Sorry to jump in if this is a private row, don't want to get sucked into this but just want to add my two pennyworth but with the MAF there is a clue in the name.
The ECU is controlling the injectors via the solenoid valves on each injector, to give a certain amount of fuel for each stroke, this amount is calculated to keep the air fuel ratio optimized, (also taking into account many other factors) .
Air has a mass which will vary with temperature, pressure, humidity, the MAF actually is looking at volume of air entering the engine ( with some natural compensation) , but the MAP also looks at pressure and temperature, this will allow the ECU to use all of the readings to calculate the actual mass of air entering the cylinder and adjust the fuel "shot" to suit the requirement to the correct ratio,
So if you are at sea level, or half way up the Alps, in the desert or possibly Finland the ECU will be working to try and give an optimized fuel air ratio for the engine demand ( also considering engine temp and load) this is described in the text of post 36.
 
...ask yourself why do they fit a MAP sensor...
Click to expand...
I know why they fit a MAP, to measure manifold absolute pressure for fuelling calculations and for overboost protection, it's part of a complex algorythm named fuelling addaptive strategy where other sensors are involved too as TPS, crank position(CKP), ECT, FT, AAP and MAF sensors... do you know that there's a part in the fuel map which is set to reduce fuelling if the fuel temp(FT) sensor input is higher than 70*C and cuts fuelling if the MAF input is above 680 cos at that flow it's a risc of turbocarger overspeed so for my limited mind the MAF is involved in fuelling calculations all the way cos i'm speaking about quantity if injected fuel electronically managed by the ECU's addaptive strategy not about what happens in the combustiion chamber ... unfortunately it seems that we'll not be able to agree on this whatsoever, let's just hope that this will be the biggest problem of our life :)

raywin said:
... this will allow the ECU to use all of the readings to calculate the actual mass of air entering the cylinder and adjust the fuel "shot" to suit the requirement to the correct ratio...,
Click to expand...
well said IMO
 
raywin said:
Sorry to jump in if this is a private row, don't want to get sucked into this but just want to add my two pennyworth but with the MAF there is a clue in the name.
The ECU is controlling the injectors via the solenoid valves on each injector, to give a certain amount of fuel for each stroke, this amount is calculated to keep the air fuel ratio optimized, (also taking into account many other factors) .
Air has a mass which will vary with temperature, pressure, humidity, the MAF actually is looking at volume of air entering the engine ( with some natural compensation) , but the MAP also looks at pressure and temperature, this will allow the ECU to use all of the readings to calculate the actual mass of air entering the cylinder and adjust the fuel "shot" to suit the requirement to the correct ratio,
So if you are at sea level, or half way up the Alps, in the desert or possibly Finland the ECU will be working to try and give an optimized fuel air ratio for the engine demand ( also considering engine temp and load) this is described in the text of post 36.
Click to expand...

The MAP sensor looks at pressure only, inlet air temperature is measured elsewhere as are fuel temperature and engine temperature. The ECU determines the amount of fuel to be injected subject to throttle demand, power request, manifold pressure. With fine adjustments made for fuel temp, inlet air temp. I will say again, for any given throttle request, power demand, manifold pressure, there is ALWAYS the same amount of air in the cylinder. The only difference between idle and flat out is the injected fuel quantity.
 
wammers said:
The MAP sensor looks at pressure only, inlet air temperature is measured elsewhere...
Click to expand...
Wrong, it's measured at the same place cos the MAP is actually 2 in 1 MAP/IAT sensor... maybe i must learn about how the ENGINE is working but you should learn about the MANAGEMENT then:cool: ...no offence
 
wammers said:
The MAP sensor looks at pressure only, inlet air temperature is measured elsewhere as are fuel temperature and engine temperature. The ECU determines the amount of fuel to be injected subject to throttle demand, power request, manifold pressure. With fine adjustments made for fuel temp, inlet air temp. I will say again, for any given throttle request, power demand, manifold pressure, there is ALWAYS the same amount of air in the cylinder. The only difference between idle and flat out is the injected fuel quantity.
Click to expand...
My MAP sensor on a 2001 90 TD5 has a pressure sensor and a temperature sensing probe.
yes engine temp, engine load, throttle position is sensed as I said "also taking into account many other factors
when you say there is always the same "amount" of air in the cylinder do you refer to volume or mass? yes volume is fixed by the swept volume of the cylinder, which is fixed, but mass is certainly not, and the effect of different air mass will be very significant on combustion and therefore power.
 
sierrafery said:
Wrong, it's measured at the same place cos the MAP is actually 2 in 1 MAP/IAT sensor... maybe i must learn about how the ENGINE is working but you should learn about the MANAGEMENT then:cool: ...no offence
Click to expand...

