High-pressure common-rail would remain, but in order to help meet the 2007 PM standard of 0.1 g/bhp-hr, a diesel particulate filter (DPF) was brought into the equation, along with a variable geometry turbocharger, the Holset HE431VE. The system could build injection pressure in excess of 29,000 psi, and its quick-reacting, solenoid-activated injectors could carry out multiple injection events per combustion cycle-ideal for quelling engine noise, lowering emissions, and making more than adequate horsepower and torque.Īs the noose tightened around diesel emissions, Cummins added a host of new technologies to the ISC in 2007. With EPA regulations calling for a 90-percent reduction in particulate matter (PM) output by 2007, Cummins (like many manufacturers) knew the most effective way to achieve it was through the use of a high-pressure common-rail. While engines utilizing the original CAPS system weren’t phased out completely until 2005, beginning in 2003 the ISC was equipped with high-pressure common-rail injection. Once again, if you’re familiar with the ISC’s little cousin-which in this case is the ’03-’07 5.9L Cummins 24-valve common-rail engine-then you know where the story was headed in 2003. The CAPS pump is supplied low-pressure fuel via a lift pump. The pump is capable of producing injection pressure as high as 1,200 bar (roughly 17,400 psi), which it sends to the injectors. The CAPS system, which was patented by Cummins, is based around the use of a computer-controlled, distributor-style injection pump with individual injection lines spanning from the pump to each injector. Precise control over fuel injection events, and in particular being able to control them independently of engine speed, is a major part of meeting those standards, and the Cummins Accumulator Pump System (CAPS) allowed Cummins to do it. Just as with any on-highway diesel engine produced around the turn of the century, the ISC Cummins was designed to meet the pending, more stringent emissions regulations that were on the horizon. Then there was the CAPS injection system… Unlike the 5.9L inline mills but just like the 6CT, the ISC retained the use of mid-stop, wet cylinder liners. And mirroring what had happened with the smaller, B-series variant, the Interact System (the IS in ISB and/or ISC), where full-authority and fully customizable electronics were on board, was implemented. The vertically mounted injectors were also centered directly above the piston to help improve combustion and low-end torque, and they were positioned over pistons that were treated to revised bowls to further optimize combustion. The ISC gained a 24-valve cylinder head for improved airflow which, ultimately, increased horsepower and torque. For starters, the ISC was treated to a stiffer block with integrated fluid lines rather than utilizing external, wear-prone hoses. The 6CT to ISC changeover took place during the same period and many of the same technologies were implemented.
If you’re familiar with the story of how Cummins replaced the 6BT 5.9L with the ISB 5.9L, the story between the 6CT and ISC 8.3L will definitely rhyme. It’s an engine that is much-celebrated in the motorhome segment, and one that continues to power countless RV’s down the road today. Here, we’re highlighting the ISC 8.3L Cummins, an engine that replaced the mechanical 6CT with an electronically controlled injection system and cleaner emissions. Used in everything from school buses to excavators (known as the QSC 8.3L in off-highway applications), and gen-sets to dump trucks to motorhomes, the 8.3L Cummins continues to enjoy a reputation for reliability, longevity, sufficient power, and ease of serviceability. What began as the 6CT 8.3L and then transformed into the electronically controlled, CAPS-fueled ISC 8.3L, followed by the high-pressure common-rail (HPCR) ISC 8.3L yielded three decades of one of the most durable medium-duty diesel power plants ever produced. In the long and storied history of Cummins engine lineage, it doesn’t get much more legendary than the 8.3L platform.
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