***Posted 1-3-2005
Has anyone logged dynamic airflow vs MAF while in SD mode with HP Tuners??? From another post, it seems this would be a very good way to build a MAF table... just line the MAF readings up with the dynamic enging airflow and voila, the MAF won't be in conflict with the VE... Anyone have good results with this??? Thanks!

***Conclusive results 2-1-2005

My Step by Step on MAF recalibration:

After SD tuning your trims out (or via wideband) plug your MAF back in that way you can read in your frequency. You still must do your logging in SD mode and conveniently we can force SD mode by setting your MAF frequency fail to zero, or by zeroing out your P0101 DTC table. In HP Tuners you can find this in: Edit>Engine Diagnostics>General Tab

By doing this we know that the PCM is using SD airflow calcs and expectancies and we also obtain a MAF signal to correlate the data to!

1.) Make sure you log Dynamic Airflow vs MAF Frequency (Hz) In HP Tuners it is measured in lb/min so we will have to convert this later for the MAF table (g/sec).
2.) Go do enough driving to log a variety of MAF frequencies. You probably won't get a whole lot of data above 10,000 Hz or below 2000 Hz, but get as much as you can. Cruising on the highway is a good place for this as you can cover all rpms and a wide range of mph.
3.) Save the log run and export the data into a excel readable format and sort the data by MAF frequency (smallest to largest). You may delete all other columns of non-pertinent data. (You should be left with Dynamic Airflow, MAF Frequency, and optionally MAF Airflow)
4.) Section off MAF frequency ranges that register with the frequency points on the MAF table (IE. For MAF table freq = 3000, you want to use the data you logged in the range of 2940 to 3065) Take the average of all the Dynamic Airflow data in this range. The reason you want to use this range is so that the average is calculated using a sort of "swing error" that straddles the calibration point itself.
5.) Once you have calculated averages for each range (this will be very tedious and take quite a bit of time, but using excel functions makes it much easier) you will have new MAF Airflow data to rebuild the table with. 1 lb/min is equal to 7.58 g/sec so do that calculation and you will derive a new MAF table.
6.) For all the calibration points that you were missing data for (above 10K Hz, below 2K Hz) you can either shoot in the dark and scale up accordingly, or if you choose to log raw MAF air readings in tandem with Dynamic Airflow and frequency, you can calculate the variance b/w your dynamic airflow and MAF airflow and scale up by the trends you see on either extreme. (IE. If as you get closer to 10K and you notice the dyn airflow is 10% higher than the stock MAF airflow, then you can go ahead and "assume" that above 10K Hz it will most likely behave the same, otherwise you could try to log 155+ mph runs )

I know this seems like a very painstaking way to do this but it worked very well for me and using alot of excel functions I was able to reduce the time on this project significantly. I have verified that my MAF reports almost exactly what dynamic airflow the motor sees and therefore does not cause any confusion for the trims (this other bit of business in this thread is not MAF related). Some people have tried using scatter plot functions to derive equations that will supercede any manual calculation, but having to "best fit" the curve for the logged data leaves an element for bias and human error. Manual calculation appears to be the most error free method that I can think of. Hopefully someone can come up with an easier way!

Until then, I will try to make a user friendly MAF calculator that takes the Dynamic Airflow averages you figure out and automatically gives you the g/sec conversion and also the % variance from your original MAF calibration. This will still require you as the user to do a little math and a little inputting...

***EDIT 2/27/2005
Thanks to redhardsupra for coming up with a "user-friendlier" MAF calculator. It's more plug an play and can be downloaded in the link at the bottom. Now any dumbass can do it! Yay!

MAF CALCULATOR - DOWNLOAD ME!!! (Old school, download if you just wanna see)

Mod Addition
Additional info contributed by RedHardSupra
http://www.allmod.net/hpt/

 

I posted on the tuners website. When i get my copy of flashscan I will make a map and test out this theory

 

I tried it last night, but all my DynCylAir values were 0.xx. How do I convert g/cyl to g/sec?

