| It probably has a lot to do with the following: It is mostly in the design of these: that 76-trim 10-blade T28 turbine wheel in the .63 A/R 4-bolt turbine housing really gets the 62-trim compressor spooled up quickly.
 Here is the spoolup response to ~18psi:
That's .91bar by 3200RPM and 1.3bar by 3400RPM. (sorry for the fuzzy image - that's as good as I could get it)
 A good bit of them being able to get wound up so quickly was because of these:
 And not having the rest of the pipework aft of the turbo to hurt that much-needed pressure-drop:
 3".
 Extensive work in these babies to get it in and out: the difference in NA and TT plugs - pic was mostly to show the deshrouding by removing the boss and using the NA plugs, also note the work around the valves at the periphery of the combustion chamber, the chamber has been radiused at the periphery to deshroud the valves during low-lift. JWT 500-series camshafts were used as well.
 This,
 plus these:
 plus these:
 plus these: (well, maybe not so much considering the recent dyno testing)
 In addition to:
 and: (note the crown design, tapered bore wristpins, Pauter rods)
 Although the setup has all of these mods done, I think one contributor to the improved spoolup is due to the lower static compression of my engine. It is around 8.2:1. I have seen it twice now where a built motor with lower static compression outspools almost everything. I presume it is due to the piston not converting as much of the combustion energy into mechanical energy, and the remainder of the energy goes out the exhaust, which drives the turbo quicker. We have also seen that when putting turbos on the non-turbo engine (with 10.5:1 compression), the stock automatic turbos (the ones that spool the quickest) spool notably slower. These are stock automatic turbos on a NA engine:
 And the tuned power/torque (with racefuel).
 I hear of people going to a 9:1 compression ratio because they say "it spools quicker", and I haven't seen any evidence that supports this - its like, bad information that wont go away. I tuned Joel Grannas's built TT with Sport600s on it with a built motor with 8:1 compression. Here are the results: The red lines denote Joel's car. The green lines are comparing to a Sport500 car with stock compression. This is, by far, the most responsive twinturbo I have seen yet - it even outperforms the best stock-turbo'd stagex-modded setup I've seen yet.
 Here's a boost plot and dynochart for a Stage5+ TT 5spd with stock turbos (850inj, HKS-SMIC, DP/TP/CB, DOOLZ, RPSFLY,Clutch, 1pcDS, UD pulley, stock internals) 
I dont want to insult your intelligence and say that it is just the static compression, as we both know all of the elements in the system are playing a role. But there is a synergy of sorts that works in these rather complex systems and with the right balance of modifications (which is almost guesswork in the build stage), you can really turn out some impressive results that almost defy typical "modding" presumptions.. like that of "if you go with bigger turbos, you will have more lag and less bottom end response", which we both know is true if that's the only part changed, but with attention to the rest of the system, you can obviously go against that grain. I know this isn't the apples to apples that everyone would like to see so please spare us all the drama for a moment. It would be nice to have more information to add to what we have here, namely boost plots on various configurations with varying static compression ratios. There appears to be a trend here though, most notable with the turbo'd NA setup vs. the Stage5+ TT setup where that's about as close as one can get to a true apples to apples as those vehicles had almost identical mods. Not to mention, the turbo'd NA had automatic turbos with a smaller A/R turbine housing and it still only produced about half the spoolup response as the 5speed with 8.5:1 compression. The power output of the turbo'd NA was also heavily compromised as a result. I came to the conclusion some time ago that slightly lower static compression improves spoolup and in the end, results in more power/torque on the bottom end. Boost is the ticket here, and is the #1 reason why my setup performs as well as it does down low. The reaons for the spoolup response, however, are a bit more involved. =)
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