Sorting: How we made an ND Miata 11 seconds faster

How did we shave more than 11 seconds per lap? Was it with a turbocharger? Massive aero? Would you believe it was just some select, relatively simple modifications and a bit of sorting?

Here’s how we took our ND-chassis Miata from fast to really fast. Not only can this car now outrun a bevy of 300-horsepower hot hatches, but it can even match the lap times generated by a Mazda MX-5 Cup car–the full-race version of this chassis, complete with sequential gearbox, trick shocks and a race-tuned ECU. 

Throughout its development, our Miata has competed successfully in various classes of autocross and time trials. Now it regularly turns laps comparing the latest tire offerings. Yet the car remains quite streetable, regularly delivering top-down smiles on twisty country roads, hence the Triple Threat moniker. 

How can one car do it all, and for what can be called a fair price? A careful evolutionary process of addressing one performance upgrade opportunity at a time. 

 

How Did We Get Here?

Our ND journey began with an invitation to partner with Mazda Motorsports and the SCCA to showcase the capabilities of the then-new ND-chassis Miata at the 2015 Tire Rack Solo National Championships. Since the ND was not yet classed, this exercise provided some data to help rulemakers decide on a best fit. 

At the 2015 SCCA Solo Nats, we got to drive the latest Miata on concrete. We had to have one. Photography Credit: David S. Wallens

It also gave competitors a good look at the cars and generated some excitement. For us, it was the start of a road to performance optimization and a budding love affair with the ND chassis.

At this time, Long Road Racing was well into early development of the Global MX-5 Cup cars to be run worldwide the following year in semi-pro spec road racing competition. For the Solo Nats exhibition, Mazda provided them two MX-5 Brembo Club chassis to prep, one for C Street and the other for Street Touring Roadster. GRM would pilot the C Street car and also help with prep specifications.

Our extensive experience with Miatas suggested we take advantage of typical Street-category allowances for tires, an anti-roll bar, dampers and alignment. As a series partner, BFGoodrich was the natural choice for tires with its g-Force Rival, already a frontrunner in SCCA autocross. But what size? 

Unlike the earlier five-speed Miatas, the ND only offered a six-speed, close-ratio transmission with a second gear that was not nearly tall enough for typical autocross speeds. Factory tire size was 205/40R17, which was a good match for the required 17x7-inch stock wheels. For gearing purposes, though, we selected the taller 225/45R17 size to reduce the need for shifting into third. The pinched fitment would be a little sloppier, but the gearing benefit was more important.

Keeping that tire contact patch working optimally would require additional roll resistance–both steady-state and dynamic. For the former, we chose the MX-5 Cup’s front anti-roll bar–a hollow 1.125-inch piece–to reduce body roll and the resultant camber loss. For dynamic control, we fitted a set of custom MCS dampers that had been early candidates for the MX-5 Cup program.

For alignment, we went with what had worked on past Miatas: maximizing the front static camber and then adding as much caster as possible without losing any camber.  This put us at about -1.8° camber and 5° caster. Front toe-out was set at 3/16 inch to aid turn-in, especially in transitions. In the rear, we dialed in a bit more camber to enhance stability and set the toe at zero to help with rotation.

Photography Credit: Rupert Berrington 

With just these simple modifications, the 2016 MX-5 was a joy to drive around cones, reminding us of our own earlier Miatas–similar handling but with a bunch more torque. Results? We turned competitive times in our exhibition runs. Moreover, we were smitten and had to have our own.

Fast-forward a few months, and a brand-spanking-new Arctic White 2016 MX-5 Club with the Brembo brake package graced our driveway via Mazda’s S-Plan discount program available to all SCCA members. That package includes a factory LSD, track-valved Bilstein dampers and the same brakes as the MX-5 Cup race cars. 

Within the first week, we ran it three times at Harris Hill Raceway, our home tire test track: once for some break-in miles and initial tire heat cycling, and then at pace for baseline times in factory form. Next, we set an initial performance alignment, picking up seven-tenths and improving the tire wear. 

This pattern repeated for the duration of the project: Find the next piece of low-hanging fruit, address it, and measure any change in pace. Meanwhile, we kept to the project’s Triple Threat goals of maximizing track and autocross potential yet staying reasonably streetable.

