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Thread: Ford Speed Density tuning on EcoBoost...

  1. #1
    Senior Tuner metroplex's Avatar
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    Ford Speed Density tuning on EcoBoost...

    I did some datalogging on my stock 2014 SHO, and the LTFT+STFT for both banks looks like it is on average, about 5% lean, when looking at the big picture.

    I found a thread on the Ford quadratic equation in this forum, but cryptic doesn't even begin to explain it: http://www.hptuners.com/forum/showth...ight=quadratic

    I know a few people do this for a living, but have any of the DIY'ers developed some kind of guide? Essentially, all I'm interested in doing is being able to correct/compensate for an aftermarket air intake or at least fix the stock tune so it is more dialed in. With the older Ford MAF systems, I could do this fairly quickly thanks to a variety of guides/resources available. Which PIDs do we log, and which tables do we modify? Where do the mapped points come into play?
    Last edited by metroplex; 03-13-2016 at 06:29 PM.

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    Its not that cryptic, It is just lots of math and not easy to wrap your head around. Ax^2+Bx +C=Y or 0 this is why all the speed density tables say at zero air mass. Y is Inferred airmass and X is the inferred MAP or if your car has a MAP sensor like the OP in that post did, you use its value. In the equation you have terms adding up to the air mass with one being squared and the other not, both being multiplied. This is why the values in the Speed density tables seem so uncorrelated. You would need to figured out how to modify your MAP value to fit into the equation.

    What might help you is revisiting how you go from Ax^2+Bx+C=0 to x = (-b +/- sqrt(b^2-4ac))/2a. this web site makes it as simple as I can find. http://www.purplemath.com/modules/sqrquad2.htm

    Chambers actually made a typo and left out the b^2. unless he had a reason to leave that out, that is the correct formula. notice how both equations don't involve Y or the inferred air mass. You should only concern your self with the MAP value.

    A is quadratic the first term

    B is slope the second term
    technically
    (slope or blow through slope) depends on VCT/load/RPM

    C is offset the third term
    This gets applied in the form of (map-(baro/29.95)) remember x is map so offset(baro/29.95) would be the compensation for air pressurizing above manifold pressure in the cylinder because of the velocity of the air. cylinders fill to pressures higher than MAP and take more from the total air mass so you subtract it.
    Last edited by murfie; 03-13-2016 at 08:53 PM.

  3. #3
    Senior Tuner metroplex's Avatar
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    I have the EcoBoost 3.5L V6, so I believe I have at least 1 MAP sensor?
    Am I solving for Y or X? And what should I be doing based on the fuel trim data I obtain? Adjust A, B, and/or C to obtain the adjusted value of Y (or is it X?) based on the fuel trim data?

  4. #4
    Senior Tuner Higgs Boson's Avatar
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    How does one disable the maf sensor in order to get the true sd error and not lose map(inferred)?

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    The eco boost have inferred MAF from a MAP sensor. It works better for turbos AFAIK.

  6. #6
    Senior Tuner Higgs Boson's Avatar
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    But what about the V8s? I know it's an EB thread....

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    Your goal is to solve for Lb/min. with a map sensor
    your goal is to solve for InHg. with a MAF sensor

    Slope is given in inHg/LBm this is pressure ratio of mass which temperature would have an effect on. IDGL is PV=nRT. (inHg)(m^3)=(mol)(j*mol^-1*K*^-1)(k*). The relationship between Lbm and mol is: mass in lb = (mol. wt.) (lb mol). K is tempature in kelvin so c*+273. J is joules. J=watts*seconds. or you could use j=(wieght)(m^2)/(s^2) to have an area and a volume in the equation. first and second derivative.

    we only care about the oxygens mol. wt. in air. it is 6.704 airs total is 28.97

    All the information is there just need to plug it all in and rearrange it.
    Last edited by murfie; 03-14-2016 at 04:19 AM.

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    Read this article published by Paul Yaw of Injector Dynamics.

    He very thoroughly explains how the Equation based Speed Density system is used to to derive a VE surface and thus a lb/min value from MAP.

    http://injectordynamics.com/articles/shelby-gt500/
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    The problem is that article describes the linear equation not the quadratic equation.

    mx+b is linear

    Ax^2+Bx+c is quadratic

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    Yeah, I posted that to get your feet in the water.

