sierrafery said:
it wasnt missed by me, see post #62 : "i'm not saying that the air flow through MAF CONTROLS fuelling, just that the MAF's input is part of the ECU's addaptive strategy for fuelling and has a certain effect on it so the MAF is not there ONLY for EGR controll as long as the electronic unit injectors management is affected by it's inputs, cos that was how this whole discussion started"
Click to expand...
I stand corrected - you didn't miss the point.

its the same principle as the engine temp sensor being used to advance the fuel lift pump etc for a cold start. its not control as such just a response to a given condition. once the condition is met an action happens, it is not giving a continued control input is my point.
When you remove the EGR, the voltage on the MAF remains fairly constant. to the point that if it failed you would be just as well replacing it with a resistor and save yourself a few quid for all the good it does. (Unless you constantly drive at different altitudes that is)
 
sierrafery said:
I'm n ot speaking about diesel engine that's the problem of out debate, i'm speaking about the electronic control unit connected to the injectors which reacts to MAF voltage signals on the output to injectors, not about combustion, air, throttle, RPM, etc. ... and according to my own measurements and tests made with reliable tools that's what happens so i'm not gonna think i've had some optical illusions only based on the theory how a diesel engine works from mechanical point of view... blame those who built the Td5 ECU to do that not me cos i'm just observing things ... also those ho wrote the workshop manuals for L322, Td4, Td6 were all stupid? , at post 25 you mentioned BMW...it seems that there are guys who are speaking nonsense about that too: http://bmwgt1.com/bmw-maf-mass-air-flow-sensor/

IT'S ABOUT THE MAF SENSOR AND WHAT THE ECU DOES WITH IT'S SIGNAL FROM ELECTRONIC POINT OF VIEW HERE NOT ABOUT HOW MUCH AIR OR FUEL IS NEEDED FOR COMBUSTION
Click to expand...

Sorry but i just realised you don't have a bloody clue what you are talking about.
 
Retrospaceman said:
When you remove the EGR, the voltage on the MAF remains fairly constant. to the point that if it failed you would be just as well replacing it with a resistor and save yourself a few quid for all the good it does. (Unless you constantly drive at different altitudes that is)
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No it doesnt, it will go from 0.5V(about 55kg/hr) to 4.5V(650Kg/hr) on a quite close pattern with the MAP or TPS track 1 voltages ... if it fails better let it unplugged cos the ECU goes to default than tricking the ECU with a resistor, see the attached file how a well working MAF behaves on a de-EGR'd engine and compare to MAP and Accel way 1 readings , at pos 157 it's at full load: https://www.dropbox.com/s/qvt88a1ncc6hlxk/Book1.xlsx?dl=0

also altitude compensation is managed based on the airbox(AAP) sensor inputs
 
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sierrafery said:
No it doesnt, it will go from 0.5V(about 55kg/hr) to 4.5V(650Kg/hr) on a quite close pattern with the MAP or TPS track 1 voltages ... if it fails better let it unplugged cos the ECU goes to default than tricking the ECU with a resistor, see the attached file how a well working MAF behaves on a de-EGR'd engine and compare to MAP and Accel way 1 readings , at pos 157 it's at full load: https://www.dropbox.com/s/qvt88a1ncc6hlxk/Book1.xlsx?dl=0
Click to expand...
Sorry but I have to disagree with you. Yes the voltage may track a similar patter, but we are talking about a trigger level in the ems. The ems won't care as long it it gets the right answer on a given "scan" of the sensor inputs. The default mode presumes there is a issue and puts the ems into a safe mode which makes everything run rough as a badgers arse. In reality the only problem you would encounter is if you got a blockage in the air system, but that is no different to pre ecu diesel engines.

The simple fact is without the egr, there is a higher volume of oxygen rich air in the cylinder than required, therfore the ems has no reason to track the MAF.
 
sierrafery said:
Sorry from my side too but i realised that YOU dont have a bloody clue what I am talking about :rolleyes:
Click to expand...

You don't have clue happy amateur, that was suspected when you talked about MOT Nox test. I am not really interested in what you are talking about, i know how a diesel works you obviously don't. Fuelling is not subject to airflow through the MAF.
 
