Quote:
Crash said:
I wonder whether VTG turbochargers are used in these kits... 
Crash,
Judging by the quoted displacement and peak HP/torque figures, and comparing to stock (with and without overboost) specs., I would guess that kits 1-3 use the VTG's, and kit 4 uses a fixed geometry charger.
Option-displacement(Litre's)-peak HP(rpm's)-peak torque in Nm(rpm's) Stock-3.6-480(6000)-620(1950-5000)[OB:680(2100-4000), peak boost from 1.0-1.2BAR]
Kit 1-3.6-544(6000)-765(2000-4900)
Kit 2-3.6-598(6550)-795(2600-4700)
Kit 3-3.8-618(6500)-845(2500-4750)
Kit 4-3.8-687(7000)-900(4700)
While data is severely limited, those broad/flat peak torque numbers from kits 1-3 are quite reminiscent of stock numbers (with and without overboost), but kit 4 "advertises" a peak torque at a point (900Nm @ 4700 rpm's), and thus looks like a fixed-geometry setup with torque as "late" as 4000rpm's. Also, if one compares the peak-torque rpm ranges of stock with OB to those of kits 1-3, one notes a torque band that is at peak for a slightly wider rev-range (1900 or 4000 minus 2100 for stock/OB versus 2100/2250/2900 for kits 1-3), but for kits 2 and 3, this begins at higher rpm's (2600 and 2500 versus 2100). I wish they would provide the peak boost for us, to see how much they achieved these numbers from boost alone, particularly kit 2 which stays at 3.6L of displacement.
I completely agree with Christian that removing the VTG's detracts from the car's setup, but not because a mega-HP fixed-geometry setup is obsolete (like my tuned 996TSCab), rather, it's just a different approach to turbocharging, so by removing the VTG's, one removes the car's most significant innovation.
BUT one point not emphasized by all of the posts on this subject of tuning a 997TT is that with stock components, the VTG's in the 997TT are relatively CLOSER to their functional maximal potential versus the K16's and 24's on the 996TT, since the VTG's are tuned stock closer to their "safe" maximal boost (1.2 with OB versus ?1.4 or so), and already have a steep torque curve with peak torque achieved quickly and early (the rationale behind the adjustable impeller angle of the VTG). So I'm not surprised early tuner cars are not dramatically faster than stock.
I do know Borg Warner HAS other VTG's for gasoline (not diesel) engines, but it will take 1-2 years for tuners to come up with comprehensive programs using them (I don't know if the reason is legalistic-like proprietary coveting of the VTG used in the stock 997TT-or more practical-it will obviously take tuners longer to test a "new-and-improved" (
) VTG than the "merely" new VTG.
And I still wonder if Porsche will use one of these "bigger" VTG's in their 997TT-PK/GT2/S, although rumours on this forum suggest otherwise-just an ECU re-tune using the base TT components with perhaps "constant" (instead of intermittent) OB.
But my preliminary impression is that a VTG that still spools fast (maintaining the VTG's attraction) but that can safely handle more boost than the stock charger will be something to wait for-along with the other proper mods.-exhaust/boost hoses/headers/manifold intake/clutch. And that proper thermal and ECU changes are implemented with it. All of this is not "Mission Impossible." But, as suggested, this combination of mods. will take TIME.
Happy belated Thanksgiving all.
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