Turbine vs. Compressor; Size

[Checkered-Member]

This is taken from the SR FAQ:

Quote »Compressor wheels and exhaust turbines should be withen similar specs ( the exhaust turbine should be about 1.1-1.4 times larger than the compressor ), this ensures quick boost response and optimum efficiencies for the compressor.[/quote]Is this a generally true statement?

So what does the KA favor closer to 1.1 or 1.4 (for 7-9 psi)?

Pros and Cons of each (1.1 , 1.4)?

[C-Kwik]

I'd say that statement is wrong. Proper turbo sizing has mostly to do with what you want out of the motor. Taking into consideration, the power goal, the response time, boost threshold, boost level, etc.

The compressor should be chosen based on the boost level intended and how well the motor works with the compessor according to the compressor maps. The turbine is usually a compromise between flow and response.

As a counterpoint to that statement, the T3/T4 turbo is a very popular and proven turbo. The typical T3 turbine is 2.559" and the largest T3 turbine available is 2.798"(this one is quite rare). The T04B compressor is 2.750" and the T04E is 2.950-3". The T04E tends to be used more. A T3/T04E directly contradicts the idea that the turbine should be bigger than the compressor. There's not necessarily anything wrong with a turbo that has a bigger turbine, but that statement is just way too general. There are way too many factors to consider.