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Thread: NGK AFX setup ?

  1. #81
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    Where are you getting min & max voltage of .5 & 4.5? Change that to 0 & 5, and use the max AFR of 16 (not 20) as specified on page 3 of the AFX manual. In addition, page 12 of the AFX manual says the formula for lambda is this:

    lambda=(Vout * 0.096)+0.62

    The numbers in the manual are no doubt truncated for print. Since HPT uses division, use the reciprocal of 0.096 (10.4167) in the formula:

    Volts
    -------- + 0.62
    10.4167

    Lambda is preferred, but if you need to use AFR Error for some reason, then use this because the sensor assumes stoich is 14.57 regardless of what you have in your calibration:

    (5-0)
    ------- = 0.71423
    (16-9)

    So the AFR formula is:

    Volts
    --------- + 9
    0.7143

    Mathematically you can get the divisors a little more accurate, but it's probably statistically irrelevant.
    Last edited by JimMueller; 09-23-2014 at 08:31 AM.
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  2. #82
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    Are we talking about the same AFX? I just got this one a few days ago. NGK AFX AFR MONITOR KIT 91101 NGK Powerdex AFR 96604 2nd Generation

    The manual I have appears to be different than yours.

    The instruction booklet says the analogue output voltage is .5 - 4.5 and AFR Range is 9 min, 20 max at those voltages.

    I prefer to use AFR over Lambda. All my histograms are set up for AFR.
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  3. #83
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    Ahh, you have the second generation unit. I can't find the manual online, but for the values you provided I come up with this AFR transfer function:

    (4.5-0.5)
    -------- = 0.3636
    (20-9)

    Volts
    ------ + 9
    0.3636

    Tangent: Found a link to this place which seems to have extended the life of the 1st generation design:
    http://news.bmotorsports.com/balleng...oduct-release/
    Last edited by JimMueller; 09-23-2014 at 08:49 AM.
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  4. #84
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    Those are the numbers that I initially used in HPT. (I cheated and used the spreadsheet that The Tuning School guys have posted.)

    I then ran the engine, got it up to temp and in closed loop. The AFR being reported on the HPT table was too high. I do not recall exactly what is was, but it was somewhere around 16/1. I have a pretty lumpy camshaft, so figuring out the average AFR from a gauge that bounces a fair amount isn’t incredibly accurate…. Hence the term “about”.

    So anyway, with engine running and idling, and knowing I should be at 14.7/1 in closed loop, I just started screwing around with HPTuner wideband multipliers in the custom configuration table for the AFX analogue input. I kept 0.363, but lowered the “9” to something like 6.9 before I was done. This offset brought the AFR value reported in HPT to “roughly”, 14.7. The AFX display was / is hovering around 14.5/1 – which I understand is normal for this sensor.

    Not knowing if I totally screwed this up, I started surfing this site and found the formula in the help / FAQ post. It says if you so not know what AFR is at ZERO Volts, you need to figure that out first, and use that in the formula.

    At this point I’m totally baffled. Is ZERO Voltage AFR needed or not?
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  5. #85
    Senior Tuner DSteck's Avatar
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    Screwing around trying to make your own calibration values is wrong. If the listed calibration values are producing bad readings, then you have electrical issues that need to be addressed.

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  6. #86
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    You know Dave, you’re a sharp fella, but this never ending assumption you have that everyone is a dumbass and doing something wrong or stupid is getting old. I have the AFX power and ground going directly to the battery posts. I soldered the connectors and the connections to the battery are tight.

    I am asking for an explanation and help in working the formula so that I can input the WB data in HPT the way it SHOULD be set up.

    This very site has these instructions posted by a site moderator, in the “Wideband general information and hookup” sticky post at the top of this sub forum, that details (poorly) how to work the formula.

    http://www.hptuners.com/forum/showth...-section-Works


    Quote Originally Posted by S2H View Post
    the Formula in the EIO(AUX) section is called a transfer function
    it works by you teling it a step value and then telling it an offset from 0

    things you eed to know to figure out the formula for you device you are trying to use in the EIO section

    A) Voltage Maximum of the Device being used
    B) Value Represented by the (Volts=0) of the Device being used
    If the device doen not output 0 Volts then you need to used math to figure out what value 0 volts would equal.
    C) Value Represented by the Voltage Maximum of the Device being used

    then its (A)/(C-B) +B

    Example #1
    Wideband O2 Sensor (LC1)
    0 Volts= 7.35 AFR
    5 Volts= 22.39 AFR

    Volts Max = 5
    AFR represented by 0 Volts = 7.35
    AFR Max = 22.39

    so 5/(22.39-7.35) +7.35
    or in our EIO Formula
    Volts/ 0.3324 + 7.35

    Example #2
    Autometer P255 Fuel Pressure
    0.5 Volts= 0 PSI
    4.5 Volts= 100 PSI

    to get back to 0 since we do not know it yet

    (4.5-0.5) / (100-0) = 0.04
    0.5/0.04 = 12.5

    0 volts = -12.5 PSI
    4.5 Volts = 100 PSI

    Volts Max = 4.5
    Fuel Pressure Represented by 0 volts = -12.5 PSI
    Fuel Pressure Max = 100 PSI

    (4.5)/(100-(-12.5)) = 0.04

    Volts/ 0.04 + (-12.5)
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  7. #87
    Senior Tuner DSteck's Avatar
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    I own four of the AFM-1600s. Each and every one on every car I do works perfect as long as a usable ground is located. Direct to the battery works great on 99% of cars. Sometimes, I actually have to use another ground on the vehicle due to corrosion, electrical interference, or other unknown issues. I had ONE vehicle that I actually had to use a standalone battery for the wideband because it had all sorts of electrical issues and would not produce usable conditions for the wideband.

