TURBOCHARGER VS SUPERCHARGER – A BRZ ODYSSEY

    19 APR 2024 - Jeff Willis

    TURBOCHARGER VS SUPERCHARGER – A BRZ ODYSSEY

     

    When the Subaru BRZ hit US markets in 2013, it was a model that gathered curiosity, excitement, criticism, and cautious optimism by the critics. Mainly because Subaru stepped outside of their rally-inspired all-wheel-drive formula and created a traditional sports car that was a rear-wheel-drive lightweight 2-door coupe. Joining the BRZ was the Scion FR-S then later, the Toyota 86. These models all shared Subaru’s 2.0-liter boxer 4-cylinder that made 200 HP, and about 151 LB.-FT of torque. The drivetrain featured a 6-speed manual transmission, with an automatic as an option. The point of this platform was to offer a fun option for drivers who could remain competitive at local autocross events, while maintaining fast speed and momentum in the corners on track weekends much like the Mazda Miata. It was lightweight, nimble, and very easy to drive that also made for a very fun daily commuter as well. Many enthusiasts in the community often wanted to see a turbocharged STI version because yes, that would be a blast to drive. However, it would defeat the overall driving purpose of the BRZ which like the Mazda Miata, driver skill triumphed over speed.

    And that’s not to say that speed compensates for a lack of driving skill. We understand that as enthusiasts, we are addicted to speed, boost, turbo noises, and supercharger whine. And since the introduction of the BRZ in 2013 continues into production today with he second generation, many of you have made the decision to upgrade your engines with some forced induction.

    What is forced induction? Just like the title suggests, forcing air into your engine to create more horsepower. You have two ways of doing it, either use a turbocharger kit, or a supercharger kit. Both serve one purpose and that is force feeding air into the intake system, but they are very different in terms of how the air is generated.

     

    SUPERCHARGERS

    HKS GT V3 Supercharger Kit w/ECU Tuning 2013-2016 BRZ/FR-S

    A supercharger forces air into the intake using a blower system that is belt-driven, and it is mounted to your intake manifold. Superchargers will either use a turbine-style unit that resembles a turbocharger, or they use a centrifugal design which almost resembles two gears that have long blades that spin together to fan-force air straight into the intake to create boost. Because superchargers are belt-driven, they deliver an almost instantaneous rush in boost when compared to a turbocharger, that creates turbo lag just before the turbocharger hits full boost in the middle of the RPM band. However, because superchargers are belt-driven, you are limited in boost and in power when compared to turbochargers. To make more boost in a turbocharger, you can use boost controllers and stiffer wastegate springs. To make more power in a supercharger, you must install a smaller pulley. And in many cases, smaller pullies are not available in some supercharger kits as they are designed to work with the rest of the OEM components throughout your engine. Once you start installing smaller pullies, then you need to compensate in fuel, tune, timing, etc. which you would otherwise have to address in a turbocharger system. The majority of aftermarket supercharger kits available for the BRZ, FR-S, and 86 models will include everything needed for the installation just like the HKS unit pictured above, but for those of you who demand more power, more sacrifices will need to be made.

     

    SUPERCHARGER PRO’S:

    • Most kits are direct bolt-on and are made to work with your OEM intake and ECU.
    • Provides a great increase in horsepower.
    • Makes up for the BRZ’s lack of mid to upper range power.
    • Some supercharger systems can be upgraded with a smaller pulley.
    • Made for naturally aspirated applications that want a nice bump in power.

     

    HKS GT2 Supercharger Pro Kit 2013-2021 BRZ/FR-S/86

     

    SUPERCHARGER CON’S:

    • Limited in boost and in power when compared to a turbocharger system.

     

    SUPERCHARGER NOTES:

    • Depending on how much power your other modifications such as an intake and full exhaust, your fuel system must be modified to supplement your engine’s gains in horsepower.
    • When making more power, tuning whether flash or standalone will be required if you are overpowering or surpassing the limits of your factory ECU’s parameters.
    • Depending on your horsepower levels, you may be surpassing the limits of your engine’s internals. Like a turbocharger system, you may need to build your internals with forged replacements.

