Turbocharging the KA24DE can produce great numbers if the tuning is right. It's easy to attain over 200rwhp with a basic turbo kit like the kind sold on ebay. Advanced tuning and internal engine modification has produced KA24 240SX's with 500+ horsepower.
For a budget turbo build, you can get a t25 turbo and 5-7 psi without having to upgrade the injectors or MAF. You will need a fuel management unit (rising rate fuel pressure regulator). A new fuel pump is recommended. You also need to be careful with the ignition timing. MSD's Boost Timing Master can retard the timing appropriately.
The stock internals have been proven to be quite resilient. There are individuals who have made 350+ rwhp on totally stock internals. Here are a few quick limits on stock KA24DE internals. Keep in mind these are NOT EXACT NUMBERS. True limits can vary signifigantly from motor to motor. Before undergoing any turbocharging project, it is a VERY good idea to do a compression test. The closer to 180 psi you are the better. Anything below 150 and you generally want to start to think twice about a turbo project. So without further adue...
Pistons - Good for approx. 275-300 hp Rods - approx. 400 hp Crank - Indestructible Valvetrain - No known issues Head Gasket - approx. 320 hp WITH A GOOD TUNE (see below) Head Studs - approx. 300-320 hp
...Ofcourse, all of this is dependent upon a good tune. As long as your compression, timing, and air/fuel ratios are all within spec, and the motor is not continually beaten upon, you can expect extended performance out of these parts. Many individuals are making 300+ hp on stock blocks with 200k+ miles on them! For a wealth of information on turbochared tuning for KA24DE and KA24E motors, visit the forums at KA-T.org.