Need MAF tuning help!
Need MAF tuning help! Have a 96 Impala with TrickFlow 195 heads, 230/236 .560/.565 @.050 on a 114, longtubes(tri-y) and full Hooker Aerochamber exhaust. Tuned in speed density and runs GREAT, but doesnt start well after warm up. Tried turning MAF back on, starts great but runs like POO! Any help would be greatly appreciated! BTW, I'm using the JET software for tuning....Thanks
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Data log the car if using DataMaster, its AFGS to look at. Check the BLMs, when lean look at the AFGS. Go into TunerCat, go to the MAF tables, find the closest number to it. If its lean you need to add to it, if its rich remove from it.
When scaling 1.xx will increase (richen) .xx will lower (lean out).
When scaling 1.xx will increase (richen) .xx will lower (lean out).
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From: Kingfisher Oklahoma
I agree with 96capricemgr here. The MAF tables are supposed to be a definite figure, if it is working properly then no need to change MAF tables. What method for SD tuning did you use, Gregrob has a very comprehensive method he has spoke of many times on this forum. Search out his name on the subject.
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The MAF needs to be tuned for changing things.
"MAF Sensor Tables
There are four tables for the MAF, which split up its total frequency->airflow grid.
First, find the airflow reading for your idle in your logs. Then, find the closest value(s) in the MAF sensor tables; you will sometimes have to alter two cells to affect one airflow range.
To richen your fuel mixture (BLMs > 128), increase the value(s) you found as mentioned above.
To lean the fuel mixture (BLMs < 128), simply decrease the appropriate MAF cells as mentioned above.
These values are also efficiently modified using percentages (%), or multiplying the values (1.xx to richen, 0.xx to lean). Start with 1% (1.01/0.99) changes for every 2 BLMs off; so, a BLM of 118 would require a 5% decrease (128 - 118 = 10 / 2 = 5), or multiplying the MAF airflow value(s) by 0.95. Again, trial and error will be needed to see if you have overshot a BLM of 128 with your changes."
From Solomon, a well known LT1 tuner.
"MAF Sensor Tables
There are four tables for the MAF, which split up its total frequency->airflow grid.
First, find the airflow reading for your idle in your logs. Then, find the closest value(s) in the MAF sensor tables; you will sometimes have to alter two cells to affect one airflow range.
To richen your fuel mixture (BLMs > 128), increase the value(s) you found as mentioned above.
To lean the fuel mixture (BLMs < 128), simply decrease the appropriate MAF cells as mentioned above.
These values are also efficiently modified using percentages (%), or multiplying the values (1.xx to richen, 0.xx to lean). Start with 1% (1.01/0.99) changes for every 2 BLMs off; so, a BLM of 118 would require a 5% decrease (128 - 118 = 10 / 2 = 5), or multiplying the MAF airflow value(s) by 0.95. Again, trial and error will be needed to see if you have overshot a BLM of 128 with your changes."
From Solomon, a well known LT1 tuner.
I understand lying to the pcm about airflow can be used to modify the AFR. I am saying that IMO it is better to change the commanded fueling for the measured airflow.
Basically don't **** with the sensor readings fix what the pcm does with them.
Basically don't **** with the sensor readings fix what the pcm does with them.
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Verdad Gallardo TECH Fanatic
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VE is when in Speed Density. For instances if the MAF fails, or when entering PE mode, or in Open Loop. They will not effect AFR when running MAF. The PCM doesn't even look at those tables, it just uses sensor inputs.
This is not correct. By that logic you shouldn't change the VE table either or you are "lying" to the PCM. The truth is when you make modifications that affect airflow, even something as simple as a CAI, you need to correct the MAF calibration.
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If you don't want to change the MAF then delete it, and run Speed Density. You do realize before MAF sensors, cars running fuel injection, cars just ran Speed Density and Speed Density as I stated is only back up for if the MAF system fails?
(Not directed to Gregrob but to the others)
I bet if you looked at your tune, since you two probably didn't tune it yourself, if you are running a MAF it will be different than stock.
2.45
2.88
3.34
3.87
4.45
5.12
5.85
6.64
7.49
8.41
9.40
10.46
11.60
12.82
14.11
15.48
16.98
18.60
20.34
22.22
That is the stock on MAF table 1.
Speed density isn't strictly a backup... the car doesn't determine fueling solely on MAF input, although it is the primary source. It uses manifold pressure and predicted airflow (VE) as well.
I do agree though if you want it to run properly MAF calibration is essential
If you're not willing or equipped to do that then delete it and run in SD only.
I do agree though if you want it to run properly MAF calibration is essential
If you're not willing or equipped to do that then delete it and run in SD only.
Last edited by gregrob; Mar 28, 2012 at 09:06 PM.
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From: Kingfisher Oklahoma
Thanks for clearing that up. I absolutely understand where you are coming from about the MAF tables, I just like to not touch them until the last resort, on my particular cars I havent had to tweak them except down low.
First off are you talking open or closed loop operation?
Let's say you're talking closed loop non PE mode operation. You go through the VE tuning process and have the as close to 0% correction STFT and LTFT as is possible.
Now you reenable the MAF and suddenly your trims are way off. Are you to then go again to the VE tables and force them to predict an inaccurate airflow amount, so the fuel trims come back in line?
I would rather tune the MAF as is the proper way, until closed loop operation both MAF and speed density overlay nearly seamleassly.
The same principle applies for enrichment mode as well. If you are commanding X wot AFR and not attaining it WHEN the VE fueling is correct then you need to work on the MAF calibration until desired matches actual output. NOT provide incorrect numbers to the VE table or PE mode adjustment tables.
Last edited by gregrob; Mar 28, 2012 at 09:21 PM.
