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Comp housings definitely are different sizes. Didn't pick any easily measurable difference on the turbine side for either housing or rotor between RB20 and 25.

Also RB20 comp impeller is smaller inducer + exducer. Just a smaller unit, flows less. Later series 2 RB25 also went to a nylon/composite impeller. Lighter weight.

Turbine housing is SLIGHTLY larger a/r for the RB25 turbo, runs the exact same wheel. The compressor housing is also slightly larger as said, and from memory is around 66mm exducer vs 60mm for the RB20 turbo. Can't remember the inducer size, but its definitely a couple mm or so larger too.

The series 2/Nylon compressor wheels seem to be a bit larger again, from the ones I've looked at

s2 and s1 33 turbos are the same size, just have the different compressor wheel material. the r34 turbo is bigger than them though.

I am fairly sure ages ago I had a S1 and S2 pulled apart side by side (back in my stock turbo days, so this is like 5 years ago and brain fade could be coming into play) and the S2 compressor was as you say, made of different material but was also a little larger... also the composite S2 wheel was a "single blade" style design while the S1 one was twin blade.

yeah the blade design is different (due to the different characteristics of the materials) but as far as i'm aware the size was the same. but i'm no expert on it so you may be right and i may be wrong. i was only aware of the r34 turbos being bigger

  • 1 month later...
anyone know if a R33 compressor housing and compressor wheel can be transfered onto a rb20 turbo? for slightly quicker boost without restricting the airflow?

Don't see why not, people do some bastardising with RB and VG turbos.... have a search for the 240kw $300 turbo or whatever it was...

cool, only reason im asking is cause im buying a cheap rb20 turbo for 100bux and theres nothing wrong with my r33 turbo except its a bit whiney when im cruising off boost (which is why im replacing it) so i thought i could do a bit of a swap between to two so im not losing out.

They are all BB.

If you perform a search and go back far enough this information has been covered so many times but every new thread that gets opened with more misinformation means there is even more for the next person to trawl through.

I understand that it can be hard to search when there are lots of threads on the same thing but it is worth the effort and there are very few questions that haven't been asked or answered on SAU over the last 7 years or so.

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