With summer coming on this is something to consider...

[Rodslinger]

Cooling Compromises With New Engines

By Phil Romba

Clean air is priceless in principle. But in today’s concrete world of pickup and delivery and diesel-powered trucks, there is a real cost that grows with each round of Clean Air Act regulations.

According to the National Truck Equipment Association, the average price of a 2007 light or medium truck grew by $5,000, thanks to the new generation of diesel engines and upgrades to associated vehicle systems.

For the 2007-compliant engines, cleaner also means hotter. The new diesel engines generate more heat under the hood, and truck makers have revamped cooling systems to handle that additional heat.

When fleet operators open the hoods of the new trucks, they find cooling systems with greater capabilities and capacities across the board. There are some similarities and some differences in the ways the original equipment manu-facturers have addressed the heat issue. The differences generally depend on how the OEM wants to incorporate the engine and the new cooling system components into what is now a more complex, integrated powertrain.

Some OEMs have enlarged radiators significantly to incorporate a formerly separate transmission cooling system into the main engine cooling system. This change, truck builders said, reduces complexity and should improve reliability. Others have developed additional small “cooler” systems for power steering systems or transmissions. Some have increased radiator size and redesigned cooling system components such as fans, fan blades and fan shrouds.

The source of the additional heat is the exhaust gas recirculation system found on virtually every new diesel-powered truck marketed in the United States.

The typical EGR system cycles a portion of the engine’s exhaust gases back into the engine’s cylinders. Mixing recirculated exhaust with the engine’s intake air lowers peak combustion temperatures, which, in turn, limits the generation of nitrogen oxides. Reducing NOx and particulate matter (soot) was a goal of the Environmental Protection Agency’s 2007 diesel emission standards.

Engine makers “generally increased EGR flow rates” as one strategy to reduce exhaust emissions, said Roger Gault, technical director with the Engine Manufacturers Association. But higher EGR flow rates increased the temperature of the gases, translating into a greater need to cool EGR gases.

The critical importance of a truck’s cooling system becomes clear when analyzing vehicle failures. According to Chris McKenzie, director of marketing for Penray, “40% of vehicle downtime is cooling-system related.” The Elk Grove Village, Ill., company sells additives and cooling system treatments for commercial trucks.

New cooling systems may be more expensive to repair “due to the addition of components or use of more expensive components,” Gault said. But systems are expected to provide the “same or more robust” performance than their predecessors.

One reason is simply better experience with EGR systems, Gault said.

“Compared to the 2002 EGR systems that were the first introduction of EGR into heavy-duty engines . . . people had a lot more real-world experience with EGR [in 2007] and have a better track record to build their designs and they are expected to be more reliable,” he said.

Another reason may be the coolants used.

More, Bigger Components
Owners of medium-duty trucks manufactured by Warrenville, Ill.-based International Truck and Engine Corp. will see some of the most significant changes to cooling systems. A larger radiator — as much as up to 39% larger, depending on the model — is now standard. The cooling system in a Durastar truck test driven by Light & Medium Truck, for example, is about 25% larger, said Al Ambrosini, marketing manager with International’s engine group.

Packaging the larger radiators under hoods without changing the design required some tweaking by the manufacturers. The radiator in the Durastar model, for example, was widened on the right to keep the same hood line. In some cases, the radiator was lowered between the frame rails.

The radiators are larger because they incorporate previously separate cooling functions for the transmission and EGR system and, in some cases, a fuel cooler coil mounted on the front of the radiator. The coil is used to lower the temperature of the fuel in common-rail high-pressure injection systems, Ambrosini said.

Kevin Carlstrom, International’s chief engineer for its medium-duty powertrain, said the company used the 2007 engine redesign project as the chance to simplify its trucks’ cooling systems. International expanded the base cooling system to reduce “installation complexity and eliminate auxiliary cooling system components on many [truck] installations,” he said.

Earlier International trucks were built with separate coolers for EGR systems. Trucks with automatic transmissions had another separate cooler to take the heat out of transmission fluid, Carlstrom said. The separate automatic transmission cooler, a small radiator-like unit with hoses or lines connecting it to the transmission, was mounted near the front of the vehicle where air moving through its fins would cool the transmission fluid.

