LE5 Turbo build questions

[cobaltssoverbooster]

you always have to have some sort of ve for maf use to reference off of because the maf only gives you a reading in flow...there is no density value to the maf.
"Dynamic Airflow High RPM Disable: Above this RPM use filtered MAF airmass for airmass prediction calculations." -- it uses it as an addition too. know where does it say it disables base running airflow to run maf.
does the ve have a lot of say in this mode...no, not really. the maf is the main variable, but it still needs to reference the other sensors to be able to tie a density to the maf's airflow output.

[patooyee]

I'm sorry if I am just being dense but I still don't see how that explains steelmesh's statement ...

[cobaltssoverbooster]

I think I'll stick to MAF for now I have VE tuned, but I shut it down after 2200 rpm.

i mentioned it 2 ways now....you cannot disable ve and run only maf. Even if he said he wanted to run maf at idle the computer wouldnt do it because you have to exceed an rpm threshold to run maf and the hysteresis value or in this case deactivation rpm has to be lower than the rpm activation limit. therefore if maf was on at idle it was on 100% of the time.
I dont know how to explain it any easier bud. if you are not understanding it then you dont understand basic ecu logic yet. I cant teach common logic because i dont have enough weeks available to answer all the questions it would stir up. Once you understand the basic logic of an ecu then you will come to a sudden realization and not only will my comments make sense the ecu tuning process will go way easier than you probably feel like its going now.

it took me 3.5 years to learn ecu logic. Its not something you read 30 pages of, sleep on it, then suddenly you got an almighty understanding of. I will even admit that although i know a lot about ecu operation, i still get it wrong every once in a while because engineers keep changing the damn transient control functions.

im not out to tell you your an idiot so dont read this post that way...im simply saying you are missing some key points of understanding and once you get them, and only then, will my post make complete sense.

[patooyee]

I feel as though I understand a lot of ECU logic but I think what you are trying to explain (and I am not getting) is moreso GM programming / methodology than computer logic. I have a degree in Artificial Intelligence from University of Georgia, have built and programmed robots, fabbed from the ground up many custom vehicles, wired from scratch many GM harnesses. I could go on and on with a list of times that my fearless method of asking dumb questions has ended up showing people with a lot more experience than me where they were wrong in multiple venues. So perhaps you could direct me to where some threads or descriptions of what I am missing are detailed if you know of any? I recognize that its not your job to explain newbie concepts to tuning freshmen. But I also recognize how no one will ever learn unless they ask. I'm not trying to be confrontational, I appreciate how many times you have helped me in threads where no one else has been willing. I also notice how people who say things are mysteriously silent when asked to explain what they are saying sometimes. So thank you again for the help past, present, and future.

[cobaltssoverbooster]

Well accomplished man... glad i get to share forum space with you.
I do not know where the exact forum post is that explains the function i am describing. In this case of maf use GM vehicles are not specific. I really wish i could just point to the thread that explains it because i wouldn't look like such an ass for just spitting an answer with no proof. Ill try and find something external to post in here.

[cobaltssoverbooster]

Source 1: HotRod.com - States Maf is not a solo unit
http://www.hotrod.com/how-to/engine/...uel-injection/

Source 2: ls1tech forum: post #4 - states maf uses external sensors similar to speed density (ve mode)
http://ls1tech.com/forums/pcm-diagno...d-density.html

Source 3: Xcceleration.com - states the maf calculates density which allows the iat and map to be left out of the equation. But how does it do that? oh yea it has an internal IAT sensor that corrects the output by using an additional function therefor making it partially reliant on a ve function to calculate density.
https://www.xcceleration.com/sd-vs-maf.htm

banish does mention in his SA Auto book (2007 Copyright) that GM vehicles have been programmed to substitute ve by formula of VE= (MAF) / (displacement x P sub stp x speed) The maf sensor still has an iat internal sensor so it can correct output. in a hot wire maf the preferred location is mentioned to be pre-turbo because it looses a fair amount of accuracy by being placed in a pressurized zone. In this case the ecu can cross check with a ve system sensor to verify density. (Map sensor).

the newer ecu's that get run off of ve coefficient have to have the maf disabled by either defaulting coding or pulling the maf signal wire out of the harness at the maf sensor + disabling the codes that pop up in the ecu due to such act. The maf has to remain in system because the IAT helps place the ecu calculation in the proper ve coef. zone. The 2007 model does not list this function as a crucial requirement like some of the newer v8 models do. In this case the ecu would be using the circuit as verification, thus, not turned off; just of massively less importance.

im trying, hopefully that information helps.

