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A Precisely Cool Condition:
How Visteon's Taking the Heat out of CAFE

BY JOE CABADAS

Visteon Corp., which is making a reputation as a vehicle systems integrator, has gone under the hood to develop a new engine coolant system that promises to improve fuel economy and reduce hydrocarbon emissions.

Known as PrecisionCooling, Visteon's technology is a systematic approach to monitoring and controlling engine temperature by regulating the flow of fluid and air through the powertrain system.

.The technology optimizes the vehicle's use of its radiator, fan, water pump, and heater core, according to Product Marketing Manager Ed Vela.

"PrecisionCooling is a revolutionary systems level technology at Visteon. It integrates several of the heating and cooling systems components as well as certain aspects of the vehicle's HVAC (heating, ventilation, air conditioning) system," added Davide Piccirilli, Visteon System Engineer.

To date, the system has been tested on a North American-built, full-size pickup truck with a V8 engine and a small European sedan. Preliminary results have been promising, Vela said.

In the tests engines on the demonstration vehicles were able to run at temperatures 10 to 15 degrees Centigrade above normal and were also able to warm up faster. This led to fuel economy improvements.


The Visteon Precision Cooling System


"Our development vehicles showed up to a five percent improvement in fuel economy," Piccirilli said. "That was achieved by operating the engine at a higher temperature, which results in reduced friction due to improved oil viscosity. And, we improved fuel economy by throttling back on the fan when we don't need it."

The PrecisionCooling system also reduced hydrocarbon emissions on the demonstration vehicles by up to 20 percent, while keeping nitrogen-oxide (NOx) and carbon monoxide (CO) levels well below EPA requirements, Piccirilli said.

Again, this was achieved due to a faster warm-up by routing coolant circuits through the engine as well as operating at a higher temperature.

In terms of passenger comfort, the Visteon system improved the heater's performance on the demonstration vehicles by 10 degrees Celsius. The air conditioner worked better too, by three degrees Celsius. "The demonstration vehicle went from a market follower to a market leader in its segment," Piccirilli said.

The result is that Visteon's customers can decide if they want to increase the performance of their existing heating, ventilation, air-conditioning (HVAC) system or, perhaps, downsize components to save weight and cost for the same output. Visteon is specifically targeting the light truck market in North America to launch this new technology due to concerns about fuel economy, Vela said.

Many of the PrecisionCooling components exist today and could be dropped into an existing vehicle, although OEMs could see weight savings if the technology was integrated and optimized for a new vehicle, Piccirilli said. The system could be launched on a 2005 or 2006 model year vehicle.

The system is also designed so it can be integrated into hybrid-electric vehicles and it will work with an existing 12-volt electrical system or the upcoming 42-volt system.

MARKET DRIVERS

Visteon developed PrecisionCooling to address the needs of the Original Equipment Manufacturers (OEMs), according to Vela. Automakers face increasing stringent vehicle emissions regulations in North America and Europe. And in Japan auto makers are concerned about improving fuel standards.

Visteon's forecasters predict that the U.S. Environmental Protection Agency and the California Air Resources Board will continue to strengthen air pollution standards. The federal government is also expected to raise Corporate Average Fuel Economy (CAFE) standards.

The U.S. CAFE standard for passenger cars has not changed since 1990 and is set at 27.5 miles per gallon. The light truck standard has not changed since 1996 and it is set at 20.7 miles per gallon.

"Inevitably, the CAFE rules will become more stringent," Vela said. "And, we have questions over the sustainability of gas prices. They're currently at $2 per gallon and there is talk that it will approach $3. Potentially, higher gas prices will drive consumers toward more fuel efficient vehicles."

In Europe, vehicle emission standards have also been tightened. Euro III, the current European standard, which went into effect in 2000, covers both gasoline and diesel engines - unlike the U.S. standard which only covers gasoline engines. The Euro regulations monitor hydrocarbons, nitrous oxide, carbon dioxide and particulate matter emissions from diesel engines.

A harsher Euro IV standard is expected in 2005 and an even more stringent Euro V standard is expected to be in effect by 2008. The move from the Euro III to Euro IV standard would require hydrocarbon and NOx emissions to decline by 46 percent, NOx levels to decline 50 percent, CO levels to dip by 22 percent and particulate matter emissions to be cut in half. The Euro V standard is still under development.

