I also done some numbers on compressor maps and for a high output 3 l running 22 psi I came up with these numbers
T66 (best matched compressor)
70% @ 7300 139 c* after turbo
76% @ 6000 129 c
76% @ 5000 129 c
74% @ 4500 132 c
Compared to the closest compressor for a twin turbo setup
T-3 60 series trim
69% @ 7300 140* (at the high end of compressor map)
73% @ 6000 134*
70% @ 5000 139*
67% @ 4500 144* (surge line)
Through the testing range of the engine they both would be pretty much the same with an intercooler.
With less boost pressure for street driving the dual turbo efficiency goes up as it drops more towards the center of the graph and the t66 goes down as it drops towards the bottem of the graph.
So the twin turbo would have a couple horsepower through the midrange over the single turbo from a stand point of just compressor maps and the single would have it in top end.
The twin turbo`s have a maximum combined flow of 62 pounds of air and the the t66 has a much higher 72 pounds of air
You could debatibly go with the t64 its smaller and would offer more midrange but top end efficiency wouldnt be as high. A trade off between the 2.
This is only on the compressor side though. My previous statement stands.
So the twin turbo setup would give you hotter temps through the topend. The single hotter temps through the midrange.
Id also like to add that beyond 22 psi there is not a good match through standard compressor maps for the twin turbo setup. Where as the the t66 has alot of room to grow. About 5 more psi across the board.
2 gt 32`s with a 52 trim would be better then Any of them by far. But who has 6000 dollars for 2 turbos?
