That's exactly what I stated!!!??? I realize this 100%Originally Posted by redhardsupra
I think you're not understanding what I'm saying--when I'm talking about over/undercompensating, I'm talking about the computer not adding or adding too much fuel to compensate for colder or hotter air. Not over/undercompensating for the ESTIMATED MAT.
Last edited by LS6FD; 12-05-2007 at 12:42 PM.
Right ... well, the idea as I understand it is to better understand the tables and be able to come up with a method to more accurately estimate manifold air temperature.
This would lead to the outcome you are describing without the need for (non-existant) additional tables by simply having values in there that cause the computer to also more-accurately calculate fueling.
Am I right red?
I completely agree that of course getting the estimated MAT as close as possible is going to make things work better all around.
My main question/hypothesis is that even if you manage to get the estimated MAT 100% dead on, would that still alleviate the over/undercompensation of fueling since there is that other hidden table that actually calculates how much fuel to add based upon the MAT? If that table is incorrect, you will be closer by having the MAT dialed in, but it still won't be perfect.
Sorry I suck at explaining things! I'll leave this to the pros, I think I'm in over my head lol
if the temp is calculated properly (which we'll never know what is correct until we stick a temp probe in the intake), and your fueling is still off, then it can be any of other reasons like imprecisions in MAP sensor, wrong VE values, etc... the hard part is knowing when to adjust which part. we used to blame all changes on VE, now you want to bullshit on TEMPS to make up for VE. either approach is wrong, you gotta properly attribute changes to their causes.
Damn, didn't notice that this thread was moving again.
I don't belive the Bias table has any effect on MAF operation. The bias table and the whole mat thing is only relative to SD, because after you resolve to a 'volume', you have to come up with the 'mass' that fills that volume. A MAF cuts to the chase. I dosen't measure volume, it already spilts out mass. The colder the air the higher the MAF reads. After you learn the mechanics of how a MAF works, it actually mackes sence.
There is again on other gm tunes, a table that scales the MAF by IAT. But I have never see it in the LS world. GM usually sets it to 1.00 for all temps except those below 0 DegC, and then only marginally scales it up, hitting around 1.15 by -40 DegC. So for most usable temps, GM feels the the MAF dosen't need any correction.
As far as the tables that set correction by MAT, like you found from a previous post, dosen't exist or isn't available to us. But you don't really need it. Like RHS said, if the estimated temp is correct, it should be right. But even if its not, just shoot for the MAT that makes it right, even if its not the true MAT. I'm all about making the models right and keeping the numbers realistic. But some times the end result is more important. Wether its oversimplification, bad physics, or just a running combination of errors from other tables... sometimes realistic numbers just don't work.
1. why would 1+2=3.5? if all the numbers are right but the result is off, doesn't that indicate that either our model isn't complete, or there are other variables that dont get accounted for properly?
2. if temp doesnt affect MAF, why are there MAF raw and MAF SAE?
I agree, but its the "other variables that dont get accounted for properly" that make 1+2=3.5 somethines.Like mentioned earlier in the thread, the computer just isn't complicated enough to do was its trying to do, things like humidity and other unaccounted for variables are always going to fudge the results a little bit.
Don't know. Never noticed a descretpency between the two. I always assumed one was filtered the the other was a derect lookup from the MAF table. Even if there is, I don't think the bias table would be doing it. Thier is probally a table for the MAF like I noted above that exists in other, earlier tunes, and it probally had values in it other than 1.00. Never logged raw much, its bitter ass cold around here right now so maybe it will show a diff. If I get change tomorrow I'll compare the two and check out what your saying.
Last edited by Bluecat; 12-05-2007 at 09:36 PM.
Bluecat, did you get any data? I'd much rather look at evidence than have a battle of the theories...
