Maf Or Pe
Maf Or Pe Car Runs Good 99% Of Time
But
In 1st Or 2nd My Wot Afr Is Rich While In 3rd My Wot Afr Is Good
Also When I Spray My Dry Shot I Run Richer Than Expected
I Was About To Adjust My Pe Tabel But Im Thinking My Maf Table Is Off
That Being Said My L-trims Are In Check And The Car Idles 14.7
Any Guesses As To Why This Happens
Also Ill Add That I Am Using A Delphi 85mm Truck Maf And That Im Using The Maf Table Values From A Truck
But
In 1st Or 2nd My Wot Afr Is Rich While In 3rd My Wot Afr Is Good
Also When I Spray My Dry Shot I Run Richer Than Expected
I Was About To Adjust My Pe Tabel But Im Thinking My Maf Table Is Off
That Being Said My L-trims Are In Check And The Car Idles 14.7
Any Guesses As To Why This Happens
Also Ill Add That I Am Using A Delphi 85mm Truck Maf And That Im Using The Maf Table Values From A Truck
PE commands a certain A/F ratio. This can only be achieved when MAF and/or VE is correct. If you are running factory values in ANY of these tables I can guarantee that your tune could be improved. You need to command a cerain PE, then make your MAF/VE match that. Only then can you experiment with what commanded A/F your motor actually likes.
TECH Enthusiast
Joined: Nov 2006
Posts: 620
Likes: 0
From: Katherine N.T Australia
PE is a commanded AFR value not a modifier. The value you specify you want is derived from airflow calculations and injector calculations. Don't think of VE as fuel as it is most certainly not. The PCM works out how much air (talking SD here) is coming in from ECT, IAT, MAP, RPM and VE. The first 4 are sensor derived so we don't screw with that. VE and its modifiers is our constant so we use that to make the calculation of airflow accurate. Once airflow is known you command any AFR you want and the PCM will work out how much fuel (derived from injector calculations) to inject to get it.
TECH Enthusiast
Joined: Nov 2006
Posts: 620
Likes: 0
From: Katherine N.T Australia
PE is commanded AFR. If your using EFI LIVE just change the properties to display fuel in AFR rather than EQ. If your using software that doesn't have this capability you'll have to do the maths 
If you are getting the AFR you command then adjust PE. If you
are seeing an error vs commanded, adjust the MAF table until
you get what you say, and then you can say what you want.
are seeing an error vs commanded, adjust the MAF table until
you get what you say, and then you can say what you want.
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You log the commanded AFR PID and the wideband AFR. The
ratio (wideband/commanded) at some given MAF frequency is
what you'd multiply the airflow value at that frequency by.
That is, say you have a 12.5:1 commanded and a 11.5:1
wideband reading; your fueling is rich, so the MAF airflow must
be reading higher than real (pushing fuel along with it). Scale
the value by (11.5/12.5) or 0.92X and it shoud true up. Now
you have to blend in the rest of the table to the pieces you
were able to get data for. Don't auto-smooth it, smoothing
function can't tell the difference between new and old, good
and bad data. You would probably hand-massage the curve.
ratio (wideband/commanded) at some given MAF frequency is
what you'd multiply the airflow value at that frequency by.
That is, say you have a 12.5:1 commanded and a 11.5:1
wideband reading; your fueling is rich, so the MAF airflow must
be reading higher than real (pushing fuel along with it). Scale
the value by (11.5/12.5) or 0.92X and it shoud true up. Now
you have to blend in the rest of the table to the pieces you
were able to get data for. Don't auto-smooth it, smoothing
function can't tell the difference between new and old, good
and bad data. You would probably hand-massage the curve.
So Basically You Log The Commanded And Actual Afr Both Of These Are Logged Against Maf Frequencies Then You Find The % Error At A Give Maf Frequency And Correct The Maf Table For The % Error
HPT has a AFR error histogram that does all the work for you as long as you log the correct PID's...(commanded AFR and your wideband). You have to load it though. It's not one of the default ones. It also helps to use the filter depending on what/where you're trying to dial in your MAF. Oh yeah, don't forget to log Maf in Hz.
Last edited by spectreWV; Mar 29, 2008 at 09:16 PM.