Twelve fuel injectors — a DI injector and a port injector for each of the engine's six cylinders — is the stuff of an injector-supplier's dreams, but the data indicate there's a meaningful gain from the novel fueling design.
Engineers indicate brake-specific fuel consumption improves about 4% compared with a comparable DI-only engine, and start-up emissions are reduced by about 20%.
Yerace says the PFI system typically is used by itself only during the actual cranking part of the engine startup phase. He adds that this is when a substantial portion of the “raw” emissions of a cold start are produced, which for DI engines typically is exacerbated by the emissions “spike” during cranking that comes from immediate delivery of highly pressurized fuel.
At most other times, sophisticated engine management mapping controls the intricate interplay of the DI and PFI systems to achieve the best results depending on a multitude of variables.
But during high-load operation, only the DI injectors are used, maximizing DI's ability to deliver a cooler, denser air/fuel mix that promotes maximum power and torque.
At 306 hp, the 2GR-FSE is one of the highest specific-output normally aspirated V-6s available in the U.S., while delivering (in the IS 350) city-cycle fuel economy of 21 mpg (11.2 L/100 km) and a combined-cycle rating of 24 mpg (9.8 L/100 km).
The city figure ties Audi's A6 (DIG 3.2L DOHC V-6) for class leadership, and the combined fuel-economy number ties BMW's 330i (3L DOHC I-6) — yet the 2GR-FSE handily outpowers and out-torques both competitors.
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