GT2 Turbochargers Explained
#17
01-04-2011 | 07:18 PM
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Great info from both Tom and Mike (and kudos to Tom for being gracious and humble).
I was told the stock 997.1tt inducer is 43.5mm, the GT2 inducer is 45mm, the "old" upgraded vtg is 46.3 and the latest (65mm version) has an inducer size of 48.5mm. That last spec is between a GT28 and a GT30. Haven't seen any performance numbers on it but it's probably what I'll get. I would love to just get the alphas but I don't want to deal with EBC, running oil/water lines etc...
I was told the stock 997.1tt inducer is 43.5mm, the GT2 inducer is 45mm, the "old" upgraded vtg is 46.3 and the latest (65mm version) has an inducer size of 48.5mm. That last spec is between a GT28 and a GT30. Haven't seen any performance numbers on it but it's probably what I'll get. I would love to just get the alphas but I don't want to deal with EBC, running oil/water lines etc...
#18
01-04-2011 | 07:20 PM
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Tom mentioned porting the turbine side...it's no secret that there is an extrude process available for the turbos. I'd be interested in Tom's comments about that given his previous post. Is it just a matter of a whole lot more labour in order to take care of the vtg vanes?
#21
01-05-2011 | 12:55 PM
The A/R is variable. That’s the great thing about VTG technology!
#22
01-05-2011 | 12:56 PM
Inducer and exducer size are important parameters but need to be considered along with overall wheel aerodynamics and the characteristics of the turbine wheel. We've found that Borg Warner leads the industry in the aero department. A properly matched Borg Warner wheel with their extended tip technology will easily outperform a larger wheel that has poor aero design and is not matched properly to the turbine side.
#23
01-05-2011 | 12:58 PM
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Inducer and exducer size are important parameters but need to be considered along with overall wheel aerodynamics and the characteristics of the turbine wheel. We've found that Borg Warner leads the industry in the aero department. A properly matched Borg Warner wheel with their extended tip technology will easily outperform a larger wheel that has poor aero design and is not matched properly to the turbine side.
#24
01-05-2011 | 01:03 PM
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Yes, I know thanks. But I'm interested in the situation when the vanes are fully displayed (i.e WOT). In any info on that?
#25
01-05-2011 | 03:00 PM
The traditional A/R measurement doesn't really apply to a VTG turbo. The effective A/R will depend on the tuning and the hardware on the car. We have not found a situation where the vanes need to be fully open.
#26
01-05-2011 | 03:12 PM
We are using a size that was carefully choosen by our Engineers and the Engineers from Borg Warner... 
Not too big...not too small. Juuust right.
Not too big...not too small. Juuust right.
#27
01-05-2011 | 04:04 PM
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OK, thanks. Maybe a better question is do you know the specs of the turbine wheel of a stock vtg? And what do think the reason is for vtgs choking up so much at the upper end?
#30
01-05-2011 | 06:04 PM
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Tom, killer post, but we noticed some points that are incorrect.
The standard compressor wheel is different on the 997.1 turbo, the GT2 wheel is larger. It is the same on the 997.2 but the compressor housing is different.
Info on wheel sizes and turbine material from the BW catalogue:
GT2 Borg Warner turbocharger specification:
BV50-2280DCB426.10BVAX0
997.1TT Borg Warner turbocharger specification:
BV50-2277DCB405.10BVAX0
997.2TT Borg Warner turbocharger specification:
BV50-2280DCB426.10BVAX0
The four numbers in RED indicate the compressor wheel size. All have the same size exducer, 56mm. The 997.1 inducer is 43mm and the GT2 and 997.2 inducer is 45mm.
The last letter that is bold and underlined indicates the turbine material. In this case O stands for Austenitic stainless steel, which is specially formulated to withstand high EGTs.
Actually, as I pointed out above, the housings are made of the same material according to Borg Warner spec.
Your cooling statement is inaccurate as well. Heat should be kept in the turbo, turbine housings are never cooled. That is why you see some people wrap their turbos or even coat them. You want to keep the energy inside the turbo and not dissipate it. Please don't confuse this with exhaust gas temperature...that is an entirely different conversation.
This is also technically not correct.
Rotational speed is controlled by the vanes, the blade profile is not a factor. Clipping the wheel is to decrease back pressure and therefore EGTs at steady state operation. This raises the flow limit of the turbine to better match the larger compressor wheel.
The standard compressor wheel is different on the 997.1 turbo, the GT2 wheel is larger. It is the same on the 997.2 but the compressor housing is different.
Info on wheel sizes and turbine material from the BW catalogue:
GT2 Borg Warner turbocharger specification:
BV50-2280DCB426.10BVAX0
997.1TT Borg Warner turbocharger specification:
BV50-2277DCB405.10BVAX0
997.2TT Borg Warner turbocharger specification:
BV50-2280DCB426.10BVAX0
The four numbers in RED indicate the compressor wheel size. All have the same size exducer, 56mm. The 997.1 inducer is 43mm and the GT2 and 997.2 inducer is 45mm.
The last letter that is bold and underlined indicates the turbine material. In this case O stands for Austenitic stainless steel, which is specially formulated to withstand high EGTs.
Actually, as I pointed out above, the housings are made of the same material according to Borg Warner spec.
Your cooling statement is inaccurate as well. Heat should be kept in the turbo, turbine housings are never cooled. That is why you see some people wrap their turbos or even coat them. You want to keep the energy inside the turbo and not dissipate it. Please don't confuse this with exhaust gas temperature...that is an entirely different conversation.
This is also technically not correct.
Rotational speed is controlled by the vanes, the blade profile is not a factor. Clipping the wheel is to decrease back pressure and therefore EGTs at steady state operation. This raises the flow limit of the turbine to better match the larger compressor wheel.
please PM im interested on going to STAGE 4 mods