Came across a small paper on variable volute tongues today while researching about turbine housing designs. Seems good in theory being able to increase the a/r at the tongue section to help reduce emp at high rpm. Not sure how good it performs as it's only changing the a/r at the very end of the volute where the rest of it remains the same. Also thinking it might cause a fair bit of unwanted turbulence introducing all that extra flow back into the start volute. Got me thinking about the terms volute and scroll, are they the same thing? I find some papers refer to it as scroll and others volute.