While the huge horsepower and the two Hellion turbos are the attention grabbers of this story, a facilitator of this new level of power is that XDI high-pressure pump. Heretofore, most tuners have relied on upgrading the port side of the equation, but Xtreme DI has long advocated the benefits of relying more on direct injection.
“The 2018 Coyote engine is a new style of engine, a lot of high-tech features,” Uwe Ostmann, owner of Xtreme-DI, said. “We are still learning and identifying, what it really likes, but it for sure likes any kind of boost!”
Because the latest 5.0-liter engine was revised specifically to benefit from direct injection, relying too heavily on the port side of the fueling can have a negative side effect.
“The 2018 Coyote engine is optimized for DI fueling. It has an increased compression ratio of 12:1 from the factory. The intake ports are optimized for air/ fuel mixture mostly in the combustion chamber. When you push more air through this refined system now, everything changes again, makes it even more sensitive,” Uwe explained. “Adding too much fuel in the port causes an already wet air/fuel mixture with too many ‘heavy’ fuel drops coming through the intake valves. When this heavy wet air enters the combustion chamber and gets hit by ultra-fine fuel vapor at 2,900 psi, air/fuel mixing dynamics do not work anymore as intended by the Ford engineers. You get more local rich zones, which are known to cause auto ignition and inefficient burn. This effect gets even worse if you run high-ethanol content blends where you add another 30 percent or more of liquid mass to the equation.”
While upgrading the high-pressure pump (and eventually the direct injectors themselves) is a more expensive path, weaning a dual-fuel engine off its port injectors might just unlock more power.
“We have seen knock sensors react right away to increased port fueling, even at slightly increased power levels, especially on pump gas. With higher direct-injection-blend ratios or even better with 100-percent DI you can run more boost and more timing at the same time, even on 91-octane fuel,” Uwe elaborated. “You should even be able to still meet emissions that way at increased power levels. We have also seen drivability issues with increased port fueling, especially in daily driving situations.”
While Ford tuners are just starting to address the direct injection side of the equation, that means there is still room for improvement in performance and driveability as this becomes more mainstream.
“Keep in mind, that there is no delay with DI, the first combustion is perfect,” he added. “The ECU algorithms are optimized for this. If you take away DI fuel now, you shift this dynamic response more to conventional EFI again, with all the wall-wetting delays, etc. This translates to all dual-fueling applications, as we are seeing the same effects on the Gen 2 EcoBoost trucks now.”