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Jarrad,
Hope all's well!
The difference in compressor vocals could be relative to balancing. There are typically two different means to balance the compressor/turbine assemblies via dynamic or non dynamic balancing. Dynamic balancing is more accurate and is a process of the entire rotating components (turbine, compressor wheel, shaft nut, thrust collar)being connected as they would be in service and fine balancing the entire assembly. Typically, the compressor vocals will be less evident with this type of balancing and you can verify that your turbocharger has a dynamic balance by looking for missing/removed material from the shaft nut (removed during balancing). Most of the Garrett T3 SAAB OEM turbochargers were dynamically balanced through the 1981-1989 model years.
Non dynamic balancing would be a fine balancing of the individual rotating components separately and then assembling these with a non balanced shaft nut. A non dynamically balanced unit will be indicated by the shaft nut being whole (no material removed from the shaft nut). This is an accurate balance but not as fine of a balace as the dynamic type and compressor vocals tend to be more pronounced.
A majority of the SAAB T3 Garrett turbochargers came with the 50 or 55 compressor wheels and the 45 was used on the early 8V pre 1984 900. A move to the 60 compressor wheel should only provide a very modest improvement over the 55 but certainly a better option over the 45 (as the 45 is only rated at 155 BHP at 15 psi). The 60 is rated slightly higher in horsepower potential over the 55 at peak efficiency (250 BHP rated at 15 psi boost pressures and at 74% efficiency). The 55 wheel, which is a common OEM compressor wheel from 1985-1989, is rated to about 230 BHP at 75% efficiency at the same charge pressure).
The higher the efficiency, the cooler the charge pressures at the rated BHP range. We tend to prefer the T4 family of compressor wheels which are rated at 76-78% efficiency and tend to generate a more dense charge pressure and additional BHP potential.
Your turbocharger sounds like a nice update and best of luck with your project!
Best regards,
Gary K at SWEDISH DYNAMICS,INC.
SAAB PERFORMANCE PARTS
http://swedishdynamics.saabnet.com
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