sierrafery said:
I dont have to google that cos i've read all 1672 pages of RAVE at least twice, i was in the same error like you based only on RAVE's description of MAF that it's ONLY for EGR then after a hard study and tests i realised that RAVE in this particular case is wrong, it's mainly for EGR but it has effect in the fueling calculations even if it's not stated, that's proved if yo unplug a 100% well working MAF on a de-EGR'd Td5 that the fuel consumption will increase, we are not speaking here of "a diesel" in general but this topic is about Td5 which's engine management makes the main fueling calculations based on MAP/IAT readings(see RAVE not google) and MAP/IAT input to ECM has nothing to do with the CKP input(rpm) cos if at the same rpm the MAP/IAT (and MAF which is not mentioned in RAVE), have different readings from one case to another there will be different fueling implemented by the addaptive strategy which compares live data with mapped information stored in memory, i think you confused the Td5 with a 300tdi though... what i said i tested on motorway and at the same rpm and throttle input i've got different EGT with MAF unplugged and MAF connected(no EGR)... so your statement: "The MAF sensor on a diesel has nothing to do with fuelling, it is for EGR control. It tells the ECU how much exhaust gas is being ingested when EGR is active, nothing more" the "nothing more" is boll*x ... i've learned that the hard way after i sustained exactly what you said and proved wrong ... though we can keep the discussion in a more friendly manner too by not using that b****x word so much cos as we see everybody, even so experienced men like you can be wrong from time to time

i'm an engineer at basiscs so i hope i can understand how an engine management works if it's well explained
Click to expand...

The MAF sensor controls the EGR nothing else. Look up how a diesel engine works, when you know that then you will understand. A diesel is throttled by fuel NOT by air, the air going in through the MAF is irrelevant to engine fuelling. Basically you don't have a clue what you are talking about. Maybe you can explain why the same engine with the same basic EDC can run without EGR (No MAF) and with EGR (MAF fitted) with no difference in performance or fuel consumption. Mechanical injection engines and common rail engines are totally different animals regarding efficiency of burn, about 20 odd thousand PSI different animals in fact. They cannot be compared, but the EGR works in exactly the same way. If you want a diesel engine to run at 2500 RPM under a certain load you inject enough fuel to maintain that engine speed and overcome that load within the confines of the fuel MAP. That fuel quantity cannot be changed or the RPM will fall or rise simple as that.
 
Your scenario in post 20 is flawed. Running with the MAF disconnect or with a faulty MAF can cause the ECU to misinterpret air conditions. Simply because the ECU is expecting readings it is not getting and gets confused by incomplete circuits. Disconnecting the MAF as a means of disabling EGR is not the way to do it. Simply removing the vac pipe and blanking it is all that is required.
 
wammers said:
...the air going in through the MAF is irrelevant to engine fuelling...
Click to expand...
^^^ that's a good one :confused:

Unfortunately it seems to me that this debate will end nowhere cos you simply insist to be agressive instead of having a scientific argumentation, though i inform you that the Td5 is not a mechanical injection nor common rail engine but a PD/EUI (electronic unit injector) engine and it's not working on EDC based on throttle request but on complex management with addaptive strategy based on 7 sensor inputs(MAF included), i'm not gonna repeat what i've already said just please, help me overcome my ignorance and answer shortly to 3 questions:
1. why did they fit a MAF on DefenderTd5 modells built for South Africa which didnt have EGR from factory?
2. why a dirty but working MAF affects engine power and consumption on a de-EGRd Td5?
3. why the ECM cuts fueling when MAF reading exceeds 680 on a de-EGR'd Td5 if the air intake flow has nothing to do with fueling?
 
