I thought the purpose of adding port injection to a direct injected engine was to keep the intake valves clean, but it also has other benefits.
http://articles.sae.org/15574/
Quote:
Pete Dowding, Ford Powertrain’s well-travelled chief engineer, told Automotive Engineering the cost of moving all the F-150’s engines to the direct- and indirect-injection layout is justified by the increased fuel economy the design permits—largely because of the higher compression ratios (CR) available from overlaying PFI onto DI. At high load, DI cools the cylinder sufficiently to maintain a high CR without high-octane unleaded. At lower loads, “the DI system bleeds off,” Dowding said, and PFI takes priority, delivering efficient cylinder-fill while still reaping the BMEP benefit of higher compression.
For the newly-downsized V6, the twin-injection system allows a CR increase from 10.8:1 to 12:1. For the heavily-revised 2.7-L turbocharged DOHC V6, the next engine up the F-150 food chain, CR goes from 10:1 to 10.3:1 and for the pickup’s lithe “Coyote” 5-L DOHC V8, CR is boosted from 10.5:1 to 12:1.
http://articles.sae.org/15574/
Quote:
Pete Dowding, Ford Powertrain’s well-travelled chief engineer, told Automotive Engineering the cost of moving all the F-150’s engines to the direct- and indirect-injection layout is justified by the increased fuel economy the design permits—largely because of the higher compression ratios (CR) available from overlaying PFI onto DI. At high load, DI cools the cylinder sufficiently to maintain a high CR without high-octane unleaded. At lower loads, “the DI system bleeds off,” Dowding said, and PFI takes priority, delivering efficient cylinder-fill while still reaping the BMEP benefit of higher compression.
For the newly-downsized V6, the twin-injection system allows a CR increase from 10.8:1 to 12:1. For the heavily-revised 2.7-L turbocharged DOHC V6, the next engine up the F-150 food chain, CR goes from 10:1 to 10.3:1 and for the pickup’s lithe “Coyote” 5-L DOHC V8, CR is boosted from 10.5:1 to 12:1.
