Building A Winner: A Top One Lap of America Team's K-Series Miata

By Andy Hollis
Jun 25, 2018 | Honda, Mazda | Posted in Features | From the June 2015 issue | Never miss an article

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Story By Andy Hollis • Photos As Credited

One of life’s maxims is that there always comes a time to move on to something new. Life is short and repetition is boring–or, put another way, variety is the spice of life. This is just as true at the race track as it is anywhere else.

So even though the One Lap CRX, GRM’s official entry at the Tire Rack One Lap of America, has had a long and successful five-year run, the time has come to replace this competition steed. Sometimes the impetus to change is a new opportunity, and sometimes it comes from reaching goals and looking for new ones. In this case, it was a little bit of both: The One Lap CRX’s 2014 achievements were as much as could be hoped for from the Little Honda That Could.

Over a 12-month period this car went 170 mph at the Texas Mile, won its class while finishing fourth overall in the Tire Rack One Lap of America, and claimed the SCCA’s Street Mod Front Wheel Drive national championship.

For each event the CRX was reconfigured to optimize its chances, but it had reached the point where the team could expect only decreasing returns in performance based on resources expended. Time to move on. The problem is that while change can be exciting, the challenges it brings can also be frustrating and disruptive. Having successfully navigated the path to the winner’s circle a number of times, in a variety of cars and disciplines, Hollis Racing has quite a bit of experience in managing the tricky feat of switching steeds. And we’d like to share those secrets to success.

This new project would have some of the same goals that guided the build of the little Honda, but with a few key new requirements added into the mix. Although the CRX was built as a track car for One Lap, we always knew it could also cross over to autocross and run up front there as well. With that in mind, every modification was done in a way that would keep the car within the rules for Street Mod FWD–or that could be easily converted. So the goals were simple: super-fast on track, streetable enough to do the transits on One Lap without kidney failure, and SMF-legal.

The new project would again center around One Lap competition, but with an eye toward NASA Time Trial. So “streetable” is still in the mix, but ultimate track performance is key. We also wanted this project to offer remedies to three fundamental design limiters that hampered the CRX: front-wheel drive, 65 percent of the car’s weight on the nose, and a limited tire height of only 23 inches.

Fixing any of these is most easily done with a change in platform, so it soon became clear that this project would involve building a totally new car. Here’s how our podium-finishing team keeps a build like this on the rails:

Step 1: Don’t Start With a Blank Sheet of Paper

The surest way to get nowhere quickly in motorsports is to build from scratch. The more variables you eliminate, the easier the job. Fewer knobs to turn also means there are fewer possible combinations to try before you find the one that unlocks success. And working with familiar knobs makes that process much quicker.

We originally drew upon our many years of Honda autocross experience to build our first track car, and the result was essentially a Street Touring Civic with lots more power via an engine swap. Once the drivetrain was working, we quickly had a running car that we could enjoy. And we also had relevant experience on which to base handling adjustments with the higher speeds.

The other car we had a great deal of success campaigning during our halcyon autocross days is the Miata. Over a seven-year period of ownership, our 1992 model competed in Stock, Street Prepared and finally hit its stride in Street Touring, where it won a pair of national championships. (The story of the latter stage’s development was told in these pages and remains an often-referenced series in digital form at We’ll employ that same development process for this build.

The spark that fired this best-of-both-worlds project was a forum thread at describing the swap of a Honda K-series engine into a Miata. The benefits were tantalizingly familiar: rear-wheel drive, 50/50 weight distribution and bigger wheel wells.

We were intrigued, and followed the build closely as it went from prototype to running track toy this past summer. Our decision to follow this path was made even easier when the swap was commercialized into a kit; we jumped in on the initial group buy.

Step 2. Get It Running and Then Make It Faster

We are big on planning, so our team keeps “to-do” lists for all of our development. The list never gets completed, but is instead prioritized into sections of “must haves,” “known improvements” and “research ideas.” Once the “must haves” are ticked off, we can start enjoying the car.

Further, and even more important, the list can evolve based on first-hand experience. Iteration is a much stronger method of development than planning everything out ahead of time. As the saying goes, “You don’t even know what you don’t know.”

Our CRX project actually started with a Civic hatchback chassis that we threw a basic suspension and wheel-and-tire package onto based on our autocross experience. The only “must-have” was more motor, so when that was complete we got on track. “More go” quickly led to “more stop” and brakes were upgraded. As speed increased, safety became more of a factor, so a roll bar and race seat and harness were added. These had always been on the “improvements” list, but the specifics became clearer as we ran the car on track.

The chassis was later upgraded to a CRX for lighter weight and better aero, the engine got bigger and faster, a splitter and wing were added, and we installed better gearing, full roll cage and so on. Having a running car throughout allowed us to test new technology–especially tires–as it came online.

We are following the same course of action with the Miata. We started with a running car with a known history, ordered the engine swap kit, and have now swapped in one of our spare K24 powerplants. Once it’s running, we will again draw upon our autocross experience for baseline suspension as well as wheels and tires.

