It's the stuff that Scion FR-S/Subaru BRZ owners dream about—boost! For quite some time, my car was viewed as the obnoxiously loud and a rather slow FR-S. And with Sam already working on his second build, I was falling behind and barely making progress on my first real project car. All of that changed dramatically after I picked up Jackson Racing's newest supercharger kit.
There are plenty of forced induction options for the FR-S/BRZ, but the JR package made the most sense. First off, it's CARB legal—sorry, po-po, you can't ticket me! Secondly, the power increase makes the stock FA20 feel like a sloth, not to mention I'm still getting good fuel mileage when I'm driving conservatively. JR's old kit previously used a Rotrex C30 blower, but we're one of the first to test the larger C38 model. Confirmed to make the same horsepower as the previous model with a CARB legal tune, this version has the potential for so much more. The Jacksons put countless hours of R&D on the dyno, track, and street to make this a solid, reliable, and user-friendly affair. The kit comes with everything you'll need for the installation, but rest assured that if you mess up, the Jacksons are there for technical support. Installation Overview
I headed to Autotuned in Monrovia, California, for assistance with the install. The first order of business is disassembling the factory components. Of course, start by disconnecting the battery, then remove the front bumper, passenger-side headlight, air guides, and wiring harness. MAF sensors and airbox components are removed and hoses rerouted. The plastic covers on top of the alternator and AC compressor are also removed to expose the serpentine drive belt that needs to be taken off as well.
This step includes prepping the engine and Rotrex unit. Before dropping in the supercharger, there are studs, brackets, a pulley, and a double-sided serpentine drive belt that need to be installed. Loctite is used on the first two threads of the studs before they're installed. A clearance check is done between the engine casting on the driver side of the crank pulley and the serpentine belt. The Rotrex unit is fitted with banjo bolts and a mounting bracket before being installed to the motor.
Next, we prepped the intercooler by installing the mounting bracket and Rotrex oil cooler. Once the intercooler/oil cooler assembly is mounted, the lower intercooler brackets are put into place.
With the intercooler mounted, we moved on to its tubing. JR recommends that you check all tubes and hoses for any foreign material that might have been left behind during the manufacturing process. We lubed all of the hoses with penetrating oil spray prior to installation. The radiator inlet neck is relocated low in the chassis and hoses are installed to the intercooler. The MAF inlet tube is installed and before the MAF O-ring is set up, we inspected to make sure there were no kinks or breaks. A replacement O-ring is provided just in case the factory unit is worn out. The throttle body inlet tube is installed next and is rotated for a natural alignment. This specific tube should never make contact with the supercharger pulley.
The preassembled Rotrex oil reservoir is installed on the top of the driver-side shock mount and a Rotrex oil hose is routed behind the hood latch's vertical support where it's met from the bottom of the reservoir. The Rotrex oil filter is secured to the ABS brake lines using the provided plastic ties. Rotrex traction oil is filled to the top of the reservoir.
The cosmetic intake manifold cover is removed and a vacuum tee is installed on the power brake hose. Bypass valves and hoses are also put into place while the air filter is installed to the intake tube and secured with hose clamps. The windshield washer filler neck bracket can then be reinstalled with the provided mounts. On the backside of the intake manifold is the PCV hose, which we replaced with a high-performance PCV valve.
For the final step, we primed the supercharger by gently blowing compressed air into the Rotrex oil reservoir. Make sure the reservoir is never empty or the damage can be catastrophic. Look for any fuel leaks and double-check all hoses, clamps, fittings, and fluid levels. Oscar Jackson Jr. finished off the install with a CARB legal tune.
Knowing that I would need a better flowing exhaust before heading to the dyno, I contacted TOMEI for one of its badass, full-titanium 80R systems. Once that was installed, it was off to Church Automotive Testing, where I met with Oscar Jackson Sr. and Jr., along with Sean Church. After an afternoon of number crunching and tests, my FR-S made a solid 271 hp and 214 lb-ft of torque, an 87hp gain over stock!
