When optimizing engine performance with the objective of minimizing fuel consumption and engine emissions, ideally this should be achieved without a penalty in engine responsiveness. From this perspective, a swift and highly dynamic turbocharger performance over a large engine operating range is preferred for downsized engines. Among others, such a turbocharger performance can be achieved through application of multiple-entry turbine concepts. Among others, such turbocharger performance can be achieved through application of a multiple turbine.
In case a larger displacement naturally aspirated engine will be updated by a smaller displacement ‘downsized’ version, i.e. smaller displacement in combination with super-/turbocharging, bi-turbo solutions can be a very attractive option. By doing so, one can still achieve the same (or even better) engine performance without a penalty in low-end torque or responsiveness when compared to an equivalent capacity but larger scale single turbocharger solution.
How does it work?
Bi-turbo technology is attractive for midsize to larger engine ranges, and typically for >2.5 liter engine displacement. Bi-turbo technology applications are characterized by parallel arrangements and differ for example from 2-stage turbocharger concepts in a sense
that these are connected in series arrangements.
The bi-turbo concepts do not differ much from more conventional single turbocharger systems. In a bi-turbo configuration a relatively large single turbocharger is replaced by two smaller turbochargers which both operate according to the same operating principle. Inherently, the smaller turbochargers are characterized by a reduction of rotational inertia compared to the larger single turbocharger. Another advantage of bi-turbo concepts is a decrease in exhaust manifold and volute volumes. The latter brings a potential for better utilization of exhaust gas pulse energy. Together this typically leads to a significant improvement in transient engine performance. In addition, engine performance can be further improved for instance by applying variable turbine geometry on twin turbo configurations.
What can we offer?
Over time Mitsubishi has gained a lot of knowledge and experience in designing, developing and producing OEM bi-turbo systems, which has been successfully applied to BMW’s award winning S55 engine, among others. Mitsubishi’s bi-turbo configurations are able to operate at very high turbine inlet temperatures (Up to 1050 ⁰C). When preferred, these configurations can include more common gasoline technologies too, like variable turbine geometry, integrated exhaust manifolds etc.