I have a turbonetics t3/t4 but there are NO numbers ar all on the whole turbo. A lot of people ask me the trims and i tell them i dont know... I feel like a dumbass. I bought the kit used and the guy who sold it said he sold it for his son and doesnt know the numbers.

 

to measure the wheels you will have to take housings off. You may need to replace the compressor/backplate housing gasket if you do this.

Trim is a generic term. It is simply the ratio of diameters on the wheel... I'm pretty sure this is how to figure out in mm.

(in)(in)/(ex)(ex)= comp. trim

(ex)(ex)/(in)(in)= exh. trim

 

hmmm its not worth it to me to know the trim if i have to take the snail apart