I found this on another forum, it might be worth having in the knowledge sections of the forum if it's of use. I have copied and pasted the page in.
Well I stumbled across this website the other day and thought it might be worth posting a couple of links on here about it.
I've seen different guides regarding turbo's before but alot seem misinformed and generally don't explain things properly or give you explainations that will help YOU. Definately one of the best I've read so thought I'd share the knowledge.
Three different links from the same site as follows...
Basic. This explains what a turbo is and how it works. Also includes roller bearing vs journal and different wastegate types...
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech101.html
Advanced. Right now we're getting there, explain's what "trims" are, A/R housing size's and how they effect performance. Fueling and Engine Knock, Compression Ratio.
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech102.html
Expert. Now we are talking. Compressor Maps explained, Boost Characteristics, Boost / Air Flow for Power Target etc etc
http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html
Hope you find it useful.