| I've been spending time getting Dee Ridgeway's DEMONZ put together and assembling the turbochargers today. This car originally had HKS GT2530BB turbochargers on it, however, both compressor wheels were FOD'd. We purchased two new GT2860RS cartridges with the intent to swap the turbine housings over (as the turbines are the same) and purchase new T04B compressor housings to fit the 62-trim wheel on the GT2860RS. All went well and I have two GT2860RS turbochargers ready for actuator bracket construction, mounting and balancing. So I have these two dead cartridges from the GT2530's on the bench and decided to take one apart. I've taken BB turbos apart before but didn't pay as close of attention to details as I did this time around. To disassemble these turbos, you must remove the flare fitting from within the oil inlet. This flare fitting has an extension that locks the bearing housing into place, holding the rotating assembly in position. This fitting is pressed into place from the factory, but it has small internal threads in the bore of the fitting to allow removal of the fitting. I found a screw of appropriate threads and removed the fitting. Just glancing over it, I expected to see a large opening in the end of the fitting, but I didn't. Upon further inspection, I located this: Note the tiny orifice just above the knurled section, pointing slightly right. There is only ONE of these orifices in the fitting.
 Measurement of the orifice size: (0.035")
 Here is the complete turbo CHRA assembly:
 This is the bearing housing/assembly:
 You can see the compressor seal on the far right of the bearing assembly (looks like a piston ring)
 Just a comparison shot of a rotating group from a ST-50 turbocharger for a 14-litre diesel (out of one of my gas turbine engines)
 I'm not sure if this is common knowledge or not, I know there is VERY limited information out there about ballbearing turbochargers, at least, the nitty-gritty details. I would presume that most everyone, including myself, was under the impression that you must jet the oil feed lines for these turbochargers as excessive oil into a ballbearing causes skidding of the balls in the races, which will lead to premature failure. But, it appears that Garrett has already taken care of this for us by jetting the turbo internally at the flare fitting that feeds the bearing group. Interestingly enough, the GT2530's compressor wheel had a part number on the back of it. It is a 63-trim compressor wheel that is supposedly exclusive to HKS, but I contacted my turbo part supplier to see if he can get it. He had two compressor wheels there with identical part numbers except for the last numerical designation and he will be measuring the inducer/exducer diameters of this tonight to see if either one are the correct wheel. Just a heads-up for the HKS people if they ever have any FOD to their compressor wheels - we may be able to repair them yet. I'm also surprised to find that although these are ballbearing turbochargers, they are NOT ceramic ball bearings which I would have expected to see. Ceramic bearings have awesome operating characteristics as compared to conventional chromium/carbon steel ball bearings, namely in the RPM handling properties (ceramic bearings can withstand operating RPMs in excess of 15 times greater than a conventional bearing of identical size). It would be interesting to rebuild a ballbearing turbocharger using ceramic bearings and machine a new bearing tube for them - wouldn't be hard to do at all and ceramic bearings of this size can be purchased in pairs for around $180. Perhaps this will be the new "trend" in ballbearing turbocharger design? (yes, I will be personally looking into this for manufacture of my own turbo design). Anywho, just thought I'd share some valuable information here - have a great holiday everyone!!
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[ agpowers@bellsouth.net ] 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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Your Thanksgiving Turbo Treat! GT turbos, ALREADY JETTED. - 
19:52:32 11/21/06
