Garrett Turbos:
Garrett basically has two lines of turbos. The ancient, inefficient T series turbos and the new, modern, ball bearing GT series turbos.
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T family has T22, T25, T3, T350, To4B, To4E, TS04, To4R ...These are 50 year old, WWII generation turbos.
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The newer line of GT turbos are ball bearing on journal and thrust bearing. The turbine and compressor wheels are improvely aerodynamically to flow more air. GT20, GT22, GT25, GT30, GT35, GT40, GT45, GT50... GT turbos produce slightly more hp then older T series turbos with the same number designation. A GT Garrett turbine wheel wil flow more air than similar sized Greddy turbine wheel. Thus GT turbos are able to boost higher and flow more.
Turbonetics and many domestic makers turbos based on T series turbos. A T3/To4E 60 T .63A/R is a hybrid turbo with T3 turbine, To4E compressor, 60 Trim compressor wheel and .63 A/R turbine housing.
Wheel "trim" refers to the squared ratio of the smaller diameter divided by the larger diameter times 100. Generally, the larger the trim number the more flow the wheel has.
For compressor wheels , larger trim tends to mean slightly lower efficiency.
For "families" of turbine wheels (those with the same inducer diameter), larger trim usually means better flow with less backpressure but longer spool time.
A/R is a ratio of the exhaust discharge area vs the distance from the center of turbine wheel to the center of the cross sectional area. Smaller A/R housing has faster spool up. Bigger A/R housing has less back pressure, more flow for the top end.
The so called "T-series': T60, T61, T66, T70, T72, T76... are T4 turbos as well. The number means the compressor inducer size. ie: T76 means it has 76mm compressor inducer.
HKS uses Garrett turbos. HKS GT series turbos use Garrett GT's turbine with GT's compressor.
For example, HKS GT 2835 is GT28 turbine with GT35 52 trim compressor.
The newer line of Garrett GT-R turbos are hybrid turbos. For example, GT30R is a hybrid of GT30 turbine mated to 56 trim GT37 compressor.
