According to Ford, the main reason that car buyers don't choose traditional sport utility vehicles is gas mileage. So for the new 2011 Ford Explorer, Ford is pulling out all the stops to improve fuel efficiency anywhere it can.
Its signature engine is the 237-horsepower, direct-injected and turbocharged 2.0-liter EcoBoost aluminum four--whose torque equals that of its predecessor's 4.0-liter V-6. Ford is aggressively expanding its efficient EcoBoost engines across more of its vehicle lines.
But the 2011 Explorer also steals several technical tricks from Ford's hybrid vehicles. In a briefing last week, Jim Holland, Ford's chief engineer, described a few modifications from the company's hybrids that his team was able to apply to the Explorer's EcoBoost engine.
"Mild Atkinson cycle"
First, the vehicle uses what he calls "mild Atkinson Cycle" combustion, which simulates a compression stroke that's shorter than the power stroke by leaving valves open during part of that stroke. This slightly reduces the power needed to pump air, improving its efficiency.
The Atkinson Cycle engines fitted to full hybrids run very efficiently at high speeds, at the cost of producing very little torque at low speeds. The hybrid's electric motor, which produces maximum torque from 0 rpm, neatly complements this.
Without an electric motor, the 2011 Explorer's engine can't run a full Atkinson cycle, but even shaving fractions from its pumping losses raises the power it generates from the gasoline it burns.
2010 Ford Fusion HybridEnlarge Photo
Second, the 2.0-liter EcoBoost four's ability to vary its valve overlap depending on power demand allows a kind of "internal exhaust-gas recirculation," feeding exhaust gases into the combustion cycle to provide a slight increase in power under certain loads.
Scott Makowski, Ford's North American inline-four design manager, notes that this alone boosts fuel economy by 3 percent and power by 10 percent over the same engine without the ability to vary its valve timing independently.
The Ford Escape Hybrid is manufactured alongside its Mercury Mariner Hybrid sibling at Ford’s Kansas City plantEnlarge Photo
Aggressive fuel shutoff
Third, the 2011 Explorer engine has "aggressive" fuel shutoff on deceleration, depending on its speed and the torque it needs to provide. Holland again pointed to hybrids' role in pioneering engine shutdown as those vehicles came to a halt.
The Explorer system could be viewed as the on-the-road version of a stop-start system; the engine continues to rotate, but fuel isn't switched on again until more power is required.
All of these design tricks, incidentally, are also used on the 2011 Ford Edge crossover that's fitted with the 2.0-liter EcoBoost four as well.
2011 Ford Edge SportEnlarge Photo
Waiting for EPA ratings
While official EPA gas-mileage ratings for the 2011 Ford Explorer haven't yet been released, Ford claims the vehicle will be "30 percent more fuel efficient" than its 2010 predecessor.
Perhaps more impressive, Ford also says the 2011 Explorer will deliver "better highway mileage than the Toyota Highlander Hybrid." For the record, the 2010 Highlander Hybrid is rated at 25 mpg on the EPA's highway cycle.
Ford provided airfare and lodging so that High Gear Media reporters could bring you these details of the 2011 Ford Explorer.