Almost every person who wants to enter the drift scene chases more power. From grassroots drifters with 500hp SR20s to Formula D competitors with 1,500hp 2Js, that never changes. What can change, however, is their method of getting that power. Some of us get these big numbers with boost snails, or turbochargers. Others of us use a big blower, or supercharger, to hit that power. These methods of forced induction each have their strengths and drawbacks, and provide power in different places.
Turbocharging your drift car will provide more power in higher RPMs, at the cost of lacking low-end torque. Superchargers will provide a nearly linear powerband, but require power from the engine to drive them.
Of course, there’s more than one turbo configuration, and there’s more than one style of supercharging. There’s even methods that use both a turbo and a supercharger, for the truly insane. I’ll get into the pros and cons of each below.
Turbocharging
Using the exhaust gases from your engine to generate boost is not only efficient, but can generate incredible power. They can spin up to 150,000RPM, roughly 30 times as fast as a normal engine, closer to 20 times as fast as a drift engine. All that RPM drives a turbine to push more air into your engine, and your new tuned ECU will dump more fuel in, making for bigger booms.
Many stock cars today come with small turbochargers on them, either for power or for fuel economy. These turbos are generally much smaller than the one you’d put on a drift car, in order to reduce turbo lag as well as to restrict power.
Single Turbo
While this option isn’t the most optimal, it achieves some of the highest power numbers for tuners. When you see a high-horsepower 2JZ, the odds are they’ve converted it to a single, large turbo. The R33 Nissan Skyline GTS-T type M came from factory with a single-turbo RB25DET, and could make close to 400hp on that stock turbo.
This configuration is common in economy vehicles as well, using a very small turbo. Having more than one turbo is expensive, and is unnecessarily complex. Having a single small turbo provides the little extra boost for power, while not having the drawback of lag.
Most high-level drifters use single turbo setups, as their car will spend most of its time on the throttle, where lag doesn’t matter as much. These cars are sometimes fitted with anti-lag systems as well, further nullifying the downsides of large turbos.
Twin Parallel Turbo
While you’ve doubled the amount of turbos in your engine with this route, you’ll still have similar characteristics to a single larger turbo (such as lag, a spike in power, and a weak low end). These turbos are set up as mirrors of one another, so they’ll boost at the same time, with the same pressure. That’ll be very important to remember for when we discuss Sequential Turbocharging.
This method of boosting is generally used in engines with an even number of cylinders, where routing all the cylinders to one turbo would be difficult (V8s and flat-6s, for example). Each turbo generates about half the boost of the equivalent single turbo, and the boost is then fed back into the intakes for their respective cylinders. This can be done via one shared throttle body, or by splitting the boost between the ITBs of each cylinder.
Another example of using this type of turbocharging is in limited-space applications. If your engine bay doesn’t have a place to fit a big boosty boy, you could use more, smaller turbos. The famous Audi B5 S4 used this tactic with the Biturbo V6 engine. Switching these out to larger turbos took some creative routing, but there was absolutely mental power potential.
The Skyline GT-R is an example of a true parallel twin-turbo configuration. With the RB26DETT under the hood, cylinders 1, 2, and 3 supply the exhaust for the first turbo. Cylinders 4, 5, and 6 power the second turbo. Each set of 3 cylinders then receives the boost made by its respective turbocharger. Converting this engine to a larger, single-turbo system is used for higher power applications, since there’s adequate room in the engine bay.
Twin Sequential Turbo
The road-friendly version of a twin-turbo setup, this incorporates one turbo that’s meant to spool sooner than the other. This can be achieved by forcibly spinning it (electric motor, pneumatic actuator), or by having a smaller, quicker-boosting turbo. Once your smaller turbo is providing boost, the larger one begins to spool, and will take over around half-way to redline. Thus, your power curve remains smooth with little to no spiking, and a predictably-driving car.