Oh hell I'm not arguing, I belive you, I just never paid any attention to there being a difference between the two. I always though SAE matched what was in the MAF table pretty good, so I never really though there was any correction going on. I usually only log 'Dynamic Airflow G/sec' anyway that way I can see what the computer thinks is going on airflow wise even is SD mode. I've got a guy late on a dyno appointment right now, if he dosen't show soon I might take my 5.3 out and log all the airflow pids and see what your talking about.
Made a log with all the total engine airflow (g/sec) PIDs availible on my person vehical. Not a really long one to draw solid results from, but I still don't see a difference in Regular MAF and MAF SAE. The are almost identical at all times. Both match my MAF table with in .2 % so I still don't think any correction via temp is being applied. Dynamic Airflow varies a little more, but should, its the most processed number since its the end result. Its filtered and even blended with the SD calc, but still matches my MAF table during stead state driving, and only varies .05 more than the other numbers as an average.
If there is a table that effects MAF via IAT or MAT, it dosen't appear to change anything, even as cold as 10 DegC. Even if it did, I still wouldn't think the bias table has anything to do with MAF generated numbers.
Now, I didn't have a PID described as RAW MAF, even though I thought I had seen that before on other vehicals. I can't imagine RAW being any more basic that just looking up the g/sec vs hz in the MAF table, but is that when you have seen differences?
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heh, this ain't no argument, iran vs iraq was an argument, this is merely a quasi-scientific discourse
so if we can assume that MAF is not a subject to corrections from TEMP, this is VERY good news. it means that if we tune our MAF against well calibrated injectors, the airflow figures in the MAF are The Truth. Then, all we have to do is to map out airflow values to corresponding VE cells, normalize it for temperature, and we should get good GMVE values. I'll play with this more once i get home.
man it's good to see some convergence in a thread, not just meandering discussions...
Forgive me if this has been covered, but from the logs I have observed, the raw MAF appears to be 'smoothed' in some fashion. All logs I have seen have the raw MAF jumping around by up to 5% (usually saw tooth looking pattern, especially at WOT)... If fueling really followed the jumpy MAF signal, the AF would be all over the place and it isn't.heh, this ain't no argument, iran vs iraq was an argument, this is merely a quasi-scientific discourse
so if we can assume that MAF is not a subject to corrections from TEMP, this is VERY good news. it means that if we tune our MAF against well calibrated injectors, the airflow figures in the MAF are The Truth. Then, all we have to do is to map out airflow values to corresponding VE cells, normalize it for temperature, and we should get good GMVE values. I'll play with this more once i get home.
man it's good to see some convergence in a thread, not just meandering discussions...
hm, good point, Dean. I just looked through 05 gto and 08 vette bins and i dont see any filter tables for MAF stuff. there's filters for dynamic airflow (SD based airflow) but nothing about MAF. So until Chris@HPT chimes in, we won't know.
From what Chris told me about the E40/38/67 the data stream MAF values are unfiltered whereas the LS1 series were filtered before being sent out as data.
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I'm running the MAF on mine and have experienced large swings in my tune due to air temps. I tuned my car when it was in the 90's outside, but with the temperature around here being in the 30's - 40's the computer is overcompensating and I've gone way rich across the board. I tried changing my bias and filter tables to what Bluecat recommended as a starting point and that leaned out my tune in the non-WOT range (Bluecat's recommended settings increased my bias #'s across the board biasing it more towards ECT).
WOT is still way rich (~12.1 vs 12.8) compared to when it's hot outside. Looking at the bias more closely, it only goes up to 150 g/sec which isn't even covering the airflow I'm hitting when I'm going WOT (well over 150 g/sec). So I don't see how this bias table could help WOT tuning at all.
Additionally, even if the bias did go up to the g/sec range needed for WOT, telling it to bias more towards ECT seems like it would lean it out across the board, since you will be raising the IAT. Thus it would run leaner at both hot and cold IAT. As per Bluecat's recommendation if the computer is overcompensating, you should bias more towards ECT. Well since my tune is perfect at high temps, if I biased more towards ECT, I would expect my tune to go lean at high IAT now since I'm effectively raising the IAT even more. So, I could then richen my tune to keep from going lean at high IAT but that would still make me rich when the IAT is cold. That wouldn't really be solving anything, just shifting the problem around.
