What is Twin-Turbocharging?
Twin-turbocharging is a kind of forced induction system utilized in internal combustion engines to improve power output. Two turbochargers are used in a twin-turbo setup conventionally. They push more air into the engine enabling more fuel to burn. This results in greater production of power. It is used when you want to get optimized power out of an engine. Twin turbocharging delivers greater torque and horsepower.
Twin-turbocharging has its downsides as well like increased complexity and higher costs as compared to the single turbocharging systems. The augmented power can put greater stress on the engine components which requires more maintenance costs over time.
What is Turbo Lag and how it can be Reduced?
Although turbocharging provides a huge amount of power, it comes with a little issue which is turbo lag. Turbo lag occurs when the accelerator pedal is pushed and when the turbocharger is boosted to enhance the engine power. Some amount of exhaust gas flow is required to spin the turbine and generate a boost. Considering low engine speeds, there may not be adequate exhaust gas flow to spin the turbocharger speedily. This causes a delay in the production of boost.
Several factors like the size of the turbocharger, displacement, engine size, and turbocharger system's design affect the turbo lag. Larger turbochargers can generate more boost but have greater turbo lag as compared to smaller turbochargers. Turbo lag can be lessened or removed by a few methods. By improving the exhaust gas flows or using turbochargers of different shapes that can easily fit into the turbine matching the exhaust gas flow and engine speed. Moreover, newer technologies like electric turbochargers and hybrid chargers can deliver greater boost response and lessen or eliminate turbo lag.
Various Configurations of Twin-Turbocharging
There are broadly two configurations of twin-turbocharging that are:
● Sequential Twin-Turbocharging
● Parallel Twin-Turbocharging
Sequential Twin-Turbocharging
Two turbochargers of different sizes are used in sequential turbocharging. The smaller turbocharger also known as the primary turbocharger works at lower engine speeds where it can speedily spool up and deliver greater boost, low-end torque, and acceleration. The larger turbocharger is known as a secondary turbocharger. It is used at higher engine speeds delivering greater power. The two turbochargers are organized in a serial manner such as the exhaust gases will first pass through the primary turbocharger and then into the second one. In order to maintain the optimized boost levels, the two turbochargers are required to be switched. The ECU(Engine Control Unit) can perform this action. They can be more prone to heat buildup and lag as the switching occurs between the turbochargers.
Pros of Sequential Twin-Turbocharging:
● Smoother power is provided across a greater range of RPMs
● The small turbocharger can spool up speedily resulting in enhanced throttle response at lower RPMs
● Fast response
● Better low-end torque
Cons of Sequential Twin-Turbocharging:
● It is more complex than parallel setups as they require a system to switch between the turbochargers.
● They have a higher cost because of greater complexity
Parallel Twin-Turbocharging
Parallel twin-turbocharging utilizes two identical turbochargers working simultaneously to generate boost. Both turbochargers are attached to individual exhaust manifolds and air intakes. This is done so that each turbocharger can work separately. One turbocharger will be connected to cylinders from 1 to 4 and the other one to cylinders from 5 to 8 in a V8 engine. This provides a speedier response and more balanced power delivery. These are usually used in sports cars or super cars where we have to provide maximum power. However, this system can also be used in diesel engines to improve fuel efficiency and lessen emissions.
Pros of Parallel Twin-Turbocharging:
● Output power is maximum when the two turbochargers are working together
● They are simple and less costly as they have a simpler design as it does not require additional parts to manage the operation of the system
● They have a better fuel efficiency
Cons of Parallel Twin-Turbocharging:
● Turbo lag occurs in parallel twin-turbo charging. As both of the turbochargers are of the same size, more time is needed in spooling up which results in turbo lag
● It may not have consistent boosts. If one of the turbochargers is working efficiently as the other one, the engine may go through inconsistent boosts.
Which is better for more power or efficiency?
Both twin-turbocharging systems come with their own pros and cons. Sequential twin-turbocharging systems are used for enhanced power delivery and throttle response. They can be more efficient as they provide optimal boosts over a greater range of RPMs. Parallel turbo-systems are simpler and cost less.
Choosing if you want to go for sequential and parallel twin-turbocharging also depends on the type of engine you have and its application. Some engines work well with sequential twin-turbocharging while other benefits from a parallel setup. In conclusion, the choice is dependent upon the specific requirements of the engine and its application.
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