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Single Scroll vs. Twin Scroll Turbocharger
Turbocharger is one of the engine parts that enhances power and efficiency without increasing engine displacement. Among various turbocharger designs, we’re doing a comparison between single scroll and twin scroll turbochargers since they’re more common on the market.
A turbocharger works when exhaust gases from exhaust manifold propels the turbine wheel and jointly drives the compressor wheel to spin and compress air into the engine for greater power.
What is a Single Scroll Turbocharger?
With single scroll turbochargers, exhaust gases from all engine cylinders feed into a single inlet housing (spiral chamber), these gases spin the turbine and propels also the compressor to force air in the engine. This compressed air increases engine performance and efficiency.
Advantages of Single Scroll Turbocharger
1. Cost-Effective: Easier and cheaper to manufacture, install, and repair due to simpler design, making them the most common type turbocharger that production cars use.
2. Compact Design: Their overall size is more compact, taking up less space, therefore easier to install in smaller engine bays.
3. Better High RPM Performance: Single scroll turbos can provide better high-RPM performance due to a less restrictive exhaust flow path, which allows gases to flow more freely and efficiently at higher engine speeds.
4. Reliable: Car producers use single scroll turbos due to their established reliability.
Disadvantages of Single Scroll Turbocharger
1. Lower Efficiency: While the exhaust gases enter from various pulses, it causes interference when they collide into each other, reducing its efficiency.
2. Turbo Lag: Less optimized airflow route leads to more turbo lag.
3. Poorer Low RPM Performance: It takes comparatively more time to fill in the single scroll volute, generating poorer low rpm performance as well as a fairly narrow effective rpm range.
What is a Twin Scroll Turbocharger?
For a twin scroll turbocharger, a turbine housing has two scrolls, this means from the manifold, the pulses are split into two different collectors to enter the two scrolls of turbine housing. Each scroll receives exhaust gases from specific cylinders.
Advantages of Twin Scroll Turbocharger
1. Reduced Turbo Lag: Exhaust pulses separation helps maintain higher energy levels, allowing the turbine to spool faster.
2. Superior Efficiency: The split pulses into two different collectors into twin scroll reduces interference, leading to better efficiency.
3. Better Low RPM Performance: A twin scroll turbocharger is more efficient due to less turbo lag, producing better low rpm performance.
4. Better Fuel Economy: Optimized airflow and combustion improve fuel efficiency.
Disadvantages of Twin Scroll Turbocharger
1. More Costly: More complex design and manufacturing lead to increased costs in installation and repairing.
2. Larger Size: Twin scroll turbos are generally bulkier due to two independent volutes, requiring more space for installation.
3. Specific Exhaust Manifold Design Required: A compatible exhaust manifold, usually harder to fabricate and find, is required for taking full advantage of twin scroll turbo design.
Choosing Between Single Scroll and Twin Scroll Turbo
There are pros and cons to single scroll and twin scroll turbos, take into consideration of all the factors before you pick one for your needs. Single scroll turbos are simpler and more cost-effective than twin scroll turbos, and they generate high RPM power due to their unrestricted exhaust flow; while twin scroll turbos offer superior overall performance, efficiency, and reduced lag. It is always important to consider your budget, performance targets, and installation constraints when choosing the “right” turbo.
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