Pajero NW Diesel 2014 EGR options

[Keithyv]

Not at all. Somewhere here there is an extract from a factory manual that explains that the air temperature from the MAF sensor is only used by the EGR system.

The engine ECU needs to know the temperature of the intake air in the intake manifold, after it has been heated by the turbo and cooled by the intercooler. That, and manifold pressure, is more relevant the engine than the air temperature by the air filter.

Roger that, this makes more sense...

[Talisker]

Nice to have some discussion.
Yes I do tend to think the engine run away issue is something promoted by the ECU tuning companies that want to get the business of electronically changing your EGR control, I doubt it is a real issue. From my own experience with some pretty old diesel tractors that I would have thought could have suffered due to worn engines it hardly happened, I doubt it will ever happen with my well-maintained diesel vehicle.

At this stage I am going to fit a Catch can as its pretty simple and I would do that irrespective of the resistor mod. l see what electronic info I can get on the ECU control an do some more research before I add that as well.

I do thing the ECU reprogramming is a nice way to address the issue but I reckon for what they do to achieve it they would want to much $$$ but then I haven't ask maybe I should.

Many thanks for all the input.

[gas55]

Fitted a full blanking plate to my NW nearly 4 years ago, with no problems. Have scan guage in case but never used it.
The car goes like a train, (diesel electric train)! and tows a caravan.

[HeavyPizzaz]

What about potential for higher combustion chamber temps without EGR and therefore adverse long term effects? I’ve read this in numerous locations.

[erad]

What about potential for higher combustion chamber temps without EGR and therefore adverse long term effects? I’ve read this in numerous locations.

From what I have read, the EGR comes into effect only at lighter throttle openings, and stays shut at full throttle, when the temperatures are at maximum. Even if it wasn't this way, how often do you use full throttle (and higher, = max boost) for extended periods? in 6 years of ownership, I have used maximum boost for more than 5 minutes only 3 times - when towing my caravan up steep mountains. Normally, in such conditions, the road speed is governed by bends or other traffic, so the engine speed drops, as does the boost from the turbo. This is what heats things up.

As for run on when shutting down, the engine runs on maybe 0.5 seconds maximum when the A/C is on. It is a minor side effect.

[pharb]

What about potential for higher combustion chamber temps without EGR and therefore adverse long term effects? I’ve read this in numerous locations.

I don't believe EGR reduces combustion temps from extremes. Only reduces combustion temps when operating conditions allow (ie throttle opening, engine load) to reduce NoX. For example at cruise conditions.

In fact the system uses the reciculated exhaust to reduce the amount of available oxygen in the cumbustion chamber to create a lesser "bang" for the same fuel input. Very laymans explanation.

Combustion temps are likely to be highest at high engine load, large throttle openings/large fuel inputs.

If the ECU was smart enough to recognise dangerously high combustion temperatures it would also be smart enough to reduce fuel input.

[nj swb]

What about potential for higher combustion chamber temps without EGR and therefore adverse long term effects? I’ve read this in numerous locations.

And in numerous locations, it's simply wrong.

Heat and temperature are not the same thing. They are related, but different. Skip to The Conclusion if you don't want the boring details.

High combustion temperatures produce NOx (Oxides of Nitrogen), which is bad for the environment, and bad for us.

Highest combustion temperatures occur when there is heaps of Oxygen, allowing a good clean burn of the fuel, and a burn of some of the Nitrogen that makes up 78% of our air.

EGR recycles some exhaust gas, which is low in Oxygen, to stop the engine drawing in so much fresh air (with a little over 20% Oxygen). While EGR is recycling exhaust gas there isn't as much Oxygen, so combustion is less efficient, which means lower combustion temperatures and less NOx. (But more diesel particulates (soot) which is bad for the environment, and bad for us - so they invented the DPF ).

The "heaps of Oxygen / heaps of NOx" scenario only happens under low load, when the engine is running efficiently, and coincidentally not producing as much heat. Higher combustion temperatures, but less heat overall, so our engine can easily dissipate the heat, and keep cool.

When our engines are working hard at high boost pressures, and the ECU is working hard to deliver enough fuel (but not too much) combustion temperatures are actually lower. But so much more fuel is being burned, and so much more heat is being produced, that our engines struggle to dissipate the heat, and struggle to keep cool. Because our engines aren't designed to run at maximum boost / fuel / power (torque) for extended periods of time, the cooling system and the exhaust system simply can't dissipate heat as fast as it is being generated - which is when we get high engine temperatures, and most critically, high exhaust gas temperatures. And, under these conditions, EGR isn't operating anyway.

The Conclusion:

EGR = lower combustion temperatures, lower NOx, higher particulates, low heat = low engine temperatures.

No EGR = higher combustion temperatures, higher NOx, lower particulates, but still low heat = low engine temperatures.

[HeavyPizzaz]

I’ve been close to pulling the pin on an EGR delete multiple times.

Why is there so much negativity on the D-Max forums?

http://www.newd-max.net/viewtopic.php?f=19&t=1669&start=50

Granted, 4 years old now, but what is it about the D-Max that makes so many owners skeptical about the operation of a delete cable??

