Tom’s Miata: Frankenstein Fun

Tom’s story began with his Mini Cooper in the fall of 2018. Then in high school, he cobbled together parts from forums and Craigslist Marketplace postings and ended up pushing a little 230 horsepower and 270 lb-ft from the 1.6-liter. It carried him through his track day foray, but the more he drove it, the more it faltered. He couldn’t keep up with the costs, the fuel, and the track day entries.

His friends suggested a simpler car to try and earn his driving spurs with. By parting out the Mini, he could put together the few thousand he needed to pick up an NC Miata with nearly 200,000 miles on the clock. The NC had lived an unloved orphan’s life; moving through seven households before ending up in Tom’s driveway. Somehow, it was still stock when he bought it. This basic package promised regular attendance at local lapping events, even with his college schedule limiting his time and his finances.

Tom didn’t have the means or the interest in going ga-ga with the mod list. The basic package of Feal 441+ Road Race coilovers, RX-8 sway bars, and Cobra Suzuka buckets did him just fine as he was making his way from novice to intermediate. The objective was to get good enough to feel comfortable at the limit and fix what broke.

Fortunately, little did. The only issue in that busy twelve months was the OEM radiator bursting. In the first year of racing, Tom and a few trusted friends logged over thirty DEs on the dependable little Miata. It actually helped him earn a few bucks, too, after reading Engine Management: Advanced Tuning by Greg Banish, he picked up enough to start tuning the factory ECU and starting a side hustle. That money went to his track fees, and it seemed like he’d found a self-sustaining system for himself. All was well with the world until it wasn’t.

After the engine blew, he borrowed his friend’s daily to finish out the final three weeks of his final semester at school, then bought the remainder of a friend’s parted-out NC track car, which fortunately still had its motor. It wasn’t an ordinary two-liter. His friend had swapped in a 2.5 from a Ford Fusion, a budget upgrade with minor architectural differences to the 2.0 it replaced. Swapping it into his car took less than three days.

Unfortunately, the stock 2.5 fell flat on its face at 5,500. With a set of OEM Mazdaspeed 3 valve springs and a set of Xero Limit “Boost” camshafts, Tom was able to raise the 2.5’s rev limit without any thinning of the functional powerband. The 170 lb-ft on tap starts around 3,000 and carries through 5,000, and the power keeps building to the 7,100-rpm redline, where it makes 197 at the wheels.

A comparison of the 2.5 on E70 (red) versus the 2.0 on 91 (blue).

“The objective has been to see how fast I can go without cutting corners or spending much money,” he elaborated. This is Tom’s main reason to try and use as many OEM components as possible. To avoid dealing with the factory rear hubs shearing, he upgraded to a set of hubs from its stouter older brother, the RX-8.

Though it required a bit of custom work to make it fit, the in-the-family RX-8 differential helped tremendously. Better, more progressive breakaway and improved acceleration from a 4.1 final drive originally suited to a torque-free rotary. After this upgrade, the car no longer lost speed going uphill between Turns 8 and 9 at Thunderhill East.

Because the RX-8 differential is taller, in order to sit in the same spot, Tom had to move the alignment area for the studs to sit in the same spot, which meant losing the alignment dowels. Without these, the powerplant frame eventually started sagging after a few months of hard driving. Eventually, this led to the powerplant frame contacting the midpipe under heavy braking and curb hopping. His attempt at notching the powerplant frame was one piece of trial-and-error that didn’t go his way, but he plans to put a set of custom locator plates to avoid this problem permanently.

Currently, he’s fighting the smaller issues like the one above which make the car hard to drive as regularly as he’d like. “Mostly just little gremlins from the engine swap,” he added. Other than that, it's the wallow from the original bushings which make the Miata a bit unpredictable at times. That’ll be relatively straightforward though time consuming.

If his first year out of school is as lucrative as he hopes, he might assemble a new motor to make the MX-5 a real S2000 rival with the following parts: a Fusion’s 2.5-liter Duratec block and pistons, and a Mustang’s 2.3-liter Ecoboost connecting rods and crankshaft, 12:1 compression and an 8,200 rpm redline, he’s hoping for 270 horsepower at the wheels. “It’s going to take a lot of development on my end, but I’ve got a small group guiding me. I’m in good hands.”

Along with the added speed comes a need for better deceleration, so in addition to a set of four-piston Wilwood calipers and RX-8 Sport rotors (which are only $30 per corner), he’s gone and picked another part within the Mazda lineup that takes a little innovation and forum-digging to swap. The RX-8’s ABS system is less prone to engage ice mode. Though this will be another trek down an unpaved path, he’s been given the schematics from others and feels confident the swap will be successful.

“It’s been fun to Frankenstein because I like doing things that not many have done, but I’m more interested in retaining a lot of OEM equipment since I don’t think it will have many issues in the long run. Hopefully, these parts will make it easier to go out and drive more miles. I still need seat time more than anything. Seat time, saving money, and keeping it reasonably streetable have been my objectives. I think I’ve achieved most of them."

Now, I’m considering making it more of a race car since I’ve got a daily now. But until I can afford a truck, there’s no point in making it a total pain to drive. The added torque is definitely enjoyable in the canyons, where I can keep it in third most of the time.”

How many Miata owners can say that?