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NADS (Nissan Anti-Detonation System)
The below is copied from .....http://www.mypatrol4x4.com/topic/57-nad ... tep-guide/
[i]The Nissan Patrol 3L di engine can have a few modifications to make it more reliable and avoid the dreaded 'grenade'. This thread is not here to debate the reliability of the engine, or compare it to the 4.2 or petrol variants, its here as an easy to follow guide for anyone interested in doing the modifications.
I have done these modifications to about 10 GU patrols now, and while I'm not a qualified mechanic I reakon I have it down pat. Many thanks to Chaz for teaching me.
Any advice on this thread is just that - advice. I am not a mechanic so if in doubt ask first!
WHAT IS NADS?
NADS or Nissan Anti Detonation is a series of simple modifications that can be done to the di zd30 engine and exhaust to avoid the well documented issues with piston and engine damage.
WHY SHOULD I INSTALL NADS? (Short version)
There are 5 root causes for the zd30 engine failures.
1. Exhaust Gas Reticulation Valve (EGR). This valve recycles inert (but very dirty) exhaust gas back into the inlet manifold in an effort to reduce emissions. However the blank gunk deposited creates restrictions in the inlet manifold causing hot spots and starvation to mainly number 2 and 3 cylinders. See the install section for photos.
2. Oil Starvation. When the early engines came out, Nissan recommended that it only required 6 or so litres of oil. After a while they noticed many failures and "fixed" the problem by recalling the Patrols to shorten the dipstick. The correct amount of oil for the Di ZD30 is 8.3 Litres.
The modified length of the dipstick is (edit)cm
3. Overboosting. The ECU on the early GU patrols doesnt control the boost very well. The GU patrol has a Garratt VNT (Variable Nozzle Turbo). The way this works is - the pitch of the blades of the turbo are changed to create more boost at lower exhaust pressure. Think about how a turbo prop planes engine works. At a constant rev range the power (or thrust) can be increased, decreased or even reversed by changing the pitch of the blades. Like a fan!. The ECU has a pretty big job on its hands trying to control boost at the best of times - different engine revs, different load, the EGR opening and closing (which increases boost in the inlet manifold, after the turbo that the ECU doesnt know about). Nissan introduced an overboost sensor to try and over come this. It basically measures the boost (in the intercooler) and if it stays over a certain psi (it seems different for many sampled patrols) if puts the car into limp mode. You will know if you have limp mode if you are driving along, and all of a sudden if feels like you have no power. If you release the accellerator and reapply, it resets. Very annoying!
4. High EGT (Exhaust Gas Temperature). The Diesel engine is made to work. Good torque at low revs so you dont have to rev its guts out to get power. Its one of the reasons it is so fuel efficient compared to petrol engines) as a lot of the power is rquired just to get your 3T car moving! Obviously for the engine to run you need fuel and air and the combination of these can determine the temperature of the exhaust. Over fuelling or underboosting are common causes of high EGT. Why should i care about EGT? Well, at certain temperatures metals change caracteristics. They can get weaker (causing failure) or even melt! If your exhaust is glowing hot, think about how the pistons, cylinders, manifolds, oil and turbo are feeling!
5. Dirty or faulty MAF sensor. The MAF (Mass Airflow Sensor) is a small device located just after the air filter which measures the volume, speed and temperature of the incoming air. If the sensor is faulty, the ECU can over or under fuel the engine, causing high EGT and failure.
A common issue with MAF sensors is that they get oil on them. This is caused by the Crank Case Ventilation hose feeding back into the air inlet, just after the air filter. If you have a look on top of your engine, you will see the pipe coming from the top most part of the engine, it goes to the air inlet next to the passenger side battery. Oil mist causes the MAF to give incorrect readings. Regularly cleaning your MAF sensor, and fitting a good qulity catch can will certainly help. Its a simple thing that can be done relativly quickly. See the how to section for details.
WHAT PARTS ARE NEEDED? WHERE DO I GET THEM?
If you have read this far, you are probably keen to learn about what is included in "the mods" - Well here they are!