 

Phase 1: Track Rat and Cone Dodger

Our initial time with the new car focused on improving its track pace and then optimizing it for autocross use in SCCA’s Street category. The rule set for the Street classes is fairly limiting, so maintaining street manners was a given.

Our approach was similar to what we did for the previous year’s autocross exhibition, though this time we measured incremental performance gains. We began with the same alignment specs as before, which produced positive results: seven-tenths quicker. Later, we employed a few tricks to find even more front camber, netting another half-second. 

With several options now on the market, we chose the more adjustable, splined-style front anti-roll bar from Karcepts. It was also a lot easier to install than the stock-style twisted bars. Result? A full-second improvement and less heeling over like a sailboat in turns.

Our final step for initial track use was to replace the OE tires with something more aggressive and versatile, the Michelin Pilot Super Sport. Now we had a car that could run consistent sessions on track in all weather and was 3.5 seconds faster.

[Maximizing an ND-Chassis Miata for Street, Autocross and Track]

With Solo Nationals approaching, we turned our attention to cone dodging. Our factory Bilstein dampers were designed for track use, but the valving was not suitable for the quick transitions needed for autocross. 

Photography Credit: Andy Hollis

Fortunately, Koni was in the process of developing its yellow Sport shocks for this application and we obtained one of the very first sets. Not only was the valving better, but we now had adjustability, so we could tailor the car’s handling for various situations.

The Konis also took advantage of a rules loophole that allowed for ride height changes due to gas pressure variations. ND Miatas come from the factory with high-pressure gas dampers, so switching to a low-pressure shock lowers the car slightly. This is typically worth about ¼° of additional camber plus a slightly lower center of gravity.

To run at the pointy end of national-level autocross requires the best tires, which in 2016 were the BFGoodrich g-Force Rival or the Bridgestone Potenza RE-71R. Both were available in our desired 225/45R15 size, but the Bridgestone had a reputation for being more tolerant as a fat tire pinched onto a skinny wheel–which was essential for the gearing benefit. Mounting those on a set of Enkei RPF1s, the lightest wheel available in the stock size, transformed the car’s autocross prowess.

Our big mods for autocross included Enkei wheels, Bridgestone tires, Koni dampers, Good-Win Racing exhaust and a Karcepts front bar. Photography Credit: Andy Hollis

The final piece of low-hanging performance fruit was the exhaust. We found a few ponies up top and saved some weight by installing one of Good-Win Racing’s SuperStreet exhausts. Together with the wheel-and-tire upgrade, the car now lapped our home track another 2 seconds faster–and sounded the part. We also brought home a Solo Nationals trophy, beating out 71 other competitors in the process.

[Upgrading the Exhaust and Testing Different Wheel-and-Tire Setups]

 

Phase 2: Building a TT Champ

Over the next two years, our time at the track increased as we moved away from national autocross with this car. We kept the car rules-compliant for C Street to run some locals, but the low cost of consumables and easy circuit access found us getting lots more seat time hitting apex curbs instead of dodging cones. 

In late 2018, Mazda introduced the facelifted ND2-chassis Miata, with the big news found under the hood. The engine still displaced 2.0 liters, but output rose from 155 horsepower to 180. The new engine could rev higher, too, with redline raised to 7500 rpm. 

Where the original ND Miata’s grocery-getter powerplant was lifted from the Mazda3, this revvy Miata-specific engine was worthy of the MX-5 badge. The freshened car also had an updated transmission addressing the rash of warranty replacements for failures in motorsports use–ours failed at 10,000 miles. To its credit, Mazda USA stood behind the product and worked to find solutions for motorsports competitors around the country. 

Soon, the very first Arctic White 2019 MX-5 Club with Brembos in the country was sitting in our driveway. A couple days later, all of our performance parts were swapped over and the car was lapping Harris Hill Raceway. The new car outpaced the outgoing one by seven-tenths. That’s not a huge improvement in pace, but the visceral experience was a game changer. This was now a proper Miata.

Our love affair rekindled, we found two new roles for our steed. SCCA’s nascent Time Trials program was gaining a foothold, as was GRM’s tire testing program. Our Triple Threat ND was perfect for both. 

