Article by Brian Hannon. Photography by Nathan Leach-Proffer, Corey Davis and Stock Subaru Images.
Welcome to the fourth installment of our Subaru BRZ / Scion FR-S platform review. So far, we’ve gone over the platform as a whole, and provided our initial impressions with our BRZ project car. Now, we start to pick the car apart in greater detail as we address the strengths and weaknesses of the various components that make this platform what it is. We’ll take our analysis to a greater level of detail with our upcoming documentary series revolving around our BRZ build, but we used the following generalized data points to help guide the direction of the Revvolution BRZ.
For assistance understanding the strengths and weaknesses of the platform, we polled some of the best in the industry who’ve already gotten their hands dirty with these cars. Mark Baer and Peter Zlamany from SCR Performance (one of the top motorsport performance shops in Colorado) pitched in for the engine, drivetrain and balance feedback, Brian Vinson from Air Lift Performance helped fill in the blanks on the suspension, and Dustin Burr from Wilwood Brakes let us know about some of the shortcomings of the braking system. We are certainly grateful to have a team like this helping to develop the car!
Let’s get to it and start peeling back the 2.0-liter, flat-four heart of the FR-S / BRZ. The first item Peter Zlamany (SCR) pointed out was the very high compression ratio (CR) featured in the FA20 engine. While the near racecar-like 12.5:1 CR is great for naturally aspirated performance and maximum efficiency, you could end up with serious detonation issues if you try pumping in too much boost from a turbocharger or supercharger. We’re not saying boosting can only be done if you lower the compression, but you could be setting yourself up for some issues if your tune isn’t spot on. Compression ratio is an area we’ll deal with in our build since we’re chasing some bigger horsepower numbers that we think won’t mix well with the stock 12.5:1 ratio.
Fortunately, the Toyota and Subaru engineers employed a combination of direct and port fuel injection to help mitigate detonation in the high compression mill. One key advantage of the D4-S system is how it both splits and combines the best aspects of port injection and direct fuel injection. At engine start, and with very light loads, the engine relies on the port injection through the intake manifold, which helps cut down drastically on carbon build-up on the intake valves and intake ports in the cylinder heads. Note that on many of the newer models equipped solely with direct injection, there is a new regular service interval requiring the removal of the carbon build-up. Never had to do that with port injection as the fuel actually acts as a cleaning agent.
As the load increases, the direct injection in the combustion chamber comes online and helps provide a more evenly distributed fuel spray, continuing to increase efficiency and fight detonation. Under heavy loads, the D4-S relies completely on the direct injection, as this is where they shine, producing the most power and efficiency, while the superior fuel spray and atomization keeps detonation in check. This can pay dividends when tuning either naturally aspirated or forced induction setups as you can push the envelope a little more.
Another feature that tuners will appreciate is the Active Valve Control System (AVCS), the variable valve timing technology. The AVCS allows the use of camshafts that make good top-end horsepower, but the variable valve timing allows for almost continuous adjustments when not in the peak power band. This allows for optimal running, as well as helping to pass emissions with modified cars. Since the valve timing can be manipulated through the ECU, it’s another tool available for tuners who want to get the high horsepower numbers without sacrificing the cars ability to be driven on a daily basis.
The next two items we’re going to talk about are some serious plusses for the everyday running and maintaining of the BRZ/FR-S. In an advancement of the solid lifter design found in older EJ-series engines, the FA20 uses roller rockers as opposed to lifter buckets that double as shims. This new design offers less friction and continues on the theme of efficiency we’ve seen throughout this engine.
The other is the employment of a timing chain instead of a belt. Again, belts require more maintenance and run a higher risk of snapping, leading to a litany of other problems. A cool feature in the FA20 is the ECU, which constantly monitors the timing chain as part of the AVCS adjustments. It will alert you if the chain is starting to stretch, warning you may have a problem on your hands. Pretty smart. Thanks Subaru!
As far as breathing goes, Peter felt the Subaru and Toyota engineers did a pretty good job. On the intake side, the intake manifold has relatively large ports that distribute plenty of air for high rpm power and, unlike previous Subarus, the factory Tumble Generator Valve (TGV) has been eliminated. Originally conceived as a device to manage airflow for improved emissions, it’s mostly seen by the performance industry as an obstruction to good airflow. Gone are the days of having to eliminate that piece, then getting your ECU reconfigured to not look for the associated sensor.
There are similar attributes on the exhaust manifold side, as the factory design isn’t the worst in the world, but it can certainly be improved by a less restrictive (or no) catalytic converter and a smoother pipe design. Kudos to the engineers for developing such good products off the shelf, but as we’ve learned, there is always room for improvement, and we’ll be documenting that part of the process.
Peter also alerted us to an area that could be a fairly significant deficiency for those who like to track their BRZ/FR-S: the stock oil pan. While there is some internal baffling and a v-shaped design to help the oil find its way to the pickup, it may not be up to the task of consistent high-g turns. This stems from a common issue with a flat engine configuration, as well as a v-shaped engine, where they tend not to drain oil from the heads. As cornering loads increase with better tires and suspension, it may be a good idea to look into a larger capacity oil pan with some more advanced baffling.