No offence taken. Ok if that is the case no problem but the engine still runs and is controlled as i say. The airflow through the MAF sensor does not control injected fuel quantity. The MAF sensor was introduced to diesel engines with EU level II emissions legislation. Where a feedback of how much exhaust gas was being ingested on EGR operation was required to limit soot particle creation. As these regulations have progressed, a much finer control of EGR has been required to reduce Nox production with engines running near the limit of combustible air. They have now reached the point where the control of EGR is so fine to reduce Nox that soot particles is inevitable, so a particle filter is now used in addition to the catalytic converter which only reduces diesel smell, to collect and store these products. They are then supposed to be burned off at higher EGT at higher speeds. If you have a modern diesel vehicle that is used around town most of the time without any long high speed runs to elevate EGT and burn off the deposits you will have big problems as the particle filter blocks and needs replacing at horrendous cost.
 
raywin said:
My MAP sensor on a 2001 90 TD5 has a pressure sensor and a temperature sensing probe.
yes engine temp, engine load, throttle position is sensed as I said "also taking into account many other factors
when you say there is always the same "amount" of air in the cylinder do you refer to volume or mass? yes volume is fixed by the swept volume of the cylinder, which is fixed, but mass is certainly not, and the effect of different air mass will be very significant on combustion and therefore power.
Click to expand...

Think the answer to that is pretty obvious. "For any given manifold pressure there is ALWAYS the same amount of air in the cylinder". Should be pretty easy to understand.
 
wammers said:
Think the answer to that is pretty obvious. "For any given manifold pressure there is ALWAYS the same amount of air in the cylinder". Should be pretty easy to understand.
Click to expand...
Good then can you understand
1 are you revering to "same" Volume
2 Are you referring to "same" mass
volume is fixed by the swept volume of the cylinder, which is fixed, but mass is certainly not, and the effect of different air mass will be very significant on combustion and therefore power. That is why turbo chargers work.
 
raywin said:
Good then can you understand
1 are you revering to "same" Volume
2 Are you referring to "same" mass
volume is fixed by the swept volume of the cylinder, which is fixed, but mass is certainly not, and the effect of different air mass will be very significant on combustion and therefore power. That is why turbo chargers work.
Click to expand...

If you have a garage compressor with a 200 litre tank, empty the tank contains 200 litre of air, that is it's volume. For any given pressure indicated on the gauge there will ALWAYS be the same amount of air in the tank. For every one bar increase in pressure the amount of air in the tank doubles. So if the gauge reads one bar there will be 400 litres of air in the tank. Is that simple enough.
 
wammers said:
If you have a garage compressor with a 200 litre tank, empty the tank contains 200 litre of air, that is it's volume. For any given pressure indicated on the gauge there will ALWAYS be the same amount of air in the tank. For every one bar increase in pressure the amount of air in the tank doubles. So if the gauge reads one bar there will be 400 litres of air in the tank. Is that simple enough.
Click to expand...
Exactly the relationship between air volume and pressure is directly proportional, you have the story but not completely, there is a reference known as normal meters cubed to allow people to work with compressed air system design.

"A normal cubic meter is
the volume of 1 m3 of air at temperature of 0°C and pressure of 1013 ,25 mbar abs."

the receiver holds 200 normal lts at 1 bar (a). When you raise the pressure to 2 bar (a) then you are putting 400 normal ltrs into 200 ltrs volume.
the mass of 400 normal Cu Mtrs of air is totally different to the mass of 200 Normal Cu Mtrs of air, so inside the cylinder has the same volume but higher pressure and mass.
Turbo chargers allow us to put much higher normal Cu Mtrs of air into the engine for each sweep of the piston in the cylinder because at 2 bars (a) they are putting in double the normal cu mtrs, ( although volume is fixed) this makes a big difference to combustion and performance.
In its simplest form this is fine let it run.
But in more sophisticated modern engines start to modify the fuel input to try and keep the mix optimized for performance, and emission,
 
raywin said:
Exactly the relationship between air volume and pressure is directly proportional, you have the story but not completely, there is a reference known as normal meters cubed to allow people to work with compressed air system design.

"A normal cubic meter is
the volume of 1 m3 of air at temperature of 0°C and pressure of 1013 ,25 mbar abs."

the receiver holds 200 normal lts at 1 bar (a). When you raise the pressure to 2 bar (a) then you are putting 400 normal ltrs into 200 ltrs volume.
the mass of 400 normal Cu Mtrs of air is totally different to the mass of 200 Normal Cu Mtrs of air, so inside the cylinder has the same volume but higher pressure and mass.
Turbo chargers allow us to put much higher normal Cu Mtrs of air into the engine for each sweep of the piston in the cylinder because at 2 bars (a) they are putting in double the normal cu mtrs, ( although volume is fixed) this makes a big difference to combustion and performance.
In its simplest form this is fine let it run.
But in more sophisticated modern engines start to modify the fuel input to try and keep the mix optimized for performance, and emission,
Click to expand...

A diesel engine is throttled by fuel. Is that to difficult to understand? Yes modern diesels are much more finely controlled that is true. But the basic principals still apply, fuel is injected into a cylinder full of air to produce the RPM required. More fuel more RPM, less fuel Less RPM. It makes you wonder how the old diesels without a MAF sensor actually ever manged to run.
 
