Depending on whether you have a 1.6 or a 1.9L car, there are a few options. Since the 1.6L had a factory turbo version, there are forged, 8:1 pistons out there. Most, however, are in EXP Turbo Coupes though.

One solution is to swap turbo parts from a Turbo Coupe. Several people have put the hardware from these cars on 1.9L EFI HO cars. Another option is to develop your own turbo hardware. The second option is not for the weak of heart, but if done properly, can yield a bit more power then the factory turbo could. Also, Turbo Coupes were rare to begin with, and age and rust have trimmed the numbers even more. If you must part one out, try and find one that can’t be restored. Either way you approach it, make sure your engine can handle it. If this means rebuilding it with all new gaskets and bearings, do so.

There were actually 2 factory turbo versions of the 1.6L; one that was US spec and the other was European spec. The Euro spec turbo was a far better set up then the US version. The exhaust manifold was a better design, the turbo was bigger and the car actually used an intercooler (the US turbo didn’t). The European Escort Turbo RS made about 135 HP @ 7 or 8 psi of boost. The US spec car made 120 @ 6 psi. I’ve heard that the Turbo RS could make as much as 190 HP if the boost was turned up to 15 psi. I wouldn’t recommend raising boost levels on a stock US spec turbo car at all; the turbo’s compressor is quite small and is already working hard to make 6 psi. Its also not water cooled, and prone to cooking shaft bearings when too hot or if the oil supply is hindered. Going beyond that puts the turbo system as a whole beyond where it is efficient, and it will heat the air too much in the process.

To get more airflow or boost pressure, upgrading the turbo to a VJ-14 (up to about 16 psi) or even a VJ-11 or 16 (up to about 20 psi) should be considered. These are both water cooled and bolt up to the manifold. The VJ-14 is better sized to the displacement of the 1.6L (it was used on a 1.6L Mazda), whereas the VJ-11 is used on the 2.2L Probes. A hybridization of the two (a VJ-14 with a VJ-11 or -16 compressor) would be a pretty good match up for a tuned 1.9L. You could upgrade the 1.6L to the hybrid too, but it would feel a little more laggish, I think.

And always, an intercooler should be used to take heat out of the compressed air. Cooler air makes more HP. The intercooler from a Probe turbo (or MX-6) is a good place to start. Reasonably compact and fairly efficient, its a decent all around unit. You can, of course, fit a larger intercooler up front under the bumper, but remember that longer intake piping means it takes longer for air to get from the turbo to the combustion chamber.

Also, if you do upgrade to where you can increase boost, make sure that you have the ability to add more fuel. More air means more O2 in the combustion chamber, and that means more fuel is needed to match so the air/fuel ratio doesn't change. If the engine goes lean, it can cause quite a bit of damage, including possibly melting holes in the pistons (I’ve seen this). Always use an air/fuel meter and an exhaust gas temp. gauge when tuning a turbo system. These are invaluable tools for telling if the a/f ratio is off. Tuning the fuel to match the boost is particularly tricky with older speed-density injection systems. The ECU had preprogrammed fuel curves that it defaults too at wide-open throttle, at which point it disregards what the O2 sensor and such are telling it. You need to get in to change the fuel map to properly change the computer's reaction. There are other possible ways around this issue, though. Some folks use bigger injectors (or an auxilary injector), so that for a given injector cycle time, for fuel flows. To back that, more fuel rail pressure is often needed. That often also means a higher volume fuel pump is in order. These methods require careful tuning, and may or may not full address the propblem. Its also possible to swap in a 2.3L turbo ECU. Apparently, the pin-outs are the same for the computers from T-3 equipped 2.3L engines, so it should work (in theory). It actually would probably support up to 18 to 20 psi of boost stock, since the displacement of the Escort engine is a bit less then the engine it was programmed for...

Thanks to EXP Jawa for this contribution