The rest of the drivetrain (clutch, LSD, transmission) is as expected and designed for light duty and daily driving. Mark Baer (SCR) said he "felt the stock differential was fine until I added coilovers, sticky tires, light wheels and a professional setup. It wasn’t until that point that any of the driveline revealed its weakness.” We’ll go into more detail in the documentary of the build, so stay tuned for that.
Now that we know the plusses and minuses of what motivates the platform, we turn to Brian Vinson (Air Lift Performance) for some insight on the capabilities and limitations of the BRZ/FR-S suspension. We agree with Brian that the BRZ certainly offers the consumer a lot of potential for a reasonable price, but, as a mass-produced vehicle, compromises have to be made. Not everyone is looking to rag this car on the track, and many may just want a sharp looking daily driver, so high spring rates aren’t going to find their way onto production models.
Brian also brought up an excellent point. When you add in significantly stickier compound tires and more track-oriented brake pads, some of those aspects of the suspension that we previously raved about tend to degrade. Higher grip could lead to more body-roll in the corners, and that composed chassis reaction to heavy braking could become a little more unpredictable. Factory ride-height certainly is in the realm of the World Rally Championship, and could be one of the first things to address to improve handling, as it was a facet the engineers had to strike a compromise on as well.
All is not lost though, as Brian informed us, "The car responds very well to all the standard bolt-on suspension pieces, and really comes alive when spring rate and appropriate damping are added.” This is good news as there are a lot of reputable companies offering suspension packages for the platform. For our BRZ, we also plan to explore an alternate path to high levels of performance, which we think is really gaining momentum for its flexibility with both function and form.
Peter had a great observation about the OEM running gear that connects the car to the pavement, "The wheels and tires from the factory are cute, and designed to make the car get good fuel economy, and the resulting lack of grip makes the car fun to drive at the stock power level. Once you put real wheels and tires on the car, it becomes much more dodgy and less fun to drive until power is added. Yeah, kind of hard to argue with that.
The stock wheels and tires have some quantifiable limitations as well. Aside from looking "cute,” the stock wheels are only seven inches wide. Technically speaking, the widest tire you should fit on a seven-inch wheel is a 225-section width. That’s not much meat if you’re starting to up the power levels of your car, or you’re trying to go for a more aggressive look.
Moving on the stock tires, we can again find room for improvement. While they are technically summer tires and should provide a lot of grip, they are "grand touring summer” tires, which again mean they’re a compromise between performance (responsiveness and dry traction) and everyday (noise and comfort) driving needs. That being said, they’re actually a great set of tires to learn high performance driving with thanks to a lot of audible feedback. And you can improve car control as they can be easily slid around with the driver aids turned off [read more about The BRZ & FR-S' driver’s aids].
Now that we have power and handling covered, we need to take a look at the brake system, a key area that should never be overlooked, especially when increasing power. Dustin Burr from Wilwood, leaders in the aftermarket brake system segment, keyed us to some of the limitations of the OEM system, as well as the advantages of ditching it for an aftermarket big brake kit.
Obviously, the stock brakes are more than sufficient for normal driving conditions, but that key word "compromise” rears its ugly head again. The OEM brake pads are designed with longevity, low dust output and noise reduction in mind. Once you start to push the pads beyond their normal operating parameters, their efficiency dramatically decreases to the point of losing their ability to slow the car. Not what you want on track or some fun back roads. Brake pads are one of the first upgrades you should look at (along with stainless steel brake lines) when putting more power to the wheels or increasing your abilities behind the wheel.
Another issue is the weight of the OEM brake system. As they come from the factory, the rotors and calipers aren’t always the lightest and, surprisingly, big brake kits tend to afford a bit of weight savings. The weight they can reduce is the ever-critical rotational mass, which can have a significant impact on acceleration and deceleration. The increased rotor size also provides improved thermal capacity so they aren’t transferring too much heat to the pads, keeping them in a more optimal temperature range.
From what we’ve covered so far, it’s quite evident that this well-balanced platform was designed to work in harmony, albeit with some compromises for economy and liability (they didn’t want it to be an over-steering beast off the showroom floor). The good news is there is a lot of room for improvement in almost every area of the car. What you need to keep in mind though is that with every performance modification you perform, you skew the balance of the car in that direction. Add more grip and handling performance, the car could feel underpowered. Add more power without addressing the brakes, and you could find yourself in some sticky situations. It’s a give and take, and that’s why we support a balanced approach to modifying your car.
Hopefully this article has provided a little more insight into some of the areas we hope to exploit during the build of the Revvolution BRZ. We also hope this is starting to help you formulate a build-path for your own FR-S/BRZ, as you gain an understanding of the strengths and weaknesses of the car in its stock form. The upcoming documentary series will go to the next level with further technical insight into the component sections we covered in this article.
As always, thanks again to our resource experts (SCR Performance, Air Lift Performance, and Wilwood) who helped put this information together. Without them our job would be a lot tougher!
Be sure to check back next week as we highlight the strengths and weaknesses of the aesthetics, trims and electronics. By the way, our build has started, and we’re making our way through the teardown stage (we barely recognize the car from when we had it on track)! While we prepare the documentary and get our media in line, follow us on Instagram to get daily updates @therevvolution!
The Subaru BRZ / Scion FR-S Platform Series Partners
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