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Thread: Sanity check, please...

  1. #11
    Lifetime Member Rich Z's Avatar
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    Oh yeah, forgot to mention that we are having rain storms passing through here so I don't take the car out on wet roads. I just barely got the last logging done before another storm front passed through.

    CorvetteFlorida.com

    2002 Corvette Z06
    427 RHS block built by LME
    STS rear mounted twin turbos
    It nearly died on the operating table, but I'm bringing her back.

  2. #12
    Lifetime Member Rich Z's Avatar
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    BTW, how exactly should I set up the MAP for calibrating the VE properly? Especially since some of the values will be ABOVE what B0101 shows? I've taken a look at all of the tutorials, and it seems that for one reason on another, they don't exactly apply to what I need. So to make sure I am doing this correctly, IS there a tutorial that steps through calibrating the VE table (or boost equivalent) on a boosted engine? If I'm going to be "measuring" the values of my VE table then I guess I need to make sure I am using the correct measuring tool(s).

    Honestly, I've got several MAPs set up showing boosted cells, but I'm not at all sure they are correct.

    Thanks.

    ps I was going to post the last log I did while working on the VE table, but I didn't drive the engine over 3600 rpm, so I'm guessing it's not going to tell you anything. If I remember correctly, there were a LOT of cops out on the road that day.... :(

    CorvetteFlorida.com

    2002 Corvette Z06
    427 RHS block built by LME
    STS rear mounted twin turbos
    It nearly died on the operating table, but I'm bringing her back.

  3. #13
    Lifetime Member Rich Z's Avatar
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    Been reading this over again and it dawned on me that I forgot a detail. I wondered why the log was showing lean in spots when I realized that the log was for the tune attached in that post. The MAF has been further tweaked using that log and is tune #0019, which has NOT been logged yet. And it was specifically in the higher rpm range that I did the tweaking of the MAF table.

    So let me back up a bit and ask something specific.

    Does the timing look safe based on what is seen in the log? 40+* just seems to be a lot to me....

    CorvetteFlorida.com

    2002 Corvette Z06
    427 RHS block built by LME
    STS rear mounted twin turbos
    It nearly died on the operating table, but I'm bringing her back.

  4. #14
    Joe (Moderator) joecar's Avatar
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    There are big advantages for abandoning the MAF...

    like BLK02WS6/Bret said, the PCM has an upper limit of 512 g/s on the MAF, and scaling any table that references airmass or airflow is very tedious;e

    it is one less part that can fail (especially when running boost, if MAF fails you could be in big trouble).

    When IFR and VE are correct, fueling will be immune to changes in weather... the VE table units are g*K/kPa, i.e. VE table is cylinder airmass normalized for temperature and pressure (or if you like, it is normalized for density).

  5. #15
    Joe (Moderator) joecar's Avatar
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    Bret's suggestion of using B3647 to set NA fueling and using B3618 to set boost fueling is an excellent idea...

    B3613 sets the MAP kPa threshold for enabling PE...

    so, PE enables when all the PE enablers are satisfied: B3613, B3616, and the others.

    then, commanded fueling is determined like this:
    - if PE has not enabled, then B3647 is used for fueling (i.e. B3647 is the only active fueling table);
    - if PE has enabled, then fueling is from the richest of B3618 and B3647 (i.e. these are the currently active fueling tables);

    notes:
    - if MAP is beyond the last column of B3647, the last column is extrapolated, so B3647 fueling is this last column (now re-read the previous paragraph with this in mind);
    - if any protection modes enable, then there will be extra active fueling tables, commanded fueling is the richest of all the active tables (e.g. COTP, EPM, PPM);


    COTP = catalytic over temp protection
    EPM = engine protection mode
    PPM = piston protection mode

  6. #16
    Joe (Moderator) joecar's Avatar
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    Make a single map that covers both VE tables...

    then simply copy 0-105kPa columns to Main VE B0101 and 105-285kPa columns to Boost VE A0009.

  7. #17
    Lifetime Member Rich Z's Avatar
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    Quote Originally Posted by joecar View Post
    There are big advantages for abandoning the MAF...
    This obviously begs the question of WHY did GM put in a MAF then? Surely they are always looking to cut costs by eliminating unnecessary hardware and circuitry. I'm sure those engineers know all about speed density tuning. So why use a MAF and bear that additional manufacturing expense if there wasn't a real good reason for it?

    Quote Originally Posted by joecar View Post
    like BLK02WS6/Bret said, the PCM has an upper limit of 512 g/s on the MAF, and scaling any table that references airmass or airflow is very tedious;e
    What happens when that upper limit is reached? What does the PCM DO? If you purposely fail the MAF at 12000 via C2901, does the VE table then take over?

