SuperK: The quest to make the fastest Honda S2000 | Articles

First Step, Re-Engine

Worldwide, Honda sold 110,673 units of the Honda S2000, from 1999 to 2009. It used an engine specific only to that model. The stock F20C put out a hefty 237 horsepower at 8300 rpm, considering the engine displaces less than two liters. The slightly larger, 2.2-liter F22C1, the version that SuperK came with, delivered 240 horsepower at 7800 rpm. However, with relatively few engines available on the market, Smedegard suggested installing a more prevalent, better-supported Honda engine — the K24.

“It was a more economical solution to replace the motor in the S2000,” Smedegard says. “You can buy a K series engine for about $1000. The K series also makes a little more usable power, they make a little more midrange.”

Today, Smedegard operates a thriving race car preparation business, ASMotorsports. But back in 2017, he wasn’t as experienced.

“The engine was the first major modification we did to the car,” says Smedegard. “At the time we didn’t think it was very simple. It was a learning experience for me. A lot of times we learned the hard way–I had to redo many things. I credit the car to a lot of what I know today.”

Getting Things to Communicate–Part I

Both engines–the original F22C1 and the new K24–came from Honda, but that didn’t make the swap easy.

“We got the engine in the car and spent a week or so trying to defeat the immobilizer issues,” Moss says.

Newer Honda S2000s have more immobilizing features that prevent changes beyond the OEM parameters. The issue revolved around them using an ECU out of an Acura TSX and their Honda S2000 ignition key.

“The immobilizer is built into the key, which communicates to the engine ECU,” says Smedegard. “They need to match. Otherwise, you turn the key, the engine will crank, but it won’t fire as it won’t turn on the ignition coils.”

To remedy this, they used an ECU reflashed by KTuner, which disabled the immobilizer.

“That ECU wound up being a bust,” Smedegard says. “We had so many issues with it. It would sometimes freeze up when we were trying to tune it. You also have a lot of limitations–sometimes emissions, sometimes safeties put into place, where there’s no workaround. We ended up going with a full, standalone AEM Infinity ECU, where you have full control.”

The Mechanics of a K Swap

The next issue they encountered was with the Clutch Masters aluminum flywheel adapter for the K series.

“We had flywheels backing out and sometimes coming off,” Smedegard says. “The solution we have now took some time. We had to work with them to produce a better part. I pushed hard to get a chromoly flywheel made. Ever since we went with this new flywheel from Clutch Masters, we hadn’t had any issues.”

Then, they encountered another problem.

“We had issues with throttle bodies falling apart, sensors failing and intake manifolds cracking,” says Smedegard. “With the K24 having a longer stroke, it made a lot of harmonics, especially the higher you rev it. Most places that make intake manifolds don’t set their manifolds to be braced back to the engine–you just mount it to the mounting flange, and that’s it. We braced the intake manifold, which greatly reduced a lot of the harmonics that the throttle body sees and the sensors mounted on the intake manifold.”

The Quest for Power

With the foundation in place, the duo now wanted to push the limits on the power band. This involved some trial and error.

“We bought a used, high-compression engine built by 4 Piston Racing, but it only was 250 to 260 horsepower,” Smedegard says. “It was still fast, but not fast enough for our ultimate goal of making this the fastest S2000.”

They then returned the stock K24 back into the engine bay, with the addition of a Kraftwerks Rotrex supercharger.

“We had to make our own mount kit, to mount the supercharger onto a K series in a rear-wheel-drive car, which no one had at the time,” Smedegard says. “The supercharger made good power–like 400 horsepower–but it still wasn’t fast enough.”

Exit supercharger, enter the Garrett G25-660 turbo.

“The turbo made a lot more power; a lot more usable power, too,” Smedegard says. “We still haven’t pushed it to its true potential, with a bigger turbo and more boost. We ran a whole season around 500 horsepower. Then, we started breaking transmissions and differentials. That’s when the DCT came into play.”

How to Deliver the Horses

“We were looking for a better transmission, but we weren’t looking at a DCT specifically,” says Smedegard. “We just wanted a transmission that was reliable, could take the power, and there weren’t really many options.”

Within the confines of the rules, Moss found the DCT (dual-clutch transmission) fit their needs.

“We couldn’t go with a race sequential or dog box transmission,” Moss says. “This is where we egged each other on. I messaged Andy and said, ‘Hey, do you want to try this DCT? This might be cool.’ He probably blew me off, saying ‘Yeah, sure.’ So, I ordered it and it showed up at his shop.”

