharged NC. I just took a page out of the NA-turbo guidebook and made sure I ducted all the coolers, made sure no air was sneaking past the radiator, and vented the hood – with R Theory Motorsports vents in my case,” he explained.

“Along with two generic vents from RGR Engineering, temperatures have been mostly good at 85°F ambient, coolant never gets above 215°F, oil temps stay around 240°F max, and IATs cap at 100-105°F.

“If it’s cold, coolant temps won’t even get above the thermostat opening temp. Above 90°F, though, I’ve seen coolant temps get up to 225°F, so I might upsize the Megan Racing radiator – the only weak link in the system.”

Driving Differences

“The turbo, surprisingly, hasn’t made me change my technique much. Because it doesn’t hit full spool until 4,100 rpm, I still apply the throttle in the same way as I always have with the 2.5. Going from 235s to 255s helped, though. When the rear end squats on this car, it toes in and shoots straight,” he elaborated.

VIDEO

“I’m still shocked at how fast things come at me now,” he admitted.

It’s a busier experience than before. With the 4.1 final drive and more power, his right hand has started getting blistered. “No joke, I counted twenty-five total shifts per lap at Buttonwillow 13CW. There’s a 3.7 FD available – I might try to ride the torque and reduce the number of shifts needed.”

His standard-rate SuperMiata Xidas are on the softer side of things. With 11k front and 7k rear, it’s significantly softer than the other turbo car he’s seen, but he doesn’t feel the need to change it as it sits, since it absorbs whatever he throws at it.

Ready to Rinse and Repeat

Moving quickly, making the right connections, and willing to chance a few untested solutions have paid off for Rustigian, who recently took third in TT3 with his toy, even 40 horses down on where he could be.

The car’s a little underclassed for TT3 as it sits currently – some extra power might be in order soon, provided the bottom end and transmission can handle it. “They’re limited to about 320, we think,” he pondered.

To mitigate that transient lag and make the most of the current output, Rustigian recently picked up an ZF 8HP45 gearbox. This eight-speed, used in 2015–2017 Jaguar XE sedans with a 2.0L Ford EcoBoost engine, shares the same bellhousing pattern as the Duratec engine in his Miata. As a result, the transmission bolts directly to the engine, and even the Jaguar starter and flex plate fit with only minimal modification. Since these transmissions are plentiful and cheap, the swap became surprisingly affordable and straightforward.

Some fabrication is still required, particularly for transmission mounts and gearing. Rustigian joined a testing program for a newly designed adapter that allows the Miata’s factory Powerplant Frame (PPF) to remain in place. Gearing also required careful planning because the 8HP transmission has limitations on its upper gears: 7th and 8th cannot handle full load or excessive shaft speeds without risking catastrophic case failure. To compensate, he plans to replace the factory 4.1 ratio with a 3.7 from another NC. Long-term, he hopes to swap to a Ford 8.8 rear end with an even taller 3.23 ratio.

Transmission control proved to be one of the most difficult challenges. Existing standalone transmission controllers rely heavily on communication with the factory ECU, but the NC Miata’s ECU cannot fully communicate with them, preventing features like rev-matched downshifts. To solve this, Rustigian purchased a MAXXECU Race standalone ECU capable of controlling both the engine and transmission. Because no plug-and-play solution exists for the NC Miata, he built a custom wiring harness from scratch using a spare factory harness and configured the ECU himself.

The whole swap took less than two weeks, surprisingly. The remaining tasks include fabricating a driveshaft, installing a transmission cooler, and flashing the transmission controller.

Rustigian’s rare combination of enthusiasm, pragmatism, humility, and resilience explain how he’s been able to make real headway into the world of Time Trial in only four years. His affinity for little Mazdas and his rapidly growing network have helped, but it’s his joy, undeterred by setbacks, that keeps him grinding away at a pace many could not manage.

“I never thought I’d have a car that could keep up with a prepped Corvette or a Shelby GT350, so I’m thrilled with where the car and I are now. Let’s see where I stack up after I polish up the driving a bit – I’ve gotta learn how to drive a turbo car first,” he laughed.