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Thread: What are all the E67 airflow limits?

  1. #1
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    What are all the E67 airflow limits?

    HPTuners will only report Volumetric Efficiency Airflow to 67.76 lb/min but thats just what it shows theres no max is there? Any way to log what its actually calculating? (If its in Speed Density then the Dynamic Airflow should be the same - I have logs where Dynamic shows 102 lb/min in SD but others where it all the sudden clips from 80 lb/min to 30 lb/min?)

    G/cyl?

    Mass Air Flow will only report to 86.69 lb/min have to watch Dynamic Air after that if in MAF mode no blending

    Manifold Absolute Pressure will max at 255 kPa - to work around that use Boost Low Res.? Is there no hard code limit to MAP it can use to calc it

    Others?
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  2. #2
    Advanced Tuner jsllc's Avatar
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    VVE which is formula based (no SD table in an e67) has a PID binary limit if 9 bits 512 g/sec. The MAF I believe uses a WORD size value and has a max of 655.35 g/sec. The dynamic value which is used for all calcs goes beyond both limits. I assume these are limited by the ecm to reduce the size of the stream.

    byte Integer variable allocated only 8 bit (i.e 1 byte) of memory. May store values from -128 to 127. 8 bits and one more and you have 512


    short Short integer, allocated only 16 bits of memory. May take values from -32768 to 32767. 65535
    2012 ZL1 - Maggie Heartbeat, Port & Polish Heads, Custom Cam, Custom rotating assembly, steel sleeved LS9, No NOS and No water meth. 16psi
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  3. #3
    Advanced Tuner jsllc's Avatar
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    2012 ZL1 - Maggie Heartbeat, Port & Polish Heads, Custom Cam, Custom rotating assembly, steel sleeved LS9, No NOS and No water meth. 16psi
    810rwhp and 820rwtq 91 Octane 6400 rpm
    948rwhp and 951rwtq 105 Octane 6400 rpm
    999rwhp and 997rwtq on 60% Ethanol 6400 rpm

  4. #4
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    Quote Originally Posted by jsllc View Post
    VVE which is formula based (no SD table in an e67) has a PID binary limit if 9 bits 512 g/sec. SAME AS WHAT I SEE IN LB/MIN
    The MAF I believe uses a WORD size value and has a max of 655.35 g/sec. THIS IS WHAT I SEE IN LB/MIN

    The dynamic value which is used for all calcs goes beyond both limits. I assume these are limited by the ecm to reduce the size of the stream. SO THERE SHOULD BE NO UPPER LIMIT IN CALCED DYNAMIC AIR???

    byte Integer variable allocated only 8 bit (i.e 1 byte) of memory. May store values from -128 to 127. 8 bits and one more and you have 512
    short Short integer, allocated only 16 bits of memory. May take values from -32768 to 32767. 65535
    Dont know what your last two lines are about I guess your just showing the math how you got there?

    Do you know if there is a upper limit in boost you can run? (assuming MAP sensor can read it and it is scaled properly)

    Do you have any idea why my Dynamic Air was clipped from 80# down to 30# instantly any time I turned boost up 1 pound in SD mode - but doesnt seem to do it in MAF mode? https://forum.hptuners.com/showthrea...it-in-MAF-only
    Last edited by GrannySShifting; 07-10-2019 at 12:30 AM.
    Factory Stock 97 SS M6 13.51 @ 104.3 mph
    Stock Longblock LS1 w/ 233/238 P.S.I. Cam
    10.81 @ 126.9 Full interior, six speed on 275 radials, a decade ago

    '99 TA trunk mounted 76mm 6 Liter
    9.0s in '09 @ 153 MPH

    Turbo 5.3 Volvo 740 Wagon
    32psi and still winding out 5th on the highway somewhere

  5. #5
    Advanced Tuner jsllc's Avatar
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    Sorry I did a piss poor job of explaining. I assume you have never written code? If so then my bad. When we write code we are forced to use certain types of data. Bit, Byte, Word etc. This equates to some decimal value but in the world of computing it is either a 1 or a zero. When you place enough in a series you get larger numbers.

    Bit - 1 or 0
    Byte - 8 on row of 1s or zeros 11111111 = 255 binary math 111111111 = 511 or if you you use 1-512 instead of 0-511 it can be 512.

    The when designed the ECM used metric values so 512 g/sec VVE vve limit makes sense as it is 8 bits or 1 byte. Any way these are just issues in the data stream of the PIDs.

    The last part is just my understanding of the math and programming in an e38 or e67. It is a MAF based ecm with VVE backup. So unless you have a 2013 OS that can be patched to a table based SD tune you do not have SD or VE in anyway. Nor can it truly be run that way. We can lie to it and force a fail to the VVE but GM never expected to exceed the 255 in fail-over mode. Normally it would see limp mode before that value and it would not be an issue. Dynamic which uses predictive, VVE and MAF allows for air flow beyond the VVE, it was the original design of the math. It depends on MAF to run correctly.

