Project STurdteen: Building the SR20DET Engine

      A connecting rod experiences a high amount of compressive and inertial loads, which distorts and ovalizes the connecting rod’s big end bore.  This distortion and ovalization causes the connecting rod bolt to undergo bending, tensile, and shear stresses making the connecting rod bolt among the most highly stressed fasteners in an engine.  Due to the high levels of stress, K1 connecting rods are equipped with ARP 2000 connecting rod bolts for their high tensile strength and excellent notch toughness.  Notch toughness is a material’s ability to resist loads and absorb energy in the presence of a surface imperfection such as a crack or the circumferential, V-shaped notch of a bolt’s threads

Since SR20’s are notoriously hard on bearings, particularly rod bearings we used King’s tough XP bearings.  The XP bearing is a tri-metal type bearing.  It has a steel backing with a lead, copper, tin intermediate layer.  The intermediate layer has a high copper content which gives it outstanding load capacity.  The intermediate layer is etched using the secure bond process which helps to assure adhesion to the pMax Black overlay.  The overlay is fortified with copper nanoparticles which further increase load-bearing capacity while reducing friction and providing improved wear.

The main bearings feature Kings U-Groove technology with 90 degree walls which give more bearing surface area. The oil feed holes are modified versions of Kings ElliptiX oil feed hold design.  The grooves are lengthened to help improve the oil feed which helps assure that the rod bearings have enough oil supply. On the 54c SR20’s Nissan uses multiple feed holes and grooved main saddles to do the same thing and these slots can perform a similar function without needing to modify the block.  King bearings are very tightly toleranced across the bearing face so the oil clearance is consistent across the crank journal.

The main bearings and the rod bearings, in particular, use King’s RadiaLock dimensioning to get the optimal crush clearance. This helps assure that the bearings will fit perfectly in their bore for good heat transfer and good resistance to spinning.  The bearings get clamped tightly in their bores without wear near their parting lines.  The bearings also use Kings Eccentrix dimensioning method which takes the oil wedge into account when designing in the bearing material thicknesses. The thickness is varied to help form a more stable and consistent hydrodynamic layer of pressurized oil on the bearings face even at high RPM.