BoostdR

I have one, just about to remove for a rb30/26 what are you after one for?

The comp cover in enlarged to whatever the inducer/exducer size of the compressor wheel is. An engineer should be able to do it all except the final balancing. The turbine housing side is pretty straight forward, you have the right idea there. I would probably go a tad smaller than 52mm..say 50mm then use a jaycar boost controller to adjust the ramp rate of the boost....which will keep it out of the surge zone. That way you are getting the best possible response. The T04S wheel will be ok with this smaller 50mm outlet as its surge zone is smaller. I would expect more power aswell. I'm not sure if the T04B wheel directly fits the RB25 shaft as I used a VG30 center which had in this case a larger shaft. Bill At ATS -Adelaide Turbo Services has made a few of these for off road buggies as price is a major factor. They make around 230rwkw at 10psi.

Sorry for the late reply, my profile is stuffed so had to make a new account... The Compressor cover(inlet side) is std RB25. This does have to be modified to fit either the T04B Vtrim compressor or the TO4S. The turbine housing is from a VG30 turbo which has a larger A/R ..ie bigger scroll but uses the same size turbine wheel. This bolts onto the Rb25 center. So the compressor housing is modified to fit the new compressor wheel, This is done by enlarging the inlet...which also takes out the std RB25 anti-surge groove so another is machined in. The VG30 turbine housing is enlarged so there is a quite noticable gap between the turbine wheel and the housing this is done to slow down spooling other wise way to much boost is made at a low rpm which the engine cannot digest and as a consequence cause surge. Hope that makes things clearer