You're right that you would have to replace the entire engine because turbocharged engines have a much lower compression ratio. That means they use different pistons, but there are a lot of other differences you have to consider.
First of all, the only engine you can use has to be from another Mitsubishi car. You can't use any engine from any other manufacturer because engine mounts, sensors, power steering pump brackets, and a hundred other things are different. A modification like adding a turbo is involved enough already, but since you're going to need a lot of parts, you're going to have to find at least one donor car in the salvage yard with the parts you need. You need a car that came from the manufacturer with that engine already in it.
Also be aware the exhaust system will be different, and some sensors will be different. One of those sensors measures engine vacuum. With a turbocharger, the intake manifold will also go into a pressure situation. The MAP sensor has to be one that can measure both pressure and vacuum, then the Engine Computer has to be changed to one that is capable of using that different sensor information. All the many computers on the car talk back and forth to each other, so some of those may need to be changed too so they can continue to work as a team.
This type of modification is pretty involved for an experienced mechanic, and most of the time they result in little annoyances like a hesitation when leaving a stop sign, and things like that which people have to learn to put up with. You are much better off looking at this as an opportunity to trade your car for what you want with the options already built in at the factory.
Tuesday, June 9th, 2015 AT 10:10 PM