Another_User

Aha. I was able to calculate my new MAF table tonight. Of course there is good news and bad news. I am running an SLP lid, and billet MAF ends, w/excess plastic removed from center support. It took me awhile, because my calculations were coming up slightly off. Here is what I did:
1) set MAF fail to 0 hz.
2) logged MAF frequency and dynamic airflow
3) plotted everything into a scatter chart
4) added trendline, poly 3 (perfect, straight through the center of my logged data)
5) calculated new table using the trendline formula, substituting the correct MAF frequency in hz for X.
The result? Poopie, worthless table. That's what stumped me. So I looked over the numbers and realized that the formula was correct. The problem is that by default Excel doesn't factor in that you could be dealing with numbers that require such excessive granularity. So, I reformatted the formula with 6 decimal places. Voila! A perfect MAF table that matched the data I logged.

And that leads me to my problem. I can't fit the values in above something like 10125 hz. They are too big. My table maxes out with values of 511.99, and my last value is as high as 609. So what is the likelyhood that I will exceed 10k hz at WOT at 6400 rpms?

Another note: It is no wonder that people run too lean with MAF ends. With a lid and MAF ends your MAF table is 30+ percent off.

I have attached links to my spreadsheets for your viewing pleasure. Please let me know what you think. DON'T POOP IF your computer takes a long time opening the large spreadsheet, Excel doesn't seem to like poly trendlines with that many values. It will take awhile. The smaller one shows a MAF flow comparison. I don't have trim results yet...too late for today.

Now I need to know if the value limit on my MAF table is a PCM limitation or something that can be corrected in the HP Tuner sofware. Anyone?

http://users.adelphia.net/~someoneelse/MAFSheet.zip

99whitews6

iTrader: (2)

Maybe I missed something. Why in your speadsheet did you sort all your data according to your logged mass air flow (Hz)?

HumpinSS

iTrader: (1)

Finally someone was able to test my theory with good results. #2 logging maf freq against dynamic air. If tuners had custom maps you wouldnt even need excel .

Txhorns IIRC used this method also but I cant remember his results...

Thread for reference


Using a WB SD tune to calculate a new maf table

HumpinSS

iTrader: (1)

Prolly for better grouping of the data.

HumpinSS

iTrader: (1)

I would prolly use the airflow values for what was hit and taper the un-hit freqs off to 511 or flatline it at 511 after the last freq you hit

HumpinSS

iTrader: (1)

Man you make me want to go back to my maf jsut to try this stuff out. How is the responsiveness and the driveablilty with it connected. Did you lose all the perks of the SD tune?

Details man, details!!!!!!!!!!!!!

Another_User

I will post some info later. I don't get to drive the Camaro until after work, LOL. A guy posting on the HP Tuners site said I should go all the way down to 30 digits for the trendline formula, but I checked it this morning and compared it to what I have, and all the values came within like .001 of each other, so I don't think I will change what I have. It should not impact anything. I am anxious to get the heck out of here so I can log some data!!!

way2slow

Anything yet?

SmokingWS6

iTrader: (1)

Did you try this using RedHardSupras formula? I going to give that a try.

JimMueller

iTrader: (9)

Anyone care to explain how altering the MAF tables affects idle quality, surging, etc? I tried RedHardSupras formula and I've now got some idle issues. I created the MAF data for another calibration based upon AnotherUser's process, but I don't think the lower numbers are right (~10g/s from 1500 to almost 3000), which makes me question the remainder.

It also seems like my wideband is indicated my real-time AFR is a bit richer; running in SD at cold start (AFR reads ~13:1 - I wonder why the AIR pump isn't kicking on?)

Another_User

Yeah, I got a run in. I was not too excited about the results. Everything is looking pretty rich. I think the problem is the SD calculated airflow is completely undependable at low airflow/rpms. And on top of that, this is where most of your data is sitting. I would imagine it would throw the entire curve off. What a PITA. Now I remember why I yanked that POS MAF out. Back to the drawing board.

MNR-0

Why do you persist with this? Ive tried and MAF re-cals are just not required. The MAF cal is what it is. Its far easier and safer just to rescale your IFRs.

txhorns281

iTrader: (12)

I've enjoyed the ease of MAF calibration based on what we know now and have seen great results with it. To answer why not rescale IFRs? Cuz I just don't like telling my PCM that I have bigger or smaller injectors when I don't

txhorns281

iTrader: (12)

Hey at what exact conditions are you rich in? Mine are at idle and low rpm take off. But even at 1600 in 6th on the highway, on the guage display my trims have settle into -1 and -3.1. Only when i get close to idle speeds (25 mph or less) do I see overly rich trimming. -5 to -8 just around that outer histogram ridge. I figure it has something to do with 02s since on the chart display, when my O2s don't oscillate tightly, that's when i generally see negative trimming. I dunno if that's a fair assumption to make, or how to fix it... Could just be something that we can't avoid... Either way, for anything above 25 mph my trims show -3 to +2 , most of them at -2 so the MAF calibration did work for me!

