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Thread: EFI RWHP and EFI RWTQ

  1. #11
    Lifetime Member Chalky's Avatar
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    I did a 3rd gear pull up to approx 103. To many traction issues with 1st or 2nd gear pulls.

    I changed the driver weight to equal mine when i achieved the 403 rwhp. I added another 100 pounds weight to equation and car RWHP jumped to almost 420. same log, just different net weight of driver/car.

    I used to always figure 85 lbs was worth a tenth in the quarter mile or approximately 10 HP. not sure how 100 lbs was worth 16 HP though.

    I am not critizing anyone's work here. i like the idea of seeing your results of your efforts. Being repeatable, this would be a great way to measure elative gains/losses from the addition of performance accessories. Furthermore, there are weather stations that can give barometric readings to help calibrate changes in hP based on the time of your performance runs.

    Unfortunately, I ran out of money just before i found this handy dandy performance pid.

    I believe the goal was to create a pid that would show similar results in HP/TQ as your would experience on a dyno. On the other hand, how much HP is used to overcome drag to get to 100 MPH.
    Last edited by Chalky; October 1st, 2007 at 02:29 PM.
    2015 Z06 A8

  2. #12
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    # ================================================== ============================
    # File details
    # ------------
    #
    # This section defines various details about the file format.

    *FILE

    #Parameter Value Description
    #---------- ---------------- ---------------------------------------------------
    VERSION 7.1.1 File version
    DECSEP . Decimal separator used in this file



    # ================================================== ============================
    # Units
    # -------------------
    # See sae_generic.txt for more information on the *UNITS section

    *UNITS

    #Code System Abbr Description
    #-------- ---------- -------- -------------------------------------------------------------
    MPG Imperial MPG "MPG"
    LPK Metric LPK "Litre X KM"




    # ================================================== ============================
    # Add slot definitions here
    # --------------------------------
    # See sae_generic.txt for more information on "SLOT" formats
    #
    #Units Low High Fmt Expression
    #------------ ------------- ------------- ---- --------------------------------------------------------------

    ################################################## #################################
    #Wide Band PID
    *CLC-00-001
    V 0.0 5.0 0.1 "{EXT.AD1}"
    AFR 10.00 16.8 0.1 "{EXT.AD1}*1.36 + 10"
    factor 0.5 1.5 0.01 "({EXT.AD1}*1.36 + 10) / {GM.AFR}"


    ################################################## #################################
    #Fuel Economy
    *CLC-00-002
    MPG 0.00 99.99 .1 "{SAE.VSS.mph}/({GM.INJFLOW.lbpm} * {GM.IBPW1} * {SAE.RPM} * 4 / 6250)"
    LPK 0.00 99.99 .1 "235.2145584/{SAE.VSS.mph}/({GM.INJFLOW.lbpm} * {GM.IBPW1} * {SAE.RPM} * 4 / 6250)"


    ################################################## #################################
    #Aero Drag, power lost to go down road without changing speed.
    *CLC-00-003
    hp -200.00 600.00 .1 "0.000070146*{SAE.VSS.mph}^3-0.0007566*{SAE.VSS.mph}^2+0.13894268*{SAE.VSS.mph}-0.1634172"
    kW -200.00 600.00 .1 "0.745699872*(0.000070146*{SAE.VSS.mph}^3-0.0007566*{SAE.VSS.mph}^2+0.13894268*{SAE.VSS.mph}-0.1634172)"


    ################################################## #################################
    #Raw Power, power you are using to to change speed.
    *CLC-00-004
    hp -200.00 600.00 .1 "((gvmlb()+({GM.FUELREM}*6.350)+130)*{SAE.VSS.mph} )*dx({SAE.VSS.mph},6)/8226.63"
    kW -200.00 600.00 .1 "0.745699872*(((gvmlb()+({GM.FUELREM}*6.350)+130)* {SAE.VSS.mph})*dx({SAE.VSS.mph},6))/8226.63"


    ################################################## #################################
    #Raw Force, force that must be applied to change speed.
    *CLC-00-005
    ftlb -200.00 600.00 .1 "({CALC.RawHP}*5252)/{SAE.RPM}"
    Nm -200.00 600.00 .1 "1.356*({CALC.RawHP}*5252)/{SAE.RPM}"


    ################################################## #################################
    #Power Demanded, Real wheel power it is taking to go down road AND change speed.
    *CLC-00-006
    hp -200.00 600.00 .1 "{CALC.RawHP}+{CALC.Powerlost}"
    kW -200.00 600.00 .1 "0.745699872*({CALC.RawHP}+{CALC.Powerlost})"

    # ================================================== ============================
    *PRN - Parameter Reference Numbers
    # --------------------------------
    # See sae_generic.txt for more information on the *PRN section
    #
    #Code PRN SLOT Units System Description
    #------------------------- ---- ------------ ---------------- ---------------- ------------------------------------------
    ################################################## #################################
    #Wide Band PID
    CALC.LM1 F021 CLC-00-001 "AFR,V,factor" Custom "A Custom PID for the LM1 WB in Voltage, AFR, or BEN."



    ################################################## #################################
    #Fuel Economy
    CALC.FuelEcon F031 CLC-00-002 "MPG,LPK" Custom "MPG o L/100kM."



    ################################################## #################################
    #Aero Drag, power lost to go down road without changing speed.
    CALC.Powerlost F041 CLC-00-003 "hp" Custom "HP Lost from air and rolling resistance."



    ################################################## #################################
    #Raw Power, power you are using to to change speed.
    CALC.RawHP F051 CLC-00-004 "hp,kW" Custom "RealRoadPower, Net HP/kW after grade, wind, rolling resis, ect."



    ################################################## #################################
    #Raw Force, force that must be applied to change speed.
    CALC.RealRoadTorque F061 CLC-00-005 "ftlb,Nm" Custom "RealRoadMoment, Net Ftlb/Nm after grade wind rolling resis ect."



    ################################################## #################################
    #Power Demanded, Real wheel power it is taking to go down road AND change speed.
    CALC.PowerDemanded F071 CLC-00-006 "hp" Custom "Estimate of crank hp. hp from accel + drag + aero."
    Last edited by 2002_z28_six_speed; January 19th, 2008 at 08:13 PM.

  3. #13
    Lifetime Member Chalky's Avatar
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    I love beta testing!

    the 78 HP used to overcome drag @ 100 MPH, is that supposed to be crank or RWHP? I am assuming this would be crank HP.

    Help me out here but assuming a known RWHP of approx 440 RWHP at approx 6600 RPM. I would assume a frictional loss of approx 75 hp putting my crank HP at approx 515.

    How close could you get to actual crank and /or rwhp with the equations?

    i haven't dyno'd my setup but it is a common package developed by Tony Mamo of AFR. 440ish RWHP is common. Tony mamo actually achieved around 475 with some fine tuning.

    A stock 02 Z06 puts down about 354 RWHP stock and can achieve 171 MPH top speed in 5th gear. Does this help to determine HP lost to drag and friction?
    Last edited by Chalky; October 1st, 2007 at 04:24 PM.
    2015 Z06 A8

  4. #14
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    Well. I modded it to include that data point. Still have to test it to make sure EFI calculates it right. I got some values earlier driving around. Now just needs tweaking.

    [edit 02 Ott 2007]

    Still haven't test it yet. Haven't touched the car for awhile. Any see if the aero drag equation makes reasonable numbers?
    Last edited by 2002_z28_six_speed; October 2nd, 2007 at 03:57 PM.

  5. #15
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    I don't think the third order polynomial approximation formula listed previously will work. I don't see any values for the a, b, or c components of the equasion. I believe that equasion works if you have determined the a, b, & c components for a vehicle at a specific speed and want to know what the equivalent losses would be at other speeds.