[HeavyPizzaz]

While I'm picking up what you're putting down, I fitted the resistor mod pretty soon after purchase on our NT and so far
Had 1 runaway situation occur and the key shut the engine off (thankfully)
Never noticed any shuddering when switching the engine off. It can run on a bee's whisker longer when hot but that's about it

Also I just re-read this and noticed the run on comment. It’s not really a run on / runaway situation if the key shut it off right? A run on situation occurs when you turn the ignition key off and it *doesn’t* shut down. So not sure what happened in your situation.

[HeavyPizzaz]

Also (sorry 3 posts in a row), just found this from a few years ago..

https://www2.pajeroclub.com.au/forum/showthread.php?t=51008

I’m surprised it didn’t get any replies at the time. If correct it seems to demonstrate that run away engine is unlikely to occur with resistor mod?

[nj swb]

I’ve been close to pulling the pin on an EGR delete multiple times.

Why is there so much negativity on the D-Max forums?

http://www.newd-max.net/viewtopic.php?f=19&t=1669&start=50

Granted, 4 years old now, but what is it about the D-Max that makes so many owners skeptical about the operation of a delete cable??

In that thread they talk about the D-Max having only one intake air temperature (IAT) sensor, which is the one in the MAF that the resistor alters. There was some confusion about the resistor telling the ECU that the engine is cold, which is a different issue, and not how the resistor works - so irrelevant.

Our engines have another IAT sensor in the inlet manifold, which is the one used by the ECU to determine approprite fuelling. The D-Max guys are adamant that this isn't required, and one of the leading anti-resistor posters (who sells a competing product) wrote:

I struggle to think of a single late model turbo diesel engine with the IAT located after the intercooler - but happy to be corrected.

Nobody corrected him about the Pajero, but perhaps they think our engine isn't "late model"?

If the D-Max only has the one sensor, in the MAF, then I can understand their concern - although I don't understand why they didn't ask more questions of those members who seem to have done some significant logging of information.

The Pajero's 4M41 measures and reports intake air temperature after the intercooler, so anybody who chooses to fit a resistor can see for themselves the intake air temperature that is being used by the ECU. I didn't notice any mention in the D-Max thread of OBD-II monitoring of engine parameters, or the intake air temperature that is reported with / without resistors.

Bottom line: not relevant to us.

[pharb]

I’ve been close to pulling the pin on an EGR delete multiple times.

Why is there so much negativity on the D-Max forums?

http://www.newd-max.net/viewtopic.php?f=19&t=1669&start=50

Granted, 4 years old now, but what is it about the D-Max that makes so many owners skeptical about the operation of a delete cable??

Appears NJ posted while I was single finger typing, nevermind

Most of that discussion seems to be about how the air temp sensor at the air cleaner is the only ait sensor on the motor and shouldn't be dicked around with (ie with a Munji cable or resistor) because the ECU relies on that information to calculate oxygen content of cylinder fill.
One contributor argues that the ECU knows the oxygen content of the volume of airfrom this sensor after it has been pressurised by the turbo and then cooled by the intercooler, seemingly regardless of boost pressure or temperature after the intercooler, and that oxygen content stays static regardless of temperature or pressure, which defies what I learnt in Year 10 science.

A quick google shows the Dmax has 2 air intake sensors, one being in the inlet manifold. One would assume to measure air intake temperature after boosting and intercooling, much like I believe every other modern CRD engine incuding the Paj.

I have fitted a resistor to my NX. Don't know if it affected fuel economy because about the same time I fitted it my wife changed jobs (it is her daily driver) and has now halved the distance travelled per week, but the in town distance has stayed the same.
I'm sure my ScanGauge has an air intake reading that shows "normal" readings to suggest it is picking up true intake manifold air temp, not a doctored reading from modified air cleaner temp sensor.

[erad]

Pharb wrote "I'm sure my ScanGauge has an air intake reading that shows "normal" readings to suggest it is picking up true intake manifold air temp, not a doctored reading from modified air cleaner temp sensor."

My Scangauge shows the Inlet Air Temperature at times in excess of 100 Deg C on a hot day when the engine is working hard at slow speeds. I don't like those levels, but assume it is within normal limits because the engine doesn't go into shutdown mode. The IAT varies all the time, but doesn't change immediately the boost level changes - there is a lag which tells me that the reading is not a fudged value based on ambient temperatures outside the car, but some values which are actually the Inlet Air Temperature.

[dhula]

Also I just re-read this and noticed the run on comment. It’s not really a run on / runaway situation if the key shut it off right? A run on situation occurs when you turn the ignition key off and it *doesn’t* shut down. So not sure what happened in your situation.

In my situation;


Run on on is talking about the very slightly (micro/mini second) longer time it takes for the engine to come to a complete stop after turning the key off under normal circumstances, usually when the engine is up to normal operating temps.


Run Away is talking about the one time the engine almost run away (ie, reved to full noise and stayed there until destruction despite turning the key off) due to the dealer not tightening/sealing the injectors pipes properly after adjusting the Vv's and the sump filled with diesel. We were lucky that time and the key did shut the engine down and no apparent damage was caused. In my experience it was bloody close to doing it's own thing tho.

[markseb44]

Hi, can someone clarify, do I need the resistor mod for an NT pajero? Or can I just blank off the EGR?