You have probably heard people talking about their cars with T3, T4 and T6 turbos. Then do you exactly know what is a T3, T4 and T6 turbo, and what are the differences between them? Let us give you a explanation here.
The T3/T4/T6 refers to the tubro turbine housing size and increase in diameter and width as the number goes up. So a T4 turbine will be larger than a T3 turbine housing, but smaller than a T6 housing.
Following picture shows the dimension of T3, T4 and T6 turbine housing flange.
T3:
T4:
T6: