evltoy wrote:Im in the process of turning my ST205 Celica into a circuit car. Im at the stage were Im trying to decide on what turbo to use.
It will be a Garrett GT25 or 30, but I would first like to hear from someone who runs either turbos on their ST205 to get an idea of what revs they make boost at.
I think the GT30 will be the more suited but the last thing I want is the car to bog down around a tight turn or out of a corner.
If the GT30 comes in around 4 grand it will be peachy, If they come in at 5 grand it'll be a dog.
All the dyno plots I have seen for the GT25 on the 3SGTE are horrible, spool up is no better than a conventional turbo (TD06 for example) and the top end is worse. There's not much data on the GT30, but IMO the response you are looking for depends more on the a/r ratio of the exhaust housing than the type of bearings. Based on experience I would suggest a turbine with a major diameter between 55 and 60mm and an a/r ratio no greater than 0.63. Depending on supporting mods this is sufficent for around 450hp; if you are looking for more than that there will be a lag trade off. The GT30 is OK in terms of turbine size, but I'm not sure there is a suitably sized housing available. I'm experimenting with one at the moment on my MR2, but I don't have any useful data to share as yet.