General Motors has filed a patent application for a new two stage turbo system.

The filing, published by the USPTO on May 19, 2016, details a two stage turbocharger where the low pressure turbine and the high pressure turbine are arranged in a series. The brilliance of the new proposal is a bypass system which allows GM to optimize both the high pressure and low pressure inlets for their respective tasks.

According to the filing, typical two-stage turbochargers are configured to operate both turbines simultaneously at low/mid engine speeds, while at high engine speeds only the low pressure turbine operates.

The issue with this design is an inability to completely isolate either low or high pressure sides, forcing inlet design compromises, which in turn can impair low end performance and result in higher pumping loses.

GM's new system proposes to eliminate the compromise.


The high pressure turbo is linked to the exhaust manifold through the high pressure inlet duct; the low pressure turbo is connected to the high pressure turbo through a low pressure inlet duct which links to a connecting channel.

Bypass is created through a single actuator which lives in the exhaust manifold, it either opens the high pressure inlet and closes the connecting channel or vice versa.


The system is actually pretty trick in its simplicity. The actuator takes direction from the ECU based on engine speed and load, the actuator is a single rotating spindle with discs corresponding to flanges on the high and low pressure sides. The spindle rotates 90 degrees isolating the respective sides of the two-stage turbos.


Isolation allows the respective inlets to be designed for the best possible fluid dynamic performance. This way the maximum available enthalpy is given to the low pressure side in full power operation, likewise to the high pressure side in maximum torque operation.

Want to bet we see it in a Cadillac first?

H/T Dennis Chung