For 2007, the automatic transmission coolers are “integrated into our cooling module a little more intelligently” to reduce the number of potential failure points, Carlstrom said. The results, he added, should be improved cooling system reliability and durability without any effect on transmission maintenance.

By incorporating both the EGR and transmission cooling functions — and the coolant used in those functions — into the main cooling system used for the engine, International limited the amount of additional coolant needed for the expanded systems to about 5%, Carlstrom said.

International also changed a number of cooling system dimensions and features such as fan diameter and placement. The fan drive ratios were modified based on specific engine-truck applications. These measures were designed to assure greater cooling capacity “without parasitic powertrain load penalties,” Carlstrom said. That means no loss of engine fuel economy based on changes to the cooling system.

The cooling system for the 6.4-liter Power Stroke diesel used in Ford Motor Co.’s Super Duty line is another example of a larger, more complicated system. Changes were made to handle extra power output compared with the 6.0-liter engine and higher EGR temperatures, said Jeff Eekhoff, engineering supervisor, Ford North American Diesel.

While Ford designs and engineers the cooling system for these trucks, International manufactures the diesel engine.

In Ford’s case, the increased complexity comes from a second, engine-mounted EGR cooler, a separate low-temperature cooling system and a 19% larger radiator that has two rows of cooling tubes instead of the one used in previous engines.

The new low-temperature cooling system, which also cools the high pressure fuel, is composed of a separate radiator, hoses and a small electric pump. The separate system requires 1.9 additional liters of coolant.

Ford’s primary cooling system also includes two thermostats. One opens when engine coolant temperature reaches 180 degrees Fahrenheit and the other opens at 192 F. Eekhoff said the dual thermostats improve engine operation during warm-up and extend radiator life by protecting it from fluctuations in coolant system pressure.

The engine’s primary cooling system requires three more liters of coolant than its predecessor, the 6.0-liter model. Eekhoff said the complexity of the new cooling system could increase repair costs in spite of the rigorous testing the company conducted during development.

Minimally higher repair costs also could be in the cards for owners of Freightliner trucks such as the M2 Business Class models, according to Ivan Neblet, vocational product manager. The Portland, Ore., company designed its 2007 medium-duty models with larger radiators according to engine horsepower ratings. Trucks with lower horsepower ratings now have radiators with 9% more surface area, while trucks with higher horsepower engines have radiators with as much as 22% more surface area.

The diameter of radiator fans, the size of fan blades and the number of blades were also modified based on truck model and application. “Better fan clutches that reduce fan on-time are also new,” Neblet said.

Besides having the transmission cooler integrated into the new Freightliner radiators, coolers for fuel and steering fluid remain separate from the engine’s primary cooling system.

Owners of Kenworth T170, T270 and T370 medium trucks will encounter similar changes in cooling systems. According to the company, radiators are slightly larger, fan system components have been revised and radiators are made from aluminum instead of copper and brass. Trucks with automatic transmissions require an extra cooler.

Cummins diesel engines found in Kenworth’s medium-duty models require a separate cooler for the EGR system. The cooler is a part of the engine and works in line with the truck’s cooling system. The EGR cooler works by transferring heat to the truck’s primary cooling system, according to the engine maker.

While truck and engine makers have taken many steps to minimize changes brought on by the 2007 diesel exhaust emissions regulations, they also have worked to rationalize a growing host of systems needed to cool engine and powertrain systems.

Despite suppliers’ best efforts, however, higher sticker prices for new trucks will also be followed by higher maintenance and repair bills. The size of those bills will depend on the make of truck and how well engineers have addressed the needs of various systems and components to keep their cool.

Link:

Light & Medium Truck Online |Cooling Compromises With New Engines

[nic0084]

another good read man

[vshortt]

Originally Posted by nic0084

another good read man

Ditto...........tenfold!

[ianstew]

it's amazing what the engineers have to go thorough to meet emmissions.