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Dec 26, 2008

RB26DETT Water Pump : N1 vs Stock

This is a photo comparison of the RB26 N1 water pump vs the stock water pump

The top bolt hole is the only issue with some blocks. If you have a N1 block , then you will not have to worry about this top elongated hole. If you have a stock block, you will need to see if this intrudes into the water jacket. Several people have installed a N1 water pump, and then had water weeping from this hole. Check it, fill it if you want to be sure. I have used epoxy and a straw to fill it in. You could weld it up if you want, although be careful with warping. 

These pictures show the differences in the impeller design between the standard water pump and the N1 water pump. The N1 pump has a backing plate that helps reduce high rpm cavitation.

update: These days- now 2019 we see some people say they have cooling issues with N1 water pumps on street cars. In Los Angeles, with 100F, 38C+ temperatures, AC on in traffic, we have never had any issues with N1 pumps on a street car.  We suspect that peoples problems are more related to them deleting the clutchfan, or other issues non related to the pump itself.

  aac aab
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According to Reimax, the OEM RB26dett water pump flows 160 l/min or 42 gallons per minute.  The N1 pump flows 192 l/min or 50 gallons per minute.  They say their High Flow Water pump flows 221 l/min or 58 gallons per minute. None of this is given with an rpm, so we will just have to assume that it is maximum flow. 


  • Higher coolant flow will ALWAYS result in higher heat transfer. Coolant cannot absorb heat after it reaches it's pressure corrected vapor point. Furthermore, coolant absorbs heat at a progressively slower rate as it approaches this point

More Radiator information

Stewart says more flow always equals more cooling.  However the faster you turn a water pump, you can create cavitation.  Cavitation is little air bubbles that are a lot more damaging than it sounds.  So an RPM number with the flow would have been nice to have.  At 42,000 yen for the pump, the price is about quadruple an OEM pump, and more than an N1 pump. 

"We have commercialized a prototype for race engine development. By brushing up the impeller shape, a high flow rate that exceeds not only the STD but also the N1 specifications is realized, and the cooling performance is improved by increasing the amount of circulating water in the radiator. It also leads to further improvement in cooling efficiency of sports radiators with increased capacity."

Outer diameterφ64φ70φ70
Discharge rate160ℓ/min192ℓ/min221ℓ/min

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