See this is the thing that often perplexed with when people (on this forum and others) say the vf52 supports ~20psi to redline on 98 fuel.
The turbine wheels share the same dimensions on the vf37/36/48/52. And the comp wheel from the size should do about 350hp max. Without having a compressor map, its hard to say definitively, but the turbine wheel itself should not theoretically be able to keep up with the exhaust flow of the 2.5 litre engine at higher rpm.
Would be keen to see a log from someone who has a vf52 on a ej255 to see what the airflow curve looks like. I'm still not convinced the vf52 could actually hold to redline on a 2.5 like so many claim.
The twin scroll housing will be better than the single scroll as its the larger a/r internally. The separated exhaust pulses will also help with reducing some of the inefficiency.
Don't get me wrong - still a good turbo for very very little change (on a post face GT). So not knocking them - just confused over the claims.
One idea I have that would definitely assist in managin this backpressure on a vf52 sized turbine wheel - weld the internal wastegate shut and run an ewg of at least 44mm size (or at least dual 38mms for twin scroll).
What does this have to do with choking the turbo? Everything. By sizing the ewg(s) large enough that you can control the amount of exhaust flow that moves around the turbine wheel, you are more effectively able to control pre turbo back pressure (to a point of course). This means you could extend the theoretical flow limit of the turbine wheel at a certain boost pressure by modulating the pre turbo back presure through one (or two in the case of twin scrolls) large orifices pre turbo.
Infact this is one way to also maximise efficiency of a given turbine housing without going up to the next size (if someone is worried about losing spool for example). Something I'm toying with at the moment
Mick
Mick