Motor Co. is utilizing two critical technologies to boost fuel efficiency and ensure most of its vehicles beginning the ’09 model year can run on less-expensive regular (87-octane) gasoline.
Key is’s aggressive fuel-shutoff system, which cuts most of the fuel flow to the injectors when the driver backs completely off the throttle while the vehicle is in fifth or sixth gear, such as when exiting a freeway.
“It’s a very straightforward concept,” Kevin Layden, chief engineer-powertrain attributes and calibration for North America, tells Ward’s. “During a deceleration event you can turn the fuel off and leave the converter locked and transmission engaged and save fuel by not running the engine.”
Several obstacles had to be overcome prior to use in production vehicles, he says, noting particularly difficult was eliminating the “clunk and bump” as fuel flow is cut off, then restarted. A team of engine calibrators solved the issue through better management of the spark and torque converters.
“As the fuel comes back on, it’s a matter of managing spark and the number of injectors that come on in each revolution so you have a smooth transition,” he says.
While some auto makers employ dash indicators to let drivers know when a fuel-saving system is activated, Ford opted not to include such a feature, Layden says.
Once the shutoff system was perfected, Ford engineers turned their attention to solving the emissions issues it created.
When the fuel supply is shut off, the air-fuel ratio can’t be controlled, allowing raw air into the catalyst.
That “loads (the catalyst) with oxygen and cools it, neither of which are good for the effectiveness of catalysts,” Layden says.
Exactly how that was solved is being kept close to the vest, but it took a keen understanding of how much oxygen was entering the system and how to manage that flow, the Ford engineer says.
The system results in a 1.5% fuel-efficiency gain during a normal drive cycle, Layden says, noting that number can fluctuate depending on driving conditions. Its first application is on the ’09 Flex cross/utility vehicle and Lincoln MKS flagship sedan, but Ford plans to roll out the technology across its entire lineup.
The technology is different than the displacement-on-demand systems used by some Ford competitors, which shut down half an engine’s cylinders when not needed, Layden says, noting the two systems could be used in conjunction.
However, Ford long has maintained DoD technology doesn’t deliver the real-world fuel savings some auto makers claim.
“We can do it with little impact on reliability and costs,” Layden says, “Whereas displacement on demand is more cumbersome.”
Layden admits fuel-shutoff systems are nothing new, but says Ford’s application is “more aggressive” and cuts flow more frequently and for a longer period than similar systems.
“There’s systems where you can turn fuel off, and that’s been done for years,” he says. “But we can do it at nearly every deceleration event for a long period of time without impacting catalyst costs and emissions. We’re leading on this at Ford.”
The second key feature is adaptive spark technology that allows vehicles to run on regular gasoline, a strategy that could save customers as much as $200 annually.
Engineers are employing two sensors on Ford’s V-6s and V-8s to monitor the frequency of knocking events through the engine block, says Stephen Russ, technical leader-engine engineering.
Monitoring knock frequencies also is nothing new, but Ford’s system employs an “adaptive strategy” that uses complex algorithms to keep track of spark ignition adjustments over time and stores them in the vehicle’s engine-control unit.
“If you were running premium fuel, it would keep track and advance the ignition timing, and as you change fuels to lower octane, it would ‘learn’ that it would have to retard the ignition timing and readjust,” Russ tells Ward’s. “In the past we would track the (knock) signals and add or take out spark, but the (system) wouldn’t learn corrections over time.”
While the system provides less costly fill-ups, it does have its drawbacks, namely a 2- to 3-hp drop in output when running on regular rather than premium fuel.
The system is being considered for Ford’s European engines as well as smaller, 4-cyl. mills, says Jim Kindree, powertrain calibration technical expert.
“We’re migrating to global solutions,” Kindree says. “The algorithm will work with 4-cyls. in the same manner, but the block structure is a little different than a ‘V’ engine, so we may be able to use one sensor and still be able to detect enough (knock) on all four cylinders.”
The 2-sensor adaptive spark ignition system currently is offered on the ’09 Lincoln MKS, ’09 Ford Escape and Mercury Mariner CUVs with 3.0L V-6 engines, special-edition Bullitt Mustang and Mustangs equipped with a 4.6L V-8.