    During startup, the wideband will output 1v, then 4v, then attempt 0v. Check this. If it is off, try different connections for power. I don't worry myself if it's 3.95 or 4.05 instead of exactly 4.

    Having said that, if the specified transfer function isn't working, then something about the entire setup isn't correct. Editing the calibration values just introduces more unknowns. How do you know that just because it's now showing stoich when it should... That at 0.8 lambda, it's outputting the correct value?

    Point being: fix the issue, don't band aid it. You can call me whatever you want, but that's the cold hard truth.

    And just because something is posted by a moderator, that doesn't make it right. There's a thread floating around where that exact person you quoted was dead wrong about calculating calibration data for a wideband.

    I realize you have the AFRM, not the AFX, and I don't know if it goes through a calibration sequence on the analog input.



    There's a much faster way to find the calibration values, and you only need to know two points, even if neither is at 0 volts.

    V1 = voltage 1
    V2 = voltage 2
    Y1 = value 1
    Y2 = value 2

    Using the AFRM as an example...

    V1 = 0.5
    V2 = 4.5
    Y1 = 9
    Y2 = 20

    The divisor value is (V2-V1)/(Y2-Y1).

    (4.5-0.5)/(20-9) = 0.36 repeating

    This can be called D. Offset is given by:

    Y1 - V1/D = 9 - 0.5/0.363636 = 9 - 1.375 = 7.625

    So the AFRM calibration values are 0.36364 in the divisor and 7.625 in the offset. I'd check your sources and check your math.

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  8. #88
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    Now that sir, is a VERY helpful response!

    It is quite difficult to filter through the threads on this site and find the correct methods/procedures. It is even more difficult when the site administrator links to a thread as if that particular thread has all the correct information (IE: how to sticky). The help option is not as good has the HPT staff believes it to be either. Maybe if a person was a software engineer, but not for a novice or someone interested in the why’s, more than the “just do this” type of information.

    Your math seems to be in line with what I have actually input into the WB configuration through trial and error. I currently have 0.363 and 7.9. The Tuning School tutorial talks about increasing / decreasing the offset to get the HPT AFR output to line up with the display. That was what I was doing, but doing that seems hokey to me. I’d rather just have the exact data, verse trying to match two bouncing displays.

    For general awareness, the manual for this particular sensor/AFRM is silent to any analogue Voltage outputs during start up and / or calibration. All it talks to is Amp draw during start up and normal operation. It also walks you through the free-air calibration, but that’s it. Also to note, regarding the display reading of stoichiometric: “The AFRM’s display is designed to show AFR values based on a gasoline scale with 14.7:1 AFR as the stoichiometric ratio.” It latter states, on the same page, same topic: “Lambda is a universal unit of measurement for AFR, regardless of fuel. A Lambda value of 1 = stoichiometry. Lambda is derived by dividing the actual AFR by the stoichiometric AFR for that specific fuel type. For example, stoichiometric for gasoline is 14.55:1 AFR. A gasoline engine running at 12.5:1 AFR means that it is at 0.86 Lambda (divide 12.5 by 14.55).”

    That to me, is contradictory. They say gasoline stoic is 14.7:1, then later say it’s 14.55:1.

    I intend to call NGK to find out if they might know what the start up voltages should be, and to clarify the stoic gas display.
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  9. #89
    Senior Tuner DSteck's Avatar
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    Any seasoning?



    Don't follow that stupid crap about adjusting offsets. That's hack job stuff. Root cause... That's what it all boils down to.

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  10. #90
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    That's why I ASKED FOR HELP DAVID! I want to do things correctly. I also want to understand the "why's".

  11. #91
    Senior Tuner DSteck's Avatar
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    That's no fun.

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  12. #92
    Senior Tuner LSxpwrdZ's Avatar
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    Alternate power source separate from the vehicle solves all 'offset' issues for me. This is validated by logging the wideband during it's startup procedure where it outputs 1V then 4V and then 0V.

    I have found that the interpretation of the voltage in the HPT cable itself also varies ever so slightly. I use customer cables from time to time and readings are slightly off sometimes due to the voltage interpretation of the different box/cable.
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  13. #93
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    Quote Originally Posted by DSteck View Post

    V1 = voltage 1
    V2 = voltage 2
    Y1 = value 1
    Y2 = value 2

    Using the AFRM as an example...

    V1 = 0.5
    V2 = 4.5
    Y1 = 9
    Y2 = 20

    The divisor value is (V2-V1)/(Y2-Y1).

    (4.5-0.5)/(20-9) = 0.36 repeating

    This can be called D. Offset is given by:

    Y1 - V1/D = 9 - 0.5/0.363636 = 9 - 1.375 = 7.625

    So the AFRM calibration values are 0.36364 in the divisor and 7.625 in the offset. I'd check your sources and check your math.

    I also have the AFRM. i'm wanting to read in lambda instead of AFR. i'm uncertain how to come up with the divisor for the transfer function. Is it the same as AFR, just replacing Y1 & Y2 with .62 and 1.37 respectively? the function i come up with is Volts/5.333 + 0.62. The graph appears correct for 0.5v = 0.62lambda and 4.5v = 1.37lambda....just wanted to double check. Thanks
    Last edited by 2000_SS; 02-04-2015 at 01:42 PM.