In addition to rules, they were also restricted by the front-engine, rear-wheel-drive format of their car. That led them to the BMW M-DCT.

“There are four different versions of the transmission,” says Moss. “You can get a short-ratio or long-ratio transmission. The short ratios were in the 135, 335, E90, and M3. The long ratios were in the F80 M4,and F10 M5. You can get either of those transmissions with a BMW inline-6 or the V8 bellhousing. We can only get the inline-6 housing to fit in the car. We have the long ratio in the car now. It gives us a good spread of ratios on the track and a good cruising rpm on the street for One Lap of America.”

Fortunately, it made for a relatively affordable choice.

“The BMW M-DCT transmissions used to be fairly readily available and cheap, but now there’s a big craze about the DCT-swap stuff,” Smedegard says. “What used to be a $1000 transmission is now $2500. That’s still relatively cheap in the grand scheme of it all.”

Getting Things to Communicate–Part II

Installing the transmission went relatively smoothly.

“We had to make some of the adapter pieces,” says Smedegard. “We have to use a dual-mass flywheel. We needed an adapter to go from this flywheel to go into the transmission on the input shaft. We worked with a company DomiWorks in Sweden.”

As with the engine, the DCT has its own computer, a TCU (transmission control unit).

“The biggest obstacle has been the transmission controller,” Smedegard says. “We’re running a standalone TCU from HTG Tuning in Poland. We had to take out the internal TCU and wire an external TCU. This is all still fairly new. It’s not something you can buy off the shelf, throw on the car and drive. It’s very much a science project, even for the company making the controller. Our struggle is learning how to tune a dual-clutch transmission.”

Then, the TCU needs to communicate with the ECU.

“The transmission bases many things off the engine,” says Smedegard. “Like on a downshift, you need to bring the revs up. It has to send a signal to the engine ECU: ‘Hey, rev up so I can downshift and we can make this happen smoothly together.’ Getting all this to work together has been challenging.”

The Big Advantage to a DCT

Besides durability, the DCT offers other benefits.

“You have a lot better gearing,” Smedegard says. “There are more gears in the transmission, so you have no problem finding the correct gear.

“As a driver, you don’t have to worry about trying to shift. You can leave your hands on the wheel and you only have two pedals for your feet.”

However, the chief advantage is how it takes time off the stopwatch.

“On an upshift, you have no loss in shift time, especially with a turbo car,” says Smedegard. “With a conventional transmission, when you let off the throttle, you let all the boost out, you get the shift done and you get back on it, it has to go boost up again. With the DCT, there’s no boost drop at all. Most tracks you’re shifting 15-or-so times a lap, and you’re losing a tenth, maybe two tenths, every shift. Add that up. That’s a second to two seconds every lap in shift time.”

As they worked with developing the DCT, they ran with the least amount of boost, bringing the horsepower closer to 400, where it stands currently.

“As we were working through the DCT issues and getting that to be reliable, we wanted to run the car in a less aggressive state,” Moss says. “It allowed us to not worry about running the engine at the ragged edge and focus on the driveline changes. FWIW data at GingerMan Raceway shows a very similar acceleration plot with the DCT at 400 horsepower compared to the H-pattern transmission at 500 horsepower.”

Other Mods

With much more power than stock to the wheels, and a transmission that delivers it more efficiently, Moss and Smedegard upgraded other components to help with handling. First step, the brakes. They went with a StopTech package, which has 355mm rotors and four-piston calipers in the front, and 335mm rotors and two-piston calipers in the rear.

“Once we had the supercharger on it, we found the limitations of the stock brakes,” Moss says. “We got a braking system back then that was far more than we needed at the time. It’s appropriate for what we have now.”

Aero-wise, they worked with Zebulon Motorsport Consulting.

“It’s an aero kit designed for our car and our rules,” says Smedegard. “Our bodywork has to stay within five inches of the car’s stock bodylines, and we maximized that area. It’s a full, 3D splitter, with integrated diffusers, and all made of carbon, so it’s super light and super stiff. It makes a ton of downforce on the front, to the point that when we put it on, it was crazy how much better braking we had.

“We got a huge, single-element rear wing, because that’s all we’re allowed. We got side skirts. We tried to clean up what’s under the car, but we’re not allowed flat floors. We added vents to try to improve the car’s aero overall.”

A J’s Racing S2000 wide body kit allows them to fit the rules and fit the 265-width, 200tw Yokohama A052 tires.

