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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,289
The Garret ball bearing turbo's and especially the newer ones and hybrid offerings with light weight ceramic ball bearings and new computer designed turbine and compressor wheels made from more exotic lightweight alloys definately_spool_up_faster and make more horsepower than the old technology K27 series Borg Warner turbos.
You can also get Garret hybrid turbos with different AR sized cast stainless steel turbine housings that weigh alot less than the older cast iron turbine housings.

The K27 uses floating bronze bearings which have an oil clearance around the inner and outer diameters so the bearing rotates on the turbo shaft inside the cast iron bearing housing in a bath of moving oil hopefully never coming in contact with anything but the oil at around half the rpms as the turbo's shaft.
Because of that bearing design the K27 turbo has to have some shaft side play for the oil clearances.
The shaft side play is much more more noticeable if you rinse parts cleaner or spray solvent like brake clean through it to clean and rinse out the oil that is in there.

Then take a stock K27 7200 turbo, remove the origonal compressor wheel and KKK compressor housing and with some fabrication to the KKK backplate attach a bigger diameter and heavier Holset compressor wheel and bolt on an aftermarket snail/compressor housing to fit around it like the hybrid K27 HF and HFS and the KKK turbo spools up even slower than the origonal K27 7200 from the increased weight, rotational inertia, and aero drag from the bigger diameter compressor wheel.
That said, the K27 HF hybrid turbo does make more boost than a stock K27, holds it alot longer into high rpms, and the pressurized air flow from it is not as hot as the origonal K27 7200 or 7006 but because of the increased weight and drag of the bigger compressor wheel the whole assembly doesn't spin as fast so it increases exhaust backpressure before the turbo quite a bit which increases heat in the cylinder heads, headers, and the turbo's turbine and bearing housing - shortening it's life and making it a really good idea to use full synthetic 20w50 oil with no petroleum based ZDDP oil additives added to it to keep it from carbonizing and coking up in the bearing housing.
Old 09-06-2010, 06:57 AM
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