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  F7     F9




  Parallel Supercharging


The system is also named 'Bi turbo', which raises the question of the advantage compared to an engine with one turbocharger. The solution shown on top is generally reserved exclusively for large-volume engines with at least six cylinders. In that case two small chargers instead of one big turbocharger make sense because the runners do not react so slowly to accelerator pedal changes. The turbo lag becomes smaller. The engine behaves as if it featured two more cylinders.
With the general race for ever more engine power, more and more reliable constructions reach their limit of performance. Applying this kind of charging the possibilities are extended without expensive new designing. Moreover, the engine also fits into smaller vehicle versions. With two more cylinders this would not be the case.
In the meantime, both parallel turbochargers are combined with petrol direct fuel injections. The compression can be held up high due to a complete engine management which encloses the camshaft adjustment. A good power output and economic operation is also guaranteed with low boost pressure.

How it works

In the scheme on top the combination of both turbines (3) with relatively short distances and particularly formed elbows (2) is well recognizable for three cylinders each. In practice there is also flow-technically a close connection by which a direct responding of the respective turbine wheels to the gas ejection is possible. The quick aerial flow is stimulated by both compressor wheels (7) between air filter (6), intercooler (8) and throttle valve (9) on the way to the engine (1). It is regulated by the relief valves (4). Afterwards it flows to the exhaust system (5). This separation does not always take place at the compressor. Here there are solutions with one and a common intercooler. Obviously the separation of the gas flow is not so important.
A disadvantage of this conception is the clearly higher load of the crank mechanism and the corresponding housings. However, the engineers will solve this with a lot of engineer's art. What remains especially externally, are two separate exhaust systems which make sense also for a six-cylinder in line.