Weighting of VE vs. MAF

[johnsZ06]

Does anyone know the percentage of weighting the PCM uses to calculate AFR between the MAF and VE table during normal closed loop operation?

[caver]

My understanding is that it uses the MAF exclusively.

[Dirk Diggler]

Below 4000 rpm and unsteady map values the pcm blends both above 4000 rpm the pcm looks at the maf. THis was posted by a member on tech. Search for a thread called "ve Cracked"

[superls1]

Below 4000 rpm and unsteady map values the pcm blends both above 4000 rpm the pcm looks at the maf. THis was posted by a member on tech. Search for a thread called "ve Cracked"

This was posted by the guys from HPT almost 2 years ago. It has been internet gospel ever since. I am not saying it is incorrect, but I have not ever seen anyone validate their description of 'how' the code works. I wish Paul or Ross would lend some input into this discussion. The basics of what the HPT guys wrote is thus:

 
RPM > 4000 *
---------- 
*trust MAF completely and ignore SD calcs (apart from MAF sanity checking purposes) 

RPM < 4000 
---------- 
if RPM <; 2400 and MAP<; 84 kPa then 
Steady MAP threshold = 0.0 kPa 
else 
Steady MAP threshold = 0.8 kPa 

If (SteadyMAP) then 
Calculate MAFAirmass/SDAirmass ratio (used for Unsteady MAP operation) 
Correction Airmass = MAF Airmass (filtered) 
else 
Correction Airmass = SD Airmass x MAF/SD Airmass Ratio (calculated during Steady MAP conditions) 

Transient Corrected Airmass = previous Final Airmass + proportion of Correction Airmass 

Final Airmass = fn(MAF Airflow, previous MAF Airflow, prev 3 MAP readings, prev 3 TPS readings, 
Transient Corrected Airmass)

The full description is here.

It would be nice to put together a couple of real world examples, indicate which tables are being used, how, etc.

[Dirk Diggler]

or better yet some type of pid which indicated the amount of smoothing/bias at different maps/rpm

[johnsZ06]

This was posted by the guys from HPT almost 2 years ago. It has been internet gospel ever since. I am not saying it is incorrect, but I have not ever seen anyone validate their description of 'how' the code works. I wish Paul or Ross would lend some input into this discussion. The basics of what the HPT guys wrote is thus:

 
RPM > 4000 *
---------- 
*trust MAF completely and ignore SD calcs (apart from MAF sanity checking purposes) 

RPM < 4000 
---------- 
if RPM <; 2400 and MAP<; 84 kPa then 
Steady MAP threshold = 0.0 kPa 
else 
Steady MAP threshold = 0.8 kPa 

If (SteadyMAP) then 
Calculate MAFAirmass/SDAirmass ratio (used for Unsteady MAP operation) 
Correction Airmass = MAF Airmass (filtered) 
else 
Correction Airmass = SD Airmass x MAF/SD Airmass Ratio (calculated during Steady MAP conditions) 

Transient Corrected Airmass = previous Final Airmass + proportion of Correction Airmass 

Final Airmass = fn(MAF Airflow, previous MAF Airflow, prev 3 MAP readings, prev 3 TPS readings, 
Transient Corrected Airmass)

The full description is here.

It would be nice to put together a couple of real world examples, indicate which tables are being used, how, etc.

Very interesting, thanks.

Would be nice if somebody could validate that.

[bink]

or better yet some type of pid which indicated the amount of smoothing/bias at different maps/rpm

Great idea- that would be really cool to see!!

[superls1]

or better yet some type of pid which indicated the amount of smoothing/bias at different maps/rpm

I would be happy with just an explanation to start, but a PID would be pimp!

[bink]

or better yet some type of pid which indicated the amount of smoothing/bias at different maps/rpm

Shouldn't there be a "DMA" type pid for this?? GMPX or Blacky?????

joel

[superls1]

ttt, Ross or Paul. Can you shed any light on this? Would it be possible for you to post some pseudo code that we could interpret for ourselves?

It seems as though MAF and VE are like High/Low spark where the computer is always interpreting between the two. It would just be nice to know if there are particular situations where one is favored over the other (just like the whole Charge Temp Blending factor). Inernet gospel says when using MAF, VE is for sanity checks and transition. Some go as far as to say above 4000RPM, use MAF exclusively.

FYI, saw this tech paper on MAF's posted on another site: http://delphi.com/pdf/techpapers/2000-01-0546.pdf

If anyone wants to discuss, I have questions after reading it.