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Rb20 < Rb25 Turbo Upgrade

Leeroy94

By Leeroy94,
in Engines & Forced Induction

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Dose Pipe Sutututu Grand Master

Dose Pipe Sutututu

Posted
Posted

^^ been told the water line doesnt quite line up when swapping the turbos over?

Hrms, don't recall having that issue back in RB20DET boat anchor days.. I'm sure all I did was remove the stock RB20 hair dryer and just bolted up the RB25 heat gun.

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Blackkers Experienced

Blackkers

Posted
Posted

As for the water line, i ended up loosening the turbo off the manifold studs to jiggle the turbo to get them in, from memory.

This is helpful for anyone fitting a stock turbo its easier to do when the turbo isn't tightened up against the manifold.

Spray the nuts and bolts with a penetrating lube like penetr8 or penetrene or something first to save heaps of hassle.

Should be doing this before pulling old nuts and bolts off anyway. If you break something its not likely you can fix it on your own.

Good luck you should be fine with the swap.

What is the condition of the RB25 turbo you are fitting? remember these are very old hardware now

Leeroy94 Enthusiast

Leeroy94

Posted
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Posted

What is the condition of the RB25 turbo you are fitting? remember these are very old hardware now

Its a 45v4 turbo. The guy said it was from a R33 and that is was also never boosted past 10psi.

From what I can tell it has 1-2mm shaft play without oil. Is that bad?

Ive read that they have factory shaft play of up to 1mm so that when they heat up it still spins freely? Or is that false?

What else should I look for on the turbo to tell its condition, type?

Blackkers Experienced

Blackkers

Posted
Posted

factory shouldn't have any play, the whole turbo will heat up pretty evenly so bearing tolerances shouldn't change much

1-2mm sounds about right for a 20 year old stocker. just throw it on and fingers crossed it doesn't blow smoke

Blackkers Experienced

Blackkers

Posted
Posted

a tune would get you a bit more power but probably no more than say 10kw. it would be more responsive and better on fuel but it's up to you. Your set up is on about the limit of the stock ECU.

Actually I'm not sure about the RB20 ecu's so maybe ask someone else; but it's worth mentioning that an aftermarket ecu + tune will be minimum $1250

GTSBoy Grand Master

GTSBoy

Posted
Posted

Without tuning you will run into the same problems as anyone else winding up the boost on an RB20 would, just at lower boost levels. The factory maps are richer and more retarded up at the the high revs and high load regions than are good for making power. The RB25 turbo pushes a bit more air at any given boost level (or more to the point, the exhaust side flows more exhaust gas at any given boost level, reducing restriction on the engine which is what allows more air to flow at the same boost, if you know what I mean). So what that means is where things might start to get a bit black smokey on an RB20 turbo at 14 psi, you may reach that sort of flow at 12 or 13 psi.

In addition, you will possibly max out the injectors in a similarly early way. It isn't wise to wind up the boost without knowing the fuel pressure stays good at high load and revs and the injectors aren't bumping up against the 100% duty cycle region.

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Even_Flow Enthusiast

Even_Flow

Posted
Posted

Also a little hurdle you will/may come across...

The stock 20 turbo comp housing has a nipple to read boost for the wastegate actuator. The 25 doesn't. You will need a nipple welded onto your I/C piping to complete the conversion completely.

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