     

    TURBOCHARGERS

    Blitz Turbo Kit 2013-2021 BRZ/FR-S/86

    The almighty turbocharger. All it takes is one ride in a really fast turbocharged vehicle that becomes life changing for many of us enthusiasts. Curiosity brings experience, the experience turns into a hobby, that hobby turns into passion, that passion turns into empty bank accounts. The sound, the thrust, the beating up on loud V8s on the highway, the intoxicating spooling and blow-off valve noises, and that open wastegate that sounds like a jetfighter. All of these sensory overloaded mechanical witchcraft experiences repossesses us into craving more, until it’s just too much. This is why whether it be a turbo kit or supercharger kit, you must boost sensibly, and keep it under control. Otherwise you start throwing rods out of the block.  

    All of that non-sensical dribble aside, and some understand, turbochargers use exhaust gases that spin the turbine wheel that forces those exhaust gases out of your cat-back. More importantly forces the compressor wheel on the front of the turbocharger to spin and compress air into the engine.  The compressor wheel pushes air through the intercooler which lowers the intake charge temperatures, and that cooler air feeds into the intake manifold which will make a burst in power. When you let off the throttle for gear changes or deceleration, the compressor wheel on the turbocharger still spins and forces air, and when the air has no where to go when the throttle body is closed. Vacuum from the intake pulls open the blow-off valve, and the compressed air exits, making the cool blow-off valve noises.

    The possibilities are endless with turbochargers because you can literally fit any sized turbocharger on a vehicle through fabrication, your engine’s life depends on how heavy your right foot is, how strong your engine’s internals are, how much fuel delivery you have in terms of injector sizes, the number of fuel pumps, and especially your tune. Many times, you can’t just bolt on an upgraded turbo kit and call it a day, you must modify everything else your otherwise naturally aspirated engine needs to survive. BUT, the kits that are available to fit first and second generation BRZ models include everything to give you a nice bump in power within your factory engine’s limits as long as you don’t cross the line and figure out how to increase the boost without safeguards in place.

     

    TURBOCHARGER PRO’S:

    • Can generate more power when compared to a supercharger system.
    • There are a variety of turbocharger options to choose from as opposed to a supercharger.
    • All the fun turbocharger noises.
    • More aftermarket support.

     

    HKS Bolt-On Turbo Kit 2013-2021 BRZ/FR-S/86

     

    TURBOCHARGER CON’S:

    • You need to be careful when turbocharging a naturally aspirated engine as they will have higher compression pistons. This applies to supercharger kits as well, but turbochargers can generate more boost.
    • You must diligently modify your fuel system to accommodate more boost levels. This is not really a con per say, you must be responsible about it. Get bigger injectors, fuel pump, fuel lines, fuel rails, fuel pressure regulator, filters, and all the appropriate fittings.
    • Irresponsibly running more boost will result in a blown motor.

     

    MAKING SURE YOU UPGRADE YOUR FUEL SYSTEM

    DeatschWerks DW300 Fuel Pump

    Disclaimer: This only applies to those of you who are going to run more boost from any turbocharger or supercharger kit.

    Anytime you add more power to your turbocharger, or in the BRZ’s case because it’s naturally aspirated, you MUST make sure that you are supplying your engine with enough fuel so you don’t lean out your engine. Leaning out your engine means that you are not supplying your cylinders with enough fuel to compensate for the amount of boost you are running. You need a higher volume fuel pump to push the fuel from the tank to the fuel rails. You need larger injectors to accommodate the duty cycle needed to pump out E85. You need a fuel pressure regulator so that you are not over fueling or under fueling the fuel delivery. If you do not provide your cylinders with enough fuel, the cylinders will get hot, and you will melt your pistons. You will know if you are leaning out your engine by a Wideband O2 gauge, and you want to make sure you’re running 10.8 to 11.8 AFR under boost. Anything south off 11.8 under boost you are at risk of burning up your motor. Anything richer than 10.8 means you are dumping excess fuel into your cylinders which will wash your piston rings out, allowing fuel to get into your oil.

