Well, I'm no expert on turbocharging, but in November 1998 I did purchase my own Sunny turbo engine and boy did I learn a lot. I have read a good bit on the topic in both on the net and in the popular import car publications. I have a reasonable knowledge of the theories and the equipment involved in turbocharging a small 4 cylinder engine.
I would like to say first and foremost, turbocharging a naturally aspirated vehicle is not as simple as buying a kit or engine and bolting it up and driving. There is a lot more involved in this if you plan on having dependible transportation that will last longer than a few weeks.
Bolt on Mods:
First, the engine you want to turbocharge cannot have a high compression ratio. The traditional compression ratio for a four cylinder engine is 8.5 to 1. You can go a little higher with multi-point injection. Most non-turbo cars have 9 to 1 or higher compression ratios. You can get away with about 9 to 1 turboed but beyond that, and the boost you add with the turbocharger will cause pre-detonation and blow your engine. Also, the higher the compression ratio, the less boost you can pump into the engine.
So you'll be rebuilding the engine with custom low compression pistons to lower the compression ratio, and at the same time, you'll be strengthining the block to take the additional stress of the turbocharger.
Obviously the entire computer system in you car has to be changed over to the the system for the used engine. You will need to get the the ECU, the engine wiring harness, all of the engine sensors, all of the solenoids and actuators and additional electronics which control the turbo system. So ensure that a trained mechanic is with you when making the purchase.
Next up , the fuel system delivery will have to be upgraded. You'll need higher flow rate injectors, a higher pressure fuel pump and sub-pump, and a rising rate fuel pressure regulator. Without the additional fuel, the engine will run too lean under the boost of the turbo, and will detonate, and blow.
You have to convert the entire induction system, which includes intake manifold, exhaust manifold, air plenum, waste gate, intake piping, and intercooler.
Now we're done with the engine up grade or replacement, it's time to look at all of the other changes you have to make.
The clutch is the most obvious, the turbo needs a stronger clutch. You'll burn your stock one out in no time with the extra power . If it's a transmission, the stock tranny is not like the heavy duty tranny used on turbo models. You may be replacing cluster gears on an annual basis if you don't upgrade or change yours for a turbo model tranny.
The crown wheel and pinion gears and differential in your stock application are most likely not as durable as those in the turbo models. You'll pop a few diffs until you upgrade to the turbo parts.
The heat form the turbo can affect the engine's cooling, thus requiring you to upgrade radiator or fans. Also affected by the heat is the paint on you bonnet, please insulate the engine room.
Do not forget the cash outlay for gauges, turbo timer, etc.
So it becomes quite obvious that it is no small task to put a turbo onto a non-turbo car. I cannot imagine that installing the turbo and accompanying parts your car would cost less than $2000. Even though if you shop around in the scrap yards you could manage to get the parts to get you going for around $1500 including installation.
There is another option though. There are several US companies who make custom turbocharging kits that work on non-turbo import cars even those whose compression ratio is a little too high for the stock system changeover. This will involve lots of custom piping and some electronics that will be piggybacked onto your ECU and sensors to trick the computer into thinking that your car is operating within normal parameters. This still doesn't solve the drive train durability issues, but the end product will likely out perform the stock turbo counterpart and additional tuning for more power will be easier, because you are starting out with more flexible equipment which won't need to be upgraded from OEM to work with.
Duane Boodasingh http://www.trinituner.com