Sorry why have you introduced throttle? not difficult to underhstand but also not part of the discussion, just a red herring here.
Quite aware of diesel principals,
AS before the old ones just ran, and when they thought of turbo chargers they just ran but did you ever see the smoke clouds when they hit the throttle
 
raywin said:
Sorry why have you introduced throttle? not difficult to underhand but also not part of the discussion, just a red herring here.
Quite aware of diesel principals,
AS before the old ones just ran, and when they thought of turbo chargers they just ran but did you ever see the smoke clouds when they hit the throttle
Click to expand...

No smoke clouds if the system was correctly set up. The fact that diesels are throttled by fuel and not by air is fundamental to the discussion. You will never believe it but some think the air going in through the MAF sensor determines the fuelling. Petrol engines that are throttled by air yes, diesels that are throttled by fuel no.
 
"You will never believe it but some think the air going in through the MAF sensor determines the fuelling"

Wrong I have always believed it, its in my posts

The fact that diesels are throttled by fuel and not by air is fundamental to the discussion
Could this be the problem here I am discussing fuel air ratio as governed by the ECU.
 
Last edited:
raywin said:
"You will never believe it but some think the air going in through the MAF sensor determines the fuelling"

Wrong I have always believed it, its in my posts
Click to expand...

Then you are wrong simple as that. So what happens when EGR is in operation and the air flow through the MAF drops telling the ECU how much exhaust gas is being ingested so it can modulate the EGR valve to control it? Is the fuel reduced because of the reduction of air flow? If it was the engine speed because it is throttled by fuel would fall, don't talk daft.
 
I dont want to repeat what i've already said cos the idiosyncrasy here is that i am speaking about how the management's addaptive strategy is conceived to work based on all the sensor inputs(MAF included) and how this complex algorythm affects fuelling in various ways and mr Wammers explains what happens in the combustion chamber after a certain amount of fuel is injected like the management should addapt itself to the combustion after it happened not vice-versa

I made various test on my own car trying to figure out things and while i was watching the injector signals with picoscope with throttle fixed to 2500rpm i gave variable voltage from a stabilised source into the MAF input and it's clearely visible on the waveform and amplitude that the MAF input has effect on the injector management also there was rpm variations too... so my own conclusion on this is that the MAF input is important part of the acceleration addaptive strategy and as the throttle was untouched and no EGR fitted for me is not relevant the certainty that "diesel is throttled by fuel" as long as the amount of fuel is managed by the ECU and it is affected by the MAF input even if the air flow was constant

also i say again that there are early td5 defenders which were made for the african market which didnt have EGR from factory but the MAF sensor was alive and kicking...why would they fit a MAF to a non-EGR modell if it was only for EGR controll?
 
sierrafery said:
I dont want to repeat what i've already said cos the idiosyncrasy here is that i am speaking about how the management's addaptive strategy is conceived to work based on all the sensor inputs(MAF included) and how this complex algorythm affects fuelling in various ways and mr Wammers explains what happens in the combustion chamber after a certain amount of fuel is injected like the management should addapt itself to the combustion after it happened not vice-versa

I made various test on my own car trying to figure out things and while i was watching the injector signals with picoscope with throttle fixed to 2500rpm i gave variable voltage from a stabilised source into the MAF input and it's clearely visible on the waveform and amplitude that the MAF input has effect on the injector management also there was rpm variations too... so my own conclusion on this is that the MAF input is important part of the acceleration addaptive strategy and as the throttle was untouched and no EGR fitted for me is not relevant the certainty that "diesel is throttled by fuel" as long as the amount of fuel is managed by the ECU and it is affected by the MAF input even if the air flow was constant

also i say again that there are early td5 defenders which were made for the african market which didnt have EGR from factory but the MAF sensor was alive and kicking...why would they fit a MAF to a non-EGR modell if it was only for EGR controll?
Click to expand...

Was going to leave this, but come on get real.. You put your foot on the throttle pedal and the ECU then knows what % of throttle RPM equal to that you need. It then increases fuel until that level is reached and maintains that level adjusting fuel up or down as required to maintain the throttle request according load requirements via readings from the engine speed sensor. The air going through the MAF will increase but it has nothing to do with gaining or maintaining the throttle level selected and does not effect the fuel required for that selected engine speed. That is a function of injected fuel, of course it will change very slightly as loads come on or are removed from the engine. That is normal. If the MAF reading fluctuates in this process it is a result of the engine speeding up or slowing down caused by adjustment of fuel as required to maintain the engine speed. It is the increase or decrease of fuel causing the MAF reading to fluctuate NOT the MAF read causing the fuelling to change.
 
You know your stuff about how the engine works i have no doubt about that off course i know that the suction through MAF will be throttle dependent but it seems you refuse to aknowledge what i'm trying to demonstrate: vehicle stationary, no load change on the engine, i fixed the throttle with a piece of wood to keep constant 2500 rpm , ECT and FT were constant as well then i played with the MAF input between 1.5 and 4.5V and the signal from ECU to injectors reacted to the MAF voltage changes so did the rpm(+/- 50)....period, even a small puff of black smoke was visible on low MAF input... I've seen this with my own eyes but next time i'll record it on video if you dont believe me
 
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