    I just tried my equasion with the data that was provided in the CATERPILLAR link and achieved the same results they listed.

    The formula for 'Power Consumed by Aero Drag & Rolling Resistance' is:

    P(HP)=(Crr X W X S + 0.5 X Rho X Cd X Fa X S X S) X S / 375
    The plus sign separates the rolling resistance calc from the aero drag calc

    Units are:
    Crr (unitless coefficient of rolling resistance)
    W (weight of vehicle & driver in pounds)
    S (vehicle speed in miles per hour)
    Cd (unitless vehicle specific coefficient of drag)
    Fa (vehicle specific frontal area in square feet)
    Rho (air density {units & derivation are cumbersome} I use the following formula for Rho:

    (Baro/(Temp+460))/22.0824
    Units are:
    Baro (Barometric pressure in "Hg)
    Temp (Ambient temperature in Degrees F)

    Try it out and see what you get. These calculations should get you very close to the power at the rear wheels that is lost. They will only be as accurate as the data you use; ie, have good weight, Crr, Cd, & Fa values for your make, model.

    Using the data I found for a 2002 Z28 (Cd=0.33, Fa=22, W=3410+150), I get the following aero drag losses:
    50 Mph = 17Hp
    100 Mph = 49Hp
    160 Mph = 203Hp

    My Crr equasion may not be as accurate as I thought. It appears that the losses are very dependant on inflation pressure of the tires. I will do some more research and post back the findings.
    Last edited by blandmiller; October 3rd, 2007 at 02:47 PM.

  6. #16
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    I would argee on the tyres' inflation being a huge issue. I have seen a couple MPG difference from bad inflation. So, if you have changed your tyres you are going to have error there.

    Do you think your 160MPH number is low? I based my data solely from the CAT data and got 289.93 HP for 160MPH. Also, I know that is about how fast you can push a stock Z28.

    I had my equation written funny, this is it:
    0.000070146*{SAE.VSS.mph}^3-0.0007566*{SAE.VSS.mph}^2+0.13894268*{SAE.VSS.mph} -0.1634172
    So if I plug in 55MPG it turns into
    0.000070146*55^3-0.0007566*55^2+0.13894268*55 -0.1634172= 16.8hp

    It would be super easy to turn your equation into a calc PID. All the parameters are already there.

  7. #17
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    I am very confident of my aero drag number for the Z28 @ 160 Mph is accurate. I have confirmed it using the SAE standard, several online calculators, and 2 vehicle performance software packages.

    How did you get 290 Hp @ 160 Mph from the CAT data? I don't remember seeing any equasions in the document. I get an aero drag loss of 268 Hp using the CAT data. The automobile data they list is; Cd=.32, and Fa of 30. The Z28 has better aero drag values than the example they used.

    I still have not figured out the equasion for Crr that takes tire inflation pressure into consideration. The information I still need is 'how to calculate the speed effect coefficient'.

    I already put my equasion into a calculated PID. I never could get all of the calculations to work together.

    I just looked at your equasion again and realized that I misunderstood how you derived it. Is it specific to the CAT automobile listed or are you entering your own Crr and vehicle weight somewhere else?
    Last edited by blandmiller; October 4th, 2007 at 01:53 PM.

  8. #18
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    I assumed that was your method. The only flaw I see is that you have to know the impact of the vehicle specific values to make the regression accurate when you convert it to your vehicle specific values.

    After much more research, I believe the Crr for the majority of all passenger tires manufactured after 2000 are in the range of 0.0085 - 0.0115. I still have not found any more information concerning the speed effect coefficient.

  9. #19
    Lifetime Member Chalky's Avatar
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    Is this still alive or has it died?
    2015 Z06 A8

  10. #20
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    What are you using now?
    2004 Pontiac GTO - Quicksilver/red/m6
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