Besides governmental action, consumers are also demanding less polluting vehicles in both Europe and North America.

"Consumers are demanding green products. We believe this will be a stronger trend in the next decade," Vela said.

THE TRADITIONAL COOLING SYSTEM

Current gasoline- or diesel-powered vehicles have a thermostat, a water pump and a fan. The thermostat is a valve that directs flow to either the engine's bypass system or to the radiator. Plus, the water pump in the cooling traditional system is a mechanical device that is linked to the fan belt and, thus, coupled to the engine's RPM.

"There is a direct correlation between the water pump speed and the engine's RPM," Piccirilli said. "Higher engine rpm results in higher water pump RPM, even in conditions where the additional flow is not necessary." Traditional water pumps also impact engine performance by leeching horsepower away.

The engine's fan is either electrically controlled, so it can be turned on or off as needed, or a mechanical fan that is coupled with the engine RPM. Just like the water pump, the mechanical fan's power is directly linked to the engine's RPM and can't be altered to adapt to different conditions.

Some vehicles, such as those made by Ford Motor Co., also have a degas bottle, which is designed to remove air from the coolant system. A tube connects the degas bottle to a nipple on radiator. So, when coolant flows through the radiator, it automatically flows to degas bottle even when it's not necessary, Piccirilli said.

THE VISTEON WAY

The first key difference between Visteon's PrecisionCooling technology and a traditional coolant system is that the thermostat is replaced with a coolant control device. This device is a five-port valve, with one input tube and four output tubes, and controls the coolant flow not only to the radiator and engine bypass, but also to the heater core and the degas bottle.

"We are now taking control of the coolant's flow. For example, maybe we want to send the full flow to the radiator instead of the degas bottle or maybe we want to send more coolant to the engine bypass circuit," Piccirilli said.

The one challenge is trying to find space package the coolant control device in the engine compartment. That isn't much of an obstacle because the device doesn't need to be located in any one particular spot, according to the company..

Next, Visteon has integrated the operations of the engine fan, the water pump and the heater core with the radiator, the engine bypass circuit and the degas bottle.

With PrecisionCooling, the vehicle's water pump and fan can either be electrically- or mechanically-powered and independently controlled from the engine's RPM. The mechanical pump and fan speeds are controlled by electronic viscous clutch. The clutch will allow both the water pump and fan speed to be controlled independently of the engine's RPM.

All of these operations are linked together by a control module, which can be separate unit or the software can be integrated into the vehicle's existing powertrain control module.

"The combination of all of these devices and how they operate to optimize the engine operating temperature at a higher set point that allows us to integrate the other systems, such as the climate control," Piccirilli said.

"By having control of the heater core, we can determine when it is necessary to send energy into that component, thereby affecting the engine performance and heating performance."

IN OPERATION

During start up mode, when the vehicle has been parked overnight and the engine is cold, the coolant is kept in the bypass loop, working only through the engine so it can warm up to operating temperatures faster. If the driver needs heat, the PrecisionCooling system will divert some of the coolant to the heater core.

The PrecisionCooling test vehicles were able to produce heat for the passengers that was 10 to 15 degrees Centigrade greater than the traditional system. Once the coolant achieves its operating temperature, the system will divert the fluid to the radiator and degas bottle, as needed so the engine won't overheat. And, PrecisionCooling will adjust the fan and water pump speeds as needed.

In power and acceleration mode, when the vehicle is climbing a hill or trying to pass someone, the water pump and fan speeds can be adjusted to maximum to help induce cooling. The PrecisionCooling system will route coolant to the radiator, degas bottle and heater core as needed.

Unlike traditional cooling systems, which react to changes in engine temperature, Visteon's PrecisionCooling system is proactive. It will anticipate what level of heat will be generated and adjust the water pump and fan settings to promote cooling ahead of time to maintain coolant temperature," Piccirilli said.

And in economy or cruise mode, when the vehicle is on the expressway, for example, the PrecisionCooling system again will control the coolant flow to the heater core and radiator while controlling the fan and water pump settings as required.


Want more info on Visteon? Visit the company's climate systems site for more details. http://www.visteon.com/climate/

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