PRODUCT INNOVATIONS Case Study
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Navistar Launches First V8 Compacted Graphite Iron Block In order to improve the fuel econ-
omy of its diesel engines, Navistar, Warrenville, Ill., needed to fi nd a way to make a lighter engine block. For more than 10 years, the company had been researching and developing blocks using compacted graphite iron (CGI), which offers higher strength, stiffness and fatigue strength than gray iron. After successfully completing prototype and then production V6 engines in the last few years, Navistar launched the MaxxForce 7 in 2010, the company’s fi rst V8 series production engine produced in CGI, produced by Cifunsa, Coahuila, Mexico. In 2004, Navistar designed
and built a lightweight V6 en- gine with a CGI block, which resulted in an 80-lb. weight reduction compared to the baseline gray iron component. In 2007, the truck engine manufacturer began series production of its fi rst CGI block for the new MaxxForce 11 and 13 big bore engines. “When we combined all
our accumulated design and development experience with
technological advancements in CGI machining, that material became our logical choice for the 2010 MaxxForce 7 cylinder block,” said Robert Olszewski, manager of base engine design at Navi- star. “We were sold on CGI’s superior strength and fatigue life, which posi- tively infl uence engine performance and weight.” Cifunsa was challenged to meet
Navistar’s dimensional requirements for the thin walls and mechanical properties of the engine blocks, which measure 22.3 x 11.7 x 21.4 in. (566.6 x 296.6 x 544 mm) and weigh 291 lbs. (132 kg). Cifunsa worked with SinterCast, Stockholm, Sweden, which supplies process control technology for high volume CGI casting production. “Cifunsa has had a relationship with SinterCast since 1997,” said Cifunsa’s chief executive offi cer Alberto Pinones. “They give us the consistency and reliability on process control, as well as a consistent microstructure and lower scrap rates.” According to Olszews-
ki, CGI offers 75% higher strength, 45% higher stiffness and twice the fatigue strength of gray iron, so engine designers
are able to put more engine performance into a smaller package, which translates into reduced weight and
better fuel economy. Engine designers at Navistar designed
the MaxxForce 7 engine block specifi cally for CGI. “In our case, the block had to
deliver optimum total performance,” Olszewski said. “It had to have su- perior mechanical properties and be lightweight, easy to cast and machine, and affordable.” Special attention was given to the core
package, which met engine designers’ objectives and was casting- and machin- ing-friendly, according to Olszewski. “All those considerations enabled us to meet not only our functional objectives but also the cost target,” he said. CGI production is forecast to represent
2.7% of Cifunsa’s budgetary production this year, according to Pinones, who added that the metalcaster has plans to add new CGI projects in the near future. Pinones said Navistar is forecasting an
order of 250,000 blocks annually, with a chance of volumes to double, depend- ing on how well the product does in the
Navistar’s MaxxForce 7 is a V8 engine with a compacted graphite iron block for medium truck and bus applications.
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light- and medium-duty truck market.MC Visit
www.navistar.com for more information.
MODERN CASTING / July 2010
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