RB26 Lightweight Aluminum Pulley side effects

[nouveau_poor]

Hey all,

I've been taking a look at new accessory pulleys (water, PS, alternator) as part of something I might want to refresh as part of my R32 GTR engine build. I'm shooting for around 450-500 wheel hp for a street car and am planning on replacing the factory harmonic balancer with one from Fluidampr if that is relevant to my question. 

I've noticed that my accessory pulleys seem to have a little bit of surface wear (surface rust?) on the ribbing where the pulleys contact the belts. No issues or abnormalities with the pulley or vehicle performance but I figured if I'm going to have them removed as part of the engine build, why not replace them while they're easy to access.

Does anyone have experience with Greddy or KTS "lightweight" pulley kits? I'm not really expecting any performance improvement but rather just replacing for durability. I've heard that they are larger than factory and underdriven pulleys can cause unwanted side effects like low alternator voltage or reduced cooling at low rpm. Has anyone experienced this?

https://www.rhdjapan.com/trust-greddy-pulley-kit-bnr32.html

https://www.rhdjapan.com/kts-sc-pulley-pulley-system-3-pc-set-bnr32.html

They are the same price, possibly cheaper where I am, as OEM pulleys, but I wouldn't want to chance dead batteries or a hotter engine in traffic. Should I bother replacing my pulleys at all if the wear is normal? 

This isn't my pulley, but shows what I mean when I say "wear" 

 

[hardsteppa]

Have used an ebay-knockoff version, on an rb25. The powersteering pulley didn't fit, and the alternator pulley caused too much voltage loss. Water pump pulley fitted but needed washers behind otherwise it scrapes on the harmonic balancer, and needs a different sized belt with it obviously. Maybe a minor difference in responsiveness? Nothing huge.

[hardsteppa]

The quality/finish of them was good though btw, no issues at all in that regard, and no real cooling issues, although my car keeps very low even temps anyway, with bonnet venting.

[Duncan]

Greddy have 2 sizes, standard and underdriven. I know this because I spent a frustrating weekend fitting a second set to the race car to discover both the alternator and power steer pulleys were standard size not underdriven as I wanted.

Yes, the alternator charges about .1 volt lower. No impact I've seen. The PS underdriven PS pulley is 140mm across compared to 130mm across factory (7% underdriven) and the (hicas removed) steering is heavy but nice.

I've been running the original set for 15 years and they have lasted well. The annodising is long gone from the belt drive ribs but as they are ally that is no issue. Having said that, I have never heard of someone having trouble with the standard pulleys either.

All I can see for the standard size, aftermarket pulleys is they look a lot nicer.

[nouveau_poor]

Thanks for the insights. So it seems that if I fit standard size pulleys then I won't have the voltage or PS side effects.

Is the wear on the OEM pulleys anything worth concern or is there a way to gauge when one should replace them? I might just replace them with the aluminum and be done with it. 

Is there a part number for the greddy standard pulley kit? There seems to only be 1 size that is sold currently. 

Edit: Dug around and back in the day greddy made an 'oversized' kit which has since been discontinued. 

https://www.nengun.com/greddy/pulley-kit-oversized

This leads me to assume the one currently available is the standard size

Edited April 28, 2020 by nouveau_poor

[GTSBoy]

What is this wear of which you speak? I've never seen a multi-V pulley wear in a meaningful way.

[nouveau_poor]

Sorry for the crap quality but this is the the best angle I could get on them. Similar to the photo up top, the belt ribbing area seems to have gotten some of what appears to be surface rust over the last 30 years, like how Duncan was describing the anodizing coming off his Greddy's I presume. If it's as easy as just giving them a good clean while they're off then I might as well do that and save a few bucks. If not, well that's why I'm looking at potential replacements.

[Ben C34]

they are not worn

[GTSBoy]

If you clean the surface rust off, it will just come back. Just pretend that you never saw it. It's a car, not a sculpture.

[hardsteppa]

10 hours ago, Duncan said:

Yes, the alternator charges about .1 volt lower. 

mine dropped down to around 12.5-12.8v (from memory, was years ago now, but something like that) at idle. The pulley was massively lighter than the stock steel one but, too low V for a daily driver.

[nouveau_poor]

It won't be a daily driver, more a weekend/pleasure car but it seems like the consensus is that light pulleys will cause some form of drop, so it'd be wise to just leave them be if the OEM pulleys can keep on chugging.