Jump to content
SAU Community

Recommended Posts

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.

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

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.

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

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

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.

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

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • More assembly going on, with all sorts of "bolt right on bro" scenarios going on here. Smartly, PTV clearance was checked. And I say smartly because it turns out that the intake was 0.009" from piston meeting valve. This is 0.23mm. This is very not okay. A fast meeting was facilitated between engine builder in Australia and engine builder in the USA which was actually incredibly helpful and constructive actually, various ideas thrown around to get around this issue including: 1) Retard the cam timing which would have brought the exhaust valve closer to meeting piston (it was 0.065") which was uncomfortably close to begin with, and change the cam profile making it 'laggier' 2) Much larger head gaskets which would reduce compression, but half the point of this was to increase compression. 3) New set of pistons ($$$$$$$$$$$$$$$$$) 4) All of the above 5) Get ghetto The concept is you get sticky sandpaper and stick it back to a valve, slightly larger than the valve you/I'm using, like say from a LS3/rectangle port head. You now have a very super advanced flycutting tool to modify your pistons in your block. Then you install it in your head, and attach the other end of the head to a drill. Then you just replicate your valve smashing into a piston with your spinning drill.   This is the result. Repeat many times. It is strongly recommended you have some kind of fixed stop when doing this for extremely obvious reasons because if you press too hard then you're well into apocalyptic repercussion land. The minimum clearance on the intake valve is now 0.075" this is still in the "Too close to be really comfortable" and into "It should be fine" land. Supposedly in the real world the clearances will be slightly bigger. Guess this is what happens when people push envelopes for N/A engines instead of adding boost! Time to move onto the new, upgraded, higher ratio roller rockers from Yellaterra, all tapped and threaded with a stronger bolt for better stability. Very nice. Lets see how they fit. For f**ks sake. Time to bring the grinder out for these aftermarket, machined and CNC'd heads. Looks like the new, beefier rocker from YellaTerra has gone from Bolt on part to "Bolt on part". Well, lets see how this bolt on crank scraper and windage tray goes then, shall we? There actually is more clearance than they specify for this thing, but seeing it all move as you check it is terrifying when you see it all so very very very very nearly hit things. But after all, this is what the item is designed to do after all and actually did bolt on perfectly and have enough clearance to everything and some very clear and direct instructions. So +1 to Improved Racing I suppose. As above with the windage tray on. Photo of breaker bar wonkiness for added lols. Next up: Oil pump/front cover/water pump/sump and then it's time to actually install the heads, pushrods, head bolts, valve cover gaskets and such is all there and ready to go. (except the oil pump bolts which were previously longer for more clearance with the previously perfectly installed double row timing chain). There's definitely a sense that someone other than us has been here before and done everything perfectly, or at least considered it and came up with working solutions. Perhaps the previous cam was 6deg advanced to avoid PTV issues with the milled stock heads? In any case when I attempt to sell this stuff the buyers are going to be very directly informed.
    • my catch can is pretty easy to empty but it overflows due to the blowby/crank case pressure etc. max I have drained is ~600ml even with a ~2.3L capacity. So it is not just about having to drain it out its the mess it makes down the firewall and under the car and rear passenger tyre from the overflow oil being blasted by screamer + air in general. Ending up on the ground cleaning the oil up and having oil on your arms when everyone else can chill and watch the other sessions gets old fast
    • Yeah - the secret learned a long time ago is that the RB likes to belch oil out the covers, and/or starve the pump because it drowns the head in oil, because the upflow of crankcase gases from piston blowby comes up through the oil drain holes in the block and prevents the oil from flowing back down. The external vents from sump are about creating an alternative path/much more XS area for gas flow to decrease the gas velocity up through the oil drains and allow the oil to get back down. So, it's not about pressure at all. It is about flows - gas up and oil down - or when it's not working, gas up and oil not going where it is supposed to after it arrives at the top, except out through the cam cover vents. And regardless of whether the catch can is vented to air or vented to the turbo inlet, it must still be vented because a sealed system would blow out the crank seals, or something equally bad.
    • I just used a can that's easy to empty after every session and pour it back into the fill hole. Takes about 40 seconds when you have 40 minutes between runs :p I don't see how changing any catch can stuff will reduce pressure if the system is sealed. And if it's vented - Does it matter where it's vented with regards to overall pressure?
    • Welp, too late already committed to the cam cover breathers to be welded on. I did think about adding a catch can in line with the drivers side sump breather as a phase 2 along with a drain to the sump on the original catch can but with an inline ball valve so I can have it closed if needed.    Likely a single breather would have been enough but I think I’m overcompensating to hopefully not have to empty my catch can and clean up oil over flow every session.    out of curiosity has anyone actually measured crank case pressure before and after various mods? I’m considering adding a sensor for science 
×
×
  • Create New...