and btw, untill now what i said was based on informations from RAVE, other construictive discussions and my own live data measurements but as you insisted so much to google out things i did ... i think you should have done that before me cos what i found is not in your behalf, maybe those guys are also some ignorants who dont have a clue about diesel engine management to make the following statement: "If the maf signal is below par the fuelling is reduced and performance suffers, if it is too high, fuelling is increased leading to smoke, and poor mpg, as well as lumpy, hesitant, juddery running. In extreme cases stalling or bad starting can occur". (para 3. prop 3) which comes in complete contradiction with your genial conclusion "the air going in through the MAF is irrelevant to engine fuelling"

the whole story here: http://tuning-diesels.com/Mafam/mafhome.htm
 
sierrafery said:
and btw, untill now what i said was based on informations from RAVE, other construictive discussions and my own live data measurements but as you insisted so much to google out things i did ... i think you should have done that before me cos what i found is not in your behalf, maybe those guys are also some ignorants who dont have a clue about diesel engine management to make the following statement: "If the maf signal is below par the fuelling is reduced and performance suffers, if it is too high, fuelling is increased leading to smoke, and poor mpg, as well as lumpy, hesitant, juddery running. In extreme cases stalling or bad starting can occur". (para 3. prop 3) which comes in complete contradiction with your genial conclusion "the air going in through the MAF is irrelevant to engine fuelling"

the whole story here: http://tuning-diesels.com/Mafam/mafhome.htm
Click to expand...

Think you should really know what you are talking about before you start spouting, obviously you don't so it is pointless to continue further. Find out how a diesel engine works then come back. The MAF does not control fuelling on a diesel engine. As i said earlier you are talking a load of bollocks. Wonder how BMW ever got the M51 pre EGR engine to run without a MAF. Then ask yourself why they fitted a MAF on the EU level 2 EGR M51 engine to give feedback control. BMW seem to think that whilst the MAF has no direct influence on air supply a malfunctioning one (or indeed disconnected one) can cause the ECU to misinterpret air conditions and cause poor running. But what do they know? The link is also a load of bollocks.
 
Ok, so be it, but it would have been nice to see some answers to those 3 questions from post #23 about Td5 though :rolleyes:
 
sierrafery said:
Ok, so be it, but it would have been nice to see some answers to those 3 questions from post #23 about Td5 though :rolleyes:
Click to expand...

Learn how a diesel engine works, you will then realise that the amount of air going through the MAF has no bearing on how it is fuelled. A diesel engine ALWAYS has excess air in the cylinders and is fuelled according to RPM/power requirement NOT subject to air flow through the MAF. It is throttled by fuel NOT by air as is a petrol engine. The air to fuel ratio on a modern diesel at idle is well over 100 to 1. Increase fuel and you increase RPM decrease fuel you decrease RPM. It is a pretty simple thing to understand. When EGR is active the reduction in airflow through the MAF at any given RPM = the amount of exhaust gas being ingested. The ECU uses this information to modulate the EGR valve and control gas ingestion to ensure there is always enough oxygenated air to clean burn the fuel needed for the power level/RPM requested. If the EGR is faulty you can get a situation were to much exhaust gas is ingested and there is insufficient oxygenated air to clean burn the fuel required for the power level/RPM requested this would create smoke and soot. Boost fuelling is controlled by the ECU from manifold pressure readings again the MAF plays no part in this function. The TD5 is a more modern engine than the M51 and the EGR control a lot more refined, the EGR system a lot finer controlled, so any fault will give problems that maybe would not be apparent in the M51 which is a little more loosely controlled.
 
i'm being in a continuous process of learning since i own my Td5 believe me, direct answers to those 3 questions would take me closer to the reality though, what i know for sure is that the Td5 ECM has a fuel-air calibration table stored in it part of the addaptive strategy in which the whole air flow graphic is based on MAF readings and the EGR management is not part of this particular ''file''
i insist:
1. why did they fit a MAF on DefenderTd5 modells built for South Africa which didnt have EGR from factory?
2. why a dirty but working MAF affects engine power and consumption on a de-EGRd Td5?
3. why the ECM cuts fueling when MAF reading exceeds 680 on a de-EGR'd Td5 if the air intake flow has nothing to do with fueling?
 
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sierrafery said:
i'm being in a continuous process of learning since i own my Td5 believe me, direct answers to those 3 questions would take me closer to the reality though, what i know for sure is that the Td5 ECM has a fuel-air calibration table stored in it part of the addaptive strategy in which the whole air flow graphic is based on MAF readings and the EGR management is not part of this particular ''file''
i insist:
1. why did they fit a MAF on DefenderTd5 modells built for South Africa which didnt have EGR from factory?
2. why a dirty but working MAF affects engine power and consumption on a de-EGRd Td5?
3. why the ECM cuts fueling when MAF reading exceeds 680 on a de-EGR'd Td5 if the air intake flow has nothing to do with fueling?
Click to expand...