Many of the incredibly famous JDM cars include these kinds of systems. The FD RX-7 and the A80 Supra are notable examples of such a system. They had one turbo that would start boosting around 1,500RPM, and would provide boost until roughly 4,000RPM. Then, the second turbo would spool, maintaining boost to redline. The RX-7 had a small dip in boost to 8PSI during its transition at 4,500RPM, but was still fairly smooth.
Along with sequential turbocharging comes a very obscure version of twin-turbocharging, known as Staged Turbocharging. This is where one turbo feeds its compressed air into another turbo, exponentially compressing the air. For instance, if the turbos separately would make 5psi each, then through this method, they would make 25psi together. This is very rarely used on cars, in lieu of simply using a single, larger turbo. This is mainly used in piston aircraft engines, where excessive noise and lag aren’t issues, and there needs to be incredible amounts of boost. A use of this in cars would be in a land-speed record vehicle, or maybe a very expensive drag car (where you can spool boost before racing).
Superchargers
Unlike their whoosh-boi brothers, superchargers use the engine’s own torque to provide boost. A pulley is run from the crankshaft to the supercharger, and that spins it to compress air and provide boost. This design actually reduces power initially, due to the addition of resistance on the crankshaft. However, once the engine starts to rev, the boost is immediate, and negates the negative effects of the supercharger.
With this in mind, a supercharger won’t be as effective as a turbo in higher-revving applications, since a supercharger can’t spin nearly as fast as a turbo. This limits the overall boost you can have, and thus, your power. However, in applications such as drag and circuit racing (where low-end torque matters), superchargers are often favorable. Their simplicity, ease of repair, and reliability provide edges over a turbocharged setup in endurance racing as well.
Twin-Screw Supercharger
Have you ever stuck two screws together and turned them, so they meshed perfectly? Maybe you have, maybe you haven’t, but that’s essentially what’s going on with this design. Y’know, except those screws have an absurdly high thread spacing. The goal of these screws is the same as a wood screw, to apply force parallel to the screw shaft. In this case, it takes air, and puts it in smaller and smaller spaces as it forces it towards the engine. This type of supercharger was used stock on the Mercedes C32 AMG, providing 350hp and 332 lb-ft of torque.
While incredibly similar in design and appearance to the Roots supercharger, they compress air in very different ways. While a Twin-Screw would push the air backwards, parallel to the screws, the Roots-style supercharger compresses the air straight down, with a much lower compression ratio. The Centrifugal-style supercharger is the black sheep of superchargers, looking nearly identical to a turbocharger. They are still belt-driven, but the belt drives a turbine in order to provide boost, as opposed to screws or other pin shapes. This design takes much longer to provide boost, making it a poor low-end power option, and a turbo can provide more boost overall, making it a poor high-end decision. With this design, the twin-screw supercharger is the second most efficient style of supercharger.
Roots Supercharger
Similar in shape and design to the twin-screw supercharger, a roots supercharger also has two screws and an almost-ovular housing. The main difference between the two is that a roots supercharger doesn’t actually compress any air, it just blows it into the engine. This provides an advantage over a twin-screw, since compressed air gets hot, whereas blown air (hence the name “blower”) doesn’t heat up. Colder air is much more dense, which allows for more fuel to be injected, which leads to a bigger boom. These are the most efficient style of supercharger by a large margin.
This design was originally used in the middle of the 19th century, in order to ventilate mine shafts. Then, Gottlieb Daimler patented this design in an automobile engine shortly after, to be used in the first Mercedes Kompressor cars. Released in 1923, these cars produced nearly 300hp and a whopping 500 lb-ft of torque. back in the roaring 20’s, that was a ton of power! Even today, cars still make use of this design. Some Cadillac models, including the STS-V, make use of this type of supercharger. This is also the most common type of forced induction for hot rods, where large blowers are mounted on top of the engine for show (and a little go).
