Limits of oem rb20 turbo?

[ToroGTS]

So I know its common knowledge that the oem rb20 turbo can flow to about 250 hp, but what about on different applications?

For instance if this was mounted to a 2.5L inline 4, would the limitation then become the exhaust wheel breaking at 12+ psi? Just interested for random knowledge... What is the specific limitation of this turbo, the flow characteristics, inducer size, exhaust wheel size, peak pressure production? ect.

[Skym]

The RB25, RB20 turbo's are identical on exhaust side with exhaust wheel size (51x43) and the difference is the housing A/R (0.4 for RB20 vs 0.5 for RB25). Intake side (compressor wheel size, compressor housing size) is where the biggest difference is (RB20 is 42x59 with 0.50 A/R and RB25 is 48x66 with 0.60 A/R). They are both made by Garrett Japan for Nissan (to their specs). Stock RB20 turbo compressor wheel is a T3 55 trim (what I could find that matched that size). RB20DET stock turbo is rated to around 250hp (pump gas rating). RB25DET stock turbo is rated to around 300hp (pump gas rating). Not sure on the boost level for those ratings, but assume 1bar (14.5psi).

Hybrid RB20 turbo is 46.5x60 (T3 60 trim) compressor side and 58.9x 48.7 on exhaust side using machined out stock compressor, exhaust housings with a TB03 CHRA (as used on non ballbearing VG30 turbo) / centre part of turbo. Hybrid turbo is using different parts from different turbo's. High flow turbo is polishing housings, backing edge of blades so they flow better, etc. Many say a high flow turbo is a hybrid turbo, but they are two different ways to modify a turbo. Hybrid RB20 turbo produces 20hp more at same boost level over factory turbo, so should be good to 350hp at 1bar.

Hybrid RB25 turbo is using same specs, except it has a To4e 50 trim compressor wheel and can surge (hit surge line on compressor map) due to exhaust housing A/R is too small (probably can use a stock VG30 turbo exhaust housing with bigger A/R or aftermarket exhaust housing). This turbo is good for over 400hp at engine on RB25DET at 1bar with supporting mods.

When turbo is out of balance it fails. As long as turbo's bearings are ok it should be ok. But if out balance, it could fail at lower boost levels. More boost = more rpm on turbo. More rpm = more out of balance turbo gets if it's out of balance already. Out of balance can happen due to age (high km), high oil temps, etc. Basically have a engine oil cooler, low km stock turbo.

Around 14 psi is the limit a turbo rebuilder in Australia recommended for stock turbo (I assume if bearings are in good condition). Some (including someone on here) have run 1 bar for around 330hp at engine on RB20DET. But it heat soaked (intercooler) and had to pull ignition timing, so lost some hp.

Max I have run is 12psi and exhaust side was intact. It failed on intake side due to age, high oil temps (lack of engine oil cooler).

Also high exhaust temps are supposedly not good for glue holding on ceramic exhaust wheel (one of the reasons why factory run engine richer), as it can suppodedly spin on shaft and go off balance, hit compressor housing, snap shaft and end up in middle of exhaust.