EPA '02 engines fare better than feared
Oct 1, 2003 12:00 PM, By Gary Macklin
Although fleet managers continue to proceed with extreme caution, recent reports suggest that the troll under the EPA engine bridge has no fangs, or short, dull ones at worst. After more than a year of speculation and fear generated by the unknown performance of engines designed to meet the October 2002 Environmental Protection Agency emission regulations, fleets contacted by Refrigerated Transporter are reporting few problems with the new engines.
Uncertainty about the engines and downright resistance to buying them is the result of little information about the new technology used by four of the five manufacturers of heavy diesels as well as a short lead time for placing the engines in service. The short lead-time came about following a consent decree signed by Caterpillar, Cummins, Detroit Diesel, Mack, and Volvo in which the manufacturers acknowledged an attempt to circumvent certain emissions testing procedures. In consequence, the government moved the effective date for regulations scheduled for January 2004 back 15 months to October 2002. Fleet operators said that the new effective date provided too little time for manufacturers to perfect their designs and even less time for fleets to validate the designs in field tests.
To meet the new standards, all heavy engine builders except Caterpillar, chose to use a technique called exhaust gas recirculation to reduce the level of particulates and oxides of nitrogen in diesel exhaust. This technology replaces up to 15% of engine intake air with cooled exhaust gas to absorb heat during combustion and reduce peak flame temperature during engine firing. Lower combustion temperature produces fewer oxides of nitrogen. However, exhaust gas recirculation adds stress to the engine cooling system and raises oil temperature, because 25% to 35% more heat is rejected to the engine coolant and, consequently, to the engine oil as the exhaust gas is cooled before it is returned to the engine intake manifold.
Redesigned exhaust systems
Exhaust gas recirculation to control emissions required significant redesign of engine intake systems, because exhaust gas is hot — much hotter than normal intake air even after it has been compressed by a turbocharger. The act of compressing intake air and running it through a turbocharger heated by raw exhaust gas raise the intake temperature downstream from the turbocharger. Since diesel engines perform best with dry, dense, relatively cool intake air, they use a heat exchanger between the turbocharger and the intake manifold to extract some heat from the compressed air. A diesel engine charge-air cooler typically reduces intake temperature from about 400°F to 110°F. Although intake air can be cooled using a heat exchanger bathed in engine coolant, most manufacturers use an air-to-air heat exchanger mounted in combination with the cooling system radiator.
However, exhaust gas recirculation requires heat to be extracted from a portion of the exhaust stream as well as from intake air. This is a bigger problem, because exhaust gas leaves the combustion chamber at 1200° F or higher and needs to be cooled to about 250° F. For this task, engine builders have hit upon using a stainless steel heat exchanger filled with engine coolant. Herein lies a complication, because the recirculated exhaust gas cannot be cooled too much or acids in the gas condense, corroding the aluminum intake manifold. An engine that ingests such corrosion products would suffer abrasive wear inside the cylinder liner, mostly on the piston rings.
In addition, fleet managers have worried about higher acidity in engine oil put there by the exhaust gas component of the cylinder charge and increased soot in the oil as a result of lower combustion temperature. Both situations are feared to cause higher maintenance costs.
Another concern has been turbocharger performance and life, because exhaust gas recirculation requires higher turbocharger boost pressure. The higher pressure is required to force a larger total air mass into the engine along with the exhaust gas if the engine is to burn the same quantity of fuel and retain the same power as an engine without exhaust gas recirculation.
Trucking interests have expressed economic concerns about the new engines as well as technical concerns. Changing the combustion characteristics of an engine obviously changes its fuel economy performance. Manufacturers predicted drop in fuel economy of 3% to 5%, enough to cause plenty of pain at a time when fuel prices were high and motor carrier freight volume was soft. Also, the new technology and the testing to back it up are not free. Predictions for increased engine prices and life cycle costs ranged from $10,000 to $15,000 per engine.
