With the ACERT design the smaller CAT C7 models used an air inlet system with multiple traditional wastegated turbos to boost air intake flow and pressure. With the upgraded ECM the technology allows for a more precise control over the combustion cycle by monitoring the incoming air and fuel as well as the exhaust after treatment. Highlights of the ACERT technology include a closed crankcase breather and diesel particulate filter using CAT’s engineered regeneration technology. ACERT stands for “Advanced Combustion Emissions Reduction Technology”. The CAT C7 includes the ACERT technology which is an air/fuel management system to control NOx emissions regulations. The two options include a taller aluminum piston with a 1.811 wrist pin for 230 hp and higher versions and a shorter 1.52 diameter one piece steel piston for engine configurations below 210 hp. Horsepower is the determining factor when choosing the piston configuration in the CAT C7. There are also various sizes and configuration of the connecting rods depending on the piston used in the engine. The connecting rods in the Caterpillar C7 ACERT are not forged, liked the CAT 3126, but consist of powdered metal with a fractured cap design. The connecting rods and crankshaft share the same journal sizes but are slight different in terms of cast size and shape. When examining the crankshaft and rods the common differences between the CAT 3126 and the CAT C7 include smaller crankshaft counterweights to include the lighter weight piston design.
The oil pump and water pump are also larger to accommodate the need to lubricate/cool more moving parts. Some speculate that the reason for the wider gear teeth is so that the gear designs can’t be interchanged with older CAT 3126 and CAT 3116 versions. The front gear train is mostly the same except for the gears which have fewer teeth and a more robust design. The most noticeable difference between the CAT 3126 and CAT C7 is within the valve train. The cylinder heads are slightly different in the common rail design, still 3 valves per cylinder but there is no oil rail cast in the CAT C7 cylinder head. Other similarities between the CAT 3126 and CAT C7 include the same bore and stroke at 4.330 and 5.000 respectively. Using an advanced 120 pin connection the amount of information the computer was able to process was astronomical. The ECM is the same hardware as previous electronic engine generations just upgraded to handle more systems. The CAT C7 was really the first heavy duty diesel engine to offer a greatly expanded ECM or electronic computer module.
The electronic configuration was also more robust to offer better fuel management and electronic sensors into the engine. Using a staged fuel distribution ratio helps improve engine combustion which ultimately reduces emissions ouput. The HEUI injector allows for multiple injections at different metered rates. The engine configuration was the same as the 3126 but the fuel system changed using a new engineered style known as the HEUI injector. The CAT C7 shares many common configurations with the CAT 3126. Older CAT engines like the 3116 or 3126 were essentially grandfathered into the older tier rating requirements and did not need to be upgraded. The Caterpillar C7 was released in 2003, only months ahead of the Tier 4 ratings change, and replaced the popular 3126 model. The stricter Tier 4 emissions requirements went into effect January 1, 2004.
Caterpillar, needed to produce a new engine that was going to meet or exceed the Tier Ratings enacted by the EPA in 1994 to curb diesel engine emissions. The Caterpillar C7 was designed mostly out of necessity vs. mostly box tucks, tow trucks, daycabs, and straight trucks. The technical classification of a medium duty tuck is a single drive axel with a gross vehicle weight of 18,000-33,000 lbs. Paccar, Freightliner, Ford and GMC all purchased the engine in droves. All of the big players in the trucking industry hopped on board hoping the CAT C7 was going to live up to the hype. The engine was produced from 2003 to 2009 and was installed primarily in over the road medium duty class 8 trucks. However, sometimes things don’t go according to plan. The Caterpillar C7 Engine was supposed to be the “golden child” in Caterpillar diesel engine lineup one that combined raw horsepower with computer controlled clean emissions. At the turn of the century there was a lot of buzz around a new diesel engine being produced at Caterpillar, one that could meet the growing emissions requirements enacted by the EPA.
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