    So if GM used a byte value 0-255 kpa (dec) for the MAP value then 255 is the MAX represented by 11111111 in a computer. to get to 256 it would be 100000000 or 0 (dec) if you only store the last 8. At this point I would assume there is some logic that says zero map is not valid some base is added in.

    if you use metric and understand binary math some of this starts to make sense. Sorry for the long explanation.
    2012 ZL1 - Maggie Heartbeat, Port & Polish Heads, Custom Cam, Custom rotating assembly, steel sleeved LS9, No NOS and No water meth. 16psi
    810rwhp and 820rwtq 91 Octane 6400 rpm
    948rwhp and 951rwtq 105 Octane 6400 rpm
    999rwhp and 997rwtq on 60% Ethanol 6400 rpm

  6. #6
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    I have a little bit, 25 years ago So well just say no haha

    Quote Originally Posted by jsllc View Post
    Sorry I did a piss poor job of explaining. I assume you have never written code? If so then my bad. When we write code we are forced to use certain types of data. Bit, Byte, Word etc. This equates to some decimal value but in the world of computing it is either a 1 or a zero. When you place enough in a series you get larger numbers.

    Bit - 1 or 0
    Byte - 8 on row of 1s or zeros 11111111 = 255 binary math 111111111 = 511 or if you you use 1-512 instead of 0-511 it can be 512.

    The when designed the ECM used metric values so 512 g/sec VVE vve limit makes sense as it is 8 bits or 1 byte. Any way these are just issues in the data stream of the PIDs.

    The last part is just my understanding of the math and programming in an e38 or e67. It is a MAF based ecm with VVE backup. So unless you have a 2013 OS that can be patched to a table based SD tune you do not have SD or VE in anyway. Nor can it truly be run that way. We can lie to it and force a fail to the VVE but GM never expected to exceed the 255 in fail-over mode. Normally it would see limp mode before that value and it would not be an issue. Dynamic which uses predictive, VVE and MAF allows for air flow beyond the VVE, it was the original design of the math. It depends on MAF to run correctly.

    So if GM used a byte value 0-255 kpa (dec) for the MAP value then 255 is the MAX represented by 11111111 in a computer. to get to 256 it would be 100000000 or 0 (dec) if you only store the last 8. At this point I would assume there is some logic that says zero map is not valid some base is added in.

    if you use metric and understand binary math some of this starts to make sense. Sorry for the long explanation.

    So do you have any insight on the other questions, or perhaps why it thinks it all the sudden has ton less Dynamic Airflow even though the VVE table is telling it otherwise in SD in the example Im having some wacky issues with I linked to?
    Factory Stock 97 SS M6 13.51 @ 104.3 mph
    Stock Longblock LS1 w/ 233/238 P.S.I. Cam
    10.81 @ 126.9 Full interior, six speed on 275 radials, a decade ago

    '99 TA trunk mounted 76mm 6 Liter
    9.0s in '09 @ 153 MPH

    Turbo 5.3 Volvo 740 Wagon
    32psi and still winding out 5th on the highway somewhere

  7. #7
    Advanced Tuner jsllc's Avatar
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    Post a log please. It was all related to your question on why no way to get VVE to run past a point.
    2012 ZL1 - Maggie Heartbeat, Port & Polish Heads, Custom Cam, Custom rotating assembly, steel sleeved LS9, No NOS and No water meth. 16psi
    810rwhp and 820rwtq 91 Octane 6400 rpm
    948rwhp and 951rwtq 105 Octane 6400 rpm
    999rwhp and 997rwtq on 60% Ethanol 6400 rpm

  8. #8
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    Quote Originally Posted by jsllc View Post
    Post a log please. It was all related to your question on why no way to get VVE to run past a point.
    Log is in link at the end of my last post

    I understand that the Volumetric Efficiency in scanner cant SHOW past 67.72, but its definitely using it in calculations well past that when in speed density mode as I have logs that show Dynamic Air well into the 80s before it decides to cut it back into the 30s
    Last edited by GrannySShifting; 07-10-2019 at 02:34 PM.
    Factory Stock 97 SS M6 13.51 @ 104.3 mph
    Stock Longblock LS1 w/ 233/238 P.S.I. Cam
    10.81 @ 126.9 Full interior, six speed on 275 radials, a decade ago

    '99 TA trunk mounted 76mm 6 Liter
    9.0s in '09 @ 153 MPH

    Turbo 5.3 Volvo 740 Wagon
    32psi and still winding out 5th on the highway somewhere

  9. #9
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    In MAF mode where it will go past there, VE is 2397where it looks like should be 2427 in table but no biggie

    VEis2159.png


    Then 2484 as its running up (looks like 2530 in table to me it had just crossed the scanners max reporting of 255kPa so maybe 260 kPa?)

    VEis2484.png

    Then it did drop down to 2159 the next frame even though engine rpm, boost, throttle everything should have bee slightly increasing?

    VEis2159.png

    Ive never heard of or hit a airflow limit tuning in VVE mode prior.
    Attached Files Attached Files
    Factory Stock 97 SS M6 13.51 @ 104.3 mph
    Stock Longblock LS1 w/ 233/238 P.S.I. Cam
    10.81 @ 126.9 Full interior, six speed on 275 radials, a decade ago

    '99 TA trunk mounted 76mm 6 Liter
    9.0s in '09 @ 153 MPH

    Turbo 5.3 Volvo 740 Wagon
    32psi and still winding out 5th on the highway somewhere

  10. #10
    Advanced Tuner jsllc's Avatar
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    I replied to your PM. When you have a chance.
    2012 ZL1 - Maggie Heartbeat, Port & Polish Heads, Custom Cam, Custom rotating assembly, steel sleeved LS9, No NOS and No water meth. 16psi
    810rwhp and 820rwtq 91 Octane 6400 rpm
    948rwhp and 951rwtq 105 Octane 6400 rpm
    999rwhp and 997rwtq on 60% Ethanol 6400 rpm