How do I know if a turbo will fit my car? Specifically a t3/t4

[volkswagensRus]

I'm looking at t3/t4 turbos. How do I know if they'll bolt up to my car? They claim they'll fit Nissan's.... but how do I know if they'll fit my Audi?

[redline380]

Literally any turbo can fit your car. Do you mean which one is appropriately sized? You will need ind/exd measurements of both the compressor wheel and turbine.

If it is a stock nissan turbo, odds are it will work dandy.

[volkswagensRus]

Sorry for the noob-like question. Lol. Yes I mean will it physically bolt up. I'm aware of sizing ind/exd comp and turb sizes.... just wasn't sure how to tell if one turbo would physically match up between cars. Thank you for the input though! I might be gunning for a t3/t4 setup thats just tuned down a touch instead of a maxed-out k04 setup.

[VanCityA4Q]

Short answer no.

Long answer....
Our stock exhaust manifold has a K03/K04 flange on it, so you would need to find a turbo with a K03 flange, 1.5" inlet and 2.5" outlet with a standard 3 bolt flange if you want it to "bolt right up" there are many options available depending on what your end goal is. I'm doing a stage 3 big turbo build that has tons of mods needed but I doubt you want to go that route. There's some great sites around with some great products for our cars like ECS Tuning, Intigrated Engineering, and for OEM stuff Hans auto parts is amazingly cheap!
Doing a big turbo upgrade is 80% research and 20% actual work, take your time and don't rush or you end up like me.....6-7 grand into parts and hours in labor so far and I just figured out I need to change my entire ecu and install a wideband lambada sensor.