The reduction of sulfur levels in ULSD means less lubricity, so circulating the fuel rapidly at high pressure keeps heat down. One of the electronic additions is known as the Cat ACERT System – Advanced Combustion Emissions Reduction Technology – involves the precise control of the combustion cycle by controlling incoming air and fuel, as well as exhaust aftertreatment. This advanced ECU was used to gain more engine control, as Caterpillar sought less smoke even upon cold start as emissions demands increased.
Cat recommends this if they are ever removed. Utilizing these electronic controls along with high-pressure oil brought about more precise engine control as well as more economy. The fuel system uses existing hydraulically actuated, electronically controlled unit injectors on medium-duty engines, and mechanically actuated, electronically controlled unit injectors on heavy-duty engines. The rods are not forged as previous versions were but are now powdered metal with a “cracked cap” design. The bore is 4.330? and the stroke is 5.000?. The compression ratio was 16.5:1. The cylinder head of the common-rail C7 is still three valves per cylinder but changed, as there is no oil rail cast into the cylinder head. The electronics were also more intense to offer further fuel control and electronic additions to the engine.
Other replacement parts are available for this engine in the aftermarket as well. The controller was upgraded to a 120 pin connection with much faster processing speeds. With all of these changes in the 3126, the power was almost double that of the 3116. In 1998, after one year, Caterpillar released the 3126B, basically the same engine configuration with improved electronics.