EcoBoost evolution: Greater efficiency, double the injectors, more speeds

By Christopher A. Sawyer
The Virtual Driver

(May 15, 2016) About the only thing that Ford’s second generation 3.5-liter EcoBoost V6 keeps from its predecessor is the bore spacing and deck height of the outgoing motor. That’s because this makes it possible to build the new engine on the same line as the outgoing version, with no major changes in plant or equipment. Where the new engine differs the most from its predecessor, however, is in its fuel injection system.

The original was a pure direct injection design that sprayed fuel into the center of each cylinder. Theoretically, this places the fuel where you need it in precisely metered amounts, which increases efficiency.

In the real world, however, direct-injected motors are not quite perfect. The fuel flow required at higher rpms runs counter to the need for precise injection through smaller holes, leading to wall wetting and greatly increased carbon buildup on the heads and the backside of intake valves. If that’s not enough, direct injection motors create more particulate emissions.

This is an increasing problem as the EPA’s Tier 3 emission regulations for 2018 greatly reduce the particulate emissions that internal combustion engines of any type are allowed to emit. Potentially, some gasoline direct-injection motors may need to run diesel-like particulate filters to pass these particulate emission standards.

To combat this, Ford has added port injectors in the intake just upstream of the intake valves. They wash residual deposits off the intake valves, and increase fuel flow so the in-cylinder fuel injectors can have smaller holes for greater control over fuel flow. Will it work? Yes, but it will not totally eliminate carbon buildup. That’s because it does nothing to eliminate the static charge on the fuel that not only makes negatively charged surfaces attractive, but keeps air trapped within the flowing fuel. But that’s a discussion for another time and place.

The new 3.5-liter EcoBoost V6 runs a 10.5:1 compression ratio and a maximum boost of 16 lb./in.2, and produces the same horsepower as the outgoing motor — 350 — but 30 more lb.-ft. of torque, for a total of 450 lb.-ft. New turbochargers with lighter turbine wheels are used in conjunction with electrically activated wastegates, which should make the engine more responsive across the rev range. The lightweight turbine wheels are made out of a high-temperature aerospace alloy known as Mar-M-247, and is just one of the areas where engineers cut weight.

The turbo V6 also has hollow camshafts with a new roller finger-follower design that helps cut weight by four pounds while reducing rotational mass. In addition, the intake and exhaust valves have been made more durable, and are mated with higher bandwidth hydraulic valve lash adjusters.

This latest version of the 3.5-liter EcoBoost is also used in the Ford GT supercar, though it’s unlikely that +600 hp application will feature the automatic stop-start system created for the F-150. This smart system is designed to reduce fuel use and emissions, but is disabled when towing or when the F-150 is in four-wheel-drive mode.

Another piece of the 2017 F-150s technology puzzle that won’t make the transition to the Ford GT is its new 10-speed automatic transmission. Developed in conjunction with GM, it is designed to fit in the same space as the outgoing six-speed unit, has a direct (1:1) seventh gear, and three overdrive gears. The wider ratio span allows the use of higher (lower numerically) rear axle ratios to improve fuel efficiency at cruising speed without affecting the vehicle's towing capability.

The 10-speed transmission, which eventually will make its way into the Mustang, Expedition, Transit, Navigator and F-250, is able to skip gears as needed, and is the first Ford automatic transmission that does not use any cast-iron components. Integrating the torque converter and turbine clutch helped shave two pounds, and reduce package size. And its integrated electric pump maintains fluid pressure during start-stop operation.

This powertrain combination, with a higher horsepower and torque rating, also will be used in the 2017 Raptor and launches this summer.

The Virtual Driver