Am I completely misundersting the mechanism behind all this? I just want to get my car to run relatively in tune at WOT when it's 90 degrees or 30 degrees outside and this table does not seem to be the answer.
Last edited by LS6FD; 01-31-2008 at 07:38 AM.
LS6FD, i wrote a program to figure out bias/filter numbers, and adjust VE accordingly. I could always use another tester, email me if you're interested.
Yes, shifting the calculated temp higher (toward ECT) will make it run leaner. That's why there were some comments earlier about this being a recursive process.
In SD tuning you would modify the VE table to account for this, because the previous numbers in the VE table would have been based on logging when the pcm thought the air temps were colder than they "really" were. (based on your new values in the bias vs. the old values in the bias)
However, shifting the temps more toward ECT will have the effect of decreasing the effect of outside air temp. Then the pcm thinks it's getting basically the same amount of air whether it's cold or hot outside. (meaning after the change, you will run leaner than before when the air is cold and richer than before when the air is hot - undercompensating)
In your case, where you run richer when the air is cold, it does sound like the pcm is overcompensating for the colder air and adding too much fuel. Then shifting toward ECT is a good thing, but it will shift the whole fueling more lean like you said, and you may have to dial-in your VE and/or MAF tables again.
Last edited by John_D.; 01-31-2008 at 09:04 AM.
Thanks for the responses everyone and not slamming a noob for this stuff lol.
Looking at the data by Bluecat he lists 150 > for WOT, so does that mean the bias for 150g/sec airflow will apply to everything above that including WOT? I just wanted to make sure that what I'm doing will even have an effect on WOT and I'm not just pissing in the wind so to speak lol.
For cruising, I just turned closed loop (with LTFT disabled) back on and that of course compensated for the other discrepancy.
Yes. Like most of the other tables that run out of range, it just uses the last value. So just imagine anything higher than 150 being truncated back to 150 before its looked up.
Yeah, what he said...
Like stated above, your previous ve numbers were dialed in for the bias table you were using at the time. If the bais table was wrong, the ve table was wrong too. So you can't just change the bias table, it takes a redialing in of the ve too.
Here is what will happen though. Moving the Bias larger will lessen the rich when cold problem your having. But it will lean it out in every temp, so if your current ve table was right @ 90 DegF, it will be to lean when it warms back up. Which will require a increase in the ve number that will fix 90 degs again, but lessen the change you made when it was cold.
If you were at 12.8 previously at WOT, and even after a increase of the bias with no ve change it only went to 12.1 when cold, your change was no were near enough. If you ended up tapering to upper 0.1's by 150g/sec, then try tappering from 1.0 to 0.3 over the table and see what that does.
In the end, because we know increasing the bias is going to make you increase the ve, it will take a bias number big enough to make your AFR leaner than 12.8 with your current ve table. Id keep increasing the far end of the table until you reach low 13's with your current ve table. Then increase the ve to get back to 12.8. That should at least make it closer to keeping 12.8 year round.
Last edited by Bluecat; 02-01-2008 at 06:51 AM.
Excellent--thanks!
Excellent, I'll give it a shot! I'm running MAF by the way, but in the lower airflow range your starting values put me almost spot on so hopefully tinkering with the higher airflow values will help as well.Id keep increasing the far end of the table until you reach low 13's with your current ve table. Then increase the ve to get back to 12.8. That should at least make it closer to keeping 12.8 year round.
I have a custom CAI (I put a LS6 in a 3rd gen Rx7) that is fairly long. I guess logic would dictate that the longer your intake tract is the more prone the air would be to heat soak since it is in the intake longer and my IAT sensor is near the aperature of the CAI. I'm sure insulating it a little better would help too. Any recommendation as to material to use for that?
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