Navistar’s MaxxForce 7 pre-empts Ford’s Scorpion
By: John Mortimer, Friday, June 26, 2009, AutomotiveWorld.com
Navistar International, in announcing its ‘all new’ MaxxForce 7, 6.4-litre V8 diesel engine four months ahead of SOP (start of production), has pre-empted the launch by Ford, its formerly much-prized and former largest customer, of Scorpion, its 6.7-litre V8 replacement diesel for F450 trucks. Navistar is now effectively a Ford competitor.
Further, Navistar claims the MaxxForce 7, which is destined for Class 4-5 trucks and smaller school and community buses, incorporates ’advanced design elements and components’ from its heaviest-duty MaxxForce 11 and 13 truck engines being built under licence from MAN in Germany. These include its high-pressure (1,900bar) common rail fuel system, compact graphite iron (CGI) cylinder block, and two-stage turbocharging.
In unveiling the new engine, Navistar asks, rhetorically: “How can MaxxForce deliver outstanding fuel efficiency, emissions control without SCR, quiet operation and maximum durability?” Navistar attributes those virtues in part to CGI, saying: “This incredibly strong platform handles the highest fuel pressures that deliver the best fuel combustion and damp NVH (noise, vibration and harshness).” Adopting CGI has let Navistar optimise engine block weight and stiffness, though with added machining challenges.
But most diesel engineers claim that CGI by itself cannot improve fuel economy. In complete vehicles, there are more significant factors affecting emissions and fuel economy than switching from grey iron to more expensive CGI. That Navistar can certify MaxxForce 7 to meet EPA 2010 standards without SCR is unconnected with CGI.
Indeed, Ford also will use CGI blocks for its Scorpion V8 diesels to be made in Chihuahua, Mexico. The Scorpion is likely to be a more successful engine than the outgoing 6.4-litre Navistar PowerStroke unit in F450 pick-ups, as many design features have been optimised from the outset. Time will tell if it outperforms MaxxForce 7. On 31 July 2009, Navistar will shutter its Indianapolis engine plant and Indianapolis Casting Corporation (ICC) foundry, heralding the end of the contract to supply Ford in 2010. The plants produced up to 350,000 PowerStroke engines a year for Ford.
Now a new 300,000 square feet (28,000sq m) facility in Huntsville, Alabama that Navistar dedicated on 24 September 2008, will build MaxxForce 7 engines for trucks and buses.
Navistar cannot reverse ICC’s closure, so now must outsource the CGI blocks that have required new tooling to be cut. Come October, close to SOP, Navistar will unveil its parts suppliers, including that for CGI blocks. It could be Brazil’s Tupy, a vendor to MAN and to Navistar’s Brazilian subsidiary MWM.
The outgoing PowerStroke, with Continental fuel injection and BorgWarner sequential turbochargers, develops 350bhp (261kW) at 3,000rpm and 650lb-ft (884Nm) torque at 2,000rpm. Surprisingly, MaxxForce 7 is being rated initially at a maximum of only 300bhp (224kW) with 660lb-ft (898Nm) maximum torque. A 4.8 litre V6 derivative could follow to replace Navistar’s current 4.5 litre V6, but that engine has never fulfilled its promise in market acceptance terms.
Navistar challenges competing diesels in one area: advanced exhaust gas recirculation (EGR). A company survey has claimed most ‘informed truck customers’ prefer EGR to SCR for EPA 2010 compliance, although the issue is still the subject of an increasingly fierce debate among the leading North American truck OEMs. Navistar selects extreme in-cylinder NOx control measures, notably high EGR and retarded timing for MaxxForce 7, rather than SCR, so that potential customers’ fleets will not require added urea handling. However, a downside of EGR is an inevitable fuel economy penalty (see SCR versus EGR: the ‘debate’ escalates, published by AutomotiveWorld.com, 12 June 2009).
If, as seems certain, Navistar initiated MaxxForce 7 development before its spat with Ford escalated, it must have originally been seen as the new generation PowerStroke for Ford? As the battles with Ford became bitter, why did Navistar not axe MaxxForce 7? Was it that without Ford’s custom, a ‘new’ engine was essential to help stay alive?
Only one outside customer, Capacity of Texas, has so far chosen MaxxForce 7. Navistar will need many more to fill Huntsville’s lines.
The opinions expressed here are those of the author and do not necessarily reflect the positions of Automotive World Ltd.
Published on Friday, June 26, 2009
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