Retrospaceman said:
Sorry but I have to disagree with you. Yes the voltage may track a similar patter, but we are talking about a trigger level in the ems. The ems won't care as long it it gets the right answer on a given "scan" of the sensor inputs. The default mode presumes there is a issue and puts the ems into a safe mode which makes everything run rough as a badgers arse. In reality the only problem you would encounter is if you got a blockage in the air system, but that is no different to pre ecu diesel engines.

The simple fact is without the egr, there is a higher volume of oxygen rich air in the cylinder than required, therfore the ems has no reason to track the MAF.
Click to expand...
the reality is different though cos if the MAF is reading low even within the accepted limits the engine will run bad and disconnecting it the default mode makes it run well...that's why the first move to prove a bad MAF is to see if it runs better with it disconnected... on a similar log like i posted(as i've studied loads of them) there's a low reading MAF which doesnt exceed 450 at full load and the engine was sluggish at high revs, new well working MAF cured it
 
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sierrafery said:
the reality is different though cos if the MAF is reading low even within the accepted limits the engine will run bad and disconnecting it the default mode makes it run well...that's why the first move to prove a bad MAF is to see if it runs better with it disconnected
Click to expand...

That is why i said if the MAF goes down the ECU gets confused because it is not receiving information it thinks it should.
 
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Y
wammers said:
That is why i said if the MAF goes down the ECU gets confused because it is not receiving information it thinks is should.
Click to expand...
You beat me to it! Disconnecting the MAF gives the same effect, the ems just enters a default value for the engine to run well enough to get you to a dealer. A low reading MAF may not provide the set point on a "scan" if it defective or reading erratic. Manually frigging the value of the MAF to a higher set point avoids other default values.

The basic principle of having a default value for the MAF is disabled proves the point.

Mechanically removing the egr is a better option in terms of air flow cooling etc.
 
wammers said:
That is why i said if the MAF goes down the ECU gets confused because it is not receiving information it thinks is should.
Click to expand...
i've aleady said that, for the ECU to go to default the MAF should fail as open or closed circuit on the signal path to ECU and then the ECU is not confused but set from factory to go to fix default stored in EEPROM, there are many cases where it can read bad within the accepted limits for example if it's dirty then the ECU accepts those readings as being good and acts accordingly on the injector outputs the result being rough running and in these cases a well working MAF is the cure. This is pure reality (EGR bypassed)
 
Retrospaceman said:
Y

You beat me to it! Disconnecting the MAF gives the same effect, the ems just enters a default value for the engine to run well enough to get you to a dealer. A low reading MAF may not provide the set point on a "scan" if it defective or reading erratic. Manually frigging the value of the MAF to a higher set point avoids other default values.

The basic principle of having a default value for the MAF is disabled proves the point.

Mechanically removing the egr is a better option in terms of air flow cooling etc.
Click to expand...

Correct and i do think that some of the technical writers at Land Rover need sacking. Describing almost exactly the function of a MAF sensor on a petrol engine in a diesel context is a little stupid.
 
sierrafery said:
i've aleady said that, for the ECU to go to default the MAF should fail as open or closed circuit on the signal path to ECU and then the ECU is not confused but set from factory to go to fix default stored in EEPROM, there are many cases where it can read bad within the accepted limits for example if it's dirty then the ECU accepts those readings as being good and acts accordingly on the injector outputs the result being rough running and in these cases a well working MAF is the cure. This is pure reality (EGR bypassed)
Click to expand...

For Christ sake the power request determines fuel injected NOT airflow through the bloody MAF. If the MAF is faulty the ECU gets confused. Bit like SISO on a computer.
 
