planning a turbo setup is a complicated art with hundreds of possible variables to consider for your application so below I'm just touching the iceberg.
what type/configuration of turbo and part's that require upgrading will all depend on ur target goal and application and is a compromise.
big destructive high end puwer or quick low end response?
daily street driving or dedicated track car?
the bare essentials are obviously turbo, induction pipes connecting turbo to TB, oil feed lines from oil port in the front of head, oil drain, manifold (alternator configuration maybe affected) & downpipe
as a start for low boost/power (3psi/90-100bhp), brief acceleration, street driving - the stock systems may handle it fine up to a point depending on their condition and preferably run 98ron but as for any engine tuning I'd highly recommend a proper ecu remap (once all the bits are fitted) such as with Nistune daughterboard via Ed at fusion motorsports to keep the mixtures safe and get the most out of a particular setup.
as ur target bhp increases towards a higher 10psi/160bhp/160ftlb setup like mine, u start to overload all the standard fuel, MAF, drive train & cooling systems, especially during long WOT on trackdays.
I upgraded alot of preventative measures (better to have too much potential than to run parts beyond their limitations) to ensure a reliable daily 160bhp with occasional long trackdays, ie:
- keep intake temps down with big intercooler, insulation, teflon inlet manifold insulator.
- upgraded fuel supply with walbro fuel pump & injectors.
- MAF from bigger engines to be able to still read airflow accurately at the target bhp
- colder plugs
- bigger clutch
- LSD to improve traction
- Bigger brakes to handle track abuse
- thicker radiator to handle the massive heat generated on trackdays
- stiffer PU lower wishbone front bush
the weakest link / parts to upgrade in order of importance as bhp increases imo are:
- tyres (increased power & speed is useless/dangerous without traction & grip)
- head gasket (recommend genuine nissan HG cos it's alot stronger than cheap ebay HG)
- Tunable ecu via Nistune daughterboard (after fitting turbo, u can tune the map at any time, starting with stock bits onwards, until the weakest part max's out/fails..then you upgrade and retune. Or another recommended remapping strategy is to upgrade everything at once then remap it)
- injectors
- pump
- bigger MAF
- clutch (fit the biggest u can to suit the max torque you'll EVER think of reaching or else you'll end up upgrading again unnecessarily)
- radiator (stock 16mm rad can only handle so much continuous trackday heat. an automatic k11 rad is direct fit but a thicker 26mm, can handle 160bhp easy)
- LSD (big torque will spin an open diff easily)
- gearbox (1.3 box is quite strong for 160bhp. only failure was a worn input shaft bearing after a long track abuse)
other preferable parts are
- wideband to monitor and save ur investment
- good flowing air filter placed in a cool air supply
- BOV/Recirc valve
- boost gauge
- good flowing exhaust system
- oil catch can to filter oil vapour out the PCV breather (to prevent oil fouling the intake system & MAF over time) before returning back to the turbo inlet
for more info here's the index of my blog
http://micra.org.uk/threads/pollymobiles-rebuild-blog-index.52496/
