rb25turbo on rb20 q

[lukew105]

I have read hundreds of threads about whether an rb25 turbo on an rb20 is a good upgrade or not.

I have an r32 and it seems relatively responsive, still on stock boost, but the midrange seems shit and just revs out with no real power. I need to get it tuned and i have a 3" front and dump pipe and hi flow cat to join onto my old 3" cat back system.

The other thing i read was that if you put on an rb25 turbo they get very fuelly, so i was wondering if you got it tuned after if it would fix this problem.

basically i want a daily that i can put my foot down on the odd occasion and feel it kick me back in my chair and beat commodore assholes ha ha!

any help would be good cheers

[Sydneykid]

I am not sure I understand the question, but I will have a go......

The RB25DET turbo produces 10% more airlfow at 7 psi, than the RB20DET turbo does at 10 psi. So if you bolt on an RB25DET turbo and use the RB25DET wastegate actuator you will get 7 psi and about 10% more power. However if you use the RB20DET wastegate actuator on the RB25DET turbo it will produce 10 psi and you will get 25% more power.

That is provided you have the support parts (intercooler and exhaust) in place to handle the increased airflow.

If you really want to get the best from the increased airflow you really need to tune it. R32GTST's have an easily chipable ECU. Either that or an SAFC (or equivalent) will do a reasonable job of removing the exccessive richness that the standard ECU provides whenever the airflow is increased over standard. There is another 15% more power to be had from simple tuning.

That's more than enough to give a 255kw Commondoor a thorough thrashing.

Hope that answered your question:cheers:

[natho]

probably a good idea to get a decent cooler at the same time, and don't forget the factory clutch will probably give up pretty soon after too

[Ronin]

RB25 turbos on RB20's deliver the power very progressivly and won't slam you back in the seat or light up the tyres. I have one on my car, its a very different feel to the stock turbo.

Makes good power though.

You will need a new fuel pump as you can see my my graph.

[jazza08]

Can i ask what other mods you have, and what boost level that was on?

Im guessing it was rev'd to 7.5k aswell? Pretty impressive figure

[Ronin]

The usual stuff

Turbo back HKS super dragger zorst

Dump pipe of some sort

Hybrid FMIC

Apexi Pod

RB25 turbo @14psi

Blitz SBC iD II

HKS cam gears

Chip remap

Catch can

[nedb]

Hmmm, very impressive Ronin. We have same mods but the cam gears.

How much difference do they make on a RB20. Did you do a before and after power run?

You are running a bit lean there, the power must of came down a bit once the fuel pump was changed. I had 137 rwkw but was running flat 14 AFR and after the fuel pump change it went down to 130 but very rich. The car was still pretty stock then.

[Ronin]

I Havnt had the car tuned with the cam gears on yet due to the fueling issues. That dyno was going to be the before run.

[Z00MxRACING]

fark ...

my r32 with stock turbo only pulled 135.5 rwkw on standard boost .. with the only mods ..

hks filter,

hks full exhaust,

standard copper ngk plugs (non iridium)

............ now that i got the fmic and new bov ...will i get more power increase??

also i have the r33 stock turbs as well but not fitted yet and i dont know if this is worth the hassle of doing without causing strain on the engine ..???

also could i boost more if i used the r33 turbo but using the r32 actuator?? will it cause damage to the turbo / engine?? and how much boost could i run? and wot power figures should i expect?

cheers

[jazza08]

With a fmic + bov + r33 turbo, id get it tuned then u cud run probably as much as u wanted, but id say to keep it safe keep it around 1bar for racing and just normal say 10psi for daily driving! Yes the r32 actuator goes onto the r33 turbo no problems aswell.

[Phil Megroin]

Hi,

What exactly is the actuator's role?

I'm also interested in upgrading my turbo to the RB25det one.. what kind of turbo is it exactly?

How much would it cost one to upgrade to an rb25 turbo, FMIC and the rb25 actuator?

