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Hmmm Rb 25 Turbo Onto Rb 20 Det

335

By 335,
in Engines & Forced Induction

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335 Rising Star

335

Posted
Posted

Ok

Before I buy this used RB 20 DET turbo to replace my dead one, what if I put on a RB 25 DET turbo? I read that people have done it but no one mentions if they had their car tuned afterwards. Do I need to tune if I put on the RB 25 DET turbo? Is it a headache to do this? alot of extra parts?

Will it be more than 10% laggy than stock turbo?

Help please, we be buying a turbo tonight or tomorrow.

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335 Rising Star

335

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Posted (edited)
You need a tune (ECU required). Simple as that.

It will be laggier across the board than the RB20 turbo... afterall, it is bigger.

Ok Thank you. Is it worth it? Will having after market cams or cam gears make up for the lag?

Edited by 335
335 Rising Star

335

Posted
  • Author
Posted

Hello

Thank you

I read that, but what is a banjo? and do I have to buy a new exhaust manifold? If so, what kind? Will the RB 20 Det gaskets match up to the RB 25 turbo?

Hydroxinol Enthusiast

Hydroxinol

Posted
Posted (edited)

Hi mate, I just did this upgrade so I thought I would reply.

First of all, all you will need for the RB25 Turbo upgrade is the Rb25 Turbo + Rb25 Turbo elbow, thats it. Its a simple install, and if you are planning on putting a turbo on anyway I would suggest going with the RB25 Turbo if you can find one at a right price. People talk about an increase in lag, and while this is likely to be true due to the increased size, it is not noticeable. I feel that the benefits in power far outweigh this anyway. It is definitely worth doing.

Oh, and I don't know about tuning the car after doing this upgrade. The most I did was an ECU reset. Don't know if it did anything but I did it for good measure. The car is running fine after the upgrade apart from an intermittent idle issue, but I don't think it is related.

Edited by Hydroxinol
335 Rising Star

335

Posted
  • Author
Posted
Hi mate, I just did this upgrade so I thought I would reply.

First of all, all you will need for the RB25 Turbo upgrade is the Rb25 Turbo + Rb25 Turbo elbow, thats it. Its a simple install, and if you are planning on putting a turbo on anyway I would suggest going with the RB25 Turbo if you can find one at a right price. People talk about an increase in lag, and while this is likely to be true due to the increased size, it is not noticeable. I feel that the benefits in power far outweigh this anyway. It is definitely worth doing.

I can get one for 150 dollars but I cant afford to get a computer and have the car tuned, so I want too but if have to tune it, I cant afford it now.

Can I run it safely without tuning?

Hydroxinol Enthusiast

Hydroxinol

Posted
Posted
I can get one for 150 dollars but I cant afford to get a computer and have the car tuned, so I want too but if have to tune it, I cant afford it now.

Can I run it safely without tuning?

Yep definitely, as I said mine has been fine. I am not 100% sure about this but I would assume that the stock computer would compensate for the increased air flow. So a tune may not be necessary. But I would wait for someone to confirm this as I am not positive, i'm still learning :P

RaZ_TuRbO Community Regular

RaZ_TuRbO

Posted
Posted (edited)

Yeah you can run it safe without tuning the std ecu will just more fuel in to compensate for the 7% or so more air going in, it usually over compensates and you will get fuel smoke on boost.. just get it tuned later down the track.

Edited by RaZ_TuRbO
WAN73D Collaborator

WAN73D

Posted
Posted

Don't forget you need to have a pressure tapping point (for your wastegate actuator) from somewhere. The r32 turbo takes its pressure off the turbo compressor housing. However the r33 turbo i believe takes it from the line after the intercooler (which you wont have). I was planning to do this mod and so have a pressure nipple threaded into my compressor elbow.

I will be advertising an r33 turbo and elbow for $200 soon if anyones interested. Elbow comes with a pressure nipple attached already. SO your basically good to go.