However, since the Miata is open top, we can’t really start to push it hard on track without some sort of rollover protection. While an off-the-shelf roll bar is the easy button there, with a car this fast we are going to jump straight to a full cage. Besides, cage installation is a fairly intrusive process that also has an impact on suspension due to added chassis rigidity and weight, so we might as well go custom. After that we’ll add brakes, aero and all the million other little things we hadn’t planned for.

Step 3: The 80/20 Rule

Here’s another adage regarding successful project cars: The final 20 percent of the job takes 80 percent of the project’s total effort. Incomplete knowledge of the problem, a tendency to overanalyze, and the desire to put the “absolute best” solution on any part of the car all make the tail end of a project take longer than expected.

Let’s look at our Miata. Initially we’re going to use the wheels and tires from the CRX because they bolt right into place. Ultimately, however, we’ll want to experiment with larger wheels and tires, since the Miata opens us to options that were not available for the CRX.

Similarly, our plan is to build up a rear end with an OS Giken limited-slip. Getting it right is going to require testing and sorting–and that takes time and effort. We’ll just bolt in an OE Torsen to get us going.

Step 4: Drive the Car in as Many Circumstances as Possible

The best way to net a running car as early as possible? Get out there and use it. Drive it on the street, run it on a variety of tracks, autocross it, drag race and so on.

Each of these venues serves as a data point and will reveal valuable and unique information to further refine your development plan. It might also expose weak points or parts failures.

If all you ever do is run at the same track–or the same autocross lot–your setup will be less versatile. Knowing how to adjust to conditions is just as important as knowing how to make it fast in the first place.

Step 5: Get On the Right Tires Right Now

The single biggest contributor to vehicle performance, outside of the driver, is the tire choice. The sooner you get on something that’s in the ballpark of the final answer, the more relevant your data will be and the less back-tracking your development effort will entail. And if you are running tires with limited life remaining, use fresh tires for setup testing. Old tires are great for having fun, but are a complete waste of time for development.

Step 6: Work With the Top Drivers and Use Their Experience

Do you know everything about everything? Of course you don’t. But there are lots of folks out there that know everything about something–or at least a lot more about it than you do. Many of them are happy to share that knowledge via forums, email, phone calls or good old-fashioned, face-to-face discussion.

If your project is unique, they may take a special interest in helping you out. That’s why getting out on track early is important.

This is also why it’s important to make connections at events like the year-end championships as well as the MSX, PRI and SEMA trade shows. In just a single day, you can vet ideas that would take months of phone calls and email exchanges to discuss. Sure, it’s very fulfilling to build everything yourself, and if that’s your style, go for it. But if actually driving and competing is the goal, farm out what you can afford.

We love rebuilding engines and transmissions, but it takes time. And if you need to rely on a component for an endurance event, pro-built parts can make or break you. One of the reasons we chose the Miata platform is that it’s the most-tracked vehicle on the planet. Off-the-shelf solutions exist for most everything, and expert, application-specific knowledge can be brought to bear. So where possible, we “buy time” in our development schedule by working with pros. That also helps beat the 80/20 rule cited above, especially when it comes down to crunch time before a big event.

Step 7: Pay Attention to Detail

When you do something, do it right the first time. This does not mean to over-engineer or over-analyze it. Use quality, proven parts, tools and processes. This will save time redoing stuff later on.

Step 8: Test Your Assumptions

Employing the iterative process allows for a constant state of testing. We always use spreadsheet analysis to run the numbers on performance expectations ahead of a build, but it is just as important to measure the results. Otherwise you can go way down a blind alley and waste time backing up. The data logger is your friend here, as is the dyno.

While planning for the Miata, we’ve analyzed how the CRX generates its lap times. Now that we have rear-wheel drive and better weight distribution, we’ve quantified how improved acceleration off the turns should make the Miata faster down the straights. Likewise, we’ve looked at saturation levels on the front tires to get an estimate of how much better that car should corner.

As we start to run the Miata, we’ll be looking not just at overall lap times, but the components of those times. If any of our initial assumptions are off, we can then determine whether the issue was bad theory or failed execution. Without measuring precisely, you are just left wondering.

Step 9: Double Your Worst-Case Time Estimates, Especially Lead Times

Today’s world of 24/7 online retailers and inexpensive expedited delivery has made us accustomed to immediate gratification. Amazon Prime has become a way of life.

But parts suppliers in the motorsports industry are notorious for late delivery, especially for semi-custom and bespoke items. Plan on it. Following the iterative process will help keep you from being too stranded, but if you know you are going to need something, do not wait until the last minute to order it.

Adding to that schedule slippage are unknown issues that will constantly crop up and need attention. When building your initial schedule, double your time estimates to accommodate.

Real life will also step in to suck up time, since none of us does this full time. Building a car under severe time pressure simply adds stress, which leads to the vicious circle of mistakes and more stress.

Step 10: Have Backup Plans

What if you were wrong about your assumptions? This can happen with a single item or the whole car. If you are building for an important event, having backup plans makes the process more enjoyable and productive.