For the same Christ sake, i'm not speaking about air flow here nor about combustion but about voltage outputs...but even accepting your theory with "confused" ECU (which is not the case) as long as the MAF signal as you say has nothing to do with injector management no matter of what input it gives cos it should not affect injection at all even with a "confused" ECU...but the ECU is not "feeling" the real air flow just the voltage so if the voltage is lower due to dirty(not failed) MAF but the air flow is good so the engine can "breathe" well the voltage should not affect it's running at all according to your theory....... but in reality it does (that lower voltage means only a bit lower air flow for the ECU, air flow which as you say and i agree doesnt matter for the diesel engine)... we can speak to infinity about that as long as you dont make your own test so if you have a de-EGR'd D2 even if you know 100% how the engine works put a resistor instead of the MAF as mr Reprospaceman suggested and go for a drive then replace the resistor with a well working MAF and go again...it would be good to have an EGT gauge fitted too to see the difference, then maybe you'll realise that the electronic management is not a diesel engine ... but maybe i'm speaking boll*x again no problem, i'm used to be misunderstood.
 
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sierrafery said:
For the same Christ sake, i'm not speaking about air flow here nor about combustion but about voltage outputs...but even accepting your theory with "confused" ECU (which is not the case) as long as the MAF signal as you say has nothing to do with injector management no matter of what input it gives cos it should not affect injection at all even with a "confused" ECU...but the ECU is not "feeling" the real air flow just the voltage so if the voltage is lower due to dirty(not failed) MAF but the air flow is good so the engine can "breathe" well the voltage should not affect it's running at all according to your theory....... but in reality it does (that lower voltage means only a bit lower air flow for the ECU, air flow which as you say and i agree doesnt matter for the diesel engine)... we can speak to infinity about that as long as you dont make your own test so if you have a de-EGR'd D2 even if you know 100% how the engine works put a resistor instead of the MAF as mr Reprospaceman suggested and go for a drive then replace the resistor with a well working MAF and go again...it would be good to have an EGT gauge fitted too to see the difference, then maybe you'll realise that the electronic management is not a diesel engine ... but maybe i'm speaking boll*x again no problem, i'm used to be misunderstood.
Click to expand...

It's not a theory it's a fact. Wrong signals can confuse the ECU it doesn't need to know the airflow for any other reason than to operate EGR.
 
And what would do the ECU if it's "confused" by wrong MAF signal then if there's no EGR fitted? ... mix up fuelling by any chance? or what would cause engine running issues with a bad MAF? ... try to use some logic this time
 
sierrafery said:
And what would do the ECU if it's "confused" by wrong MAF signal then if there's no EGR fitted? ... mix up fuelling by any chance? or what would cause engine running issues with a bad MAF? ... try to use some logic this time
Click to expand...

You do try hard don't you?
 
Not hard at all for me cos despite of what you think i know exactly how an electronic system works as i have 30 years experience in the electronics field... so to sustain my point here's some analogy:

- the coolant temp sensor is used by the ECM for the coolant gauge, electric cooling(aircon) fan and injectors management.... if it gives a bad signal it will "confuse" the ECU according to your theory and affect at least the gauge and the fuelling but according to it's fault it can trigger the fan too
- the fuel temp sensor is used only for injector management so a bad signal will not affect other systems only fuelling so even a confused ECM will not mix up the coolant gauge or EGR based on bad FT signal cos it's not linked to them
- the MAP sensor is used for injector management(fuelling calculations) and boost controll...it will not affect other systems no matter how confused the ECM is by it's signal,
- and so on
if the ECM gets "confused'' by any sensor's signal it will act only on the systems which are internally "linked" to that sensor's signal

use some logic and figure out what's internally linked to the MAF signal beside the EGR if a "confused" ECU by it's signal can affect engine running

even though i reiterate that the ECU is not "confused" whatsoever, it just does what it was built to do from electronic point of view, .... and I AGREE THAT DIESEL ENGINE IS THROTTLED BY FUEL NOT BY AIR
 
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Just read this entire thread and it is very interesting. I have no idea who is correct but it is a shame that one contributor feels it necessary to be abusive to the others. It adds nothing to the argument and shows an ignorance of how to conduct oneself in a public forum.
 
sierrafery said:
Not hard at all for me cos despite of what you think i know exactly how an electronic system works as i have 30 years experience in the electronics field... so to sustain my point here's some analogy:

