Tech Analysis – 2010 Fusion / Mercury Milan Hybrid…

October 31, 2008

With great thanks to AutoblogGreen, here is an analysis of the 2010 Ford Fusion/ Mercury Milan’s hybrid system:

The long-awaited redesign of the Ford Fusion and Mercury Milan is almost upon us and we got our first look at the new powertrains this week in Dearborn. As expected, increased fuel efficiency has been the number one priority for Ford’s engineers, followed by power and refinement.

In the conventional models, the sedans have picked up the redesigned engines that we first saw last spring in the 2009 Escape and Mariner compact SUVs. We did learn some new information about efficiency improvements to the 2.5L four cylinder and the 3.0L V6 that Ford hadn’t revealed previously.

Even more importantly, the sedans will now be available with a hybrid powertrain for the first time. While the 2.5L engine in the hybrid is shared with the Escape, the electrical part of the system is almost entirely new. The whole system has been designed in-house by Ford and if what we were told pans out, this mid-size sedan will be the most fuel efficient car in the segment on the road in the U.S. One thing the Ford staff emphasized during the briefing was the company’s emphasis on affordable fuel efficiency. VP of Global Powertrains, Barb Samardzich, told the assembled media that “we don’t want our sustainability strategy to be public affairs exercise.” In reviewing the company’s plans for the coming decade, Samardzich focused on affordable technologies that can be applied to almost all cars in the near term. That means that over the next five years, almost all Fords will have transmissions with at least six gears and well over half of the company’s North American products will have EcoBoost engines. Read on to find out more about what Ford has in mind for the Fusion and Milan in 2009.

[Source: Ford]

The 2010 Fusion and Milan that will be rolled out in Los Angeles next month will go on sale early in 2009 with twice as many powertrain options as the 2009 models. The entry point as expected is the 2.5L four cylinder already available in the Escape and Mariner CUVs. Compared to the 2.3L that’s currently available, the new engine gets a 14 hp bump to 175 hp along with 172 lb-ft of torque. Like all other 2010 Fusions (save the hybrid which we’ll get back to later) both manual and automatic transmissions have 6 forward gears. The extra ratios provide a broader overall ratio spread while at the same time reducing the steps between ratios. Compared to the competitor’s automatic transmissions, Ford claims the new 6F35 has significantly lower losses across the board, particularly at lower speeds.

The engine itself has been heavily reworked with a new block, pistons, crankshaft, and, of course, cylinder head. The new head features variable cam phasing on the intake cam and better flow through both the inlet and exhaust sides. Ford engineers have made an effort to improve the torque of the engine which makes it feel stronger to the driver. When the engine feels stronger, the driver might not push it as hard, which can help efficiency. It also makes the four cylinder a more appealing alternative to the larger V6 engines, helping Ford’s fleet average economy if they can sell more of them.

Among the features that help improve the efficiency of both the four and the 3.0L V6 are adaptive knock control and aggressive deceleration fuel cutoff. The former allows the engineers to calibrate the fuel delivery and spark timing to minimize the fuel consumption without triggering damaging engine detonation. The fuel cutoff disables fuel delivery when the driver lifts off the accelerator. However, the engine management doesn’t just abruptly disable the injectors. That would cause bumps and hesitation that the occupants of the car would be able to feel. Instead, the control strategy uses engine torque as the control variable. A desired engine torque is calculated based on a combination of driver demand, speed, gear ratio and other variables. When the accelerator is released, the torque is ramped down to zero. The fuel delivery, spark timing and electronic throttle position are determined from the torque demand. This causes the the injector pulses to be ramped down so that the overall power delivery is kept smooth and seamless without abrupt changes.

The extra power and gear ratios improve the Fusion’s 0-60 mph acceleration by 1 second to 9.5 seconds and bump the highway fuel economy by 5 mpg to 33 mpg. The final EPA numbers for the 2010 Fusion and Milan aren’t complete yet, but Ford expects its cars to beat the four-cylinder Toyota Camry by 2 mpg on the highway and the Honda Accord by 3 mpg.

The 3.0L V6 also gets a bump from 221 hp to 240 hp and the sedans also get the ability to operate on E85. If the fuel tank is filled with ethanol, the engine management system is calibrated to take advantage of the higher octane rating to produce an extra 10 hp. The V6 gets stronger valve seats and new higher flow fuel injectors along the fuel content sensor.

