ESL Maf scale adjusting
 

So, it's looking like my maf scaling needs altering at the low voltage side due to an induction cone on it which is causing lean spots at low load .

My MAF scaling is set on a 6k ecu which I believe is a V2 sti .

Would adjusting my scaling to say , an orange or purple MAF scaling table help with the fuel to air ratio at low load ? I'm not mathematically savvy enough to work out how to adjust my current scaling lol

I did read adjusting MAF scaling is a bodge to correct incorrect injector scale but when I've adjusted my injector scale it didn't help flat spot low down

Weird lol


Cheers

if your running stock injectors and stock fuel pressure you shouldn't need to adjust the injector scaling too much to hit fuel targets. If you've changed the intake though that's where the MAF scaling comes into play.

Overall it's a little complex, but break it down into bitesize chunks and it's not so bad. The maf scale table is very simple, voltage from the sensor on one side and a corresponding amount of air on the other. The ECU uses the amount of air value along with the requested fuel target and injector scale to decide how long to open the injectors for at a specific point in time. It's not relative to the engine speed and if you find the MAF scaling doesn't match up at different RPM's then it's more likely to be the injector settings that are out rather than the MAF.

To properly scale the MAF the main thing you will need is time, lots and lots of time! You have to get enough log data to calculate a value for maf error (using fine/course correction values in closed loop and current AFR vs Lambda Signal (converted to AFR from your wideband) in open loop.

The idle part should be easier to start with it as you can simply hold the throttle open whilst stationary to adjust the MAF reading (more revs = higher airflow = higher MAF reading). Hold the revs steady and allow the ECU some time to make a correction before moving on to the next MAF point. Use a nice bit of excel to work out what your average fuel correction is for the maf points and then apply that average value to the scale.

It's a similar process when your on boost too - use the logs to determine how far out your MAF value is based on AFR error (actual AFR from the wideband vs the target AFR from your fuel table). If your value is leaner than it should be then you must increase the MAF values - if your reading richer than target then reduce the MAF values. Again a bit of excel magic can save you some time here as well as making your target fuel table a bit more basic (instead of a lovely smooth transition to 11.1 AFR try a sharp transition at a lower load so that more of your log data will be aiming for the same wideband voltage). Doing this means you could make the changes on the fly as your just looking in the logs to compare the MAF reading vs raw wideband voltage (work out what your voltage is for 11.1:1 AFR or whatever your fuel target is and then aim for that).


Now - all good in theory but you could be at this for days and find yourself going round in circles. If your planning to put the time in to get it right why not just switch over to mafless and be done with it? You'll not have to worry about maf scaling and the adjustments to the fuel table are much quicker to work with.

Cheers bud, im running yellow 440`s on standard FPR, think the 6k ecu was based on grey 380 injectors ? ( i used to have 380 grey`s on my old Z4 ecu) but not sure on the 6k MAP / Or the MAF scaling of the 6k

A good explanation and like you say, it needs days of logging which i dont have lol and what with our varying temperatures lately what i log one day could be different on another due to denser/colder air etc, its a vicious circle :-(

If i cant live with the lean spots i might just go back to Mafless, as you say, no more scaling to worry about, im just not looking forward to re-doing my fuel table as i have it nice at the moment (once off closed loop ha )

going back to MAF scaling, i only need to adjust from around 1.1v to about 2v , the rest of the scaling seems to work well even with the induction cone fitted, im just suffering low load with lean spots when cold.

I was thinking of reducing each side of the right column of the MAF scaling table by a value of 60 from 1.1v to 2v to see if this did anything as it seems i need the MAF to report less Air due to the cone being fitted ?

Cheers again bud

hi, u should not touch the scaling, i think u mean calibration and ju should tell the ecu that there is more air than it thinks to get out of lean condition, if u reduce the right column numbers, u make the opposite and take more fuel off.

Yeah sorry , meant calibration .

So increasing the air figures on the right hand side of the calibration table will richen up at those voltage levels ?

Makes sense , as a quick dabble I removed 100 from each cell from 0.25 v up to about 1.92 v , where I'm experiencing lean conditions and it ran even leaner lol .

