wammers said:
It is there to control the EGR Keith. That is why it is fitted, the ECU takes readings from it to control and measure the amount of exhaust gas allowed into the engine. The more exhaust gas enters the engine the less flow will be shown by the MAF the ECU reads this and modulates the EGR valve within mapped parameters depending on air flow measured at the MAF and engine temp. As exhaust gas is entering the cylinders the combustion will be less efficient so engine rpm will fall measured by the CPS, fuel will be increased to maintain RPM. Using a MAF the EGR can be more finely controlled than it could with none MAF controlled EGR systems. Engines with EGR control meeting EC level 1. No MAF. Engines with EGR (feedback control MAF fitted) meeting EC level 2.
Click to expand...
I can't be bothered to argue this again, it's another of the RAVE errors. You have more or less confirmed above that the MAF fine controls fuelling, without it the car does not run well even with the EGR blocked. Without the MAF/MAP or IAT/MAP on earlier cars, the electronicly controlled injection would be hardly more efficient than a mechanical injection pump.
 
Datatek said:
I can't be bothered to argue this again, it's another of the RAVE errors. You have more or less confirmed above that the MAF fine controls fuelling, without it the car does not run well even with the EGR blocked. Without the MAF/MAP or IAT/MAP on earlier cars, the electronicly controlled injection would be hardly more efficient than a mechanical injection pump.
Click to expand...

Keith the MAF does two things. It measures inlet air temp for fuelling just as the IAT sensor did. Albeit from a different position, so the air will always be regarded by the ECM as cooler for EGR purposes. So in that sense it controls fuelling. But that function is no different from what the IAT sensor did on a none EGR engine. So basically it is the same fuelling arrangement. But it also measures air flow something the IAT alone could not do. This is needed to fine control EGR. When EGR is applied at any particular RPM the air flow through the MAF falls. From this reading the ECM knows how much exhaust gas is flowing into the manifold. It uses that information to modulate the EGR valve to maintain a mapped amount of gas flow, subject to readings from all other sensors. Turning the flow up or down as needed. As the exhaust gas flow is turned up or down the airflow reading from the MAF changes. This change in flow is monitored by the ECM to maintain the correct ratio of air to exhaust gas in the manifold. So basically the fuelling is much the same but the MAF is there to fine control the EGR.
 
wammers said:
Keith the MAF does two things. It measures inlet air temp for fuelling just as the IAT sensor did. Albeit from a different position, so the air will always be regarded by the ECM as cooler for EGR purposes. So in that sense it controls fuelling. But that function is no different from what the IAT sensor did on a none EGR engine. So basically it is the same fuelling arrangement. But it also measures air flow something the IAT alone could not do. This is needed to fine control EGR. When EGR is applied at any particular RPM the air flow through the MAF falls. From this reading the ECM knows how much exhaust gas is flowing into the manifold. It uses that information to modulate the EGR valve to maintain a mapped amount of gas flow, subject to readings from all other sensors. Turning the flow up or down as needed. As the exhaust gas flow is turned up or down the airflow reading from the MAF changes. This change in flow is monitored by the ECM to maintain the correct ratio of air to exhaust gas in the manifold. So basically the fuelling is much the same but the MAF is there to fine control the EGR.
Click to expand...
And the fueling.
 
wammers said:
No fuelling remains as none EGR controlled in exactly the same way.
Click to expand...
More or less, air mass from IAT and manifold pressure from MAP on pre EGR control fueling,
Air mass from MAF and manifold pressure from MAP on EGR versions control fueling. The difference is that the MAF provides more accurate air mass info than could be calculated from the IAT and of course air volume info is required for the EGR which could not be obtained from the IAT.
 
Datatek said:
More or less, air mass from IAT and manifold pressure from MAP on pre EGR control fueling,
Air mass from MAF and manifold pressure from MAP on EGR versions control fueling. The difference is that the MAF provides more accurate air mass info than could be calculated from the IAT and of course air volume info is required for the EGR which could not be obtained from the IAT.
Click to expand...

Air flow measurement is for EGR control only. Everything else is as none EGR.
 
Datatek said:
No, tell me what you think it's purpose is? Why does the EDC need to know the temperature of the incoming air?
Click to expand...

The IAT measures the temperature of the inlet air in the manifold so the ECU can calculate the density for fuelling. Just as it calculates the fuel density from fuel temp sensor data. The temp sensor for EGR engine has to be in the MAF otherwise the MAF will give false readings. The MAF has to know the temp of the air passing through it, as hot air will give a different flow rate than cold air.
 
wammers said:
The IAT measures the temperature of the inlet air in the manifold so the ECU can calculate the density for fuelling. Just as it calculates the fuel density from fuel temp sensor data. The temp sensor for EGR engine has to be in the MAF otherwise the MAF will give false readings. The MAF has to know the temp of the air passing through it, as hot air will give a different flow rate than cold air.
Click to expand...

