Originally Posted by Garage19
Can anyone explain to me the point of a roller baering T4?
Why go to all the trouble of fitting a roller bearing journal to a turbo with less efficient compressor / turbine wheels when you could just bolt on a GT30 with an internal gate?
Because from what I understand, the GT30 in integrally gated form, is not a particularly efficent turbo (the standard T4 has a better compressor map - it's downside being the lag* due to it's greater rotational mass with larger shaft etc, which the full ceramic bearing core is designed to overcome). However, I can only go by what I have been told by someone that knows turbos (Vince Osborne formerly of UT, now at CR Engineering), I have never actually tested a GT30 in integrally gated format.
*Please do NOT confuse spool-up with lag.