EGR Bypass for CRD

[Auberon]

Thesis....please!!

I make no apology for using relevant and correct terms and trying to explain an extremely complex situation in quite a brief form. I do apologise for posting at all, however.

It IS HIGHLY relevant to this part of the engine management system.
It is NOT for control engineers......
BUT isn't someone looking to modify their engine feedback something of an ameteur control engineer?

If I wrote the following first it would have been found condescending. I have no need for the hostility, perhaps some questions or just letting it go.

1 The ECU has very limited abilty to learn.
2 It expects certain things to happen under certain conditions.
3 Change the expected and it can get confused.
as we have seen.

It is supposed to make it work better not "bugger it up".....there has to be a reason.

I would suggest that bean counters have taken shortcuts rather than modify on a whim. Some work quite sweetly.

Glend: Perhaps your "MAF" is at fault?

I do apologise for posting at all.
It probably won't happen again.
Auberon

[Pipeliner]

Auberon,
No hostility intended. I am a professional engineer and frequently come acoss the situation where terms that I think are quite common are incomprehensible to others - even to engineers in a different discipline. PI controllers, open loops, and gain will mean a lot to a control engineer, but to guys like Glend and myself it is just words. All Glend knows is that he has a problem which goes away if he unplugs the MAF. What (I think) you are trying to say is that there may be other parts of the system which require the MAF to be connected: the effect of these may not be immediately apparent but may well affect the overall efficiency and life of the engine. Probably very true, but since the Jeep mechanics here can only go by the built-in computer diagnostics (which say nothing is wrong) what else can Glend do to keep his beloved KJ running smoothly?

[cmohr]

Aubs... I dont think anyone is Unhappy with your post or the info, very happy with yours and any input in good. Understanding the system as a whole is great, yep it was High Tech Info, dont get the guys wrong, we are all just good friends on here and tend to make harmless quips at each other knowing the other person understands. the thing that most of us are trying to eliminate is the recirculation of soot back into the system and thus sooty carbon buildup in the oil working like sandpaper on engine components. Improving lag and engine response, and in the end fuel economy and engine life.

Yes they have designed the system for reasons, most being to comply with the European Carbon Emissions Rules.

Dont take it to heart. I for one find it hard to believe that the MAF is solely for the EGR, It must have someting to do with fuel as well surely. But I dont know.. Where di dyou get all that info from... the Bosch site??

[glend]

Auberon, a thick skin is sometimes required on AJOR - just wait till the solid front axle guys get stuck into you.

There are very few cases of MAFs failing (a few that have failed seem to be where people unplugged them for long periods of time (and did not cover the pins and connector) and connectors got water into them, and/or pins may have been damaged by people unplugging and replugging over time. I was reading several posts on LOST where KJ CRDs have been driven with MAFs unplugged for over 50,000 miles with no impact on the rest of the system (that is noticable to the driver), other than increased performance and mileage.

The EGR valve is not there "to make it work better" nor does it (as unplugging the MAF shows), the EGR valve is there to satisfy the NOX standards in place in California or Europe at the time of the CRD emissions system design and manufacture (which have changed again since then and thus no CRDs are sold in that California market anymore, but Europe continue to take them). We get them because they assembled all the CRDs engines with them. The MAF is there to provide info to the ECM and thus downstream the EGR and really has no other purpose in engine management that I (nor many others) can determine. If you have information that the MAF is important to fuel management, or other sub-systems then I'd like to hear it.

As Pipes has indicated, I'm just trying to get my KJ fixed. It has run sweetly for 32000kms and now it has developed this problem - which histroy of the breed says is the EGR system.

Even if I do get Jeep to fix it I will still probably run long trips with the MAF unplugged. I feel that we need some solid data as to the degradation of the performance capability of the engine (and fuel economy) that EGR introduces and I will be trying to record that in the future (with my MAF unplugged).

Ideally, GDE will adopt CRDSTU as their agent in Australia and I will get the GDE ECU flash that minimises/disables EGR.

[Auberon]

I offer this reluctantly but as you are a Jeeper and in a spot;

I have not had these issues but I have done SOME preparation in case.
I am one of these freaky people who makes a point of understanding this stuff because I have to. I am an engineer......probably the most adaptable kind---Agricultural so new technology is familiar to me and I have worked with it thru its inception and early development even to the earlier colour sorters used in grain processing (that should answer the questions from others about where I got my information). I have had to adapt and learn this stuff and was programming computers way back in the days of punch cards.

Now, please read this in parallel what I posted before, and it should gel.
If you are not OK with what I am saying please ask questions. I have not looked at this in absolute detail so some of this is based on general approaches to fixing problems of the highest technical orders when "techs" were nowhere to be found......