[patooyee]

Haha, OK, give me SOME credit here. If you are thinking I didn't understand the basic concepts in your link then I think:



Let me try to explain. (I'm actually sitting here laughing right now, not at you, but rather at the situation!)

I understand SD vs. MAF, even so far as to know that some OS's flip in and out of blends between during normal operation. This concept is explained somewhat here:

http://www.hptuners.com/forum/showth...9-Engine-Modes

I understand how an ECU uses VE all the time and simply MAF as a means by which to fine-tune external changes that affect VE real-time.

I even understand that, in theory, one could eliminate VE tables completely by using a MAF and a MAP. But it takes time to for current to heat a filament and therefore the MAF responds slowly to rapidly changing conditions. Thus, in practice using just a MAF and MAP is terrible because the computer would be compensating essentially for an average of recent conditions moreso than real-life brief throttle blips, etc. that an engine actually sees. So for rapid changes the computer uses the VE table modified by average MAF readings to compensate for environmental changes that are not so temporally brief. As such, the system never uses just MAF. You can use just VE, but never just MAF. That's why the below statement is confusing to me:

I think I'll stick to MAF for now I have VE tuned, but I shut it down after 2200 rpm.

It seems like he is saying that he stops using VE and resorts to MAF after 2200 rpm. Or is he saying he turns to strict VE after 2200? Because that makes more sense to me despite the way the sentence is structured.

If you are saying that he does in fact disable his VE tables after 2200rpm then you are right, I have missed something very large in my learnings thus far.

Maybe its just the lingo I don't get?

[Robotech]

I think the issue is Patooyee that he meant to say he shuts off the MAF after 2200 rpm. In my (VERY VERY) limited knowledge of how all this works, that statement makes more sense to me than saying he is shutting off VE after 2200 rpm since, if what I understand is correct, the factory settings have an RPM point where they shut off the MAF sensor too.

One thing that I want to figure out...

in a hot wire maf the preferred location is mentioned to be pre-turbo because it looses a fair amount of accuracy by being placed in a pressurized zone. In this case the ecu can cross check with a ve system sensor to verify density. (Map sensor).

In my setup this is EXACTLY where the MAF will be...



In every build I've seen using this stock kit, this is where they put the MAF. Does this mean the builds they are doing run a strictly VE tune or can the MAF still be referenced with it stuck in the cold pipe this way (technically in my picture the MAF isn't bolted in and just hanging there but you can see the bung in the pipe to the left of it).

I still need to learn a lot about tuning this car, that's for sure. Luckily I have a friend who is a pretty good tuner helping me with this.

[patooyee]

I think the issue is Patooyee that he meant to say he shuts off the MAF after 2200 rpm. In my (VERY VERY) limited knowledge of how all this works, that statement makes more sense to me than saying he is shutting off VE after 2200 rpm since, if what I understand is correct, the factory settings have an RPM point where they shut off the MAF sensor too.

That's what I'm thinking as well but the sentence structure is pretty specifically not that. Sorry for hi-jacking your thread.

[cobaltssoverbooster]

I think the issue is Patooyee that he meant to say he shuts off the MAF after 2200 rpm. In my (VERY VERY) limited knowledge of how all this works, that statement makes more sense to me than saying he is shutting off VE after 2200 rpm since, if what I understand is correct, the factory settings have an RPM point where they shut off the MAF sensor too.

you can not define the maf activation this way. you can only define it to active above X rpm. thats why the statement is confusing. Maf can only be disabled above an rpm and ve cant be 100% disabled therefore said statement is conflicting points. So how is it really being run? as a maf tune with active maf and secondary ve or as full sd file?

that's the best wording I've had yet and it still doesn't sound clear when i read it back to myself...sheesh i should just stop.

[Robotech]

No worries about hijacking the thread. Through your discussion I'm getting a better understanding of ECM logic. Better...as in I'm looking at the peak of an iceberg with a magnifying glass. LOL

So much to understand and so confusing...actually not so much confusing just would be nice to know where to start and what questions to ask, you know?