Although the total fleet population still is fairly low, results for the new engines have been somewhat better than predicted. Of the fleets contacted by Refrigerated Transporter, C R England Inc in Salt Lake City has the largest group of post-October engines. In a fleet of 2,600 tractors, England has 800 of the new engines in service — 750 from Detroit Diesel and 50 from Cummins. The majority of the new engines are 12.7-liter Detroit Diesel Series 60s rated at 430 horsepower for the company driver fleet. A small group of engines are 14-liter Detroits rated at 500 hp for the leased fleet. All these engines are installed in Freightliner tractors. The company also has 50 Volvo tractors equipped with Cummins ISX engines rated at 500 hp. Those tractors have been in service only since May 2003 and are leased to independent contractors.
The company doesn't have much data about those tractors, because they are operated by contractors who do not always report their operating costs to the company. However, C R England has heard that the Cummins engines are providing slightly better fuel economy than the Detroits, says Todd England, vice-president of maintenance. In general, fuel economy of the new engines has decreased by 0.2 mile per gallon across the board, he says.
Slightly elevated soot levels
Also, as expected, oil analysis is showing slightly elevated soot levels in the engine oil. However, C R England's lubricant supplier, Chevron, has not recommended any change to the oil change interval. The oil companies have done a good job with their formulations to keep problems from happening, England says.
The 12.7-liter engines have been basically trouble-free and mechanically reliable, he says. Shortly after delivery, some software problems cropped up with the 14-liter engines. They were prone to stumbling under acceleration, and the resultant lack of constant power generated some comments from drivers. The problem did not occur with all engines — only 20 to 30 of the total, but the reprogramming performed by Detroit Diesel did result in a lot of downtime, England says.
The biggest problem with tractors equipped with the new engines has not been engine related at all. C R England equips its tractors with alternators from Delco. In an apparent attempt to forestall problems from higher temperature inside the engine compartment, Delco modified their product and used solderless connections in some places. Those solderless joints had a tendency to vibrate loose, England says. He reports that Delco has been quick to replace the failed components with alternators built to the previous standard.
Engines meet expectations
In Lincoln, Nebraska, Pat Donohue, director of maintenance for Acklie Maintenance System, the maintenance arm of Shaffer Trucking and Crete Carrier Corporation, says the 300 Detroit Diesel 12.7-liter Series 60 engines in service have done exactly what the vendor told AMS to expect. The engines have performed reliably, but with 3% to 5% degradation in fuel economy. The oldest engines in the Acklie companies have logged only 80,000 miles, so no full assessment of durability is possible.
Donohue says that the Acklie companies experienced the same alternator problems reported by C R England. However, if no more major problems show up, the company will resume buying tractors at its usual rate. That will amount to 1,200 to 1,500 tractors per year. “With a fleet this large, we have to follow our normal trade pattern, or we could possibly disrupt the economy of the company,” he says.
The timing of delivery has affected the results seen by some purchasers of the new engines. Central Refrigerated Service, located about a mile down the road from C R England in Salt Lake City, received the first 35 of its total of 50 Detroit Series 60 engines in June 2003. The engines have logged between 30,000 and 70,000 miles. The 12.7-liter engines are rated at 430 hp, and another group of 14-liter engines are rated at 435 hp.
Late start helps
“We got our engines after the reprogramming campaign was already complete,” says Mark Hadley, director of maintenance at Central. “We heard all the stories about engine control problems, but we have not experienced any. We also heard about the alternator problems, but we use alternators from Leece-Neville instead of Delco, so we missed that situation as well. We seem to have received our engines at the top of the learning curve. Really, we're glad to have got in the game late.”
Central has not been able to avoid all the growing pains that come with adopting new technology. Some Central drivers have experienced an annoying loss of power when the engines heat up in high ambient conditions. When the engines reach a certain temperature, the engine controls automatically derate the horsepower, dropping the maximum road speed to 35 to 40 mph until the engine cools back down, Hadley says. Most of the problems occurred around Phoenix or when climbing hills in the Nevada desert.
Shortly after the problem appeared, Detroit Diesel put out a letter to engine users explaining the situation and letting drivers know that the engines would return to full power as soon as the temperature dropped. Now, Central drivers know to move to the side of the road when engine power drops so that the engine can cool down, Hadley says.
