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Старый 14.03.2021, 11:40   #1
ALFAMAF
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По умолчанию ALFA ROME0 2.5V6 VAF to MAF Conversion Function

I have developed the following method to determine the relationship between Bosch VAF output and the HFM5 MAF I will use. ( Bosch 0 281 002 537).
I arrange the airflow through both sensors via adjustable bleed off valves to vary the airflow and connect to 2 X Vacuum cleaners. The airflow through both VAF and MAF will be the same. See the attached photos. Note the slightly unstable nature of the MAF signal in my setup so I plot Min/Max/Avg values.
Apply appropriate supply voltages to both devices and the following graph produced. I should then be able to load this data into Pilot VAF/MAF configurator and get a very close tuning result. I hope.
I will ignore the low value data.
I will smooth the mid flow lump as I suspect not real.
I can extrapolate the curve to the higher airflows which I could not achieve.

Последний раз редактировалось Pin; 14.03.2021 в 12:53.
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Старый 14.03.2021, 14:03   #2
Pin
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Hello.
Sorry it seems that attached pictures are crashed during relocation of this thread.
But i saw them.

This method will not work correctly at all, because the air pressure after you will remove AFM will be much higher and you will get too lean mixture with a new MAF.
We already tried to compare signal and make conversion table with the same method. Moreover earlier versions of firmware and software had a special algorythms and did such a job in automatic mode, but in practice it gave a very bad and unstable results. Thats why we removed this feautures. And it is more better simlier and precise to make a new conversion table with a new maf directly according to oxygen sensor signal.
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Старый 15.03.2021, 10:25   #3
ALFAMAF
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По умолчанию ALFA ROME0 2.5V6 VAF to MAF Conversion Function

Pin,

Thankyou for you observation.
The additional resistance to airflow introduced by either the VAF ( significant) or MAF(probably insignificant) can be thought of as a contribution to the throttle. The VAF vane is just like another butterfly - yes?
At the end of the day the voltages I have measured must be reasonably correct and are absolute regardless of the engine requirements.
Yes, there will be more airflow when the VAF is removed (for the same throttle opening) but this then just equivalent to moving along along the graph to the right a bit.

I will see how this goes when I get it all running.
Cheers
Doug

PS.. I attach the graph again.
Миниатюры
Нажмите на изображение для увеличения
Название: Screenshot 2021-03-14 153628.jpg
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Старый 15.03.2021, 17:11   #4
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The main issue that air pressure drops a lot after AFM flap , because of spring force.
In another words you need to make some vacuum to rotate flap.

MAF can compensate changes in air pressure which is not too big - weather changes or if you are climbing from sea to the hills. But in case of AFM before MAF you get very high decreasing of air pressure, so MAF cant compensate it correctly.

You can connect maf to the " maf" input and AFM to "tps/vaf" of the converter, start dashboard and blow all that stuff together with air. Next stop the dashboard and in the log by double clicking on tps curve( which will be AFM signal) you can get direct conversion table AFM to MAF - you can make all graph.
After that store this conversion table to the converter , install new maf and try to drive and check the mixture - you will be surprized that direct coversion table will not work correctly and you will need to adjust it

We tried this several times at the beginning. But if you will make such a table it will be much more simple to start engine with MAF.
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