I was looking around on the KA-t forums and found this:
http://www.spracingonline.com/store/...ool_Valve/3659
Basically, you need a divided turbine housing and a non-divided manifold. Basically half the turbine housing is blocked off under a certain boost pressure then an actuator opens the other side of the housing to allow full exhaust flow. Supposedly this will decrease spool time. In my head, I can see it working, but I dunno how well it would work in the real world.
Anyone heard of people using something like this?
Threaded Mode