| I've spent a little bit of time collecting information about the spoolup characteristics of the GT2860RS turbocharger with varying turbine sections; those vehicles being Seb's TT of SpecialtyZ, Dee Ridgeway's TT, and my personal TT. Since I put together that initial graph, I have been really curious to see the real data so we can all check it out. I had made a post with some approximations on boost levels to RPM and plotted it out across the GT2860RS's compressor flow map. This was the original approximation: 
and this is the corrected version based on the dynochart presented of Seb's car showing the boost response from this link: [ http://twinturbo.net/net/viewmsg.aspx?forum=general&msg_id=1839454 ] the boost data collected on Dee's car with the ZEM during our tests and boost data collected on my Z via the Blitz SBC-iC. RED: GT2860RS w/ .86 A/R turbine, 9-blade (Seb)
BLUE: GT2860RS w/ .64 A/R turbine, 9-blade (Dee)
GREEN: GT2860RS w/ 10-blade turbine & .63 A/R housing (Ash) 
I've entered in the actual boost pressure in psi rather than in pressure ratio to make the map a little easier to read. The black lines with the x000 value at the top represents the airflow of the engine at that RPM. Here is the new dynochart comparing Seb's 66xRWHP numbers to Dee's car and my own (the old dynochart I had only had a max of 58xRWHP) RED: GT2860RS w/ .86 A/R turbine, 9-blade (Seb)
BLUE: GT2860RS w/ .64 A/R turbine, 9-blade (Dee)
GREEN: GT2860RS w/ 10-blade turbine & .63 A/R housing (Ash)
 Here is the difference in torque between these cars, which shows an even bigger difference: RED: GT2860RS w/ .86 A/R turbine, 9-blade (Seb)
BLUE: GT2860RS w/ .64 A/R turbine, 9-blade (Dee)
GREEN: GT2860RS w/ 10-blade turbine & .63 A/R housing (Ash)
 Dee and I both have the same wastegate actuators and I personally set his up - I know that making them any tighter isn't going to improve the peak boost his car will make. This may be augmented towards improvement with the modifications his car is undergoing in the next couple weeks(full 3" exhaust, 60mm throttlebodies), but what I am suggesting here is that the .64 A/R housing appears to also be a little on the large side - preventing the turbocharger from achieving its peak boost potential, but I'm not committing to that statement just yet. I think the .64 is an excellent match for this turbo on our engines and we will likely see improvement in manifold pressure after the exhaust and throttlebodies are upgraded. All three cars at their maximum outputs are making basically the same peak power, however, there are differences in peak torque and some vast differences in the area under the torque curves. For those that may have missed this post, or haven't been following it over the past few days, there has been some more activity that may be of value to you. You can see the beginnings of this exchange here:
[ http://twinturbo.net/net/viewmsg.aspx?forum=general&msg_id=1838097 ] It is very interesting to see (although not so surprising) that although my setup (the green plot) is using a lesser-efficient region of the compressor's operating range, it still makes more power through bottom end and midrange. Goes to show how proper intercooling can go a long way and that looking at a compressor map really isn't a good indicator of what kind of power you are going to make, at least, in terms of looking solely at its efficiencies.
[ ashspecz.com ]
[ agpowers@bellsouth.net ] Enthusiasts soon understand each other. --W. Irving.
Are you an enthusiast? If you are out to describe the truth, leave elegance to the tailor.
Albert Einstein
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A follow up post to the recent discussion regarding boost. - 