[jazza08]

Actuator regulates the boost level, (ie rb25 actuator = stock 7psi, rb20 actuator = stock 10psi)

rb25 turbo is just bigger than the rb20 turbo really.. series 1 r33 turbos are the strongest (but usually are older remember). Actuators generally come with the turbo, if not put ur rb20 actuator on there (or maybe do that anyway...)

rb25 turbo = $400 (+ install.. $100-200)

FMIC (inc install) = $700-1000

So your looking $1500ish for it all done, if your exhaust is done ull notice one hell of an improvement

[Cool Hand Luke]

Actually i wouldnt run too much boost with the rb25 turbos. S2's have a plastic compressor wheel, and both have ceramic exhaust wheels, so its possible to drop the wheels off still. I was running 16psi constantly with my S2. Before i had it tuned, and with a small boost leak which lost a lot of bottom end i still ran a 13.0 @105mph with a 2.1 60ft on crappy tyres. That was in a 180sx, but a R32 gts-t isnt that much heavier, so you can beat most commodores if thats what your worried about. One of the biggest differences was getting it tuned, top end was a little better, but the most noticable was normal driving and the mid-range... fuel ecomonmy was much better also. As someone said before, your clutch will go quickly, mine lasted about a week

[Munna]

  jazza08 said:

Actuator regulates the boost level, (ie rb25 actuator = stock 7psi, rb20 actuator = stock 10psi)

rb25 turbo is just bigger than the rb20 turbo really.. series 1 r33 turbos are the strongest (but usually are older remember). Actuators generally come with the turbo, if not put ur rb20 actuator on there (or maybe do that anyway...)

rb25 turbo = $400 (+ install.. $100-200)

FMIC (inc install) = $700-1000

So your looking $1500ish for it all done, if your exhaust is done ull notice one hell of an improvement

Series 1 turbos are not really any stronger as both s1 and s2 have ceramic turbine wheels which is the weekest part of both turbos. The S2 has a plastic compressor wheel which gives better responce.

[Lithius]

So whats the maximum boost you can run with an R33 Turbo in an R32? (Provided you have a decent FMIC setup). I know 14psi is the limit of the standard one.

[TTT]

there is no specific amount.

just stick below 14 psi to be safe.

people have broken turbo's at stock boost levels and some have had them on about 16psi for over 2 years without a problem.

it's your $500 turbo.. you decide what you want to risk.

[Phil Megroin]

Is it possible to put a t28bb onto an rb20det?

If so, would it be better than the rb25turbo?

Sorry, i must be a dumbass.. i still dont really understand the role of the actuator.. i understand that it regulates boost.. but i dont understand how the rb25 one is better than the rb20 one. How do they differ?

[Munna]

  Phil Megroin said:

Is it possible to put a t28bb onto an rb20det?

If so, would it be better than the rb25turbo?

Sorry, i must be a dumbass.. i still dont really understand the role of the actuator.. i understand that it regulates boost.. but i dont understand how the rb25 one is better than the rb20 one. How do they differ?

A t28 smaller than the turbo you have already got.

Its not a mater of one actuator being better than another. is all the actator does its push the wastgate open once a certain amount of boost is reached. An rb25 actator is designed to open when it sees 5psi where as a rb20 actuator will open when it sees 10psi.

cheers

[CerealKiller]

  nedb said:

Hmmm, very impressive Ronin. We have same mods but the cam gears.  

How much difference do they make on a RB20. Did you do a before and after power run?

You are running a bit lean there, the power must of came down a bit once the fuel pump was changed. I had 137 rwkw but was running flat 14 AFR and after the fuel pump change it went down to 130 but very rich. The car was still pretty stock then.    

I'm fairly sure you want to run a 12:1 AFR

[TTT]

putting a T28 from a S14-S15 on a RB20 would be useless exercise.

it will cost more to fabricate a new flange for your manifold and I'm not so sure if would actually be called an UPGRADE.

actuator.

the RB20's don't have a boost controler at all.

the factory boost setting of 10psi is set that way due to the spring that is in the actuators diaphram (that round part at the front)

that spring is hard enough to keep the wastegate closed enough to provide the engine with 10psi of boost.

The Rb25's have a solenoid that controls boost. this solenoid is controlled by the ECU.

so the actuator diaphram has a spring in it that is weaker than the RB20 one.

the spring alone can only hold 7psi.. and the ecu/solenoid combo work together to provide more if needed.

so when people upgrade their RB20 turbo to an RB25 turbo, because their stock engine doesn't have a boost controller, they use the RB20 actuator.

this means that they can still get 10psi with no other boost mods on the new bigger RB25 turbo.

as Sydney kid said earlier, the RB25 turbo will flow (meaning produce) 10% more at stock 7 psi than the RB20 turbo does at 10 psi.

so even if you use the Rb25 turbo and it's own actuator, at 7psi you will have more power than with the rb20 turbo at 10psi.

but use the rb20 actuator on the Rb25 turbo so you have 10 psi on that as well and you end up with a 25% increase in power/flow at same boost on the new turbo.

does that help?