I'll try tackle this to the best of my ability, get nick to correct but i think this is how it works.

Don't forget your pistons, conn rods, crank, and its blow off valve, not pop off.., better clutch, gagues etc.

d00d, its not as easy as you think to set up a turbo setup. the problem is getting all the parts to work efficiently to create max boost with the least amount of work on the whole engine setup *including turbo*. If you want a simple way to turbo your engine, look for a turbo kit, otherwise lookout for rising costs as things WILL get pricey. if 6-7 lbs of boost is all your going for, try a t3 or t3/t4 hybrid turbo from garrett, or even take a turbo from a previously turboed car (ex. Supra, Rx-7 etc. and that would save plenty of money) Research is the key, as there are many different turbo manufactuers out there, from KKK, garrett, and turbonetics to name a few, and getting the right turbo, from the maker to exhaust housing and impellers, is essential for the system to work properly.
Now to answer your questions directly...
1 - Turbocharger (favorite; garrett)- First, find one that will fit in your engine bay.. sounds silly but think about it, if it doesn't fit then whats the point in trying it. secondly, try to calculate how much exhaust pressure there is, because dpending on the exhaust pressure, your impellers and exhaust housing will be very different in terms of efficency. (Theres a crap load more in selecting the right turbo but we can leave that for another thread)
2) intercooling (Spearco Air/air)- Now you wanna cool the air that goes into the intake, but try not to cool it too much as the pressure of the exiting air from the intercooler will be lower than what goes into the intercooler due to ?density? (if i can remember correctly) and you have 2 main ways you can go with intercooling, water => air cooling and air = air cooling.
3. blow-off valves and wastegates (HKS!) - ahh there are so many different types of each.. so many explanations... but look, you invest so much money into this turbo setup... get an excellent make of both... i say HKS , cuz if you have a crappy BOV heh, buh bye engine.
and ya, they would have to be welded into the plumbing depending on where the wastegate prefers to be (pre or post intercooler)
4. Custom oil PAn - okae, this is a little tricky.. as you probably know, that turbo needs to be lubricated with oil constantly. no oil pressure, and buh bye turbo. whoever told you to get a custom oil pan might not know the exact setup of where your turbo will be located in relation to your oil pan. The oil from the turbo has to be pumped from the oil pan into the oil inlet on the turbo and then drops from the oil outlet on the turbo back into the oilpan. What they mean by custom is, depending on how low your turbo sits compared to the oil pan, you gotta get it custom made, (dry sump or wet sump systems) just because the oil has to go back to the pan.

now i believe this sh** is right.. i studied a book on turbo setups and such but that was march break. So just don't rely on this piece of information alone and hopefully nick has some corrections to this.

 

pop-off and blow-off are interchangeable. it sounds like i might be better off letting someone else figure out what i'll need. i'll definately get the turbo used.

i never thought it was easy. there is no turbo kit available. that's interesting that i shouldn't cool the air charge too much. i realize the cost is gonna be high, but it'll be worth it if i can get some good gains.

 

Don't forget your pistons, conn rods, crank, and its blow off valve, not pop off.., better clutch, gagues etc.

They aren't necessary, but suggested. A turbo setup can run on any car as long as it's tuned properly and compression on the motor is good. A BOV and POV are completely different. A BOV releases pressurized air between the turbo and throttle body in order to prevent the air from travelling backwards into the turbo once the throttle plate is shut. A POV is more or less a secondary wastegate.

if 6-7 lbs of boost is all your going for, try a t3 or t3/t4 hybrid turbo from garrett, or even take a turbo from a previously turboed car (ex. Supra, Rx-7 etc. and that would save plenty of money)

I would suggest a straight T3. It will be much less laggier than the hybrid turbo.

Research is the key, as there are many different turbo manufactuers out there, from KKK, garrett, and turbonetics to name a few, and getting the right turbo, from the maker to exhaust housing and impellers, is essential for the system to work properly.

I agree. Proper selection of trim sizes, housing sizes, etc. is extremely important.

2) intercooling (Spearco Air/air)- Now you wanna cool the air that goes into the intake, but try not to cool it too much as the pressure of the exiting air from the intercooler will be lower than what goes into the intercooler due to ?density? (if i can remember correctly)

Cooler air = denser air = more power

get an excellent make of both

This is true especially for the wastegate. Don't bother with the POS Turbonetics Deltagate. Go with the Tial or HKS wastegate. A BOV is more or less the same across all manufacturers. I like the Greddy ones the best.

, cuz if you have a crappy BOV heh, buh bye engine.

No, this is incorrect. A crappy BOV could potentially cause turbo failure due to the compressed air travelling back into the turbo. It can't damage the motor cause the throttle plate will be shut. A defective/crappy wastegate will cause engine failure.

and ya, they would have to be welded into the plumbing depending on where the wastegate prefers to be (pre or post intercooler)

A wastegate is always in the same place - off the turbo manifold or built into the turbo. A BOV will always be after the turbo before the intercooler/throttle body.

4. Custom oil PAn - okae, this is a little tricky.. as you probably know, that turbo needs to be lubricated with oil constantly. no oil pressure, and buh bye turbo.

This is not always necessary. It will depend on the car. I dunno much about your car, so I don't want to misinform you.

 

the cooler air less density is an old theory. yes, on paper its true, however, many racers, including drag racers, have sweitched from air to air and now use liquid to air. Luiqid to air intercoolers have dynoed a significant increase in hp and a substantial drop in charged air temp.

I've always liked, and had my eyes set on the mitsu 16g or even 20g turbo (off of the talons). Very durable, a good size and i think each is capable of 12 and 28 pounds respectively. DSM guys will know quite abit on this turbo. in either case, do not go too big of a turbo...you will face lag problems the larger you go.

sw20 is right about the POV...basically a wastegate. However, you need both BOV and wastegate.

Manifold selection/construction, in my mind is the most essential part of a turbo. its the skeleton of the turbo. a good cast iron one is the best....tubular....well, they're okay but will not have the durability of a cast iron one.

one thing overlooked but in mymind should be on the frontlines is fuel. all this air and no fuel = detonation. get a good high power fuel pump that has a sufficient GPH and high flow injectors. the rule of thumb is 5cc per hp per piston (ie: 100hp L4 = 25 x 5 = 125cc) although sometimes you're better off going bigger than that.

hope this helps a bit

 

sorry, the 20g is capable of around 18 psi...not 28...typo

Nick

 

I will be going the air-to-water route for the IC in my car. I'll be placing an additional rad and fans in the rear trunk. I am also awaiting the results of another MR2 owners who is doing a refridgerate air-to-water setup.

The Mitsu turbos are very good, especially for the money. Those are the turbos used on the Greddy turbo kits for the MR2 and Supra. I'm probably gonna go with the Garrett GT30 turbo myself, but it costs way more than the Mitsu turbos.