Thread: K27 vs K28...
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DSPTurtle DSPTurtle is offline
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Join Date: Jul 2001
Location: Suntree, Florida, USA
Posts: 2,265
Does the K28 take longer to spool up? Since it is bigger it probably has more mass to start moving but that coudl help keep the boost up between shifts. Plus, you can only put so much air into a 3.3L engine... and once you hit max boost all the extra goes through the wastegate anyway. Then again, your motor may be built to spin 10,000 rpm... is it? So far my research shows the K27 is the quickest spooling turbo that can pump the required amount of air, but I am still looking into this (there is another thread on Turbos that I started a few days ago). It seems that all the specialist stay with the same size frame (K27)and tweak the blades to accomplish more boost or quicker spool. I don't see too many people offerring a K28 option but then again I have only looked at 20 or so different sites so far. Someone had an equation for how many horsepower per .1 bar of additional boost but that seems to just be done via a stronger wastegate spring or an adjustable wastegate. Other then the fully race prep'd motors I haven't seen anything that talks about going beyond 1.2 bar that the K27 makes easily. But, that may just be because they haven't played with a bigger turbo... or they may be a thermodynamisist and know that you can't physically plow more air into the motor beyond that point
JB - BreitWerks
Engine Rebuild & Restorations
Old 09-26-2007, 02:36 AM
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