 

spreadsheet time Jim...HPtuners has a calculator in their software that will convert the numbers, but you would have to enter them in one at a time (pain in the ***). If you could figure out the formula you could make a spreadsheet to paste the data into. Look through your PID's I thought there was a PID to log dca by g/sec.

 

I found the formula on Chris B's site....

g/cyl=(15* MAF(g/sec))/RPM
g/sec=(MAF(g/cyl)*RPM)/15

I'll see what kind of chart I can come up with in Excel. The cells in the MAF table - do the Hz references indicate the beginning or the end of the range? i.e., does the 1500 column refer to 1500Hz through 1624Hz, or from 1375Hz through 1500Hz, etc?

Also, opening my cutout leaned me out during SD tuning. I primarily run with the cutout closed, but am trying to tune with the cutout open. Any problem with that?

 

Sweet that could end up being very useful!!!!!!!!!!!!!!

 

How close to your cutout is the WB02? or are you using narrow band?

How much leaning are we talking about?

 

The cutout is in the standard location just before the rear axle. The WBO2 is under the driver seat, pre-cat. At WOT, it was ~0.7 leaner.

 

Ok I got a question for ya JimMueller...

Do we want to log DCA vs the MAF or do we want to log Dynamic Airflow vs the MAF???

I see that in the HP Tuners default scanner config it already reads in MAF (SAE) in lb/min,g/sec. I also see in the PID we can monitor Dynamic Airflow that is also measured in lb/min,g/sec.

Would this combo work for dialing in the MAF???

 

There is another pid you can use its the dynamic airflow like txhorns stated. when i posted the initial thread i didnt know we had that PID

 

so we can use this??? Sweet....

 

I didn't see it either. Guess I know what I'll be doing tonight

 

Thank you jim I have been wanting to put this to the test for a while now

 

My first few logs included both MAF (g/s) and Dynamic Airflow (g/s).

The MAF reading is very smooth with a couple of exceptions.

The Dynamic 'curve' had a lot of spikes in it. With my current results, it looks like a curve could be easily created up to about 8000Hz. The sample set above 6000Hz was pretty small, though (only 500 out of 18000 rows).

Maybe a dyno would be a better place to grab these values if we don't need to worry about the load and enough pavement

 

What you do is take that data, and export it to a CSV. The you can load it up in Excel. After you load it up in Excel, you can sort it by frequency, and make a line chart, or even better, a scatter chart. The you can click on it and add a "trendline". You may need to mess with the different types until you get one that goes smoothly through the bulk of the dots. Then you can use that to make a perfectly smooth MAF table. I would recommend doing another spreadsheet, lay out both the stock and new MAF tables, one over the other, and then make a third row that shows you how many percent variance there is...just neat to know, and let's you know how close to the old table you were. Then put it in your editor and load it up!

 

ok, so i'm an intermediate excel user, can you spell out a step by step for what you described above? Seems like this is the perfect way to build a MAF table!

 

I've played with trendlines before, but I was unclear on how to export the trendline values into a table format.

Man, this chart update on the 18K rows is kicking my laptop's posterior.

 

Yeah....I haven't actually turned a trendline into a table yet either. I never had the need. I will play with it later and see if I can put together a spreadsheet...or at least part of a spreadsheet.

 

This is getting good

 

Stock MAF table appears to be a perfect fit with a 3rd order poly, and looks pretty good for the custom table as well. To clarify an earlier statement, once the trendline is added to the large dataset chart, things get REAL sluggish. Looks like we need an array formula using the LINEST function to convert it to a table.

My modified MAF table regression formula (from trendline):

y=3E-10x^3-8E-07x^2+0.0039x-2.9051

My stock MAF table regression formula (from trendline):

y=4E-10x^3-1E-06x^2+0.0058x-6.1464

Now to see if I can get that array formula working...