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If you've seen the press release for the new 4-cylinder Silverado, it has a 2.7L turbo with a new BW turbo. It also has a very VTEC-like twin-lobe cam that apparently is on some other GM vehicles.
Anyway, the twin volute is supposed to spool significantly better than a twin scroll. No aftermarket turbos yet, but the current BW line including the EFR has been around for a while and Garrett now has the G-series in both G25 and G42 sizes. Maybe 2019 SEMA?
This is a pic, a press release, and a 2009 SAE paper. The paper also talks about a version with VTG. Surprisingly, the version GM is using does not have VTG. Given that the GM engine has an electric water pump and electronically controls water flow to block, head, and turbo/exhaust manifold and a processor-controlled oil pump that does the same for bearings, turbo, valvetrain, and oil squirters (computer-controlled piston oil squirters?).
Biggest benefit i see is more 'reliablity'. The twinscroll design as i see it merges the two separated exhaust banks into the turbing wheel through an inside and outside lane if you will. The new design feeds the turbine on two inside lanes via an inside lane and an underground subway lane underneath it. Basically applying two forces on the inside of a bearing vs applying the same force on the inside AND outside will give better bearing life and can make the turbine housing amd wheel slimmer. Think of using wheel spacers and how they affect bearing life the further they are from the hub, same thing with the distance exhaust flow hits from a turbine, the closer you can get it to the bearing the better. Atleast thats my take at a glance but i am no expert at all.
Twin-Volute Turbos Coming???