    Quote Originally Posted by joecar View Post
    it is one less part that can fail (especially when running boost, if MAF fails you could be in big trouble).
    Reading between the lines, my impression is that the VE table is a backup for the MAF. So if the MAF fails, then the VE table is used. Isn't the output of the MAF compared with another table somewhere indicating what acceptable variances are acceptable compared with the VE table?

    Quote Originally Posted by joecar View Post
    When IFR and VE are correct, fueling will be immune to changes in weather... the VE table units are g*K/kPa, i.e. VE table is cylinder airmass normalized for temperature and pressure (or if you like, it is normalized for density).

    CorvetteFlorida.com

    2002 Corvette Z06
    427 RHS block built by LME
    STS rear mounted twin turbos
    It nearly died on the operating table, but I'm bringing her back.

  8. #18
    Lifetime Member Rich Z's Avatar
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    Quote Originally Posted by joecar View Post
    Bret's suggestion of using B3647 to set NA fueling and using B3618 to set boost fueling is an excellent idea...

    B3613 sets the MAP kPa threshold for enabling PE...

    so, PE enables when all the PE enablers are satisfied: B3613, B3616, and the others.

    then, commanded fueling is determined like this:
    - if PE has not enabled, then B3647 is used for fueling (i.e. B3647 is the only active fueling table);
    - if PE has enabled, then fueling is from the richest of B3618 and B3647 (i.e. these are the currently active fueling tables);

    notes:
    - if MAP is beyond the last column of B3647, the last column is extrapolated, so B3647 fueling is this last column (now re-read the previous paragraph with this in mind);
    - if any protection modes enable, then there will be extra active fueling tables, commanded fueling is the richest of all the active tables (e.g. COTP, EPM, PPM);


    COTP = catalytic over temp protection
    EPM = engine protection mode
    PPM = piston protection mode
    I think perhaps I have just been looking at Power Enrichment as something different that is not correct. I've been looking it as being the programmable equivalent of the accelerator pump on a carburetor. Back in those days, the manual accelerator pump would give an extra squirt of fuel directly into the carburetor upon spirited gas pedal pressure. I presumed that this function must be incorporated somewhere into the PCM tuning software, and PE just sounded like the logical equivalent.

    Have I been barking up the wrong tree?

    I believe I had PE disabled when I was doing what I thought was calibrating the MAF. Of course, I just now stumbled on that B0120 setting that I somehow overlooked, so I'm not even sure WHAT I was really doing....

    CorvetteFlorida.com

    2002 Corvette Z06
    427 RHS block built by LME
    STS rear mounted twin turbos
    It nearly died on the operating table, but I'm bringing her back.

  9. #19
    Lifetime Member Rich Z's Avatar
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    Quote Originally Posted by joecar View Post
    Make a single map that covers both VE tables...

    then simply copy 0-105kPa columns to Main VE B0101 and 105-285kPa columns to Boost VE A0009.
    Somewhere along the line I must have done that because I do have a MAP that shows kPa columns from 15 to 285. When I look at the log file included in this thread, I have to make the map display all cells with at least one hit to see much above 100kPa. Apparently even rolling into those high revs still doesn't give a lot of sampling for each cell. But from what I can see, the highest value there is only 1.09. I was thinking that that isn't TOO bad, now is it?

    CorvetteFlorida.com

    2002 Corvette Z06
    427 RHS block built by LME
    STS rear mounted twin turbos
    It nearly died on the operating table, but I'm bringing her back.

  10. #20
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by Rich Z View Post
    This obviously begs the question of WHY did GM put in a MAF then? Surely they are always looking to cut costs by eliminating unnecessary hardware and circuitry. I'm sure those engineers know all about speed density tuning. So why use a MAF and bear that additional manufacturing expense if there wasn't a real good reason for it?
    GM has produced many EFI vehicles without MAF's.

    What happens when that upper limit is reached? What does the PCM DO? If you purposely fail the MAF at 12000 via C2901, does the VE table then take over?
    When upper limit is reached, the MAF is pegged at 512 g/s.

    You have an interesting point about failing the MAF at 12000 Hz... it will fail immediately (DTC triggers, and now VE table is the sole source of cylinder airmass)... but it won't re-enable when the frequency falls below 12000 Hz... for the MAF to re-enable, the MAF DTC must be cleared by the PCM, this involves some amount of drive-cycle (it doesn't just clear instantly).

    Reading between the lines, my impression is that the VE table is a backup for the MAF. So if the MAF fails, then the VE table is used. Isn't the output of the MAF compared with another table somewhere indicating what acceptable variances are acceptable compared with the VE table?
    You are correct, the VE table is the failover when the MAF fails...

    but also note that at lower airflow the MAF does not deal very well with flow transition, so the PCM temporarily does use VE during airflow transients.

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