While i'm here...i beleive the banjo bolts have to be changed if your car is BASICALLY an early 1989 model i think. Mine's a 1990 model and i measrued the banjo size and they were fine.

huddy Veteran

huddy

Posted
Posted (edited)

yeah only with the year difference you may have banjo problems... as my cefiro 1990 had different size banjos compared to r32 turbo when i upgraded (and to hks 2530 & hks 2540 & now GT3076r) i changed to banjo's to suit, and the standard 32 ones (later model suited all my upgrades).

Edited by huddy
Simon-S14 Grand Master

Simon-S14

Posted
Posted
Yep definitely, as I said mine has been fine. I am not 100% sure about this but I would assume that the stock computer would compensate for the increased air flow. So a tune may not be necessary. But I would wait for someone to confirm this as I am not positive, i'm still learning :P

you can run the 25 turbo with the stock ecu no worries, just dont expect the performance to be much better then stock... there will be more lag also. for the BEST gains, remap the ecu and tune to suit. then the car will perform a LOT better and you'll wonder why you didnt do it sooner rather thenw asting time with an ECU reset :(

335 Rising Star

335

Posted
  • Author
Posted
Don't forget you need to have a pressure tapping point (for your wastegate actuator) from somewhere. The r32 turbo takes its pressure off the turbo compressor housing. However the r33 turbo i believe takes it from the line after the intercooler (which you wont have). I was planning to do this mod and so have a pressure nipple threaded into my compressor elbow.

I will be advertising an r33 turbo and elbow for $200 soon if anyones interested. Elbow comes with a pressure nipple attached already. SO your basically good to go.

While i'm here...i beleive the banjo bolts have to be changed if your car is BASICALLY an early 1989 model i think. Mine's a 1990 model and i measrued the banjo size and they were fine.

Hello

Mine is a 91 so I should be fine?

I have a choice of buying a used RB 20 det turbo or the RB 33. I need something but dont want to get the RB 33 if I have to spend alot more money to have it work. Both are the same price.

I have to decide today.

Which choice is the best?

bubba Grand Master

bubba

Posted
Posted

More than 10% lag over stock? yes.

Need a remap/ecu? no. It would help with the extra lag but not needed.

My RB20 made 183rwkw with a 25 turbo @ 12psi untuned and definately went better than the stock 20 turbo on 14psi. The only thing I would say you NEED is to make sure you have a decent fuel pump (I have an 044 intank).

Get the RB25 turbo over another stocker mate, easy upgrade and will be fine - just pay attention for knock when you're winding the boost up, 12psi was all I could run untuned without dropping the timing back which would make the offboost even worse.

335 Rising Star

335

Posted
  • Author
Posted
More than 10% lag over stock? yes.

Need a remap/ecu? no. It would help with the extra lag but not needed.

My RB20 made 183rwkw with a 25 turbo @ 12psi untuned and definately went better than the stock 20 turbo on 14psi. The only thing I would say you NEED is to make sure you have a decent fuel pump (I have an 044 intank).

Get the RB25 turbo over another stocker mate, easy upgrade and will be fine - just pay attention for knock when you're winding the boost up, 12psi was all I could run untuned without dropping the timing back which would make the offboost even worse.

Ok, thanks for the heads up. I don't have a fmic or boost controller yet, so if this is a safe bet, then I will probably go with the 25 turbo, just don't want to damage anything else, having a turbo die was not good.

So this nipple thing is the thing I really don't understand. I guess if I had a fmic, I would probably have the nipple already on the piping, so since I don't, where would I add this so called nipple? And what does the RB 25 turbo elbow look like?

bubba Grand Master

bubba

Posted
Posted

Get a fmic asap or at least an r34 smic, your stocker is going to heatsoak pretty quick with the extra air and will be restrictive too.

As for the nipple, stock RB20 turbo's have a nipple on the compressor housing, this is for a vac hose to the wastegate actuator. Any boost source will do (before the throttle body) but best to put it as close to the compressor outlet as possible :P

The elbow is an alloy 90deg elbow that bolts to the turbo compressor outlet, 25 item is bigger than the 20.

bubba Grand Master

bubba

Posted
Posted

SAFC would help but to get the best gains you need to adjust timing in offboost areas.

Another thought, preferable to get a s1 25 turbo with the steel front wheel, the nylon compressor wheels really don't like extra boost.

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