How to completely get rid of MAF on de-EGR'd TD5

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18th July 2014, 06:09 AM
Dougal

Quote:

Originally Posted by sierrafery

i must disagree though...no offence, my apologies as a newbie but i must sustain my case:

You can disagree all you like. But simple physics shows the remaining sensors are incapable of replacing MAF functionality.
Which is, of course, why these engines have a MAF in the first place. Because they need one.

Two different scenarios with exactly the same MAP sensor output.

1. Turbo boosting at 15psi with 60% efficiency (edge of compressor map) and a heat soaked intercooler only removing 30% of the heat.
The intake temperature is ~96C and density is ~1.6 times intake.

2. Turbo boosting at 15psi with 75% efficiency (middle of the compressor map) and intercooler is working great taking out 80% of the heat.
The intake temperature is 37C and density is ~1.9 times intake

With a MAF the engine knows it's getting 19% more or 15% less air (depending on point of view) and allows more or less fuel based on the air/fuel calibration tables.
Up to of course the next fuelling limit.

Quote:

Originally Posted by sierrafery

all my theory is based on official data but my tests confirmed that also

Unfortunately you don't understand engine operation enough and your simple tests aren't comprehensive enough to understand why a MAF is necessary.
Without a MAF the engine would need another array of temperature sensors throughout the intake manifold and pre/post intercooler to know what the real airflow actually is.

Ever heard of "chesterton's gate"?
Chesterton

Quote:

Originally Posted by lpower85

While this is correct, you need only pressure or airflow not both.
Either can be used to calculate the mass of air entering each cylinder and hence the required amount of fuel.

Incorrect.
You can't calculate mass-flow without knowing the pressure and temperature at the manifold along with engine RPM and VE. There is no inlet manifold temperature sensor and VE varies with temperature as the speed of sound (speed of air pressure pulses) changes with temperature.

Which is, of course, why they use a MAF. Because once mass-flow is known, calculations are possible at all other points with only one sensor and a fraction of the calculation overhead.
18th July 2014, 07:24 AM
sierrafery

OK sir, then to cut a long story short.... why a de-EGR'd Td5 runs better with this mod than with the original MAF? ... shakespearealy speaking: this is the question:) ...or the whole ofiicial data which explains that the Td5's management addaptive strategy is based on all the other sensors is wrong???...if you can demonstrate with scientific arguments that what RAVE sais about the engine management is wrong i'll stand corrected and apologise again......... just take into account that Td5 is a special engine, a kind of hybrid between classic turbo diesel - common rail and PD(EUI) technology that's why it was named "Project Storm" and you can't compare it with other "normal" TD diesel engines for which your theory works whatsoever

i rest my case.... and you have my full respect:)
18th July 2014, 07:35 AM
Dougal

Quote:

Originally Posted by sierrafery

OK sir, then to cut a long story short.... why a de-EGR'd Td5 runs better with this mod than with the original MAF?

It's not running better. You are simply using one hack job to cover the symptoms of another hack job.

EGR can be turned off and shut-down in the ECU with a couple of switch bytes.
Blanking EGR and not turning it off in the ECU causes the ECU to look for EGR flow it's not getting. This is your original problem and the solution is a remap without EGR activated.

Disabling the MAF and dummying the output to the ECU is not a solution. The TD5 uses exactly the same speed-density measurement system as virtually all other EFI diesels. It requires a MAF input to know the incoming airflow so it can limit fuelling based on safe A/F ratio.

If you want a landrover diesel without a MAF, then buy a 300tdi or a 4BD1T Isuzu.
18th July 2014, 08:11 AM
Dougal

Aside from all othe others, I missed the huge original problem with this.

Connecting ECU MAF input to TPS means at full pedal it thinks it is getting full airflow.
Yet in reality full airflow only happens at full boost and max rpm.

Apply full throttle at 1000rpm and your fooled ECU thinks your engine has airflow potentially in excess of that seen at 4000rpm.:eek:
18th July 2014, 08:15 AM
sierrafery

but what about the official description then? ...that the MAF is only for EGR controll?

i really want to learn about that so please explain what you mean by a "remap without EGR activated" ...cos afaik the remap is about different fuel maps, and also afaik the EGR is not part of a fuel map whatsoever.... but i might be wrong as untill now though

the fact is that i made close to 30.000 km with this mod and i've got the best consumption and throttle response than ever... so i can't accept the statement that it's not running better as long as it does:D ...or i can accept that maybe i'm subjective on this:cool:

just explain me then why all the boost boxes like e.g. this one(but actually all are the same) [ame]https://secure.bellautoservices.co.uk/wp-content/uploads/2010/08/td5booster.pdf[/ame] are working exclusively with the MAP input and there's nothing mentioned about the MAF?...cos on stronger boost there must be higher air flow too but as the MAF signal is neglected there must be an "air floe too high" fault code logged then...which is not.:cool:
18th July 2014, 08:18 AM
sierrafery

Quote:

Originally Posted by Dougal

Aside from all othe others, I missed the huge original problem with this.

