Equipment World Digital Magazine
Issue link: http://read.dmtmag.com/i/894232
EquipmentWorld.com | November 2017 47 W ith the emergence of the Tier 4 Final era, most of the big changes in diesel en- gines have been on those above 75 horsepower. They required new emissions reduction systems using selective catalytic reduction (SCR) and diesel exhaust fl uid (DEF). But in most cases, engines below 75 horsepower hit their air quality targets by upgrades from mechanical to common rail fuel injection and electronic control. This technology has been featured in larger engines for more than a decade. It's proven, well-known and not nearly as expensive or as complex as SCR and DEF systems. "Electronic control paired to the high-pressure common rail fuel system allows for extremely precise control of the fuel-injection events several times throughout the combustion cycle in all op- erating conditions," says Rob Shailes, strategic business development manager for Kubota Engine America. "This methodology al- lows for the cleanest possible raw emissions from the engine prior to introduction into the engine aftertreatment device." DOCs and DPFs Many of the smaller engines also can, as a general rule, absorb and chemically convert contaminants in the exhaust using a diesel oxidation cata- lyst (DOC), rather than need- ing the larger diesel particulate fi lter (DPFs). More common on engines above 75 horsepower, DPFs require regular regeneration, or "regens" as they're sometimes called, to turn trapped soot par- ticles into ash. Some of the fi rst generation (Tier 3 and Tier 4 Interim) of these big engine DPFs required periodic cleaning to remove the ash, but manufacturers have tuned the performance of the engine so that today's DPFs last the life of the en- gine with no maintenance require- ments and perform the regens automatically and invisibly to the operator. DOCs are also zero-maintenance devices. But some smaller engines still use DPFs depending on the size constraints on the equipment, application requirements and how the OEM tunes other elements in the exhaust reduction system. maintenance | by Tom Jackson | TJackson@randallreilly.com For Tier 4 Final engines under 75 hp, smaller really is better Deutz TCD 3.6 events several times throughout the combustion cycle in all op- erating conditions," says Rob Shailes, strategic business development manager for Kubota Engine America. "This methodology al- lows for the cleanest possible raw emissions from the engine prior to introduction into the engine aftertreatment engines also can, as a general rule, absorb and chemically convert contaminants in the exhaust using a diesel oxidation cata- lyst (DOC), rather than need- ing the larger diesel particulate fi lter (DPFs). More common on engines above 75 horsepower, DPFs require regular regeneration, or "regens" as they're sometimes called, to turn trapped soot par- ticles into ash. Some of the fi rst generation (Tier 3 and Tier 4 Interim) of these big engine DPFs required periodic cleaning to remove the ash, but manufacturers have tuned the performance of the engine so that today's DPFs last the life of the en- Deutz TCD 3.6