The following subjects will be covered:

Blow Off (Dump) Valve - Which to choose
A Dumpvalve is just as the name implies a valve that dumps the airpressure that builds up in the intake when releasing the throttle. This pressure would otherwise make the turbocharger stop abruptly which results in unnecessary wear and long spool-up time. With a dumpvalve the vacuum formed behind the throttle is used to open the valve and release the high pressure in front of the throttle right out in the engine compartment with a characteristic PSSSSHHHH-sound.

A recirculating dumpvalve maxes exactly the same thing except that the dumped air is recirculated to the pipe between the turbocharger and the airmass meter and thus not have the caracteristic sound. The reason that the recirkulating type works better on a 200SX is that the dumped air is already measured by the air mass meter, and are expected to come into the engine. The ECU (Engine control unit) adapts the amount of fuel to expected airmass. With a open dumpvalve the mixture gets a little wrong when throttle opens after gear change, which can result in some jerks and pops. When the turbo is not charging there is always vacuum in the intake chamber, which makes the dump leak a little and give a strange idle. A way to compensate for this is to not let the valve open until the vacuum gets a little stronger, but then you lose some of the purpose with the valve...

When you have a recirculating valve, it doesn't matter if it leaks. The air always gets where it is supposed to anyway since it is recirculated. In fact, the 200SX ECU can not handle the air released with an open dump. Some say their cars works just fine with it, others not.

The Bosch valve 1. Cost: 250 skr 2. Makes no PSSSHHH-sound 3. Does not dump air out, instead recirkulates 4. Opens at -0.25 bar 5. Works with a closed loop system which does not gives uneven idle.

Dumpvalve (Different Brands)
1. Cost: From 1500 skr and up. 2. Has a distinctive PSSSSHHH-sound. 3. Dumps the measured air. 4. Can not open earlier than -0.7 bar 5. Can give uneven idle and wrong mixture if not completely tight.

As the 200SX has approx. -0.6 bar at idle -0.4 bar at even speed (70-150 km/h) and max -0.9 bar, the valve cannot open until earliest -0.7 bar. The recirculating valve can open much earlier since the air is "reused".

The effective interval of the Boschvalve is -0.25 bar to -0.9 bar

The effective interval of the Dump is -0.7 bar to -0.9 bar

The advantage with bot types of valves is that they relieves the pressure on turbocharger and throttle, giving lower wear and longer life. They also gives much better throttle response after gear change under acceleration.

Electrical Cooling Fan - Mounting
The original visco-coupling fan gives good cooling and does not steal much effect, but however...an electrical fan looks better. You have to install a temperature sensor / relay, or have it always running. When removing the old fan you must use a spacer to be able to tighten the waterpump´s beltdrive. You can use M8-nuts as spacer.

Pros and Cons with grooved Brake Discs
The advantage with both grooved and drilled brake discs are that when the brake pad is pressed against the disk, hot gases are generated. These gases are evacuated in the grooves or holes and the pad lies directly against the disc. Most effect are noticed when the brakes are used hard. In the end of a long braking you don´t have to break the steering wheel to make the brakes work. I have not noticed any excessive wear on neither pads or discs, on the opposite it seems like the pads lives longer.

Melted Pistons
Melted pistons can occur when the combustion chambers gets too hot. This is often a result of not enough fuel on high revs with high turbopressure. (High pressure = lots of air = needs lots of fuel to get the right mixture) A similar but milder damage is that the piston jams a little in the engine because of too high temperature. This can be avoided by using an oil cooler.

Lambdameter
A "Lambdasond" or oxygen sensor reads the amount of oxygen in the exhaust gases and tells the ECU which fuel/air - mixture that is optimal. It is mounted on the front exhaustpipe just behind the turbocharger. A small round thing with a wire connected.

There are no problems leaving the sensor in place even if you drive without catalytic converter. Since the exhaust gases ar more easily evacuated without cat, the temperature at the sensor is even lower.

