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Different Diameter Water Pump Pullys On Rb26

Shaun

By Shaun,
in Engines & Forced Induction

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Shaun Mentor

Shaun

Posted
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Hi,

Ive got a standard water pump pully on my rb26, but its a bit out of whack and it wobbles more than id like it to. Actually, its throwing off very small pieces of rubber from the belt, so i want to get rid of it.

My question is: If i replace the pully with a smaller diameter one (ive got an rb20 one), will it spin the water pump too fast and result in cavitation, therby reducing the cooling efficiency of the coolant?

The RB20 pully is 120mm in diameter and th RB26 one is 145mm in diameter.

A new RB26 water pump pully is $143 from nissan and im a tight arse, so im trying to save some coin. But if someone has a good second hand one, let me know!

Shaun.

Jmaac Proficient

Jmaac

Posted
Posted

Cavitation wont effect cooling effiiency, it'll just eat away your engine from the inside out. Wouldnt worry about this unless yout constantly pushing the motor at high rpm.

The only difference b/n them all i think are the impellor size & design (apart from the diff bolt ptrn)

Go RB30ET pump and elongate one of the holes? Ive got a pretty much new RB30et one if u want it

Shaun Mentor

Shaun

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I got one you can have if ya wan't, err somewhere.

Mate, if youve got a standard rb26/30 water pump pulley thats straight, ill grab it for sure. Let me know.

Thanks,

Shaun.

Shaun Mentor

Shaun

Posted
  • Author
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Cavitation wont effect cooling effiiency, it'll just eat away your engine from the inside out. Wouldnt worry about this unless yout constantly pushing the motor at high rpm.

The only difference b/n them all i think are the impellor size & design (apart from the diff bolt ptrn)

Go RB30ET pump and elongate one of the holes? Ive got a pretty much new RB30et one if u want it

Thanks but the water pump is a brand new N1 item i think. Its definately not stressed in regards to high rpm for lengthy periods. I was just concerned about the different sized pulleys, but i think your right; im probably splitting hairs. Ill just get rid of the wobbly one and put an rb26/30 item on.

Shaun

Scooby Veteran

Scooby

Posted
Posted
Cavitation wont effect cooling effiiency, it'll just eat away your engine from the inside out. Wouldnt worry about this unless yout constantly pushing the motor at high rpm.

The only difference b/n them all i think are the impellor size & design (apart from the diff bolt ptrn)

Go RB30ET pump and elongate one of the holes? Ive got a pretty much new RB30et one if u want it

cavitation does affect cooling efficiency as it means the coolant is not being circulated efficiently. sometimes in the extreme. it also creates bubbles, a big no for mr cooling system. i've seen a test rig with a perspex housing stuck onto the back of chev and ford water pumps driven by a washing machine motor. seeing the flow stall, and even reverse in some circumstances was a bit of a wake up call. serious mods to the impeller fixed it however.

cheers

Shaun Mentor

Shaun

Posted
  • Author
Posted
cavitation does affect cooling efficiency as it means the coolant is not being circulated efficiently. sometimes in the extreme. it also creates bubbles, a big no for mr cooling system. i've seen a test rig with a perspex housing stuck onto the back of chev and ford water pumps driven by a washing machine motor. seeing the flow stall, and even reverse in some circumstances was a bit of a wake up call. serious mods to the impeller fixed it however.

cheers

Yeah, i thought cavitation was a bad thing; hence my efforts to avoid it. Everyone actually says to go an oversized pulley if anything.

So just to confirm; the rb30 pulley is exactly the same?

Shaun.

Jmaac Proficient

Jmaac

Posted
Posted

Well it does decrease efficiency but not to the extent of what you think, its almost neglible as air is compressable. Your impellor design probably improved the flowrate somewhat

Sorry I wasnt sure about the pulley size on the Rb30et - I was just saying the impellor flows much more than the standard n/a item, probably suffice for the 25det

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