I apolagise Sani, I should have had more faith.
I have to say I don't know anything about the Tipo, but I have a Brava TD they may be the same engine but I'm not sure. I looked into how to tune it and was planning on doing it as soon as I put it through a mot (so I dont have to worry about emmisions for 13 months) but a cracked sump has halted my plans, or I would have done it this week.
The principle is the same for any TD with a manual pump, we are looking at adjusting the pump to give more fuel and the turbo to give more boost.
How far you can take it I can not say, you should consider the condition of your engine, the milage and how it has been treated over the years. Before you do any tuning you should make sure that the cam belt is in good condition, the EGR valve is working correctly and ideally the pump timing is right. The overall limit is likely to be how much boost you can run before the charge temperature negates any point in raising it any further. This and/or the appropriate amount of fuel without a unreasonable amount of smoke.
The first thing to do is to check the level of boost, you will need a boost guage. You may find it is running less than standard in which case your gains could be better. If its drasticly lower, it may be worth investigating why.
Turbocharger and Boost
The Brava/o and Marea TD100 were fitted with a Garret T15 which is designed for around 110BHP maximum on a diesel engine, a bigger T2 is about 130BHP. I'm not sure how much of a limit this will be, these specs are from the Garrett docs, but I have seen claims of figures of 160+ hp for cars with the T2 so there may be some headroom.
There comes a point when the performance gains are limited by the temperature of the air. As you raise the boost above the turbos designed limit the temperature rises rapidly. You get to a stage where any increase in boost is offset by the rise in charge temperature. I would aim for about 17 or 18 PSI but really trial and error will tell.
There are various ways to increase the boost pressure, you can shorten the arm on the wastegate. If you look you will see there are two sections of the arm, a rod and a sleeve over it. The sleeve is threaded, and must be screwed onto the bar to make the arm shorter. In order to screw this sleeve further onto the bar, the arm must be released from the other section (the flat plate). This is done by removing the spring clip, the wastegate arm can then slide off, and the flat plate can be moved out of the way. You now should be able to turn the wastegate arm (sleeve part) shortening the arm, in relation to the flat plate. As a rough guide every full turn is about 1 psi this may not be the case for all cars though. If the arm is too rusted some people just bend the arm on the wastegate.
Another and possibly easier way is to use a bleed valve or boost valve. This is a valve that goes in the pipe between the turbo compressor housing and the wastegate. It fools the wastegate by bleeding off some of the pressure, so the wastegate doesnt see the full pressure and so stays closed longer.
The boost pressure and fuelling are not independent on a diesel engine. The waste gate is a final mechanical pressure blow off, if the fuelling is the limiting factor, additional boost will not be gained. So when tuning the car check the boost as the fuel is increased.
Pump and Fuelling
There are two main kinds of pump, Lucas and Bosch. The TD100 has the Lucas.
The majority of the improvements to the power band are achieved by increasing the maximum fuel setting and the boost compensator fuelling. The standard car like all diesels is set up very lean. The procedure to adjust the fuelling is not difficult, but requires many careful and small incremental changes, and many test drives until the optimum settings are found.
The maximum fuel setting has the greatest effect on performance controlling about 80% of fuel delivery, for this reason I would adjust the boost compensator fuelling first.
Boost compensator Fuelling
The procedure to increase the boost compensator fuelling is similar on both the Lucas and Bosch pumps. The boost compensator unit can be recognised by a brass coloured diaphragm assembly connected to the intercooler by a vacuum hose. Unscrew the external 14mm lock nut and turn the adjuster anticlockwise. The adjustment range is about 1.5 to 2.5 turns (adjustment can be made in half turns). The setting is not so critical, running the car rich from the compensator does not make a great performance difference.
Maximum Fuel Settings
The maximum fuel setting is located in different positions for the Lucas and Bosch pumps. On the Lucas pump a large plastic plug is found on the front of the pump. This must be unscrewed and the pump will empty its contents of diesel. Using a small mirror look inside the pump and you may see a hole with a recessed socket head bolt. I think it's about a 5mm size Allen key. If this can not be seen put the engine in gear and rock the car. You will see a cylinder assembly rotate in the pump. It will need to rotate about 180 degrees to reveal the maximum fuel screw. The screw will need to be turned clockwise. To access the screw you will need to insert the long part of the Allen key. Don't use a ball type driver, as the ball may break-off in the pump. The screw to quite tight and so a spanner will need to be used on the end of the key. The range of adjustment is a relative 20 to 40 degrees (40 degrees is rich, make adjustments in about 10 degree increments). Replace the plug, prime the pump and test drive. Look for evidence of smoke off-boost. Repeat the procedure until the desired performance, smoke level and economy compromise is reached.
With the Bosch Pump the procedure is much easier. The maximum fuel screw is located on the top right side of the pump. It will have a tamper proof fitting on it, which will need to be removed. This screw is adjusted clockwise up to about 90 degrees (again use about 10 to 20 degree increments).