When it comes to forced induction systems, the turbocharger and supercharger are two of the most popular ones.
The turbocharger, however, has a significant edge over the supercharger since it doesn’t diminish engine power, making it the more efficient choice.
A single turbocharger is already efficient enough on its own. But how would two turbochargers in a single setup affect engine performance?
A twin turbo is essentially a dual turbocharger setup that aims to improve engine performance and power.
A twin turbo helps reduce turbo lag, which is the waiting period between hitting the throttle and the turbo spinning to generate boost.
Turbo lag is a common issue in single-turbo vehicles because the turbo is bigger. In a twin-turbo setup, two smaller housings are used to reduce turbo lag.
To further understand the mechanics of a twin turbo, it’s important to have a clear understanding of turbocharger operation.
Using a turbocharger is a means of increasing air density by pumping air into the cylinders.
A forced induction system like a turbocharger uses an air pump to pack dense air-fuel charge into the cylinders to create the following scenarios:
A turbocharger uses exhaust heat to power a turbine wheel, converting heat energy into mechanical energy. The turbine wheel’s shaft passes through some bearings and on the other end of that shaft is the impeller, which is in the intake stream.
The faster the exhaust flow, the more intense the impeller’s action at forcing the air into the plenum, pressurizing. Naturally aspirated (non-turbo) engines depend on the movement of the pistons and the opening of the valves to create less than atmospheric pressure to “draw” the air in.
The turbine wheel helps compress incoming air, forcing more air and fuel into the combustion chamber, so the engine can fire faster and more powerfully than a naturally aspirated system.
When working with a turbocharger, it’s important to position the component near the exhaust manifold. This lets hot exhaust pass through the unit with minimal heat loss.
A twin turbo can boost your engine’s horsepower output by 50 to over 100 hp, depending on several factors.
Turbo size and design, engine configuration, intake and exhaust system performance, fuel delivery performance, and engine tuning and programming are some of the factors that can affect a turbocharger’s performance.
Size is arguably a major factor to consider when it comes to turbocharger performance. A small turbo rotates faster and provides a significant boost under low speeds.
Meanwhile, a big turbo can produce more boost and horsepower at high speeds.
There are several types of twin-turbo setups: parallel, series, twin-scroll, sequential, and cross-bank.
Two turbochargers of the same size are used in a parallel twin-turbo setup. Typically installed in V6 and V8 engines, a parallel twin turbo is considered the most common aftermarket twin-turbo design.
The parallel design equally divides the exhaust gases for each turbocharger. Each turbocharger is assigned to one cylinder bank to minimize exhaust piping.
In a series twin-turbo setup, the turbochargers work in a sequence. The first turbo boosts the initial intake charge while the second compresses air.
Series twin turbos can generate large boost levels at lower RPMs, making them ideal for diesels, boats, and airplanes.
A twin-scroll turbo uses two separate exhaust paths to drive one impeller under a single housing.
Similar to a parallel design, a twin-scroll setup separates the exhaust in half. Doing so can maximize exhaust efficiency while permitting a wide overlap camshaft profile.
A twin-scroll turbo is commonly found in smaller engines, particularly four and six-cylinder systems.
In this setup, one turbocharger can be used for low-speed efficiency while the other is for high-speed efficiency. In some cases, both turbochargers function at high speeds.
The design of a series twin turbo eliminates the problem of turbo lag because the turbochargers work in a sequence. However, this type is considered to be less efficient than others.
The cross-bank twin turbo is BMW’s version of the twin-scroll turbo intended for V-shaped.
engines. This design features two twin-scroll turbos that feed half of each bank.
Having a cross-bank twin turbo setup also means that the engine is operating backward, with the exhaust coming through the interior of the V and the intakes outside of the V.
Yes. It’s possible to install a twin turbo on a four-cylinder engine. You can add one turbo for each cylinder.
Installing a turbocharger is a great way to draw more power from a small engine without compromising fuel economy.
However, it’s important to consider the powertrain and model first before installing a turbocharger on a small engine to ensure its reliability in the long run.
Yes. Twin charging is the process of combining a supercharger and a turbocharger to generate significant power gains.
Twin charging is usually done on custom builds, high-performance street cars, and racing applications. A hybrid induction system is required to accommodate a twin charger.
In a twin charging setup, the supercharger provides instant boost at low RPMs to eliminate turbo lag. As exhaust gases flow, only then will the turbocharger start its operation.
Twin charging aims to capitalize on the strengths of both the turbocharger and supercharger while mitigating their shortcomings.
A broad power band, reduced turbo lag, and increased torque are some of the benefits of twin charging.
However, flexibility is arguably the setup’s strongest suit, as it can adapt to various driving conditions.
Installing a twin-turbo system can cost anywhere between $4,000 and $6,000, depending on several factors.
The twin turbochargers alone can cost around $1,500 to $4,000. Depending on your engine setup, you might need to add a few more components, including an intercooler, blow-off valve, and wastegate, among others.
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