The pressing question when it comes to turbochargers is whether multiple turbos better than one.
When you want to increase performance of an engine, a turbocharger is one of ourfavourites go to components. In a normal piston engine, air at standard pressure flow into the cylinder to full up the space freed up by the moving piston. The volumetric efficiency is around 80% and that’s as good as it gets.
So, to give perspective, a 500cc engine will only take in around 400cc of air during the opening and closing of the intake valve. So, when forcing air into the engine using a charger, theoretically this should mean that we should be able to achieve 100% volumetric efficiency.
When it comes to a 4-cylinder engine, a single turbocharger is quite enough to force feed the air to increase efficiency but there are scenarios where two turbos have been used on 4-cylinder engines.
A good example of a two turbo 4-cylinder engine is the Subaru Legacy B4 1999 model. What Subaru did was, they used two differently sized turbo in a sequential arrangement. The smaller turbo provided power at low speeds therefore the turb lag which is one of the main drawbacks of a turbo charger is reduced. The larger turbo only powers up at higher air speeds, only when more is required.
BMW then released a 6-cylinder forced induction engine and called it twin turbo. Here they used two similar sized turbochargers to power3 cylinders each. Both turbos work together.
Deciding Factors: Single or Twin
So, when deciding on whether single or turbo charger, what exactly are the factors that need to be considered?
The main factor that need to be considered is the turbo lag and with the latest engine and hardware technologies, turbo lag is almost nullified. Therefore, a single turbocharger is ideal for most of the engines today, but a twin turbo is always welcome.
Twin Turbos in V- Engines
For a 4-cylinder engine a single turbocharger works well but if you want a twin-turbo charger then the most ideal scenario would be a V6 engine.
When it comes to a twin turbo setup on a V6 it’s all about balance of efficiency and power against the reliability and cost. You need to think about components like inter-coolers as well.
Another drawback to twin turbo engines apart from the cost is the maintenance which can be more compared to a single turbo counterpart due to the multiple components. However this can be reduced by buying your components from Australias top supplier.
Twin Scroll Turbos
This is something you would have come across at some point when looking for turbos. The term twin scroll turbos don’t actually indicate the number of turbos but instead the internal design.
Scroll refers to the spiral pathway the exhaust gases enter the turbocharger. To separate the exhaust pulses and prevent the interference of gas-flow, the pathways are split and hence the term “twin-scroll” term.
So, our suggestion is to stick to a single turbocharger if you have a 4 cylinder engine, however if you are not restricted in terms of a budget then a V6 engine with a twin turbo is always welcome.