RB25 turbo conversion on RB20?

[Cool Hand Luke]

What sort of power gains would i get just by putting an RB25 turbo on my 20? I have a good frontmount and exhaust, but it irritates me how the std turbo runs out of puff at high revs... I was also told that it could run safley at 16psi with the smaller engine, is that true?

EDIT: Or what other OE turbo would be good to use?

[lowlux]

either the vg30 or the rb25 turbs are good and cheap, but you might wanna look around for a hks turbo or something as there prettty cheap at the moment and would be alot better

[Guest 382 GZV - 4 Door R33]

Hey Luke...

pm Mick51 (may have seen him at the drags or QR). He has an R20 which he put a RB25 turbo onto. He'll be able to tell you how it goes and what sort of gains you should expect.

Steve

[rb20-calais]

i am also doing this conversion will report when it is done my findings

evan

[bbenny]

well im a little dissapointed. went out to buy myself an RB25 turbo today and SSS asked for $1,000! thats for a 2nd hand one too! i know i can get my RB20 turbo high-flowed for that price and that means steel wheels... does anyone have a cheap RB25 turbo out there for sale? and do you think it would be worth getting the std turbo highflowed? which would be better? i figure that the high flowed option would allow a higher boost setting as the wheels wont fall apart (but i might be sacraficing low down power as the steel wont spool up as quick) , but would it flow as much or less than the RB25 turbo?

[Cubes]

Its not really that the steel wheel wont spool up quicker the point is that for $1000 you won't be getting a ball bearing center. It will be a conventional old school plain bearing center that do lag like hell on a RB20 (4-4.5k rpm fulll boost)

I have looked in to different turbo options for the RB20DET. Really the only option that isn't laggy and is the perfect balance so to speak is the HKS GT2530. That will pull around 220rwkw on 1.1 bar approx. BUT you have to get the car above 5k to start pulling hard as the mid range sucks compared to a lot of S15 SR20's and RB25's.

This is why I'm spending money on a RB30DET.

$1000 - RB30E Short Motor Rebuild

$0900 - RB25DE Head

$0300 - Dump Pipe Mod

Then turbo etc... Personally for a turbo I will stick with a standard housing highflowed to around 500hp or so .. i.e GCG Stage 2 turbo. It looks stock and doesn't require fabrication of manifolds or external wastegates. Its all about looking stock if you are sent over the pits.

[Cool Hand Luke]

I just went for a drive in another 180 with an rb20, but with the 25 turbo. With the standard dump, crap cat and cheapish exhaust, ca18 fuel pump, and standard intercooler it was much faster and pulled noticably harder. Cant wait to get mine in, for the few hundred it costs to upgrade

[Roy]

Plain bearing turbos work fine, and arent always laggy. Granted ball bearing is the preference but dont assume plain bush (360 degre type) turbos are all laggy.

Plain bush turbos dont handle axial loads on their shafts as well as ball bearing type. Imagine a big compressor wheel, small turbine, the shaft assembly will not only want to rotate but also move back in its housing (turn your house fan on/off and see how the fan will move back due to the axial force.)

Now ball bearng turbos handle this a lot better then the old bush setup, meaning as well as having improved aerodynamics they are better able to run different/more varied turbine/compressor pairings. Manufactures have embraced the more expensive ball bearing turbos due to their increase in durability as well as repsonse.

So my thoughts are that like any re-built turbo, a plain bush type will only be as good as the guy bolting it together. Ultimatley i wouldnt be as concerned with boost response as i would durability.

Give a 360degree thrust bearing turbo the same compressor/turbine as a ball bearing core and i don think there would be a lot of difference in response. (say 500rpm) Now how long they last at 1.5bar is a completely different story.

[Cubes]

I havn't seen any plain bush bearing turbo that make full boost (1bar) at 3.5k on a RB20DET. On a R33 it is possible. Generally all highflowed plain bush turbo's look at 4000rpm if you aim for lower full boost you will be dissapointed.

It also depends on what power you are chasing with that turbo. If the plain bush only ends up making 170rwkw then it is possible that it will make full boost by 3.5k however if you are aiming for 200rwkw 4000rpm is a minimum.

The HKS GT2530 is a BB turbo and makes full boost (as on the car featured in Zoom) made full boost by 3700rpm (According to Tilbrooks). However it did make 220rwkw.

You are right Roy the response is difference is generally 500rpm. Which to me is a lot .

I had a VG30 BB Ceramic turbo on mine that made full boost by 4000rpm+ and OMG that was slow on the street.

You really had to go hard in to corners and launch hard to get it going.

It really depends on you driving style also.. I like to use lowish rev's if possible and not rev it out. If I rev first out to 4000rpm lightly then click second and nail it she will get up on boost reasonably quickly and go. With the VG30 terd I had to give her 5500rpm to be able to hit boost in second otherwise I would have to sit around and wait for a couple of seconds.

hahaha ... Can you tell I don't like lag?

[Roy]

Which RB20 in Zoom had a 2530? IF your talking about the R31 wagon then the article states its a 2540 (although i think earlier articles on the conversion stated it was a 2530???)

Having been for a ride in an RB25 with a 2530, im guessing that the turbo on the R31 is a 2540 as its making more power then the RB25 i know of.

I recall an old Zoom that had a silvia with an RB20. It used a plain bearing turbo to good effect before going to an externally gated Trust turbo. When you say plain bush are you refering to an OE turbo or an aftermarket/high flow?