Torques
Connecting rods 4.2-4.5 kg (in two turns) Crankshaft 4.5-5.5 kg (in two turns) Camshaft 1.0-1.2 kg (in two turns) Cylinder head screws 10.0-11.0 (in two turns)

IMPORTANT 1: First clean the threads then apply some motor oil to them to get correct torque!

IMPORTANT 2: Do NOT use higher torgue than recommended. This can deform the bearings. Use torque wrench.

Oil Cooler
An oil cooler is highly recommended when tuning the engine. If you drive at high revs for a period of time, the oil temperature rises very fast. This wears the oil down quickly with result that the bearings in the engine takes damage. The most expensive that can happen is that the crankshaft is damaged. You also get a more effective total cooling of the engine. The original mounted oil cooler is applied directly to the oilfilterconsole and is in size like a swedish "messmör"-can. It is cooled by the engine´s cooling water. An oilcooler is not very expensive and it is recommended to invest in a new one. If you buy an used cooler you don´t know if it is dirty inside. Because of it´s construction it is almost impossible to clean. You should of course use steelthreaded hoses and a thermostat. There is no use cooling the oil before it gets hot...

Starting problems with Bosch fuel pump
Unlike the Bosch pump the original pump has a reverse valve, it is really not necessary but it helps when starting your car because the fuel pressure is contained even since the motor is turned off. When you have a Bosch pump you have to turn on the ignition and wait for a few seconds for the pressure to build up before starting.

You are also recommended to use a separate relay for the Bosch pump:

1. Check which wires are power and ground for the pump. 2. Cut those wires a few cm from the cover. 3. Attach a 2.5 sq.cm cable from the ground cable to a suitable ground spot on the car body. 4. Attach a 2.4 sq.cm cabel from the power connector on the pump to a relay that you can hide behind the trunklight. 5. Take the two cables previously attached to the pump and connect them to the relay´s coil. 6. Install a 2.5 - 4 sq.cm cable from the battery (positive) to the relay. 7. Insatll a fuse on that cable, near the battery. 8. Start the car.

Detonations
Detonations comes from spontaneous ignition in the combustion chamber. Spontaneous ignition can be caused by differnt things such as: Heat and pressure. Pressure is also causing heat! That´s why the air after the intercooler should be as cool as possible to get the engine to accept higher boost before generating so much heat in the combustion chamber that it self-ignites and causes detonations. When the ignition from the detonation collides with the ignition from the spark plug, it can cause marks and dents in the piston and cylinder head. These collisions can be so fierce that they´re breaking the piston or that material are grinded off from bad places on pistons and cylinder head.

If the spark comes too early, the pressure in the combustion chamber raises so that self-ignition occurs before the piston has reached it´s highest point.

It is therefore very important with exact ignition timing when you are running with high boost.

Ignition - Timing
Get an extra ignition wire, remove no 1 ignition coil (closest to the radiator) and use the extra wire as an extension cord between spark plug and ignition coil. Attach the stroboscopic light on the extension cord and start the car.

On the belt-wheel you have six marks, ssen from the front top they means 5 deg after, 0 deg ,5deg before, 10 deg before, 15 deg before, 20 deg before. When engine is idling the ignition shall be set to 15 deg before. You adjust the ignition point at the sensor located in the front side of the exhaust camshaft, fitted with three screws. ATTENTION! It is very sensitive so be careful and make small movements.

If you are still uncertain how to do, let someone do it for you since it can be expensive to fail...

Spark Plugs - Mounting
Remove the cover between the camshaft-covers, the one marked "twincam". You can see four ignition coils thereunder, unscrew and remove them carefully so you can see the sparkplugs. If you remove all dark screws you can remove all ignition coils at once.

Platinum spark plugs are named PFR6ES or similar, where P = Platinum, R = Resistor, 6 = Heatnumber, E = Long thread, S = Type of electrode. You can use for example BCPR7ES where B = Thread, C = Small wrench, R = Resistor, 7 = A little cooler than 6, E = Long thread, S = Type of electrode

The following plugs works fine:

Single Electrode BCPR7ES (NGK)
Triple Electrode BCP7ET (NGK)