Comparing Z31 turbo to RB25 turbo for RB20 upgrade.

[Gold Digger]

Searched, couldn't find anything unless I just didn't type it right.

I have heard of people using a Z31 turbo on the RB20's and was curious to know how they fared against a swapped RB25 turbo. I might need to change turbos and instead of getting the same thing, I thought I would look into getting a slightly bigger turbo, as I am only looking for 250-300whp.

I have heard the RB25 turbo will do this with ease.

How does the Z31 turbo do on the 20? Anyone done this one yet?

[Bronze MFP]

Check out some of the australian sites ( skylinesaustrailia.com skylinesdownunder.com ) I know i've seen some dyno sheets there. I think the z31 turbo was good for more power than the rb25, but both will be slower to spool, and i dont think you can expect much more than 275 - 300hp out of either. i may be wrong, so someone correct me if i am, im going off of old memory that has been ravaged by alcohol

[Sil240]

Yeah same here bad memory.From what I remember Z31 turbo is a straight T3 standard bearing. Think it has steel wheels as well. You will have to do some bending of the lines i believe. Don't think its water cooled either.

RB25 is a T28 turbine/T3 compressor ceramic wheels ball bearingCan't go over 14psi the wheels will shatter.Not sure if both or just the turbine.Straight bolt on. I have it on my motor

Just from looking at that info the 25 turbo will spool up faster, but the Z31 turbo will take you farther but start up slower.

[Bronze MFP]

rb25 turbine blades are ceramic, the compressor blades are some sort of high strenght plastic IIRC

i thought the z31 turbo was water cooled as well, anyone know for sure?

[SeVa-S13]

rb25 turbine blades are ceramic, the compressor blades are some sort of high strenght plastic IIRC

i thought the z31 turbo was water cooled as well, anyone know for sure?

84-87(?) are water-cooled I believe. After that they are T25's. The pre 84's had the same T3, but are oil "cooled" only I think.

Edit: And what you guys have said about both turbos is pretty accurate as far as I know. If it were a longterm choice, I'd probably get the Z31 because while it'll sacrifice some spool, it's actually made out of metal, rebuildable, and seeing as it's been around a lot longer there's more support/mods for it available.

[Gold Digger]

Thanks guys. This information is very good, and helpfull to. Keep it coming if anyone has any more info.

[Kansei240sx]

84-87 = T3 with a max efficiency around 15 psi on the VG30ET87.6 - 89 = T25 with raised compression on the VG30ET

Both are oil lubed and water cooled...

from 1981 - 83 they're t3 off the 280zx, and only oil lubed.

[Gold Digger]

How about the fittings for the oil and coolant lines. Do the RB fittings and lines work or do they need to be swapped or modified?

[Kansei240sx]

If i remember correctly you can bend them a bit and the banjo fittings should line up.

[RB20DETodd]

They are turds save up for a real turbo, and save your self the bloody nuckles

[themadscientist]

They are turds save up for a real turbo, and save your self the bloody nuckles

THat's enough

[RB20DETodd]

THat's enough

SWEEEt then i say throw on a rb25 turbo it will be awesome prolly wont notice a difference

[themadscientist]

You know what I mean Todd, smartass

[RB20DETodd]

You know what I mean Todd, smartass

[themadscientist]

hehe Keep it up and I will play no jazz flute for you.

[DJButton]

Haha Todd... I would take a Z31 T3 over an RB25 turbo any day... but sadly as someone else mentioned *cough cough* I personally wouldn't bother.

[DriftingisLame]

My roommates car made 205 hp 215 tq @ 12 psi on his rb20 turbo, then 258 hp 259 tq @16 psi on his rb25 turbo... but yeah thats not a noticable difference

Maybe the larger z31 turbo at 1 bar would make the same hp and be safer than spinning that ceramic wheel at the unsafe boost he was running.

Sounds like a worthwhile upgrade to me if that meets your goals and budget.. Me, I'm looking for 300 *safe* hp with a turbo that fits on the stock mani and DP (around $600)... Anyone have any suggestions?

http://cheapturbo.stores.yahoo.net/gat3su.html

That looks like a pretty comparable turbo to the z31, No?

[themadscientist]

A healthy VG30ET turbo should support that, The R25 one should too but I can't vouch for how long.

[DriftingisLame]

You really think I could hit 300 with a z31 turbo on an rb20?

How much boost would I have to push?

[themadscientist]

It was a popular swap for RB20s back in the day. I try not to push Nissan turbos past 14 or so PSI. I would ask the guys in the Z forum as the donor car is the Z. Some Z31 owner over there is bound to have explored the limitations of the stock turbo.

[DriftingisLame]

Well, I'd rather keep the turbo safe and reliable.. If its kinda sketchy pushing it past 14 psi, then 300 seems like quite a stretch.

Then again, the turbo would be dirt cheap.. and if I popped it, and rebuilt it, I'd probably still spend less than a new garrett! lol.

[themadscientist]

If my RB20 turbo will do 250ps and my buddies RB25 turbo will do 300ps then a rugged old-school VG31 turbo should do ya. Nice new moderately-sized turbos are so cheap these days though it's hard to argue for junkyard rescues.

[DriftingisLame]

Whats your idea of "so cheap"? The cheapest I'm seeing garretts for nowadays is about $650. Anything less than a name brand like garrett/turbonetics, or the bling brands (trust/HKS), basically just scares me..

$100 on a junkyard turbo, and $300-$400 on a rebuild after it blows dont seem like to bad of a plan to me..

I think I was sitting on about 230 hp @ 12psi before my cams/gears, on my stock turbo.. Maybe with a decent tune, and 15/16 lbs I could reach my goal..

Thanks for the info!

[RB20DETodd]

I can vouch for the rb25 turbo being a turd cause i had one, just putting in my 2 cents. And C33LaurelRacer you are in jdm land i never thought you would ask about this swap, just throw a gt2535, -40, gt-rs and call it a day.

[Bronze MFP]

HKS GT-RS for teh win!

FYI HKS turbos are made by garrett and Trust are made by Mitsubishi, so you can usualy find a comparable, lower price turbo by the manufacturer.

[Carl H]

if anything get the z31 turbo and have the rb20's exhaust housing machined out to accept the larger wheel...that way you get 'better' spool out of the turbo.

[Bronze MFP]

might work, might not...http://www.nissanperformancemag.com/april06/nerds/

[foCk]

with the z turbo you need a new downpipe made up, the rb25 turbo is a direct swap and (according to skylinesdownunder.com) can be run up to 16psi

http://www.project32.net/tutorials.php
Modified by foCk at 12:46 PM 1/27/2007