Thursday, July 10, 2008 - 04:57 pm, by: Cihan Aday(Cihan)
There is no set method of detailing the specs of a turbo like this, it is very easy to make mistakes.
For example; - You can't simply use a magnet to determine whether turbo's are steel wheeled or not. Not all metals are magnetic, especially metals used for hi temperature applications (ie. turbine material).
IMO the best way to determine whether the turbine is metal or not is to clean it with acetone and check its colour and feel. Ceramic material usually feels room temperature or close to it and is a light red / cream brown colour. Steel wheeled CT12a's usually have more clearance between the turbine housing and the turbine inducer tip. Another step to confirm is to take off the turbine housing, exposing the CHRA side of the turbine which is usually clean and again, inspecting its colour and feel. In high flowed applications, apart from the compressor and turbine striking the eye as physically larger, the compressor side shaft nut will most certainly look completely different to the standard CT12a nut.
I'm personally not a fan of high flowed turbochargers for a few simple reasons; because the compressor housings are never able to be augmented enough to attain a suitable AR, the turbine housings and their respective nozzle diameters are rarely in the correct proportion to the larger turbine size and in most cases the new wastegate flap is not large enough to reduce back pressure with the larger compressor stage. In most high flow jobs the turbine side is barely touched so the in/ex ratio climbs undesirably high when attempting to push above the power level the factory turbochargers were able to achieve.
In any case, the condition of the bearings and oil seal is much more important than the turbine material used. As long as the engine is tuned and serviced well the turbos will be reliable ceramic turbine or not.
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