Initially, we found ways to gain track pace that could be easily undone for local Street-category autocross use. A Karcepts rear anti-roll bar netted us a full second in circuit pace for 10 minutes of install time. A similar 1-second drop came from shorter, lighter versions of the RE-71R we had been running–easily swapped between events.

Eventually, our priorities shifted to making the car more competitive at SCCA Time Trials in the Sport category. And while cars prepared to Street category autocross rules are legal for the TT Sport category, it’s not the optimal prep. Further, we were chewing up tire shoulders long before the rest of the tread was gone. Time for a change.

The two big gains for the Sport category are off-the-shelf lowering springs and wider wheels. For the former, we selected Flyin’ Miata’s springs, which drop the car about an inch and double the spring rate. While these contribute a lower cg and less body roll, the biggest benefit is more static negative camber. The double A-arm suspension gains camber as it’s lowered, and we were now able to achieve a full 3° in the front and as much as we wanted in the rear. Not only was the car now another seven-tenths quicker, but the tire wear had also evened out. Win-win.

Wider tires are rarely quicker without wider wheels, and the Sport category rules allowed us 17x9-inch wheels–so we could fully use a 245/40R17. 949Racing was first to market with the unique 4x100 ET45 fitment needed for the ND, so that was a natural choice. There was a downside, though, as this combo was taller and heavier than our previous setup. But the improved lateral grip outweighed any longitudinal losses. Net gain: seven-tenths.

For track work, we added a roll bar and lowered the chassis with Flyin’ Miata springs. The lightweight wheels also came from Flyin’ Miata. Photography Credit: Andy Hollis

As we moved to bigger tracks with higher speeds and more consequence, two other improvements were needed. Blackbird Fabworx builds top-flight roll bars that fit under the ND’s soft top, so we installed one. We backed that up with Aurora Automotive Design seat-lowering brackets to bring our helmet below the roll bar height. All of this worked perfectly with our Simpson Hybrid S, the only head-and-neck restraint effective with factory three-point belts.

And while the stock brake pads were fine for Harris Hill, it was time for real track pads. We sourced ours from Pagid, the supplier for the Global MX-5 Cup cars. Bonus: We picked up a couple more tenths in lap time.

The results speak for themselves, as we were undefeated for three years straight in SCCA TT, including a Sport 5 win and track record at the 2019 TT Nationals.

 

Phase 3: Further Development Still

As our primary tire testing mule, the Triple Threat ND has turned thousands of laps at Harris Hill Raceway in search of comparative tire data. We’ve also accumulated eight sets of wheels, the bulk of them now Flyin’ Miata’s Kogeki brand. 

Photography Credit: Chris Tropea

Testing requires consistency, and our home track has been suffering from bumpy conditions of late due to cycles of drought and flood. To remedy this issue, we worked with RedShift Motorsports on a true coil-over program to move beyond the travel limitations of our drop-spring setup. The result wasn’t just more consistency; the pace was a full second quicker.

While better for testing, the new setup moves us beyond the SCCA TT Sport category and into Tuner, where we’re underprepared. It does, however, make us more competitive again for SCCA autocross as an STR-lite entry for regionals. 

Photography Credit: Chris Tropea

While in Florida, we recently ran the Triple Threat Miata at the Florida International Rally & Motorsport Park, our official test course. It set a fastest lap of 1:19.70, two-hundredths quicker than an MX-5 Cup car. And a baseline against a stock car? Four years ago, we ran a 1:27.51 in a bone-stock 2020 Mazda MX-5 Club.

[The Grassroots Motorsports ultimate guide to track car lap times]

What’s next for this car? We’ve also begun to explore NASA’s Time Trial program, where we’ve had podium finishes in TT5. We’ve yet to fully exploit those rules, but the wheels are in motion for a tune and some aero improvements. We’ve come a long way, but this project is far from over.

 

Sorting Sequence

 

Triple Threat MX-5 Vs. Global MX-5 Cup Race Car

Our Triple Threat runs right with a full-race MX-5 Cup car at the FIRM, but the data shows differences. Cornering speeds are similar as our wider wheels and tires overcome our harder compound. While the race car posts faster speeds down the straights, a lower weight allows us to make up time through the curbs of the esses and in some brake zones. 

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