We launched the Supertec Racing Spline Drive RB26 oil pump gear kit in mid 2014 after a long R&D process. A new product that not only improves the over all strength of the pump gears as upgrades for the N1 and OEM pumps, but also changes in the way in which the gears engage with the crank. As per Toyota’s 2JZ GTE engine we found the best solution would be to incorporate a spline engagement which would totally eliminate the underpinnings of Nissans troublesome flat drive design.
The RB26 is a legendary engine in its own right and an iconic powerhouse amongst enthusiasts and tuners all over the world. One aspect of the engine that is considered its Achilles heel is certainly the oil pump. Over the years there have been reports of numerous failures where the inner and sometimes the outer gears have broken during hard use of the engine be it on the road or on track or drag. Contrary to popular belief the wider nose crank which was introduced on BNR32 models from Feb 93 onwards and standard on BCNR33 and BNR34 models, while reducing the possibility to a degree did not eliminate the issue fully.
Various attempts were made over the years to address the issues, Tomei, Jun, Greddy, HKS and Reimax (Japan) and Nitto (Australia) all made uprated pumps with bigger diameter and thicker pump gears to increase flow and overall strength which is much needed on track or on a high revving RB26 to ensure the engine has ample oil supply and durability. However they are based on the flat drive design.
Nissans own OEM pump (81mm outer pump gear) as supplied from the factory along with the N1 pump (77mm) utilise gears made from sintered metal which is weaker than billet steel equivalents. The Nismo pump is a steel version of the N1 with same flow and pressure. Reimax offers a billet steel gear upgrade kit for both OEM and N1 pumps, but upon testing we found clearances to be greater than stock N1, OEM and Nismo pumps, which in our view would increase potential failure.
Tomei Oil pump is considered the mother of all RB26 oil pumps. Picture below showing Tomei gears vs Supertec Spline Drive gears. Spline Drive with a Spline collar fitted to the crank provides a more efficient drive of the inner gear due to multiple splines that provide equal grip compared to a 3/16″ contact as per the OEM Nissan flat drive.
There is absolutely no cause for concern regarding clearances of the spline engagement to the collar. Much has been said by some that this concept does not work and there must be ample clearance like on the flat drive setup which is true as, the RB26 crank is long and has some flex. However this is why we undertook rigorous R&D and having sold several hundred kits since we started production and zero spline gear failure should be a testament. An independent review by a customer: https://youtu.be/5o4B6vR0lmU
The design of pump used on a RB engine is where the inner gear runs at the engine speed – at high RPMs they tend to suffer from cavitation.
Picture left shows the inner gear from an RB Tomei pump which after approx 5000 miles of road and track use appears to have become out of round by approx 0.5mm. This would be enough to cause binding of the gears and potential for failure.
So what causes this? Cavitation occurs at higher rpms and the forces and stress placed on the gears have known to break the inner gears most commonly on N1 and OEM pumps but to a lesser extent also on the heavy duty Jun based and Tomei pumps. Spline drive will not eliminate cavitation but would offer much improved strength due to reasons mentioned above.
Failure does not result from cavitation only, but also when using launch control or frequently hitting the rev limiter. The back and forth movement coupled with shock loads are enough to shatter the gears.
What is involved in fitting the gear kit? The process is relatively straight forward on the pump side, N1, Nismo, OEM (3 pc kit consisting of inner and outer gear and collar) Jun and Greddy and Nitto pump kits (2 pc kit consisting of inner gear and collar only using existing billet outer gear). The Tomei kit which we have recently revised is now supplied with a replacement billet alloy backing plate and collar only this removes the need to machine the original backing plate, you simply remove the inner most gear while the collar will slot into the middle splined gear.
Fitting the collar will require the crank to be machined and the splined collar to be press fitted, for additional reliability it is recommended that grub screws are fitted.