ct26 turbine wheels, JDM ceramic versus USDM steel, differences? Are they noticeable or negligible? Options

[Darkchylde]

Soooooooo, I have had to send my 26 out to be rebuilt and in the process have found that the turbine wheels need to be changed. The shop that has the turbo says that they can't get the JDM ceramic wheels so they will have to use steel ones.

1) how will this affect my spool time/ Lag? (new to forced induction, understand the basics but am still a little fuzzy on the intricacies)

2) anyone know where to get the ceramic wheels?

3) any one have a JDM importers # or a 26 or 20b they can spare?

Thanks for your input and assistance all.

[delusionz]

http://www.mrcontrols.com/primers/turbo.htm

There are very few options (at least in the USA) for changing the turbine housing or wheel. The single entry CT-26 turbine is easily available, but it does not bolt to the stock MR2 turbo elbow, so serious modifications are required to use it. The most widely available alternative is to clip the turbine wheel. Clipping the wheel does reduce its ability to extract energy from the exhaust, but since there is so much exhaust at the higher RPMs where the stock turbine wheel chokes the engine, clipping is a reasonable choice. Dyno runs with a 12 degree clip have shown ~15 rwhp improvements in peak horsepower and moved the choke point from around 5.5K to 6K RPMs. There is a slight increase in turbo lag, but this can be kept to a minimum if the compressor wheel is kept to a modest size (since there is really no need to go with a large compressor wheel as we determined in the 3S-GTE turbo sizing primer).

At the current time, my suggestion for a twin entry CT-26 upgrade is to add a TO4E-46 trim compressor wheel and perform a 15 degree clip on the turbine wheel. Those who have ceramic turbine wheels (only used in Japanese spec 3S-GTEs) cannot clip due to the brittleness of the material, but the smaller ceramic turbine is already a little less restrictive than the metal one and naturally supports about 10 rwhp more that its unclipped sibling.