     

    PLANNING ON RUNNING HIIGHER BOOST LEVELS? YOU BETTER MAKE SURE YOUR ENGINE CAN HANDLE IT

    Any vehicle that comes from the factory with forced induction will have pistons with a lower compression ratio. This is to make sure that when you’re at the top of boost, the power and torque can be as linear as possible. However, at the top of the RPM range when the turbo is at full steam ahead, the turbo and engine are operating at peak efficiency. Naturally aspirated engines will have higher compression pistons to deliver higher low-end torque off the line. This is why with some naturally aspirated engines that are in muscle cars for example, they have higher compression pistons that make all the power down low and will usually plateau after 4k RPMs. Then turbocharging a motor with high compression engines sounds perfect right? You have that power down low, and the turbo can make up power on the top end. Not exactly. Although yes, you can turbocharge a high-compression naturally aspirated engine as there are obvious kits for the BRZ, you just cannot run high boost otherwise you can hurt your engine. The internals can only spin so fast, and it will be the rods and rod caps that will stretch. Sometimes people will try to compensate for adding a turbo on a high compression piston motor by adding a thicker head gasket to compensate. Either way, too much boost will fry your engine.

    This is the inherent risk with turbochargers. For those of you with the OEM engine with factory guts, a supercharger kit will be the safer ticket because boost has a limit with the pulley. You can increase boost and power with a smaller pulley, but again you put your engine at risk.

    If you’re planning on running more boost through your motor anyway, then more than likely you will be running forged pistons with a lower compression ratio, forged rods, and race-grade hardware. At this point you’re more than likely running a standalone EMS system, have a custom flash tune, and all the fuel, drivetrain, and cooling mods to accommodate everything.

     

    OTHER OPTIONS YOU WILL NEED

    Whether turbocharging or supercharging your BRZ, there are a few more safeguards you will need to keep your engine intact.

    The first item is one of the most important. And that is a Wideband O2 gauge.  

    AEM X-Series Wideband AFR Gauge

     

    Required by all tuners, and most likely installed on any modded vehicle. Monitoring your air/fuel ratios is a must to know how your engine is running especially under full boost. This gauge includes a separate O2 sensor and a bung that is welded into your downpipe. It provides you with real-time air/fuel ratios. Good ratios under boost range from 10.8 to 11.8 AFRs. Typically, mid 11s is in the strike zone. Anything higher than 11.9 and into the 12s is lean. 13 AFRs is going to damage something, and you need to check to see if you need new fuel filters, if your injectors are clean, or if your fuel pump is weak. Anything below 10.8 means that you’re running too rich under boost, and you need to see why you have too much fuel delivery.

    Another item to consider is one-step-colder spark plugs to avoid spark blowout. A good set of iridiums will do the job and helps promote a smoother powerband during boost.

     

    BE SENSIBLE, KEEP YOUR CAR ON THE ROAD, HAVE FUN

    Because of the reasoning behind what it takes to run more boost, do it sensibly.  and many enthusiasts can attest, if you choose to boost, be responsible about it. There are those out there who think that just because they spent x thousand dollars on a turbo kit, spent x amount of dollars to have a shop install it and x amount of dollars in tuning, that everything will be fine and indestructible. This is not the case at all. All cars break, and cars with mods and upgrades break sooner because it forces us to drive the cars harder simply because it’s fun. As owners, we are responsible for the overall welfare of our cars. If you don’t change the oil, or are lazy about maintenance, your car won’t run well, won’t look good, and won’t perform good. You can buy a quality turbocharger or supercharger kit, but just don’t overdo it. Keep the boost levels at the safe side and enjoy the ride.