- the coolant temp sensor is used by the ECM for the coolant gauge, electric cooling(aircon) fan and injectors management.... if it gives a bad signal it will "confuse" the ECU according to your theory and affect at least the gauge and the fuelling but according to it's fault it can trigger the fan too
- the fuel temp sensor is used only for injector management so a bad signal will not affect other systems only fuelling so even a confused ECM will not mix up the coolant gauge or EGR based on bad FT signal cos it's not linked to them
- the MAP sensor is used for injector management(fuelling calculations) and boost controll...it will not affect other systems no matter how confused the ECM is by it's signal,
- and so on
if the ECM gets "confused'' by any sensor's signal it will act only on the systems which are internally "linked" to that sensor's signal

use some logic and figure out what's internally linked to the MAF signal beside the EGR if a "confused" ECU by it's signal can affect engine running

even though i reiterate that the ECU is not "confused" whatsoever, it just does what it was built to do from electronic point of view, .... and I AGREE THAT DIESEL ENGINE IS THROTTLED BY FUEL NOT BY AIR
Click to expand...

To be honest i don't really care how the electrical engine control system works. I can manage with ease normal electrical problems but electronics are not my bucket. EGR systems seem to have got more and more complex possibly to avoid tampering. I hear that on some very modern motors any attempt to disable it results in the engine shutting down or at least going into a limp mode. The early P38 M51 EDC engines ran perfectly well without a MAF sensor. It was only in 1998 with the introduction of EGR with feedback to conform to EU level 2 emission regulations that a MAF was fitted. This was needed to measure exhaust gas ingestion and control the quantity ingested by the ECU modulating the EGR valve, to control flow subject to readings from the MAF sensor. This system is very easy to trick by just removing the vac pipe from the EGR valve and blanking it off. Leaving the MAF and modulator valve connected and the ECU had no idea that EGR is disabled. There are no MAF flow readings available on diag and the only thing you will get back from that is "Air flow fault" if you disconnect the MAF. As far as i can see the Lucas engine management unit is a completely different animal with a mind blowing set of variables available. Which can be selected or disabled to suit various markets and needs. Looking at it's available functions on the Nanocom emulator it would seem EGR can be disabled or enabled as needed possibly subject to market needs. All i set out to do was establish contrary to what some believe, that airflow through the MAF dictates fuelling on the diesel engine. It does not and cannot if you understand how a diesel engine works.
 
The Lucas Td5 ECU is a very strange unit cos it's developped from a petrol ECU which initially was, it seems that those who made it didnt really care or understand how the diesel engine works from your(physical) point of view cos they included the MAF input in the air mass calculation table of the fuel map and the fuelling is managed mainly on MAP reading but it takes into account the air flow too so that's what the ECU does and it seems that the engine can live with it, for the Td5 to work perfect a well working MAF is needed regardless of EGR as the ECU uses the reading in conjunction with the MAP input to calculate air mass per cycle for the addaptive strategy... in this link http://www.discotd5.com/ecu-tech/ecu-reverse-engineering in the first two images it's shown how the ECU uses the MAF input for that too, those images are confirming my own measurements as well, second paragraph from bottom here http://www.web-rover.co.uk/nav.php?p=td5kb/intro too.

so THE REALITY is that the Lucas Td5 ECU doesnt care or understand how a diesel engine works but it gives the fuel to it based on MAF reading too... that's another fact, and i'm sure there are other more modern ECUs which are doing the same cos the air mass in the cylinder will be more accurately calculated from two inputs which are not unlinked as the greater the MAP reading is the higher the MAF reading should be that's why the Lucas ECU can throw "air flow too high" fault code if there's a leak after the turbo cos it compares the MAP and MAF readings for fuelling and at a certain air flow there must be a certain boost to match the fuel map and all the other elements are included in this calculation as ambient pressure, wastegate ratio, EGR ratio, rpm, driver demand, FT and ECT... also the Lucas ECU will log a "EGR stuck closed" code if the vacuum is removed from the valve without touching the modulator's electrics based on the same complex calculations....that's how the ECU works regardless of how mr Rudolf Diesel conceived the engine to run at it's beginning
 
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