When the upgraded V6 debuted in the Escape last spring, Ford told us about the variable cam timing system but didn’t provide any details about the innovative mechanism that changes the angle of the camshafts. Most cam phasing adjusters use hydraulic pressure to twist the camshafts. This pressure is generally provided by a larger capacity oil pump. That pump increases the parasitic draw on the engine. To overcome the need for a larger oil pump, Ford worked with Borg-Warner to devise what they call Cam Torque Actuated VCT. The CTA system utilizes the energy that builds up inside the camshaft itself as the lobes ride up on the valve followers. The resistance of the valve causes twisting force to build up within the camshaft. As the peak of the lobe passes the valve the force is released, causing the camshaft to “spring” back.

This energy is captured in the phasing mechanism mounted on the end of the camshaft. The mechanism contains an electronically controlled spool valve along with check valves that manages the oil pressure build within a pair of chambers that adjust the relative angle of the camshaft. The new mechanism is able to make adjustments much faster and to a greater degree than the traditional systems. The CTA system can provide 40 degrees more cam advance at 1,500 rpm and an additional 35 lb-ft of torque. According to Ford, the CTA system accounts for a 0.8 percent improvement in mileage thanks to elimination of a larger oil pump and the improved thermodynamic efficiency achieved by the variable cam timing.

The variant that ABG readers will likely be more interested in is the new hybrid. The sedans get the most extensive revision yet of Ford’s hybrid system. The size, weight and presumably the cost of the battery pack has been substantially reduced. The cells inside remain nickel metal hydride and are still supplied by Sanyo, which also provides the Escape pack. The chemistry however has been revised so that each cell now produces 20 percent more power than before. The total number of cells has been reduced by 20 percent keeping the capacity at 1.3 kWh, the same as in the Escape.

The changes to the battery mean that the pack is now 30 percent smaller in volume than the Escape pack, and weighs 23 percent less. It also means the pack no longer needs its own air conditioning system like the one in the Escape. Instead, cabin air can be routed through the pack to keep it cool. The pack integration was done by Delphi while Ford engineers handled all the battery management software and electronics internally. The battery management system of the Escape was done by Sanyo.

The reduction in cell count means a reduction in the nominal system system voltage to 270 V. The reason Ford has reduced the voltage is improve the efficiency of the power electronics. Higher voltage causes more resistance and heat build up in the switching circuits and lower efficiency. Normally the voltage reduction would mean a corresponding reduction in power for the electric drive system. However, Ford’s engineers have added a variable voltage controller (VVC) to the Fusion hybrid that allows the voltage from the battery to be stepped up on demand. During most driving conditions when comparatively little power is needed, the lower voltage increases the efficiency of the electric drive system, while the VVC allows even greater output than the Escape when it’s needed for acceleration or heavy regenerative braking.

The hardware package for the hybrid drive and transmission generally remains the same size as the Escape although the power electronics are now integrated in a sealed container mounted directly on top of the transmission. This eliminates some of the external high voltage wiring most other hybrids have, easing vehicle assembly and improving reliability.

Nancy Gioia, Ford’s director of sustainable mobility technologies explained that the company wanted the Fusion/Milan hybrid to have a fun driving experience while still achieving best in class fuel economy. To that end the internals of the hybrid transmission have been reworked, substantially improving the output of the motor and generator. The motor power is now up to 93 kW compared to the 70 kW output of the Escape while the generator has gone from 45 to 70 kW. With the on-demand voltage increase of the VVC, the new motor can now drive the Fusion and Milan on electricity alone at speeds up to 47 mph, an increase from the 40 mph EV speed of the 2009 Escape and the 24 mph speed of earlier Escapes. The system can now support automatic start/stop twice as often as before.

Ford hasn’t received the final EPA certification yet for the new new hybrids, but the company is expecting a major improvement compared to its most direct competitor, the Toyota Camry hybrid. The 2009 Camry hybrid is rated at 33 mpg city and 34 mpg on the highway. Ford is expecting to get at least 5 mpg in the city, putting the Fusion at 38 mpg, putting it near the 40 mpg of the smaller and significantly less powerful Civic hybrid.

We’ll be anxiously awaiting our opportunity to see how the Fusion hybrid does in the real world early next year. However, combined with the new SmartGauge information and eco-coaching system that will be standard in the Fusion and Milan, it certainly has the potential to put the lie to the story that Detroit can’t build high-efficiency cars. The other big question that remains is price and availability. Hopefully, Ford will loosen the reigns a bit and build more examples of the hybrid sedans than they have been willing to do so far with the Escape and Mariner.


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