Saturday, April 19, 2014

Is a GT1749V a VNT15 turbo ? - TDIClub Forums

Is a GT1749V a VNT15 turbo ? - TDIClub Forums

That is the larger VNT15 with 49mm compressor wheel instead of the 46mm one.

ere are the Model Designation and Wheel Diameters for the older T-series and the new GTVNT Series Garrett Turbochargers:

(mm) (mm)
Model Compress Wheel Dia Turbine Wheel Dia
T2 48.0 47.0
T25 51.4 53.0
HFT25 54.4 53.0
T3 60.0 59.0 
GTVNT15-46 45.7 41.2
GTVNT15-49 49.0 44.2
GTVNT25-52 52.2 47.0
GTVNT 25-56 55.8 50.3 

The GTVNT15-46 replaces the T2 Garrett Turbo, the GTVNT15-49 replaces the T25 series, the GTVNT25-52 replaces the HFT25 model, and the GTVNT25-56 replaces the T3 model. 

The inlet diameter of the newly designed impellers of the GTVNT series is slightly larger (0.56mm) than that of the corresponding T-series it replaces. When compared at a pressure ratio of 1.8:1, the flowrate efficiency at 65% on the surge side for the GTVNT is similar to that of the previous T3 turbo, while producing a much higher flowrate at 65% efficiency on the choke side! A significant improvement of 19% in useable flow rate is achieved. With a pressure ratio of 1.8:1 and a flowrate of 9kg/min, an increase of 7.5% in efficiency is noted. 
During the initial phase of the development of the new GTVNT15/25 series Garrett turbochargers, a number of objectives for improving the current production turbines were sought. These objectives were: to improve the turbine flow characteristics, minimize size and weight, minimize inertia, improve transient response times, and to improve the aerodynamics of the turbine housing. 
The new GTVNT turbine housing features improvements made through the modification of the waste gate housing as well as that of the tongue location. The wastegate flow section was improved by providing a straighter gas path for the bypass flow to exit. The tongue was positioned closer to the wheel inlet to minimize wall frictional losses in the region of high trangential flow and high gas velocities beyond Mach 1. 
The new turbine wheel of the GTVNT25-52 series features a smaller blade count as compared with the earlier T2 model (9 vs 11) and also features longer blades and a higher trim than the T2 model (67 vs 57), although the turbine tip diameter is the same as that of the T2 (47mm). Turbine corrected flow plotted against turbine housing size for a constant turbine pressure (P1T/P2 = 1.8) for the new GTVNT25-52 shows turbine flows within approximately 4% of the larger T2 turbine and 30% higher than the equilivant sized T2 turbine. The new compressor wheel design shows the compressor wheel diameter vs airflow for the entire GTVNT family as compared to the T2-T3 series, has successfully achieved wheel size reduction for equal air flow rate. 

Comparison of Features of older T25 and new GTVNT15-49 Turbochargers of Equal Compressor Flow Capacity: 

Diameter (mm) 51.4 49.0 4.7
Weight (g) 33.1 26.3 20.5
Inertia (kg-m2) .0000057 .0000043 24.6 

Diameter(mm) 53.0 44.2 16.6
Weight(g) 148.4 112.5 24.2
Inertia (kg-m2) .0000148 .0000103 30.4 

TOTAL TURBO WT(kg) 5.43 4.55 16.2
SHAFT DIAMETER(mm) 9.2 7.9 14.1
ROTATING INERTIA(kg-m2) .0000208 .0000149 28.4 

Corrected TURBINE FLOW (kg/min) at 1.7 Pressure Ratio and .47 Housing Size for: 
Garrett GTVNT15-46 = 3.85 kg/min
Garrett GTVNT15-49 = 4.30 kg/min 

Corrected COMPRESSOR FLOW 9kg/min) at 1.8 Pressure Ratio and 65% efficiency in 55 Trim for: 
Garrett GTVNT15-46 = 7.8 kg/min
Garrett GTVNT15-49 = 9.8 kg/min 

This data show that the new GTVNT15-46 turbocharger flow the same as the older and larger T2 series turbo, while the new GTVNT15-49 turbo flows slightly less than the older design T25 turbo. The reduction in size of the turbine housing, turbine wheels, and compressor wheels in the new GTVNT series turbochargers while maintaining comparable flow characteristics and improving the Performance Maps efficiency on the choke side of the Map has resulted in significant improvement in useable flow range over the previous T2-T3-T25 series turbos. 

As the data from Garrett Motorsports Turbocharger Division of Allied Signal shows, there are two models of GTVNT15 turbos, one (GTNVT15-46) has a 41.2mm turbine blade and a 45.7 compressor wheel, while the other (GTVNT15-49) has a 44.2mm turbine blade and a 49.0mm compressor wheel. the larger turbine wheel and compressor wheel of the GTVNT15-49 compared to the GTVNT15 gives an 11% increase in turbine gas flow as well as a 13% increase in compressor flow.

[ September 12, 2002, 05:11: Message edited by: SkyPup ]