The most noticeable difference on my first drive was the sound of the blower, which resembles an airplane getting ready for takeoff. But right off the bat, the instant power delivery is the main benefit of having a supercharger, and it can be felt at a moment's notice. Whether maneuvering around cars on the freeway or accelerating along highway onramps, the linear power felt light years better than the factory output. Along with the increase in power, I can still average about 300 miles on a full tank, which are mostly comprised of freeway miles. When and if the time comes for me to look for more power, it's just a high-boost pulley and E85 conversion away. The Jackson Racing supercharger kit is absolutely sensational and it's no wonder it's always on back-order. After one little test drive, it will convince you that this is how Toyota should have sold the car from the factory.
Rotrex vs. the World
Which boost is better and why
By Aaron Bonk
A Rotrex supercharger is nothing at all like the regular, old, centrifugal type you think it looks like and even less like the roots-style one your uncle's got on his Firebird. Aside from all three of them being driven by a belt and a crankshaft, they've got very little in common with one another.
As it turns out, Rotrex superchargers just don't work like the rest. They're also a whole lot smaller, more efficient, and don't make as much noise. Inside, they're made up of something Rotrex calls a traction-drive system that generates boost through friction created by a whole bunch of rolling bits. All that means to you is that torque's on tap all the time, all the way to redline.
ROTREX VS. OTHER CENTRIFUGALS
Your first mistake is assuming that a Rotrex supercharger is just like every other centrifugal blower. After all, they both share the same kind of compressor housing, they've both got impeller wheels, they both mount to the engine similarly, and they both allow for easy intercooling. The similarities end there.
Other centrifugal superchargers are made up of a series of toothed gears that drive their impeller wheels. These sort of gears limit how fast the whole thing can spin, though, which means an oversized wheel's got to be used in order to generate respectable power at higher engine speeds. But, as is often the case with oversized wheels, all of this happens the at expense of low-end torque.
Compare a Rotrex's impeller against all of this and its smaller diameter is obvious, but it's the Rotrex that can spin a whole lot faster, making the sort of gains that'll make you happy at any engine speed. All of this is made possible through planetary gears, which don't have teeth but create enough friction among themselves to spin the impeller wheel faster than you'd expect.
ROTREX VS. POSITIVE DISPLACEMENT
You won't mistake a Rotrex supercharger for a Roots-style or screw-type blower that bolts on top of your cylinder head, but you don't know why. These sort of positive-displacement superchargers generate boost by cramming air in between a couple of intermeshing rotors. Here, low-speed torque isn't embarrassing, but that's where the compliments end. Positive-displacement blowers like these can only spin as fast the crankshaft will let it, they can't always be intercooled, and they can make a whole lot of noise.
Rotrex's traction-drive system means it's able to spin a whole lot faster than what the crankshaft says it can. In other words, while your crank's turning at a measly 6,000 rpm, your Rotrex could be rotating 20 times faster. And that's a good thing, because the faster all of this spins, the more air's entering your combustion chambers.
ROTREX VS. TURBO
Turbos are driven by exhaust gases, not belts. That's the obvious difference. Like a Rotrex, though, turbos operate at higher speeds, which means their top-end power-making capabilities are hard to beat. Turbos aren't perfect, though. They generate all sorts of heat, which can lead to detonation, and their responsiveness will never match anything that's driven directly off of a crank. Because Rotrex superchargers are driven by the crank instead of smoldering exhaust gases, temperatures are kept at bay. Spool-up time also isn't so much of an issue since nobody's got to wait for enough exhaust waste to spew from the combustion chambers to spin that turbine wheel that it doesn't have. And unlike turbos, Rotrex superchargers are self-lubricated and don't share oiling systems with the engine, which doesn't just make installation easier but also makes for cooler operation.