Centrifugal Supercharger
The black sheep of superchargers, the Centrifugal design looks very similar to a turbo, due to the turbine housing shape. In performance, they act quite similar as well, with boost being peak-y, poor low-end performance, and better top-end boost. The biggest issue with this design is how long it takes to build boost. Through the low RPM range, the supercharger is just a power draw, without providing any boost. It takes a long time for the supercharger’s boost to make up for its own drag on the engine. If you try and use more aggressive pulleys in order to get boost sooner, you run the risk of damaging your supercharger. Not only that, but the more aggressive you get with the pulleys, the more strain you put on your engine before boost kicks in.
Despite the many drawbacks of this supercharger type, it’s still used on lower-end sports cars, and entry sports car builds. The late 60’s Shelby GT350 came with one, and the limited run Scion tC also could have one. It’s also a popular choice for adding power to VQ engines, or the famous F20C/F22C1 engines from the S2000. If you’re looking for around 350-400hp, these superchargers will do the trick, for relatively cheap. They’re incredibly simple to install as well, far easier than any other method of forced induction. Installation on most motors is simply bolt on, and if there’s any cutting whatsoever, it’s usually just plastic. When they come in kits, they’re even easier to install, as seen when EngineeringExplained installed one on his Honda S2000.
Twin-Centrifugal Superchargers
We’re crossing into the land of insanity now. You’ve heard of twin-turbos, now get ready for twin-superchargers! Two of the very few cars that feature this from factory are the Koenigsegg CCR and the Zenvo TSR, both of which are borderline hypercars. Despite their age, their horsepower figures and 0-60 times are still relevant today, thanks to their odd blend of V8s and twin superchargers. While their low end performance is lackluster for a hypercar, these cars aren’t meant to be in low RPMs. Once they’re screaming at 7,000RPM, that’s when they can truly shine!
I wouldn’t recommend attempting to make a setup like this at home, but it is cool to see in a hypercar. The draw on the engine at low RPMs is incredible, having to turn two superchargers with negative boost at idle.
Twin-charging
We’ve talked about turbochargers. We’ve talked about superchargers. One provides high-end power with draw at the bottom end. The other provides low-end power and falls off at high RPMs (pretend centrifugal doesn’t exist for this analogy). What if we could use both, to get the low-end grunt of a supercharger, and the top-end power of a turbo?
That, my friend, is twin-charging! This by no means is popular, but was primarily used in rally. Namely, Group B featured the Lancia Delta S4, which had a twincharged engine, featured a roots-style supercharger mixed with a single turbo. The polar opposite of that car was the Zenvo ST1, a track monster supercar with a twin-screw supercharger and single turbo. Both of these cars tended to have fiery exits, but they were monsters when they weren’t (literally) on fire.
There are two main struggles when making a twincharged car. The first main struggle is the supercharger’s massive draw when it isn’t providing boost at high RPMs. Most of the time, this was solved with a supercharger bearing that could disconnect from the supercharger. It would stay locked until around 4,000RPM, then disengage once the turbo kicked in. The other big issue is tuning an engine like this. It would take an absolutely massive fuel map to account for every possible configuration of forced induction, level of boost, throttle position, and air/fuel ratio. It takes an incredibly experienced tuner to be able to make a car like this run!
For Going Absolutely Bonkers…
Have you ever looked at an engine with both a turbocharger and a supercharger and thought “Man, this isn’t crazy enough”? Me neither! Apparently the folks over at Volvo did, though. They took their twin-screw supercharged, single turbo 2.0L I4 engine, and then strapped not just one, but two electric motors on it!
In their T8 SUV, Volvo sports this exact engine, putting out about 400whp and 480 lb-ft of torque. This engine isn’t tuned to its max potential, however even in its current state, it can lug a 5,100lb SUV from 0-60 in under 6 seconds! That’s entry sports car-levels of speed, and enough torque to hall the family boat doing it!
While we haven’t seen any other engines with this many forms of power, I’m sure that the rise of hybrid hypercars will show us some incredible innovations, such as the Koenigsegg Gemera!