MAF v. Dynamic Airflow
08-31-2005, 10:50 AM
#1
MAF v. Dynamic Airflow I tuned in Ltrims reasonably well in SD mode and hooked my MAF back up and the car runs like crap. I did some logging (couple year old version of ATAP) and saw that my LTRIMS indicate the MAF is causing the car to run rich by as much as 10% or more in certain cells. (e.g. LTRIMs went from -2% to -12%)
I can log MAF frequency and airflow rate in ATAP. Is the MAF airflow number rate the same as the Dynamic Airflow that is described in the sticky on MAF tuning? If no, is Dynamic Airflow available in ATAP and what is it called?
For now, I'm using the change in LTRIMs (MAF v. No MAF) vs. MAF frequency to estimate the change and make the car drivable.
I can log MAF frequency and airflow rate in ATAP. Is the MAF airflow number rate the same as the Dynamic Airflow that is described in the sticky on MAF tuning? If no, is Dynamic Airflow available in ATAP and what is it called?
For now, I'm using the change in LTRIMs (MAF v. No MAF) vs. MAF frequency to estimate the change and make the car drivable.
08-31-2005, 10:52 AM
#2
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Dynamic airflow is derived from your ve table. and should be different from the MAF Airflow if you have dialed the car in, in SD mode. Redhardsupra has a spreadsheet that will take frequency and dyn airflow and plot out a new MAF table for you
08-31-2005, 10:56 AM
#3
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Humpin, I'm in the exact same boat as Ragtop. I went through the SD process, but when I started to tweak on the MAF tables (via RHS's sheet), it turned my table rich to the same degree in the <4k RPM range.
I was advised to hand tweak the MAF table to get this back in line, but I haven't really understood how MAF Hz relates to RPM/load. The suggested reason hand tweaking is needed is possibly because the MAF is inaccurate at low airflow levels.
I was advised to hand tweak the MAF table to get this back in line, but I haven't really understood how MAF Hz relates to RPM/load. The suggested reason hand tweaking is needed is possibly because the MAF is inaccurate at low airflow levels.
08-31-2005, 11:53 AM
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I think Dynamic Airflow is the final result of the "blend"
that is done between SD and MAF inputs, plus smoothing
and other fudgery. The extent to which DA differs from
MAF, is indicating the amount of SD mode contribution
I expect (if things are fairly steady state).
that is done between SD and MAF inputs, plus smoothing
and other fudgery. The extent to which DA differs from
MAF, is indicating the amount of SD mode contribution
I expect (if things are fairly steady state).
08-31-2005, 12:08 PM
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I just tuned my maf with my fuel trims. I can honestly say it works great that way now that I have LTFT's @ -2 to -4. Above a certain frequency, I just upped the stock MAF table by a flat percentage based on the values recorded at mid-range airflows.
So, from 2250Hz to 6000Hz or there abouts, I used STFT's (LTFT's off since they were within +/-10). Then, I looked at the difference between that part of the curve and stock. It had gone from a 1:1 ratio down low to a 1:1.055 ratio by 3500Hz and pretty much stayed there. I took that 5.5% increase and applied it to the top end of the MAF table that I didn't hit with the STFT's. No problems since. If you're not intimidated by Excel, I have a file that makes it a piece of cake. It's on the second MAF tab. Just put in your stock table, your current table, your STFT averages (scroll right), and number of cell hits for each range (scroll right) and you're good to go.
https://ls1tech.com/forums/pcm-diagnostics-tuning/366409-excel-worksheet.html
So, from 2250Hz to 6000Hz or there abouts, I used STFT's (LTFT's off since they were within +/-10). Then, I looked at the difference between that part of the curve and stock. It had gone from a 1:1 ratio down low to a 1:1.055 ratio by 3500Hz and pretty much stayed there. I took that 5.5% increase and applied it to the top end of the MAF table that I didn't hit with the STFT's. No problems since. If you're not intimidated by Excel, I have a file that makes it a piece of cake. It's on the second MAF tab. Just put in your stock table, your current table, your STFT averages (scroll right), and number of cell hits for each range (scroll right) and you're good to go.
https://ls1tech.com/forums/pcm-diagnostics-tuning/366409-excel-worksheet.html
Last edited by SSpdDmon; 08-31-2005 at 12:17 PM.
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08-31-2005, 01:19 PM
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Originally Posted by jimmyblue
I think Dynamic Airflow is the final result of the "blend"
that is done between SD and MAF inputs, plus smoothing
and other fudgery. The extent to which DA differs from
MAF, is indicating the amount of SD mode contribution
I expect (if things are fairly steady state).
that is done between SD and MAF inputs, plus smoothing
and other fudgery. The extent to which DA differs from
MAF, is indicating the amount of SD mode contribution
I expect (if things are fairly steady state).
09-01-2005, 09:50 AM
#10
Originally Posted by Ragtop 99
I tuned in Ltrims reasonably well in SD mode and hooked my MAF back up and the car runs like crap. I did some logging (couple year old version of ATAP) and saw that my LTRIMS indicate the MAF is causing the car to run rich by as much as 10% or more in certain cells. (e.g. LTRIMs went from -2% to -12%)
I can log MAF frequency and airflow rate in ATAP. Is the MAF airflow number rate the same as the Dynamic Airflow that is described in the sticky on MAF tuning? If no, is Dynamic Airflow available in ATAP and what is it called?
For now, I'm using the change in LTRIMs (MAF v. No MAF) vs. MAF frequency to estimate the change and make the car drivable.
I can log MAF frequency and airflow rate in ATAP. Is the MAF airflow number rate the same as the Dynamic Airflow that is described in the sticky on MAF tuning? If no, is Dynamic Airflow available in ATAP and what is it called?
For now, I'm using the change in LTRIMs (MAF v. No MAF) vs. MAF frequency to estimate the change and make the car drivable.
heres my spreadsheet.
You can use LTFT STFT or a combination of both
usually you get dead on witin 3 logs
http://www.audiohelix.com/hptuners/M...-Worksheet.xls
09-01-2005, 09:33 PM
#11
i've had some mixed results with my spreadsheet for values < 5500Hz. I guess there's just not enough of pressurized air to make the MAF readings really consistent. I can get it closer with MAP based filtering, but still not too good. however for >5500rpm, it works out _really_ nice. and for lower values...well, i just start with stockers, and fudge where necessary to get barely lean idle, as i don't like idling rich.
09-02-2005, 08:40 AM
#12
Below 5500 Hz is the key area too. That's where most of the daily driving ends up. I did a scatter plot of LTRIMs v. Hz as well as (LTRIM + STRIM) v. Hz and it was all over the place, especially below 4000 hz.
I'm going to give it a few more miles on my rough cut and go out and log and see what is going on. I may use SoundEngineer's spreadsheet, but I don't like relying on something that has the math hidden. I think I did something pretty similar, except that I did not control for small populations like he does.
I used the OLFA table to lean out my cold idle. I start up in a 50+ MAP and knocking that down below 100* F helps alot.
I'm going to give it a few more miles on my rough cut and go out and log and see what is going on. I may use SoundEngineer's spreadsheet, but I don't like relying on something that has the math hidden. I think I did something pretty similar, except that I did not control for small populations like he does.
I used the OLFA table to lean out my cold idle. I start up in a 50+ MAP and knocking that down below 100* F helps alot.