Exactly, so with no IAT, the MAF is used for calculating the air density for control of fuelling and it does it more accurately than could be done with the IAT.
If you leave the MAF connected electrically but remove it from the intake, according to you with the EGR disabled it should make no difference to the running. I can assure you it does.:)
 
Datatek said:
Exactly, so with no IAT, the MAF is used for calculating the air density for control of fuelling and it does it more accurately than could be done with the IAT.
If you leave the MAF connected electrically but remove it from the intake, according to you with the EGR disabled it should make no difference to the running. I can assure you it does.:)
Click to expand...

Nop the air density changes going through the turbo because it heats. Density for fuelling is done by extrapolation from other sensors and variable mapping. What is the point in wearing an overcoat in Benidorm because it is cold in Glasgow? If you disconnect the MAF as you describe you also lose the temp reading.
 
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wammers said:
Nop the air density changes going through the turbo because it heats. Density for fuelling is done by extrapolation from other sensors and variable mapping. What is the point in wearing an overcoat in Benidorm because it is cold in Glasgow? If you disconnect the MAF as you describe you also lose the temp reading.
Click to expand...
There is no temperature reading with the MAF as confirmed on diagnostics, it measure airflow.
 
wammers said:
How does it do that? I know but just remind me.
Click to expand...
Temperature sits at -38.8.
Look at this:-
INTRODUCTION.
maf1.jpg

The maf or air mass meter or airflow meter is the biggest cause of poor performance and economy on modern diesel engines
Unfortunately, they are not a reliable component and this means that as many as 50% of diesel vehicles on our roads could have an out of spec maf sensor to the detriment of economy, performance and emissions, which is ironic because its an important component in emissions control!!.
These are the main symptoms of an out of spec or faulty maf:
1) poor performance especially below 2000rpm
2) an unexplained rise in fuel consumption.
3) flat spots, hesitation, juddering, exhaust smoke, stalling.
4) very poor throttle response - engine takes ages to accelerate to 2000rpm even in neutral due to a very weak or non existent maf signal
5) engine won't start - with no maf signal no fuel will be injected so the engine does not start.
6) engine won't rev out in the lower gears nor even in neutral
WHY DOES THE MAF HAVE SUCH AN IMPACT?
The engine management system uses the maf sensor to measure the mass of air entering the engine. At low rpm when the turbo is not working efficiently and there isn't an abundance of air available, it is important for performance, emissions and fuel consumption that the air is accurately measured. 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.



The egr valve...
The ecu also uses the maf signal to control the exhaust gas recirculation (egr) system. When exhaust gas is admitted it replaces inducted air so the maf signal drops. The ecu can therefore determine how far to open the egr valve. If the maf signal is unusually high, too much exhaust gas can be admitted or the egr valve does not close quickly enough or sufficiently when the throttle is opened. This causes hesitation and flat spots as well as performance issues.
 
Datatek said:
Temperature sits at -38.8.
Look at this:-
INTRODUCTION.
maf1.jpg

The maf or air mass meter or airflow meter is the biggest cause of poor performance and economy on modern diesel engines
Unfortunately, they are not a reliable component and this means that as many as 50% of diesel vehicles on our roads could have an out of spec maf sensor to the detriment of economy, performance and emissions, which is ironic because its an important component in emissions control!!.
These are the main symptoms of an out of spec or faulty maf:
1) poor performance especially below 2000rpm
2) an unexplained rise in fuel consumption.
3) flat spots, hesitation, juddering, exhaust smoke, stalling.
4) very poor throttle response - engine takes ages to accelerate to 2000rpm even in neutral due to a very weak or non existent maf signal
5) engine won't start - with no maf signal no fuel will be injected so the engine does not start.
6) engine won't rev out in the lower gears nor even in neutral
WHY DOES THE MAF HAVE SUCH AN IMPACT?
The engine management system uses the maf sensor to measure the mass of air entering the engine. At low rpm when the turbo is not working efficiently and there isn't an abundance of air available, it is important for performance, emissions and fuel consumption that the air is accurately measured. 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.



The egr valve...
The ecu also uses the maf signal to control the exhaust gas recirculation (egr) system. When exhaust gas is admitted it replaces inducted air so the maf signal drops. The ecu can therefore determine how far to open the egr valve. If the maf signal is unusually high, too much exhaust gas can be admitted or the egr valve does not close quickly enough or sufficiently when the throttle is opened. This causes hesitation and flat spots as well as performance issues.
Click to expand...

And you believe that bull****?
 
Datatek said:
More than I believe your bull**** on the subject.
Click to expand...

If you believe that crap there is no further point in discussing it then. We are talking P38 EDC here not common rail applications.:)
 
Last edited:
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