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Oct 26, 2021

Fan Clutch, Clutch Fan, Water Pump Pulleys, and Water Pumps

Fan clutch, pulleys, and belts. Hayden 2650 is Z

Horsepower makes heat. Gasoline (ICE) engines are inefficient. The more power you make, the more heat you have to shed. That waste heat needs to be carried away by some medium, normally water/coolant in most gasoline engines. 

The OEM R32/R33/R34 fan clutch are part of the heritage parts program which means they are pretty expensive. The way it works is there is a metallic strip that is on the fan clutch that opens and closes an internal valve to control flow/ lockup of the clutch.  

OEM R32/R33/R34 GT-R fan clutch - 21082-RHR30   - About $400-$500

Hayden 2650 for Z, supposedly sounds like a jet! $~70

Dayco 115847 (only available in Australia. I emailed Dayco USA, they said they don't have it, nor will bring it to the US) ~$200

By about 180F the valve is in this position

Playing with the bi metallic strip and #clutchfan for an #rb26 today. The #rb clutch fan isn't serviceable like some cars. I have a few used ones, and honestly it's hard to tell if anything is happening when spinning by hand off the car. I can see the actuation of the valve, but it needs centrifugal force to work. The valve starts to move fairly quickly then is fully open by about 180 F surface temp. #gtrtech

This was room temperature or about 74F

OEM fan clutch on the left. Hayden 2650 on the right

OEM on the left, Hayden 2650 on the right. A couple mm height difference. 
Dayco 115847 on top OEM on the bottom
Dayco 115847 on left - OEM on the right


Is this what they mean, whey they say Only Fans ?

These are not the only fans you see on the RB26, but here are most of them. Along with the several styles of OEM, GK Tech also does an aftermarket fan.   Some people have broken the GK Tech fan, but I do believe its just because their engine is rocking. The material of the GK Tech fan is a little thinner, and not as forgiving as the OEM fan. The OEM will wear down/grind down. The GK Tech will break.  Overall its a sign you have a bad mount or something just isn't lined up right. 

R32 OEM Fan - 21060-55S01
R33 OEM Fan Blade -21060-75T01
Late R33/R34 OEM Fan Blade (96 R33, R34, AWC34)- 21060-5L300 

GK Tech RB fan.  Super easy to install, simply remove your factory fan (4 bolts) and install the new fan, it is a direct replacement clutch fan to suit RB, VG engines

- Direct replacement of the standard fan
- Pulls 40% more air than the factory RB fan

Water Pumps for RB Engines

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

Z1 overdrive 300ZX pulley on an RB26. 

Last year I was messing with some different fan clutches, and pulleys to see if I could get a nice handle on cooling, but I never really came to a final conclusion, or wrapped it up. So in the meanwhile, here are some of my random notes. 

OEM water pump pulley on the left, Z1 overdrive on the right

Some info from an Skylines Australia

Crank     Size         Belt Speed/Ratio 2000 3000 4000 6000 7000 8000 10000

RB26      140mm 4PK875   1:1.07       2140 3210 4280 6420 7490 8560 10700
RB30       114mm 4PK850    1:1.315     2630 3945 5260 7890 9205 10520 13150
VG30OD 100mm 4PK835   1:1.5        3000 4500 6000 9000 10500 12000 15000

OEM water pump pulley

Z1 has a 300ZX lightweight overdrive water pump pulley. I have installed that on one car, and I didn't really get enough data to know if it helped. 

Boostdoc EWP Electric Water Pump Kit for RB

Boostdoc EWP Electric Water Pump Kit for RB

RB25, RB26 RB30 EWP - electric water pump kit.

The kit comes complete with everything needed to mount and run the electric water pump.
This kit includes the Davies Craig control box (when option is selected) , which is a stand alone unit that does not require connecting to the engines ECU, allowing the control box complete control over the coolant temperature.
The control box is powered directly from the battery, allowing the unit to control the water pump and fans while the engine is switched off!!
Davies Craig have a preset control program in the unit, that testing has shown to work very well, however, should your engine package require a different coolant temperature strategy, the unit is configurable to target different setups.

Boostdoc EWP Electric Water Pump Kit for RB

Buy USA Legal R32, R33, and R34 Skylines at Toprank Importers!
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