The 80/20 iterative process helps a lot here: If the 99-percent-final version doesn’t work out, we can always go back to the 80-percent solution for any given item.

For example, we plan to employ some über-trick electronic suspension on the Miata, but we can always go back to basics if it doesn’t pan out. Likewise, the CRX will be kept running while we develop the Miata so we can keep our driving skills fresh, do recon days at new tracks, and test new parts. Testing opportunities do not always synchronize with your development plans.

Step 11: Have Development Parts as Well as Race Parts and Spares for Wear Items

Iterative development relies on track time. That means you go through consumables and need to be prepared for that maintenance. Brakes, fluid changes and so on are all important to maintain. Save some time in the plan for that, or you’ll pay a bigger price later.

There will also be unexpected wear and damage that should be considered in your schedule. More time in the seat means more possibility of a missed shift, an “off” or a parts failure. Building up the spares stash early on will help reduce the impact on your schedule. Fully loaded uprights, axles, fresh calipers, engine sensors and a splitter blade are just some of the items that could save your valuable testing weekend should an issue arise. Taking that one step further, keep your fresh race engine and transmission out of the car during the development cycle, especially if you have had these professionally built. You’ll want something making similar power levels to get good testing numbers, but when competition starts you really don’t want to have to rely on a drivetrain with tons of track miles being able to provide its best power and reliability.

For the Miata’s transmission, we’ve already set aside a low-mileage, six-speed Mazdaspeed Miata box while we abuse a garden-variety six-speed removed from a friend’s wrecked 2000 Miata SE. Initially we’re going to swap in a bone-stock Honda K24 engine, while later we’ll move to a 280-horsepower version built from junkyard cores.

For One Lap itself, the car will get a pro-built 300-horsepower unit.

Like we said, success comes from a series of steps.

Meet The K Miata, Perhaps The best Engine In The Best Chassis

When Honda’s K20A2 engine hit the market with the 2002 Acura RSX-S, it set a new record for power-per-liter in a mass-produced production car. Its 240 horsepower from just 2.0 liters, all without any forced induction or even direct injection, set the bar high.

The new heads flowed like rivers, and variable valve timing as well as sophisticated electronic engine management yielded the flexibility to run lofty compression ratios. Yet this engine could still idle smoothly and putt around town like a grocery getter.

The motorsports aftermarket quickly recognized the potential of these K-series engines and upped the ante even more with simple re-tunes and bolt-ons. Suddenly that inline-four could make another 50 horsepower. Honda then gave us a 2.4-liter version of this lightweight, aluminum engine. Along with well-developed aftermarket internal parts, it could achieve a reliable 300 horsepower and 9000 rpm–all on pump fuel.

David Calzada is an avid track-day enthusiast who swapped a K-series engine into his Acura Integra in the quest for more speed. It was a dependable and satisfying combination until about a year ago, when he did a few lapping sessions in a friend’s Miata.

Sure, the Miata didn’t make as much power, but that chassis lured him in: On the way home David hatched the idea of blending the best engine with the best chassis. He convinced Adam Jabaay, another friend who is skilled at fabrication, to join him on this quest and a prototype was put together in record time.

Proudly chronicling his efforts on a variety of forums netted a lot of interest from folks looking to duplicate the result, so David decided to produce a kit that would clear the major hurdles for these enthusiasts. K Miata was born.

The basic package includes an adapter plate and custom flywheel to mate the Honda K-series engine to the Miata transmission. A custom oil pan and pump, along with a replacement tubular front subframe, drops the Honda engine into the chassis. An adapter harness makes wiring simpler, while a variety of intake manifold and exhaust solutions are being developed to support a range of power levels. Figure $3750 for the complete conversion kit minus the exhaust header and manifold adaptor.

Despite making well in excess of twice the power, the all-aluminum Honda engine weighs the same as the iron-block Mazda lump, so handling and weight balance are preserved.

The first group buy sold out quickly, and a second run of kits is now in the works.


K Miata
(877) 587-4255

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View comments on the GRM forums
te72 Reader
6/25/18 11:12 p.m.

Good Lord, if the last 20% of my Supra takes 80% of the total project time, I'm in for a LONG project. Took 6 years just gathering parts, and nearly two years putting them all together. It's nowhere near done, but it is getting a little bit better each time I tinker with it a little more, fix the little stuff, get rid of squeaks and rattles, eliminate leaks, etc...


Also... as much as I love my Miata, the K swap seems a bit odd. I love the idea of a high revving, naturally aspirated engine that makes good power for the size and weight all through the RPM band, but... S2000. Yeah, they're a couple hundred pounds heavier, and I don't think the F20/22C engines have quite the development level as the K series do, but, in the end, it's a high revving, naturally aspirated engine in a nice handling roadster. Isn't that the end goal here?


Good thing I live at high altitude, makes the choice easier for my car. It's either gonna need boost or a V8. Small NA engines tend to be a bit anemic above 6500', most unfortunately.

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