Need some help on MAF tuning

**Sandman** · 09-02-2011

I'm trying round 2 of tuning my fuel. I'm going by the Russ K method and I've got all of the tables set correctly with wideband reading. All of the tables get readings as well. My beef is that when I flash the PCM for the Russ K method my LTFTs read 0% on all of the tables and but once I flash back to my current tune they are back to all over the place. Can anyone think of what I am doing wrong? I am resetting the LTFTs everytime and unplugging the O2 sensor to put the car in open loop as mentioned in his thread on the HPT forums. I'd like to get this issue figured out as I am borrowing a friends cable and I'm shipping it back to him after this weekend.

As my tuning file is to large to attach, unless someone sends me their email, it's not getting posted.

I also went by this method with the same results:
http://www.grandprixforums.net/start...ers-43997.html

**Sandman** · 09-03-2011

BUMP

**Silver GTP** · 09-03-2011

If the O2 is unplugged and you are in open loop, your ltft's will read zero. The PCM uses the O2 to read the exhaust and set the fuel trims so if it's unplugged, they have to read zero. While in open loop, you need to log your AFR error% and use this to adjust your MAF hz. To do this, you need to log commanded AFR from the PCM vs. actual AFR from the wideband. Log this error% and plot it against MAF hz to know how much to adjust.

**TheOtherNick** · 09-03-2011

Yeah you need the 02 plugged in thats your issue. When he said to do that he is wideband tuning.

**Sandman** · 09-04-2011

So for the percent error would I use this function 100([PID.2811]-[14.7])/[14.7]

The PID being for the WB though the EGR

edit:
Tried that function and it didn't do anything. I modified it to (([PID.2811]-14.7)/14.7)*100 and was getting values at like 80% just driving around so I know that has to be wrong. I understand what I'm trying to do, just don't know how to put it into HPT.

**TheOtherNick** · 09-04-2011

I just use narrow band to get the trims dialed in then once they are locking into zero WOT i wideband tune wot.

**Silver GTP** · 09-04-2011

No. This is my calculation from HPTuners for AFR error:

100*([USER.9004]-[PID.6000])/[PID.6000]

USER.9004 is my wideband calculation through the A/C pressure switch. Replace USER.9004 with your wideband afr through the egr. PID.6000 is the commanded afr by the pcm. To calculate afr error for maf tuning you need to compare actual afr from the wideband to commanded afr from the pcm. Log this new afr error vs. maf hz and you will know what to change and how much.

**Sandman** · 09-04-2011

Got it, I figured it was something in my function.

**Sandman** · 09-06-2011

I got everything dialed in or so I thought. I was wondering if this is something to worry about or not and if I need to tweak it or not. I got all my part throttle dialed in to 0 LTFTs then did my WOT tuning. I did make sure to reset the fuel trims between each scanning. Right now it's 11.0 AFR with stock 05+ timing.

Well since it won't accept this scan file I have LTFTs as high as +12 in a couple of cells and as low as -5 in a couple of cells as well. Should I start back over?

**Silver GTP** · 09-07-2011

Look at the count in those cells that are off. Sometimes you get one or two readings on a cell that happened at a quick change in throttle and the numbers are no good. If you aren't filtering the data, try to keep your throttle transitions smooth to minimize bad numbers.

**Sandman** · 09-07-2011

I was probably driving for a good 10 min and scanning the counts were 200+ in the high areas. I was sure to keep the transitions smooth for logging. I'll go out tonight and see where they are after driving all day. Going to bump up the timing a little bit tonight so I'll keep those in mind.

**Sandman** · 09-08-2011

Did some more scanning and my LTFTs are still high/low with plenty of counts in those cells. Could it be from this temp change that we had this week where I am.? When was doing all the part throttle stuff my LTFTs were 0.

How would I filter the data?

**darkhorizon** · 09-08-2011

Temp changes have little to no effect on fuel trims. The maf is pretty smart.

"Tuning your maf" to work in the system that is closed loop using a narrowband... is really just a play on words. As much as you would like to think you are "tuning" your car, you are really just playing games with the narrowband sensor. Any time you are in closed loop, the narrowband sensor is the boss of everything fueling related going on, so any tuning done with the narrowband out, is a complete waste of time. Also trying to tune the narrowband with a wideband is also flawed, as it will always read differently (due to MANY reasons) than a narrowband will.

**Sandman** · 09-08-2011

I completely understand that it won't be perfect. Most of the LTFTs are fine, the LTFTs in the low RPMs are high, figured its just where I'm tuning I'm not hitting every cell.

**darkhorizon** · 09-08-2011

Originally Posted by Sandman

I completely understand that it won't be perfect. Most of the LTFTs are fine, the LTFTs in the low RPMs are high, figured its just where I'm tuning I'm not hitting every cell.

But just remember that you are not tuning anything in the "maf" really, so you really need to be "tuning" the o2 sensor at this point and using the maf to do so.

I suggest to everyone to just leave a stock maf file in, filter out anything less than 2-4% throttle and hit your injectors by the complete average of every LTFT in a scan.... You can do this in excel quickly and easily... You are always going to have trims, there is really no way around it because the narrowband is a touchy sensor.

The way I look at the maf.. GM spent millions of dollars to have hitachi develop these sensors, as well as millions to have them write base frequency curves for them.. then they spent millions to have engineers do on car tuning of these sensors to the point that a $30 o2 sensor crammed into an exhaust pipe and a kid scanning it for 20 minutes is probably going backwards.

**Sandman** · 01-08-2012

Bumping this

I'm tunimg again for this L26 swap. Im using the same scanner file that I used months back so i know that it should work. My problem is that the scanner won't read LTFTs at all. Live been scanning the past 3 days and the LTFTs aren't showing up at all, reading 0 across the board. I've been adjusting the MAF table, the WB looks good, and the narrow and readings are locking in at 450 across the board. I want to know that my LTFTs are locking in at 0 but I'm not sure, I want to be sure for WOT tuning. I do have the LTFT setup in the table so it should be reading them but HPT has not shown anything but 0 even starting from the stock MAF table.