Sure, it's fun to talk about turbochargers, sweet wheels, suspension, and aero, but all too often we forget an essential component for putting down the power to the wheels—a clutch. Chances are you'll never hear somebody say, "Dope clutch, bro! What's the power rating on one of those?" Clutches will never be headline news, nor will they ever steal the spotlight at a SEMA show, but when you start hearing your car screech and grind, that topic you never talked about might be your greatest concern.
For the past two years, I've been building my six-speed FR-S for the street and occasional track usage. I'm a firm believer that suspension should be top priority, so in went a set of KW V3 coilovers first. The next step in tuning is up for discretion, but I focused on exterior mods. I tried going for something a little timeless yet unique, so I went with a mix of TRD and Rocket Bunny parts, sprinkled with a bit of Seibon carbon-fiber pieces. Performance-wise, the FA20 is upgraded with an HKS premium suction intake, Tanabe Medallion Concept G exhaust, TOMEI Ti straight pipe, and a DC Sports race header. After my last dyno, I made 174 hp.
My next plans call for some forced induction, but since I drive the car in LA traffic everyday and take it to the occasional weekend track event, my throwout bearing went out when I hit 80,000 miles. The timing made sense to source a better clutch and flywheel in preparation for more horsepower, so I hit up SPEC for its upgraded stage 3+ clutch.
Clutches aren't as complex as you think. The main components are the flywheel, the clutch disc, and the pressure plate. The flywheel is bolted on to the engine's crankshaft to transfer torque, and it also has other duties like engaging the starter when you first fire up your engine. The heavier a flywheel is, the harder an engine will work to rev up. SPEC's billet flywheels are manufactured with the highest quality steel and aluminum to keep them lightweight. They're also one of the few flywheels on the market manufactured to a 0.001 machine tolerance. This is important for the next component, the clutch disc. When the flywheel's surface comes in contact with the clutch disc, it begins to rotate. Depending on what the friction surface is made up of, that will determine the engagement of the clutch. Naturally, OEM clutches will give a smooth engagement. SPEC's high-performance discs are constructed with carbon semi-metallic material that will provide great grip. The disc also contains other parts such as its hub and springs. For my Stage 3+ clutch, the hub is double sprung and the springs are heat treated for extra strength. Lastly, there's the pressure plate, which has the job of engaging and disengaging the clutch. When you're not pressing the clutch, the pressure plate will push to get the disc to the flywheel with the throwout bearing. Inversely, when the clutch pedal is engaged, the flywheel and disc spin independently.
I took my FR-S to my local friends at Auto Tuned for an expert install. First order of business is to disconnect battery terminals. Next, you'll need to remove the center console inside the car to access the shifter. Pry center panels and unplug the small electrical connector underneath the traction control buttons. Remove the USB/AUX trim and disconnect the USB connector. From here, you'll have to remove six bolts, two near the USB/AUX trim, two directly below the traction control buttons, and two below the cupholder area. Unplug the 12v receptacle and the center console should lift right off. There are two white plastic push clips that hold down the shifter insulation. Underneath shifter insulation will be a bracket that can be removed by unbolting four bolts. Remove the four bolts holding down the reverse lockout plate.
Auto Tuned tip: Use a Sharpie to mark the position of the bolts and placement so when you put it back together you can align it to the original spots. Otherwise, you'll have trouble getting into reverse. At the base of the shifter you'll need to remove a clip and a washer to disconnect the actual shifter.
In the engine bay, you'll want to disconnect the engine harness and tuck it so it won't get in the way and have a chance of getting crushed. Next to the transmission you'll need to disconnect the starter and clutch master cylinder.
Underneath the car you'll need to remove heat shields and panels. Unbolt your front pipe and exhaust. This will expose the driveshaft. Before we removed it, we flushed out the transmission fluid. Unbolt the four bolts that connect the differential and the driveshaft as well as the two bolts holding up the driveshaft bracket.
Now that the driveshaft and exhaust are out of the way, you can unbolt the transmission mount and the two bolts holding the exhaust hanger. Next, remove the bolts holding the transmission to the engine. Use a jack to tilt and hold the weight of the engine. We recommend using a transmission jack, but if you don't, you'll need to call Auto Tuned's Young Tea to bench press the transmission out.
As you can see, the throwout bearing was in pretty bad condition. SPEC provides a brand-new unit that will clip right on, but before replacing the bearing, you'll want to clean and apply high-temperature grease on the shaft.
There are six bolts to unbolt that hold the pressure plate to the clutch. Remove the plate and the clutch disc. Remove the eight bolts holding down the flywheel. Install the new flywheel using the stock bolts. Torque them to OEM specs in a star pattern. Refill the transmission fluid and put everything back together in reverse order. Voila!
When to expect to change out your clutch. If you own a Scion FR-S or Subaru BRZ, the unfortunate truth is that your throwout bearing will go bad. Reports say anywhere from the 65,000- to 85,000-mile range. Mine disintegrated at 81,000 miles.
How does the car drive with the Stage 3+. Since the friction area on the disc is constructed of carbon metallic, it made for a really rough engagement. But it's the trade-off you get for high-performance clutches. One day of driving and you'll get the hang of it. There are other minor issues such as noise, but they don't bother me too much. If it means I get a clutch that's durable and can hold the power I'll be making, I'll gladly endure the small inconveniences.
Approximate Costs. Clutch jobs usually run about $600-$900 without parts. My Stage 3+ kit included the flywheel, disc, and pressure plate, priced at $758 MSRP. If you just need an OEM replacement, the Exedy replacement is $355 MSRP, but it doesn't come with a new flywheel. If you don't want to purchase a new flywheel, another option is to resurface your OEM unit.
Update: Forced Induction OTW!
Shortly after the SPEC clutch install, I received good news in regards to the power that I've been waiting for. When I was looking up forced induction options, there were a couple of things that I had to keep in mind. First, since the Hot Lava color isn't exactly discreet and my aero is an open invitation for cops to pull me over, I had to go with a boosted solution that was California-state legal. Secondly, with a magazine editor's salary, it had to be cost effective. At the end of the day, I decided on Jackson Racing's supercharger kit.
Jackson Racing was founded and still operated by a father-son duo. Oscar Jackson Sr. is an engineering genius and a fountain of knowledge when it comes to racing. His son Oscar Jackson Jr. is just as brilliant and quite the racer. At the time of the clutch install, they told me their kit were back ordered; however, a couple weeks passed by and I'm stoked to finally have their supercharger kit in hand, which includes a bigger Rotrex C38 blower.
It was an honor and to see Oscar Jackson Sr. himself deliver the supercharger kit to me. We talked about the importance of cooling for a good half hour before laying out the kit's components at Auto Tuned. To put it into perspective, the Rotrex C38 unit is about the size of a swole pitbull and is said to make the most horsepower for any FR-S/BRZ supercharger kit in the market. Stay tuned for the install and the dyno numbers in an upcoming issue!