This new crank shaft is constructed from the same 4340 chromoly high-tensile steel alloy billet and hardened/tempered for a target tensile range of at least 930-1080 MPa (135,000-157,000 psi), incorporating 0.40% of carbon, proven to provide the highest degree of tensile, compression, and sheering strengths. The 87.0mm stroke affords a major advantage; it can be dropped into an unmodified (i.e. unsleeved) block with no need for longer sleeves (that have to be notched to preserve the oil jets), as is the case with the 90mm stroke crank. In this Hi-Rev iteration of the crank, two key improvements were made: lowered weight and, most notably, optimized oil passages.
Some material was removed from counterweights of the crank in a fashion that would not significantly affect its strength, yet afford VERY significant weight savings. This makes the engine much quicker-revving, and makes the crank capable of spinning at approximately 10,000rpm while staying within its tensile design limit (counterweight /journal maximum travel speed is 6,300fpm, corresponding to 10,000rpm). Of course, many more provisions have to be made to actually spin the engine to the said revolutions, such as further, more significant, weight improvements in rods (Ti) and piston speeds. The weight of this new Hi-Rev crankshaft 37.5 lbs, compared to the factory Nissan crankshaft weight of 41.5 lbs, representing a significant weight saving of 4 lbs.
This revision of the crank design is a definite first in the VQ35DE realm. There has been a lot of discussion in the past years about cross-drilled crankshafts and high revolutions. Cross-drilled refers to the configuration of the oil passage network running through the crank. In this case, at the main bearings, the oil passage is drilled through the cross section of the crank at the main rod bearings “through-and-through” perpendicular to the centerline, connecting to the main oil passages running through the centerline of the crank at a 90 degree angle, which then feed the crank journals at the rod bearings. This configuration is the mainstay of OEM design since the beginnings of the modern internal combustion engine, is considerably cheaper to manufacture, and works well for street cars with reasonable RPM limits. However, at
very high engine revolutions this design has a flaw, as the oil entering the main crank journal has to overcome the centrifugal force that forces the oil outward, hence starving the downstream centerline passages and the rod bearing journals of oil.
Enter the Hi-Rev crankshaft. Instead of the perpendicular cross-drilled passages, the oil passages are drilled directly from the main crank journals to the rod crank journals, completely removing the centrifugal force effect of starving the centerline passage of oil at high revolutions, as the centerline is no longer the main supply line for the oiling of the rod bearings. In fact, there is no longer a true oil passage centerline running longitudinally through the crank. Instead, the passages are direct from each of the main journals to the rod journals. This design is the exclusive design used in true high-revving race cars, including Formula 1.
The Hi-Rev crankshaft is currently available in 87.0mm stroke variety, 90mm and 81.4mm (stock) stroke varieties.