| be built. Last time I ordered a pair of the turbines I was told by my Garrett distributor that only 12 more of them exist in the world and that Garrett has no intentions of building more of them. What makes them "tweaked out" is this turbine. The 79-trim turbine has 10 blades vs. the GT2860RS's 9-blade 76-trim version. The additional blade on the 79-trim version is capable of absorbing more impulse AND reaction energy from the exhaust gases. This results in notably quicker spoolup of the rotating group. The higher trim number relates the major diameter (inducer) of the turbine wheel to the minor diameter (exducer) of the wheel - the higher trim number tells us that the exducer of the 79 trim version has a larger diameter - thus a larger free-flow area through the wheel. The additional blade does take up some of the free-flow area, but from experimental data it appears that the larger exducer area has a larger contribution compared to the flow detriment caused by an additional blade. GT2860RS exducer diameter: 47mm = 1735 mm^2 area
10-blade 79-trim diameter: 48mm = 1810 mm^2 area appx a 4% increase in flow area, but with 11% increase in the impulse energy absorption due to the additional blade. This results in about the same % of increase in spool rate. Here is a balls-out dynochart with wastegate hoses disconnected so you can see the open-boost response: 
She was at the absolute limit of the stock ignition system here, which resulted in some misfire at the top, but you can see how the response of the turbos contributed to the bottom end - somewhere around 340RWHP at 4K, ~440RWTQ. =) Try finding a comparable dyno chart showing 600+RWHP with that kind of power/torque at the 4K metric. =) Because of the peak power/torque this setup is making, that is the experimental indication to me that the small detriment to flow area by adding an additional turbine blade is outweighed by the increase in flow area due to the larger exducer diameter. Pretty wicked turbos for sure - it is a shame that the turbine wheel required to make them isn't available anymore.... This was the best turbine for a 1.5L engine and the 62-trim comp wheel - it drives the compressor to spool up very rapidly - just shy of its surge line. At this point, if I do any new turbo stuff, I'll be looking into using axial flow turbine wheels and duplexed angular contact full ceramic bearing sets.... Still dont know why no one is producing axial flow turbine based turbochargers..... :)
Enthusiasts soon understand each other. --W. Irving.
Are you an enthusiast? If you are out to describe the truth, leave elegance to the
tailor.
Albert Einstein
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Unfortunately that is a breed of turbo that can no longer - 