Connecting ECU MAF input to TPS means at full pedal it thinks it is getting full airflow.
Yet in reality full airflow only happens at full boost and max rpm.

Apply full throttle at 1000rpm and your fooled ECU thinks your engine has airflow potentially in excess of that seen at 4000rpm.:eek:

yes, but as long as the EGR is bypassed it doesnt matter:cool: ... i must remind all the time that we are not speaking about a standard Td5 but about a de-EGR's one which is already modified;)
18th July 2014, 08:49 AM
lpower85

Quote:

Originally Posted by Dougal

Incorrect.
You can't calculate mass-flow without knowing the pressure and temperature at the manifold along with engine RPM and VE. There is no inlet manifold temperature sensor and VE varies with temperature as the speed of sound (speed of air pressure pulses) changes with temperature.

Which is, of course, why they use a MAF. Because once mass-flow is known, calculations are possible at all other points with only one sensor and a fraction of the calculation overhead.

IAT and MAP are combined into one sensor. From this the ecm calculates the mass of air entering the cylinders.
18th July 2014, 08:52 AM
Dougal

Quote:

Originally Posted by sierrafery

but what about the official description then? ...that the MAF is only for EGR controll?

Where does it say this?
You do realise that workshop manual descriptions are extremely simplified for all components?

Quote:

Originally Posted by sierrafery

i really want to learn about that so please explain what you mean by a "remap without EGR activated" ...cos afaik the remap is about different fuel maps, and also afaik the EGR is not part of a fuel map whatsoever.... but i might be wrong as untill now though

The binary file in an ECU which contains all the maps controls EVERYTHING.
From startup to shutdown.
VE and air consumption.
Normal operation and limp modes.
All the error codes.
All the emissions equipment.
Air/fuel ratios across all engine speeds/loads
Pedal movement to torque requests.
Injection timing across all engine temperatures.
Injection timing across all engine speeds.
Torque limiters across all engine speeds.

And thousands more factors.

Quote:

Originally Posted by sierrafery

the fact is that i made close to 30.000 km with this mod and i've got the best consumption and throttle response than ever... so i can't accept the statement that it's not running better as long as it does:D ...or i can accept that maybe i'm subjective on this:cool:

You've got better throttle response because the engine thinks it's always sucking a massive amount more air than it is. It is likely overfuelling with excessive EGT and likely some smoke too.

Quote:

Originally Posted by sierrafery

just explain me then why all the boost boxes like e.g. this one(but actually all are the same) https://secure.bellautoservices.co.u...td5booster.pdf are working exclusively with the MAP input and there's nothing mentioned about the MAF?...cos on stronger boost there must be higher air flow too but as the MAF signal is neglected there must be an "air floe too high" fault code logged then...which is not.:cool:

Because the ECU expects an upper limit for boost pressure and flags an error if that is exceeded.
It has absolutely nothing to do with the MAF sensor. It's a protection system in case (when) the wastegate jams shut.

Quote:

Originally Posted by sierrafery

yes, but as long as the EGR is bypassed it doesnt matter:cool: ... i must remind all the time that we are not speaking about a standard Td5 but about a de-EGR's one which is already modified;)

:confused:
18th July 2014, 08:55 AM
lpower85

Taken from the workshop manual as previously quotes by sierrafery:

The MAP/IAT sensors are combined in one unit located in the inlet manifold. It provides pressure and temperature
information about the air in the inlet manifold to the ECM. The ECM compares the voltage signal to stored values and
compensates fuel delivery as necessary. The ECM uses the signal from the MAP/IAT sensor for the following
functions:
l To calculate the delivered fuel limits.
l To calculate the air mass in the cylinder.
l To calculate the air speed density.
l To calculate air temperature.
18th July 2014, 08:57 AM
Dougal

Quote:

Originally Posted by lpower85

IAT and MAP are combined into one sensor. From this the ecm calculates the mass of air entering the cylinders.

Has the airflow of your engine deviated from factory? How accurate are your VE tables and temp readings this many years on?

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