EGR Block on 2007 Patrol

While the Theory of EGR sounds good, in practise it has proven to have many issues. CAT engines for one abandoned EGR in 2006.

On the Nissan 3.0TD the EGR enters directly opposite pistons 3&4 hence they see far more hot gases than pistons 1&2. Thus 1&2 run lean while 3&4 run rich and in a diesel running rich = hot and this is arguably one reason why these pistons in particular hole in the series II 3.0TD.

So, blocking off the EGR and turning down the turbo boost (to compensate for the increased exhaust flow) is one way to minimise perforated pistons. I have yet to hear of a single holed piston failure amongst anyone who has blocked the EGR off.

I don't think the common rail 3.0TD would be any different than the earlier multipoint injection and that it would benefit from blocking the EGR - however I have not heard of any reports either way.

Cheers

Captain

Hi Captain,
I have to agree with your comments and I would like to add a bit more.
The intension of EGR is to reduce PEAK combustion temps to reduce Nitrogen emissions. This doesn’t have too much relevance to exhaust gas temps, but will alter fuel mixture for those cylinders which will have some relevance as you suggested.

EGR on a diesel does offer a small benefit to the environment, but it destroys the engine by fowling the inlet manifold with hot gasses mixed with blow by oil. It reduces power and increases fuel consumption.
EGR on the late CRD Patrol is water cooled which is an improvement, but it will still fill the motor with rubbish and eventually the EGR control valve will loose its ability to seal and fail. It’s just a mater of time.

I find it interesting that so many people that have blown their 3.0Di Patrol motor say it wasn’t modified. It seems that most of the blown ones weren’t, but one or two have had problems because the mods weren’t done properly. There are many getting around that have had EGR blocked that don’t have problems, run lower EGT’s and improved performance and fuel consumption.

Chaz

Captain, Chaz,
I understand what you mean, however if the EGR enters directly on pistons 3&4 then the result is that they are cooler, because the result of recirculated air (which has no oxygen) is that the combustion for those two cylinders is lower.
What I meant with my reply refers to the latest common rail diesels, not the previous 3.0L
EGR was initially used merely as a means to reduce Oxides of nitrogen levels but engineers have found a way to at certain parameters inject inert gas lowering combustion temperatures thus controlling those temperatures whilst maintaining peak performance.
That is also the reason why the EGR is now controlled by the ECU, it is cooled before re-entering the engine and they also use a butterfly to offset turbo pressure that would otherwise act against EGR pressure.

If you block it, you get elevated combustion temperatures and subsequent perforated pistons etc

People tend to think EGR in diesels is the same as in petrols but its not and whilst I agree that it is one more thing to gunk up the engine, engineers are doing their best to make the most of something they have to use.

Some of the latest CRDI engines (Euro IV) such as that fitted to the new Sorento 2.5 CRDI also measure exaust gas oxigen and EGR flow, in other words (close loop) and based on those readings it controls the EGR and injection parameters.

In other words, EGR is becoming an intrical part of the engine management system rather than an add on.

Be aware if you intend to go modifying it.... unless you are modifying an older one.
Check the engineers designs on the engines and workshop manuals (some of which are available online)

Hi GUPatrol,

I know the THEORY of EGR should result in lower temperatures, but practise has shown the opposite result in the GU 3.0TD. This is from many web site reports where owners have installed boost and EGT gauges.

The ECU averages the fuel load and EGR over all cylinders but the mechanical design has resulted in biasing to 3&4. Thus when using close to full throttle (EGR partially open) it can result in 3&4 being too rich due to flow biasing and displacing more oxygen than designed.

Additionally, the EGR valve itself is know to stick. If this happens in any position other than closed then EGR is always entering the cylinders and resulting in richer temps under heavy throttle.

The problem is, in a diesel, running richer results in higher combustion temps and the displacement of too much oxygen by EGR results in enrichment.

Its not that the theory of EGR is wrong, its just the way it has been applied mechanically in the GU 3.0TD.

Also, while a truly inert gas would be fine, exhaust gas is hot, has particulates and is the last thing I would want to recirculate around in my engine. The proof is in the pudding, blocked EGR results in a much cleaner oil as seen during oil changes.

While I believe it is possible to design a decent EGR system, the Nissan system is far from decent.

Cheers

Captain

Gents
Just an update in relation to where I am with the above.
My car (2007 3 LITRE CRTD)is currently at a specialist Turbocharger Tech Business.
The proposed outcome is I am looking for better power and torque for towing a van (1.6 Tonne on the beach)
As the engine is fairly new (so to speak) the mechanic explained that they will test the engine under load etc top see what it is doing and if it has the same type of problems that older engine had frequently.
An early update which shocked the Turbo company is the boost Lb are between 14 -20lb.He said this was a good sign a this is the first 3 Litre patrol he had come across that did not over boost significantly.
Secondly he explained that the engine did appear to be staying a lot cooler than previous models did but we are still going to adapt a 9 inch intercooler fan (Slightly bigger than older models could take supposibly) to give it the best chance.
A larger exhaust is to be fitted a per what appears to be normal requirements for more power and he is still talking to DP chip in relation to adding it and whether it can help this engine as other measurements/findings are so different to older direct injection engines..
I will post an update as to his findings and the cars performance once I get it back for those that would like to know.