So as a test I might add 100 to those cells / voltage columns and see if it richens up

I find when cold it's worse/terrible and if I say accelerate and go into neutral to coast to a stop it goes uber lean to 22 !! Then corrects back to stoich , only does this from cold tho.

Cheers

Try to think more like in %, not in a specific number, cold is worse because lamda control is not active until your car heats up. You can log fine learned fuel correction and mafV, there you see where you have problem and how big problem.

also don't forget the tables you can't see in the background so there will be a lot of temp based compensations going on until you reach full running ECT too so things that are normally a little % out will soon become a large % out when the comps are added on top (if that makes sense).

Ok cheers guys , at 0.0 v I think the air value starts at 157 .
I experience most lean spots from here up to about 1.92v .

When cold , AFR goes to say 19 or 20 briefly at low engine load , when warm at same points AFR goes to 17 or 18 briefly .

I was going to add 100 to every cell value upto 1.92v , but working on a percentage level that's about 62% increase . Think I might add 70 which equates to 45% increase and try that

Cheers

when the AFR hits 19/20, whats the target AFR at that point? Use target AFR vs Actual AFR to decide what the AFR error % is, apply about half the error % to the MAF scale and and repeat the process :)

It's on closed loop so I'm guessing target AFR is 14.7 , it's around 1000 rpm to 1400 rpm on cruise , slight throttle / light load

My maths is terrible , what does that make the AFR error % ?

Cheers

I think the percentage between 14.7 and 19.7 is about 35% , do if I add 20% to each cell value and go from there

Cheers

yup - also it's good if you can run through the bad area a few times and then take an average value from the logs. What you might find is on just 1 or 2 runs there can be other things taken into account - so with the average data you've a better chance of getting it closer to where you want. Just remember to disable the closed loop corrections whilst your making changes so the ECU isn't fighting you from across the table.

ok cheers bud

i increased the cells from 0v to 1.92v by 20% , so 157 became 189 i think and so on upto values of around 4999 at 1.92v

It made a world of difference !

didnt go lean half as much, didnt go to 20 on my wideband when i put it into neutral , pulled away in 4th gear at 1000 rpm beautifully

But, im thinking 20% might be a tad too much, my wideband reads from 12 to 14 for a short while while crusing until the MAF/lambda make corrections etc and my fuel trims have gone a bit negative lol, low load cells are around 87

so i might re-do the maf calibration but only at 10% instead of 20% , its a fight between having it lean like it was, no thanks ! or rich like it is, so finding the inbetween but for now, rich is better than lean driveabilty wise anyhoo ha

i havent the time just yet to log results, im going by good old fashioned driveablity and wideband readings plus fuel trim adjustments

passed 1.92v the calibration is fine/ high load etc

cheers again guys

Heres a quick data grab after a reset running with 15% higher values from 0.00v to 2v on maf calibration.

Car drives much better at low load even with these fuel trims

i have a spike in AFR at 5k, it goes lean momentarily, im going to see where on the MAF calibration scale this occurs and i will add 2 % or so to the value to see if it stops it going lean at 5k.

https://cimg0.ibsrv.net/gimg/www.sco...f19715a5ed.jpg

On mine the maff calibration wasn't changed just the scaling as manual shows to adjust scaling so load it about 24 per 1 bar mine could do with tweek as mapper set it to 30 at atmosphere 44 at 0.5 bar then makes full load not much after that so most map is on vacuum same load at 1 bar and 1.4 bar
My coarse fuel is about 7 correction on closed loop noticed can just keep adjusting fuel map in closed loop and ecu just tries to correct it so used coarse fuel to set it up with less corrections

Not used coarse fuelling as a guide , another learning curve lol , I have found tho that in closed loop if I set my low load fuel table to a leaner figure the girl trims are not as bad

With lambda disconnected idle is 12 on the wideband ( 14.9 when lambda connected ) so if I set my low load to 17.9 fuel trim isn't pulling as much , naturally . Also wideband readings don't hang at 12 when coasting with lean AFR at low load like they do if I have 14.7 in the fuel table .

My fuel trims may be a bit out of whack but it certainly drives better now than before at low load since the MAF calibration increase of 15% upto 2v .

Cheers