MNR-0

Fair enough. But who says the stock IFRs are more correct than the MAF cal? In the end, we are just playing with numbers to suit the particular characteristics of our engines. Whenever we make a chane, the baseline needs to be reset. Its how we get to that baseline that is in question here. Now if you were MAFless then absolutely you would play with the VE. But the IMHO the MAF cal. has been calibrated correctly. Its just the air we intake is not a constant. So why chase a moving target?

RedHardSupra

iTrader: (1)

txhorns, all good points, you saved me typing
also, it's a good point about IFRs being not too precisely tuned for your injectors. that's why i have a set of 30svo's in the cleaners/doing the flow. tuning is about getting everything in line properly, so there's less guessing. i refuse to change IFRs until i do something with the injectors. Maf we figured out how to calibrate, stick to that. It is the VEs that you supposed to use to account for particulars of your setup, and that's what you ought to be changing. The fact that it works, doesn't make it right.
Just retune your VEs after you get new MAF numbers, it's no big deal and it shows you how much out of whack your setup was. I just redid everything becuase I put on a LS6 intake, took me one trip to my parents. on the way up i got enough data to create new MAF and get a first try on VEs, on the way back I put the new settings in and verified that all my math rules (or at least works well with each other )

Another_User

I am rich in nearly all conditions, except a few weird STFT spikes of almost 20 in weird places. Something is not right. I think my VE is too far off to give a good dynamic airflow calculation to base everything off of. Back to work...

HumpinSS

iTrader: (1)

Damn this sucks.....

AU are you using the NB or a WB...


If a NB is being used i am curious to see what happens in open loop with a WB

txhorns281

iTrader: (12)

Well, I guess my train of thought is that GM engineers spent hahaha knows how long getting their parameters as close to perfect as possible. So let's say that they've come up with the optimal IFR for the 26#ers I'm running right now. No where in my whole modding experience did I ever change those injectors, so I'm not sure why I'd want to play with that. I'd hate to push the duty cycle of the injectors.

I have however, completely changed the amount of airflow my car is receiving. This is shown when i graph the airflow my motor's VE calcs come up with vs. my stock MAF curve. (VE airmass calcs aren't as resolute as MAF airmass but with enough sampling you can paint a good picture) So yes, we do need to account for this change by adjusting fuel. The question is though, how do we get an accurate measure of this change in airflow. Well, like you said, airflow is not constant, but if you can do airflow logging in a moderate weather condition for your climate, you can basically tune your car at the medium b/w your hot and cold weather. Once you have your VE tuned in, at the same type of weather, you can get a pretty close approximation of what kind of airflow your motor is using and adjust the MAF tables from there.

For the fueling aspect, we can control the fueling with the VE referencing the PCM does and that takes care of rich/lean spots on the fuel map, true and proven. This allows me to keep my IFRs at whatever GM thought was good for them! It keeps all my fuel commands consistent whether I'm at WOT, just cruising around, open loop, etc.

I guess what it comes down to is this, I don't like changing IFRs b/c I haven't changed my injectors. It does makes sense to me however, that after changing airflow dynamics in a motor, you would want to tell your airflow measurement devices how much more air you're really pushing. (As best as you can and it looks like we can get pretty dang close) Keep in mind the MAF curve is a user inputted function and isn't adaptive. Based on many logs b/w my stock MAF calcs, and my VE airmass calcs, there have been discrepancies of up to 30% That's a pretty big swing, I know I wouldn't want my MAF telling my PCM that the motor was receiving 30% less combustable air than it really was.

IFR = Injector Fueling
Airflow = MAF or SD

txhorns281

iTrader: (12)

lol... yeh, could be the VE being "thrown off" from weather. I know that when i originally tuned in SD, I got it nailed pretty perfect. Then the weather dropped like 30 degrees. I ran consitant richer over the whole VE table.

Tuning day i nailed 13.0 in open loop SD, at 70 degrees, about two weeks later, I plugged the WB back in and logged 11.5 in open loop SD, commanding 13.0 at 40 degrees. It's like the whole VE table "jumped" up but it didn't, i never even touched it. For the last week now though, I corrected my VE in 70 degree weather, tuned the MAF in 70 degree weather, and so far the tune has been holding very consistently! We will see what she does over the long haul