All that has been explained if you read through the posts and take in what was said. The TD5 has a variable turbo does it not, it would therefore need a MAP based on variable boost? As i said find out how a diesel engine works. Then you can answer your own questions.
 
I thought i knew but it seems i'm not, unfortunately my limited mind doesnt let me watch the diesel engine behaviour unlinked to it's electronic management...thanks for the answers which didnt containt the b****x term... on a second thought for those too, i think we can agree that we disagree then, for me it was a good discussion
 
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Most of this beyond me but can I pick up on one statement and ask a question. 'The MAF sensor controls the EGR nothing else.'

Mine is de-EGR'd and I recently suffered a faulty MAF sensor (one of the elements had broken), it really effected the amount of power I had prior to the turbo kicking in. It wasn't exactly a pushed back into the seat job at 1800 revs but it was very obvious that anything lower than that was lacking power. Simply unplugging it improved things and a new sensor brought power back to normal.
 
AceB said:
Most of this beyond me but can I pick up on one statement and ask a question. 'The MAF sensor controls the EGR nothing else.'

Mine is de-EGR'd and I recently suffered a faulty MAF sensor (one of the elements had broken), it really effected the amount of power I had prior to the turbo kicking in. It wasn't exactly a pushed back into the seat job at 1800 revs but it was very obvious that anything lower than that was lacking power. Simply unplugging it improved things and a new sensor brought power back to normal.
Click to expand...

Read my earlier answers.
 
I've re-read everything again and again 3 times but it seems i'm too dumb to find an answer to those 3 or to AceB's question cos as long as that "MAF sensor controls the EGR nothing else" statement is correct IMO unplugging or plugging faulty or new MAF on a de-EGR'd engine should not make any difference .... i'm sure that you'll agree with at least one of my statements in this post : that i'm too dumb :(:confused:

which really confused me was that one : "The TD5 has a variable turbo does it not, it would therefore need a MAP based on variable boost?" ... what do you mean by MAP here ?
 
maybe it's hard to believe but i dont want only to sustain what i said, i was the most fervent sustainer of the theory that MAF is there ONLY for EGR controll untill i was proved wrong with scientific/technical arguments(while i was named idiot too) by those who know well how the addaptive strategy works and after i made many live tests on my own and other cars i admitted i was...maybe i still am cos i'm really trying to figure out things exactly as they are and i'm making serious research for that, so maybe my perception about "fuelling" is wrong not the theory, ... in a previous post there were some statements about EDC and BMW engines, as the TD4 is BMW engine, corroborating 1 and 2 ,a statement of mr. wammers and an unanswered question of mine:
1. "Wonder how BMW ever got the M51 pre EGR engine to run without a MAF. Then ask yourself why they fitted a MAF on the EU level 2 EGR M51 engine to give feedback control."
2. but my question was "why did they fit a MAF on DefenderTd5 modells built for South Africa which didnt have EGR from factory?"

maybe it's interesting to see what RAVE states about Td4 engine management(underlined with red at the bottom of page):
it sounds correct to me and very similar with what in the Td5 happens as the MAF working principle is 100% the same.... so where is the true then ??? ...cos it seems that on the Td4 the MAF output has double purpose?

MAF TD4.jpg


to not fill too much the page, in this document http://www.landroverweb.com/Pdf-files/Manuals/Workshop Manual L322 Range Rover.pdf
page 64 ENGINE MANAGEMENT SYSTEM – TD6 is stated:
The MAF sensor output is an analogue signal proportional to the mass of the incoming air. The ECM uses this data, in conjunction with signals from other sensors and information from stored fuelling maps, to determine the precise fuel quantity to be injected into the cylinders. The signal is also used as a feedback signal for the EGR system.
also BMW engine

in this document http://www.mgroverparts.se/verkstadsinformation-2014/index.php?dir=Tekniskt+Kurs+material/Diesel+kurs/&download=diesel+engine+management+workbook.doc
= MG Rover Group Electronic Diesel Control at page 16 :