[patooyee]

you can not define the maf activation this way. you can only define it to active above X rpm. thats why the statement is confusing. Maf can only be disabled above an rpm and ve cant be 100% disabled therefore said statement is conflicting points. So how is it really being run? as a maf tune with active maf and secondary ve or as full sd file?

that's the best wording I've had yet and it still doesn't sound clear when i read it back to myself...sheesh i should just stop.

Can you please paraphrase steelmesh's statement as you interpret it?

[cobaltssoverbooster]

What I'm hoping he is saying... I run a maf tune cause its easy, I had done VE tuning but.now the maf is active above 2200rpm.

What I understand from his writing... I run a maf tune now. I did some VE tuning but now I shut VE off at 2200

[patooyee]

Just putting this here for my own reference. Read if you want.

http://www.hptuners.com/forum/showth...l=1#post338607

[patooyee]

What I'm hoping he is saying... I run a maf tune cause its easy, I had done VE tuning but.now the maf is active above 2200rpm.

This makes sense to me somewhat but wouldn't one want the MAF disabled at some point?

What I understand from his writing... I run a maf tune now. I did some VE tuning but now I shut VE off at 2200

This doesn't make sense to me ... does it to you?

Note that now I'm not so much worried about what he originally meant, just trying to extract info from you for learning purposes.

[cobaltssoverbooster]

The maf is a fast responding sensor. Back to the lsj days the maf was the default airflow measurement when it was active at wot. If your going to use it you don't need to deactivate it. If you can't figure out how to extend it's range then you disconnect it or remove it.

As for part 2...it makes sense to me but not when applied to ecu logic.

[Robotech]

Coming from the L67 world, I believe we ran the MAF all the time as well. I believe we would reference the MAF readings (in conjunction with 3-bar MAP readings) at WOT to check for belt slip on my Whipple setup.

[steelmesh]

I understand that that is how is is supposed to work ...



... but this post implies that he is using MAF to avoid having to tune the VE coefficients and / or avoid having to use the virtual VE tool. Or am I misunderstanding?

My concern is that my VE table only goes to 105 kpa, so I tried to avoid using VE during boost conditions (above 105 kpa). With my driving style, I will get above 105 kpa in the low 2000 RPMs, so my logic was to avoid the VE table and start using MAF in this area. I still kept tuning the VE up to 105 kpa thinking that in a MAF failure condition, I could drive the car safely at low RPMs and load.

Cobalt just crushed my assumptions on this, when I said I disabled VE. I developed my assumptions in the Camaro write up on tuning VE with EQ<>VE. He said it did not matter if I tuned VE or MAF first...so I extrapolated this into VE and MAF are independent and one does not rely on the other. Other bits I can remember in my research is that VE and MAF work together when they're both "enabled" at the same time.

[steelmesh]

Here are my settings in question:

Engine > Airflow > Dynamic
High RPM Disable = 2,100
High RPM Re-enable = 2,000

Engine Diagnostics > Airflow
MAF Frequency Fail High = 11,500
MAF Frequency Fail Low = 10

I learned most of what I know about tuning with HP Tuners and the E67 in this post here: http://www.camaro5.com/forums/showthread.php?t=196696

" Due to the fact that the PCM uses a blended airmass figure from both MAF and VE for much of the operating range, this is a two step process. First, we have to simulate a failure of the MAF sensor. When the MAF fails, the PCM reverts to Speed Density operation, in which it sets fueling using only the calculated airmass derived from various sensor inputs crammed through the VE coefficients. When we're running solely off of VE, we can log the fuel trims (or alternatively AFR error if using a wideband) and use the resultant data to tune our VE coefficients."

"Now that our VE tuning is done, we're going to go back into the tune file and return our “MAF Fail High” Hz value back to normal. You saved the stock tune like I told you to, right? Copy the value over from there. Now, we have to force the PCM to only run off the MAF airmass and ignore the calculated airmass from the VE coefficients. To do this, we're going to go to “Engine>Airflow>Dynamic” in the VCM Editor. Under “Dynamic Airflow”, we're going to change “High RPM Disable” to 2, and 'High RPM Re-enable” to 1. This will prevent us from entering Dynamic Airflow mode"

You can see why I am assuming it's turning off

[cobaltssoverbooster]

All he said was you are strictly running maf priority. You still have to tune VE first because it sets the control to which you tune your maf too. If VE is off far enough it will skew maf because it's not 100% disabled. This maf mode is called enhanced dynamic mode. Starts with a good VE reference then puts maf as highest priority because it's a faster calculation and thus improves accuracy.