    I can write up on the basis of the new system when I get some time.

    I do a lot of EcoBoost tuning and have it pretty down pat.
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    do you have a spread sheet or how do you track everything as far as changes?

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    https://cobbtuning.atlassian.net/wik...rdcalculateVE?

    Thought this was pretty awesome for free information. at the bottom they have a spread sheet. its too big to upload here. its not exactly the same but you can get the idea.

  14. #14
    Senior Tuner metroplex's Avatar
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    So was Joshua.Levin's first post (the equations) correct in determining the formula for finding airmass? What units are we using for the molecular weight of O2, 6.704 is in kg/kmole from what I could find.
    Are we solving for "n" in the IDGL? Where are we getting the volume from?

    I assume the pressure would be the MAP sensor reading? Do we account for the atmospheric pressure (14.7 psi) by subtracting it or do we use the direct value?
    And when do the VCT weighted points come into play? While datalogging, the only PIDs I could find related to weighted points produced percentages for some of the points. On the EB 3.5, the only tables with valid weighted points figures were for points 0-5 (qty of 6).

    What are we exactly changing based on the AFR results? The only tables that show up in VCM Editor are Max Load, Offset, Quadratic Term, Blow through slope, and Slope - and these tables are only RPM dependent.


    I was doing more thinking about this, if Inferred Mass is 0 (Y=0) for the tables, then we'd solve for X using the quadratic formula, which is Inferred MAP. The only tables I can change are the A, B, and C values for the quadratic formula. While datalogging fuel trims, should I be plotting those fuel trim values in a table with RPM vs MAP? Am I adjusting the A, B, and C values to correct the fuel trims by tweaking them so that the inferred MAP (X) is adjusted by the appropriate amount based on the fuel trims?
    Last edited by metroplex; 03-14-2016 at 08:09 AM.

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    You get where in coming from.

    In physics/chemistry you keep your units the same and manipulate them with the correct math.

    I would say the mapped points are a function of time.

    Distance> speed> acceleration> snap

    Snap to point and snap to line would be first and second derivative so speed and acceleration.

  16. #16
    Funny cause I was tuning a '15 Eco boost and I was like HTF do I adjust the fueling LOL. Its true as to the OEM making it more difficult for us to tune these cars.
    So the only way to modify these tables is use the above posted calculation. What table would need to be the ones changed? I havent seen a Cobb map yet but I would believe they have the table defined in a way we CAN modify fueling the "standard" way?

    If you have to modify all the tables under SD then surely there should be a way to make a virtual map to make adjustments to and it recalculate of the other SD calculation tables.

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    Even Cobb hasn't addressed the quadratic speed density function. Since the late model F-150s are all SD-based, you could look at some NA and FI calibrations (e.g. Roush) for some insight.
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    Advanced Tuner GapRider's Avatar
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    great info in this (old) thread. I'm trying to catch up but behind you guys.

    One off handed question: Why are the speed density table parameters such jagged lines, I thought they'd follow a smooth progression?
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  19. #19
    Quote Originally Posted by GapRider View Post
    great info in this (old) thread. I'm trying to catch up but behind you guys.

    One off handed question: Why are the speed density table parameters such jagged lines, I thought they'd follow a smooth progression?
    If you actually plot out the final airflows modeled by each of values and plot the surface, the surface is typically okay in smoothness. Keep in mind outside the normal operating range for MAP vs RPM, it may not be as accurate as they're going for accuracy over the operating range of the motor. The ending surface is still quite smooth.

  20. #20
    Advanced Tuner AKDMB's Avatar
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    Does anyone actually tune the SD on MAF Based 2011+ Fords? Are you doing a disservice by only tuning the MAF for fueling ? All I think of when I see this stuff is VVE for the Gen 4(? I don't know my GM's very well, I guess they VVE was the Gen 4 cars) and the tools needed to full calibrate it. I know my math pretty well (at least from a practical standpoint, never had a good theoretical understanding of certain concepts), but applying it here looks tricky.