If you go to Jeep armed with this type of language they will get worried. VERY worried....as you will have it over them. The codes take it only so far and that is alland as you have no codes...there is a ROOT CAUSE. The same aplies to flow charts.

I am suggesting the direction to explore to solve the problem and determine what is actually wrong. If you are well versed with an oscilloscope that could change things but I don't know where you are at.

This is the starting point that will determine for sure, the fault. The voltage drop numbers are good to go but the rail voltage would have to be checked....I am pretty certain it is right.
The exact how to's to design the test are well known to a good aut electrician but that is Jeeps place in this case. They need a GOOD auto-electrician.

This is what should have happened in yours and all previous cases.

All of this comes from the point of view of a hands-on engineer who also understands and applies the theory.

1 The flow charts and guessing are a waste of time. In fact, too much guessing has happened in the past.
2 As this is a warranty issue, then, Jeep need to conduct a voltage drop test using a good auto electrician. This would apply to the MAF, EGR. This will establish that the sensors are switching when they are predicted by the computer as I indicated before. that is, are they talking to one another.....offering PI's (you may have heard of PIDS-they are similar) to one another for enterpretation by each other. This determines that the messages they get, are received as expected and have the right details and are at the right time.....as expected.
Otherwise they poop themselves and send a failed message back to the next processor in the chain.
This is where it goes wrong.
2a It determines what I mentioned in my previous post as the predicted values.
This will indicate that there is a signal going from the sensor to computer 1 and computer 2 and eventually the ECU.

I know you expressed disinterest in how it works but you won't know for sure that it won't repeat itself later.....If you know as much about diesels as I am lead to believe then you will know that 50 000 miles is nothing in the running of a motor in capable of the duty cycle of the VM.

I expect Rail Voltage should be +5 Volts....but I need to check this. So if the units are sending this out to the computer, then it needs to be established if the message is intermittent, or the form of the signal.

How V changes is critical to control of the devices like the EGR.

If they back-probe, then a needle as fine as an accupunture needle is necessary...this is what I use. If they pierce a wire in a usual way lacking any finnesse, it needs to be resealed immediately.
They should ground back to the negative terminal on the battery, not a chassis point. That can give false readings.

After checking for TSB's and replacing the recommended components then:

They should also verify computer ground...max allowable drop there is
0.100V max
Verify sensor ground to block......engine running, module operating ....Max 0.050V max
Sensor ground to battery between the battery (-) terminal and any module sensor ground, engine running, module operatring maximum allowable V drop is 0.050V maximum.
Module Voltage feed between (+) battery termianl and any module voltage feed wire with the engine running maximum allowable voltage drop is 0.5V.
Low current load ground/s between the (-) battery terminal and the output pin of any low current load with the engine running and load on is 0.100V maximum.

Rail voltage should be +5V but I would need to clarify and the gradation of this may influence the actual action of the EGR. It is this I expect is wrong, the trigger or trip Voltage is not being achieved through voltage drop somewhere so stepping up cannot happen.

Don't tell me it isn't to make it run better it is. It is an integrated system and systems diagnostics is one of the things I do in analysis. It is being over-simplified well and truly as diesels and NOX are BS.

This was an attempt to be helpful if you don't want it then don't use it.
Auberon

[Lancer]

Thanks Auberon. Speaking for myself (but I expect most will agree) it's always good to have more info and more detailed info - even if it just lets us say to a Jeep tech "did you do such and such to check..." I think the problem with your post - certainly for me, was that although undoubtedly very good, it was in a technical language that most of us simply couldn't understand. My reaction was that I recognised a lot of the words, but had no comprehension of the meaning A Dummies guide to sum up would have helped a bit

I think we are all grateful though that you have taken the time and put in the effort to help out. Think of this place as a bit like a club bar; what you say is good, but that doesn't stop your mates taking the p**s and blowing raspberries

[glend]

This appeared in LOST overnight relating to blocking off the EGR pipe.

Just got this from Keith at GDE:

"There is no eminent harm in blocking off the EGR at the exhaust manifold, it would be cheaper than the new pipe. If you decide on a tune in the future the CEL will be turned off for the EGR code caused by blocking it off.

Just one word of caution, with our tunes we still use the EGR valve for a certain situation to prolong the life of the turbocharger. After a hard acceleration and then pedal release at cruising speed, we will open the EGR valve for about a ½ second to bleed off the residual boost in the intake as this reduces the stresses on the compressor wheel. In this situation the EGR circuit is flowing in the opposite direction (from intake toward exhaust). If you block off the EGR, this feature will not function for you, but in the end it is not a big deal. Let me know if we can be of further assistance."


GDE is presently looking for an Australian distributor. I suggested someone and have tried to facilitate them talking. We shall see.