The suspension consists of two-way adjustable coil-overs from Reinharte Racing Suspension. It has a big front sway bar (aka Gendron bar) from Small Fortune Racing and a rear sway bar out of a Miata.

“It’s a stock front sway bar off a NC Miata for the rear sway bar,” Smedegard says. “It’s basically half the spring rate of a stock S2000 rear sway bar.”

The duo went to great measures to reduce weight, too, cutting roughly 250 to 300 pounds off the stock curb weight. They stripped down the car and removed every bracket that was no longer needed. Moss and Smedegard took out the motor for the convertible top and replaced the top with an inexpensive, fiberglass hardtop version. Then, they ripped out the wiring and installed a PDM from Hardwire Electronics in the U.K.

Getting Things to Communicate–Part III

With the PDM (power distribution module), they essentially added another computer to the car.

“It’s like a standalone ECU for all your power,” says Moss. “Instead of using relays and running wires everywhere, we have one computer that sits behind the passenger seat that everything gets wired into. We have keypads and switches in the car that turn on and off the electrical systems in the car. We can also program the PDM based on engine parameters–when fans come on, water sprayers, lights.”

The PDM provides a few benefits.

“Let’s say you trip a fuse, and it’s your fuel pump,” Smedegard says. “Instead of being dead in the water until you physically replace that fuse, the PDM can automatically reset that fuse and turn that fuel pump on, and it can keep trying. The PDM can make things more reliable, but it’s only as good as the person who sets it up.”

Fortunately, Moss enjoys programming the PDM.

“The PDM we have on this car requires a good understanding of how CAN bus protocol works,” says Smedegard. “Alex already knew some of that stuff. I understand the power side of it, but how to program CAN bus messages and stuff is a little tricky.”

However, the chief advantage the PDM provides is that it shaves weight. Lots of it.

“Some of these cars have multiple fuse boxes, relays, and a ton of wiring,” Smedegard says. “A lot of it we didn’t put back into this car. It doesn’t have a radio or speakers now. We saved close to 70 pounds.”

Not Your Sunday Cruiser

Both Moss and Smedegard agree that SuperK is a blast to drive on the track. While legal for the street, it doesn’t offer many of the creature comforts one might like while cruising–and that’s not including the lack of a working radio.

“You can’t just jump in it and drive it–you need a training session,” Moss says. “You need an owner’s manual with the car.”

Smedegard provides an example of that.

“Sometimes you have to reboot the ECU, because the throttle body goes into limp mode,” Smedegard says. “It’s a process to restart with this car. It’s not simply turn a key to turn it off and on. You have to come to a stop, shut everything off, power everything back on, turn the ignition on, and fire it back up, and hopefully the TCU puts it in the appropriate gear.”

Starting, in general, provides a challenge.

“It’s on E85 and has a full standalone ECU–starting can be a little finicky,” says Smedegard. “Sometimes, it doesn’t want to idle the greatest. The TCU isn’t always the smoothest–it’s clunky during shifts.”

On second thought, don’t worry about lack of a radio. You might not hear it.

“It’s got a side-exit exhaust–it’s literally right off the engine, into the turbo and two feet right out the side fender,” Smedegard says. “That’s all the exhaust you get. It’s quite loud.”

Hold your drink, too.

“There’s no rubber in the suspension workings,” says Moss, “so it’s harsh, clunky, and noisy.”

Lastly, the possible dealbreaker for SuperK as a Sunday cruiser.

“There’s nonstop heat coming from the engine bay and through the firewall,” Smedegard says.

“It’s so hot in that car,” says Moss. “Everything else, you could learn to live with. It’s a car you could drive on the street, but you would never want to.”

However, At the Track…

So, it may not be a great grocery-getter. But at the track, SuperK rises to the occasion.

“It’s an absolute rush,” Moss says. “It feels like there’s no time to think about anything–it’s all happening so fast. You just got to drive, react and deal with things as they happen.”

Fast. That was their goal. They seemed to have achieved that.

“This feels like you’re autocrossing a road course,” says Smedegard. “It’s not like you plan out your corners–it’s reactionary. That’s how it’s like driving the car on a road course compared to something slower.”

Moss, who has raced much slower cars prior to SuperK, now has a new appreciation for bigger road courses.

“I never enjoyed Road America until I took that car there,” Moss says. “It’s a ton of fun, because you’re not waiting for the next corner to come up, for what feels like an eternity.”

Moss and Smedegard say they still have a lot more to do with SuperK in their quest to make it the fastest S2000. Stay tuned. It sounds like Road America may get much more fun, although the road to Road America may get a tad more uncomfortable.