RB20/25/26 N1 water pump
The N1 water pump is not technically an upgrade for people using OEM blocks. The pump has 6 blades instead of 8, as well as an anti cavitation plate on the impeller. The reason for using an N1 pump (which is ideally used with an N1 block, due to the different coolant jacket sizes) is more specifically beneficial for people involved in road racing, drag racing, etc... Anything that you consistently see high engine speeds. The OEM pumps cause a large pressure change in the coolant at high speed which results in cavitation.