The MAF sensor output is an analogue voltage proportional to the mass of the incoming air. The ECM utilises this data, together with information from the other sensors and the fuelling maps, to determine the correct fuel quantity to be injected into the cylinders. It is also used as a feedback signal for the EGR system

i quoted only those links which are sustaining that the MAF is used in fuelling calculations too but to be fair there are other engine management descriptions where is stated that it's used only for EGR controll like the 300Tdi and Td5(here's the dillema :confused: ) .... IMO we should accept that there are engine managements which are using MAF signal for fuelling calculations too not only for EGR and nothing else, IMO we can't speak about this thing only condidering that fuel and air gets into the combustion chambers then explodes there under compression but to admit that there can be many ways to achieve that when microprocessors/EEPROMs and sensors are involved ... or stick to the principle on which the diesel engines were made in 1897 and say that all those official documents or different oppinions are loads of B***ox

an interesting graphic in this thread http://www.aulro.com/afvb/showthread.php?p=2037475#post2037475

I rest my case
 
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Just to complete this thread with a bit of live experience beside the theories, yesterday i felt that the car became sluggish, a delay in throttle response at low revs also the engine ran too hot 98-104*C and the EGT was higher than usual with 100* under load, plugged in nanocom and realised immediately that the MAF is reading low(betreen 40 and 350 tops) cleaned it without result so new one is needed, unplugged it and the engine started to run better, the coolant temp went back to normal(92-96) andf the EGT dropped too... not to normal level like with the good MAF but better than with the bad one... my conclusion is that on low air flow readings the management tried to compensate and overfuelled that's why the temperatures were both higher.... couldn't see if it was black smoke or not in the mirror ...to me that's a live proof that the MAF is involved in fuelling calculations
 
sierrafery said:
Just to complete this thread with a bit of live experience beside the theories, yesterday i felt that the car became sluggish, a delay in throttle response at low revs also the engine ran too hot 98-104*C and the EGT was higher than usual with 100* under load, plugged in nanocom and realised immediately that the MAF is reading low(betreen 40 and 350 tops) cleaned it without result so new one is needed, unplugged it and the engine started to run better, the coolant temp went back to normal(92-96) andf the EGT dropped too... not to normal level like with the good MAF but better than with the bad one... my conclusion is that on low air flow readings the management tried to compensate and overfuelled that's why the temperatures were both higher.... couldn't see if it was black smoke or not in the mirror ...to me that's a live proof that the MAF is involved in fuelling calculations
Click to expand...

Think you had better read through my answers again. In particular the one referring to a faulty MAF confusing the ECU.
 
I did many times, but in my logic if it was there only for EGR the "confusion" of the ECU should have affected ONLY EGR controll not the way the engine is running with bypassed EGR, IMO the ECU was not "confused" in this particular issue cos the MAF was giving readings on a normal pattern just that lower than it should have at that air flow, if it's not involved in fuelling calculations it should have not affected ECT, EGT and throttle response or the ECU should have been confused with it unplugged too in the same way,,, no matter how many times i re-read your statements i can't see it your way as long as the injected fuel quantity is managed by the ECU based on sensor readings(including MAF)
 
sierrafery said:
I did many times, but in my logic if it was there only for EGR the "confusion" of the ECU should have affected ONLY EGR controll not the way the engine is running with bypassed EGR, IMO the ECU was not "confused" in this particular issue cos the MAF was giving readings on a normal pattern just that lower than it should have at that air flow, if it's not involved in fuelling calculations it should have not affected ECT, EGT and throttle response or the ECU should have been confused with it unplugged too in the same way,,, no matter how many times i re-read your statements i can't see it your way as long as the injected fuel quantity is managed by the ECU based on sensor readings(including MAF)
Click to expand...

No effects ECU and confuses it, if your theory is correct you may like to ask yourself why do they fit a MAP sensor. Fuel is injected subject to throttle position power demand. I will say again for any given throttle setting, power demand, manifold pressure there is ALWAYS the same amount of air in the cylinder. The only thing that changes to allow the engine to reach the requested RPM, power demand is the fuel quantity. Diesel engines are throttled by fuel NOT by air.
 
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