Anyway im not saying plain bush turbos are better, im just saying they dont deserve to be thrown in the same basket labelled "laggy" , especially well built hi-flows

[Cubes]

The zoom mag that I am talking about is the R31 White Wagon it was quite some time ago now.

Origionally he had the following Specs:

ATS Highflowed Turbo (VG30)

2 Welded Piazo Cores

Not sure how much he made at the rears I think it was around 200.

Then.... The turbo kept crapping its self running the high boost it had to to make the power and it was laggy as hell.

So he got him self a GT2530. It them made 220rwkw with more mid range etc etc.. heaps better until the motor blew due to running to much boost & detonation etc.

They ditched the welded Piazo cores and grabed a 33GTR FMIC and made the same power 220rwkw on less boost.

He was also running a Auto until it died which didn't take long.

That was the last I heard of it for a while until some one mentioned it was featured again not so long ago.

I asked Tilbrooks when I was down the regarding the HKS2530 on that R31 wagon where it made full boost etc. He said.. 3700rpm. That R31 wagon was some how related to some one at Tilbrooks I think it was his Nephew.

When I say plain bush I am refering to a aftermarket Highflow.

Honestly I was being a little optimistic with regards to 4000rpm making full boost. JMS said to stay away from plain bush highflows as they generally make boost at 4500rpm if they make decent power. Same thing Tilbrooks said to me.

When a car makes full boost is hard to compare as my RB20DET with the stock turbo can make full boost at around 2500rpm when loading her up in a high gear, where as in first it makes full boost around 4000rpm second around 3500rpm maybe 3000rpm then third 3000rpm maybe a touch earlier then fourth 2500-2600rpm.

The problem is Roy it is extremly difficult to get a local well built highflow.. I know that in SA there is no one that can build a decent highflow that doesn't require 18psi to get 200rwkw from a RB20DET.

Whatsisnames turbo is an unreal turbo. 257rwkw on 13psi boost is definately an achievement. It makes full boost by 3500rpm but generally 4000rpm.

Would you have the mag number for the r31 wagon that had the 2540.. I'd like to compare the 2530 and 2540 dyno graphs.. OR.. can some one scan it?

[bbenny]

Yeah i have two friends with a high flowed RB20 turbo. one of them has the exact same, filter, exaust and cooler as me. however i have the standard turbo. on the dyno i actually made 222hp at the treads and his only 203hp. apparently we both had the same timing set up too. mine did come on full bost about 1000rpm before his(4000+rpm). so im thinking i will steer clear of the high flow.

I am becoming more interested in the HKS 2530, like a few of you are saying ive read of cars pulling over 1bar at around 3500rpm. I guess the real question is - How much would a second hand one cost and if they are as good as everyone seems to say, how hard is it to get your hands on one?

[Roy]

Same car... it would seem Zoom cant make up their mind if it has a 2530 or 2540. One of the articles that states its a 2540 is No.57

Ive been in a 220rwkw (@1.2bar) 200SX that has a T3/4 plain bearing turbo. It is a gem, im of the understanding Nizpro bolted it together.

It has slightly more lag compared to the stock turbo, but is still very responsive. I suppose it depends alot on the turbines and compressors they use, i think this impacts on the power and its delivery more then the beaing type. Could be wrong though.

[Cubes]

Roy the SR20's seem to have more balls in the mid range and spool the turbo up quicker.. Maybe due to the longer stroke of the 4 cyclinder pushing the turbo or spooling the turbo up better. That really is the RB20DET's down fall and why it rev's harder than the SR's not that reving is bad but for the street I don't like it A Rolling run with a S15 on the weekend from around 80kays in third he was making around 10rwkw less than me and left me standing still until I got up around 5500rpm where we had to back off due to cars etc.. at around 5500rpm the acceleration started to even out and he was no longer pulling.

With the standard RB20DET Turbo mine made 164rwkw (219rwhp) on 15psi with the stock ECU, stock air box, 3" turbo back exhaust on RPM's DD Dyno.

It was running extremly rich and only made 150rwkw on 15psi previously so Tim tweaked the fuel reg a little to bring the AF to a more respectable 11.8 and thats when it made 154rwkw also it was running 17degree's timing. Previously on the same dyno it made 115rwkw when it was dead stock (exhaust stock etc).

[Roy]

My point being on the same engine the smaller ball bearing Nissan Turbo was only marginally more responsive then the plain bearing T3/4 turbo, but had nowhere near the power.

[Cubes]

[RB20LagWagon]

Has anyone actually made 500 hp out of the cgc stage 2, id suggest that would be an engine hp too? Im just thinking that 500 either at the wheels or engine would be a big number for an internall gated turbo. Biggest garret internally gated i know of is 2835 at 420...

At the moment ive got r32 rb20 with a vg30det Non bb highflowed using vl turbo inducer wheel back cut and t04e compressor wheel. Although i admit it is more laggy then standard, in a race, you really only get lag once. I have made 290 rwhp and with a little more tweaking 350 is hopefully possible.

The car is in a r31 and have done a 12.78, sorta shows you what lag means at the strip.

[bbenny]

Damn nice time!

what sort of engine management mods have you got? ie complete aftermarket?

and does 290bhp require bigger injectors, fuel pump, reg. etc? because thats the sort of power im aiming for and hopefully with an RB25 turbo... am i dreaming with that turbo?

[GiJOr33]

yes... do tell!!!

[Cubes]

RB20Lagwagon I've heard of surging issues when bolting on the GCG 500hp turbo on the RB20.

May have just been an isolated case however he had to have the compressor changed down to the 450hp one.