WHAT ALL OF THIS MEANS FOR THE FA20
Nobody ever accused the FR-S's FA20 of being too powerful. At only 200 hp, it does, however, as they say, make for a balanced package. But you don't care about balance; you want more power than what, say, a Honda Prelude delivered almost 20 years ago. You also want it reliably—without having to crack open the boxer engine's bottom end—you want it to be emissions legal, and you want it with reasonably good gas mileage, damn it.
There aren't a whole lot of ways to go about getting all of that this side of a Rotrex. That's mostly because of the Rotrex supercharger's ability to deliver its power in a linear sort of way, free of the typical forced-fed power surge drama you're used to. The results are you being better able to manage all of that extra power but also lower cylinder pressures, spared rod bearings, and an engine that'll last about as long as Toyota and Subaru hoped it would. Your tires will thank you, too.
According to Jackson Racing's Oscar Jackson Jr.—the company responsible for manufacturing the most powerful CARB-legal forced induction system for the FR-S and BRZ, the FA20 isn't necessarily weak, but it has its shortcomings, which've got to be considered when bolting on the boost. Its connecting rods, for instance, are soft, and its rocker arms can fail when higher engine speeds meet forced induction. The answer is the sort of straight-line power curve that the Rotrex delivers, which, much like a naturally aspirated engine, is free of any cylinder-annihilating torque spikes. For everything bad you can say about the FA20 and however it might fall short, though, its fuel system just about makes up for all of that. According to Jackson, it's the car's high-pressure, direct-injection fuel system that makes sure you don't have to worry about swapping injectors, pumps, or whatever other nonsense you might've expected, making the whole deal simpler than you'd think and more reliable than you'd have ever thought.
Q&A WITH JACKSON RACING
Nobody knows more about Rotrex superchargers than the people at Jackson Racing, and nobody's put together a more comprehensive Rotrex-based kit for the FR-S and BRZ. Here, Oscar Jackson Jr. elaborates on the FR-S, the FA20, and Rotrex superchargers.
SS: What can you tell us about he FA20 and how it responds to the Rotrex supercharger?
OJ: It's a good engine right from the start. It isn't anything crazy, power-wise, but that wasn't part of the initial concept; that's why Toyota and Subaru hasn't [developed] a turbo model. What it is, is balanced and efficient. The Rotrex works hand in hand with that balance because of its linear power delivery, allowing it to rev like a naturally aspirated engine throughout the powerband.
SS: Were there any particular challenges with developing the FA20 system?
OJ: There were a lot of challenges, mostly because it's a unique engine. It's a Subaru boxer engine, of course, but then the direct-injection fuel system is entirely Toyota. The compression ratio is also pretty high and oil temps can be, too. All of this meant we had to do a lot more testing just to figure out what could possibly fail first.
Clean on the Outside
I know my friends at Meguiars will kill me when I say that I've never really detailed my Scion FR-S. Quite frankly, I was fine with just the basic car wash. Since the car is always parked outside, my mentality was that it was never going to stay clean, and it's going to be exposed to Los Angeles pollution or some idiot would eventually leave a door ding. The inevitable happened, and notorious oxidation appeared on my carbon-fiber hood. Before I could polish or wax it, it was too late and the oxidation spread like cancer. My hood was ruined. I decided to go for a cleaner look and paint the carbon body color. We reached out to our friends at Microfinish for some AutomotiveTouchup paint. The colors are custom-formulated from the most comprehensive library of OEM colors to create an exact match for my Hot Lava Scion.
Since my painting skills are as good as a juvenile graffiti artist, I enlisted the help of Macias Auto Body in Santa Ana, California. The AutomotiveTouchup included everything needed to get the job done, such as paint prep surface wipes, primer, basecoat color, and clearcoat. On the first day the guys sanded down the hood. The next day is when all the action happened. After laying down the primer, the basecoat, and the clear, we let it dry overnight. All that was left to do was a color sand and polish.
In conclusion, the guys at Macias Auto Body said, "The paint mixed well and was easy to shoot. Also, the clearcoat covered well and dried fast." I was extremely impressed with the finished product. As you can see, the color match is identical. Yeah, buddy, rollin' like a big shot!