Fuel economy has not been a major issue at Central Refrigerated. Some trucks report economy as low as 5.4 mpg, and others have run as high as 6.5 mpg. The average for the new engines seems to be about 6.1 mpg, down roughly the 0.3 that Detroit Diesel predicted. The fuel economy average for the entire fleet is 6.4 mpg, Hadley says. He also says that fuel economy is highly dependent on driver behavior. For instance, in one recent reporting period, a driver had 69% idle time with a resultant 5.4 mpg for fuel mileage. A different driver idled the engine only 28% and posted a fuel economy average of 6.4 mpg.
No maintenance interval changes
Maintenance intervals at Central have not changed. Oil analysis has shown no change in oil performance, Hadley says. “We use Exxon XD3 Extra motor oil, and we plan no change in our regularly scheduled 30,000-mile oil change interval,” he says.
Apparently Edwards Bros Inc in Idaho Falls, Idaho, got its Detroit Diesel engines early in the game, because its tractors have suffered from low fuel economy and repetitive engine reprogramming, says Morgan Edwards, president of the truckload carrier with 200 trucks. The bugs are working out, but slowly, he says. At first, fuel economy was down almost a full mile-per-gallon from the fleet average, but now has climbed back close to the previous average. In the process, Detroit Diesel has changed the engine software three times increasing fuel economy from 5.8 mpg to 6.2 mpg.
Part of the fuel economy loss may be caused by the higher operating temperature of the new engines. The trucks cool alright, even in 100°F ambients, Edwards says. However, coolant temperature rises quickly when the truck accelerates, causing the cooling fan to come on. The more the fan runs, the lower the fuel mileage always will be, he says.
Edwards Bros also experienced some of the mechanical problems that fleet managers have worried about. “We had one engine failure at 3,000 miles,” Edwards says. “To their credit, Detroit Diesel replaced the engine promptly and provided a replacement tractor while the work was being done.”
The Detroit engines at Edwards Bros have logged an average of 80,000 miles with no noticeable change in oil performance. Oil analysis by Lubrizol has showed no potential problems.
Exhaust system problems
In addition to its Detroit engines, Edwards Bros has one Caterpillar C13 engine that uses the new ACERT technology. That particular engine has not fared as well as the Detroits, Edwards says, because the exhaust system keeps breaking. So far, the engine runs about three weeks before a crack shows up in the exhaust manifold. “Its not hard to replace, but the part is never available locally,” he says. “Cat has to fly out a new part, and it usually takes six to seven days to get it. Obviously, they are still working on the design because the manifold looks different every time we get a new one.”
Some fleets have yet to adopt the new technology completely. For instance, Conley Transport in Searcy, Arkansas, runs a Cat engine that it describes as a bridge between pre-October 2002 designs and full ACERT technology. The company has ordered 10 new Kenworth T600s with the Caterpillar C15 engines. Bridge engines already in the fleet are averaging about 0.2 mpg less than older engines, a significant change for a fleet that puts more than 200,000 miles a year on tractors, says Jim Hayes, service manager.
Hayes says that the new engines run a little warmer than previous engines, but so far no problems have appeared. He also says that Caterpillar has been extremely responsive to Conley comments. Factory support from Cat was the primary reason for selecting the C15 engines, he says. In addition, Conley has negotiated an extended warranty for the new engines — three years or 750,000 miles compared to the standard warranty of two years or 500,000 miles.
Some fleets stubbornly refuse to switch to the new engines, waiting as long as possible to ensure that all development problems have been solved. Arctic Express in Hilliard, Ohio, falls into this category. The company has 420 tractors powered by Cummins N14 engines rated at 460 hp. The oldest engines in the fleet have logged about 400,000 miles and are performing fine, says Denver Fannin, maintenance director. “We anticipated replacing bearings in the engines at about 400,000 miles, but Cummins said we would be wasting our money,” he says. “Factory advice is to run the engines at least 750,000 miles before considering any internal work. We have also been advised to give up oil analysis as an unnecessary expense.”
© 2013 Penton Media Inc.
Acceptable Use Policy blog comments powered by Disqus