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Thread: Transient Fuel: Tips, Tricks, and Info. A how-to guide

  1. #21
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    Quote Originally Posted by 5.7ute View Post
    It all boils down as to what value your tuning tool applies to the hex value at a certain address. For example, if the hex value at the address for minimum fuel in mg is $0064 (which is 100 in decimal) The tune tool will display the value 0.04883. ( my last post was ass about as HPTuners uses 0.0004883 as the scaler).
    The correct value that should be shown is 1.5198 which is the correct scaler for ms. (0.015198)
    This puts the tune tool out by a factor of 31.124308.
    So as a work around, divide your injectors minimum pw by 31.124308 & place this value in the minimum fuel in mg & this will prevent the pw floor from being hit with large injectors.
    One thing to remember though is if this low pw value is hit it will not use the default minimum pw value. If you want it to switch to the default min pw you need to set this value lower than your min pw table.
    This makes sense, but in a raw bin file I have of my OS, the numbers in HP Tuners matches the raw hex value. I would really love to get to the bottom of this.

  2. #22
    Advanced Tuner HartRod's Avatar
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    Does anyone know how you are supposed to update this on the later E38 computers? There isn't a place to change "min fuel" under the transient tab.
    69 Suburban Bagged & Blown: http://67-72chevytrucks.com/vboard/s...d.php?t=200387
    68 Farm Truck build thread-LS3/6L80/TVS1900: http://67-72chevytrucks.com/vboard/s...d.php?t=358692

  3. #23
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    Quote Originally Posted by HartRod View Post
    Does anyone know how you are supposed to update this on the later E38 computers? There isn't a place to change "min fuel" under the transient tab.
    Looking at that right now. Since I do not have an E38 computer, I cant play with those settings. You live in the same town as me...maybe we can meet up and figure it out?

  4. #24
    Advanced Tuner HartRod's Avatar
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    Didn't even notice that, LOL. Since I can't drive mine yet, if you want to come over some time, that would be cool. I live in Pace, just north of Spencer Field. LMK.
    69 Suburban Bagged & Blown: http://67-72chevytrucks.com/vboard/s...d.php?t=200387
    68 Farm Truck build thread-LS3/6L80/TVS1900: http://67-72chevytrucks.com/vboard/s...d.php?t=358692

  5. #25
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    Wait.....and you are from Oklahoma and a Sooner fan? So am I.

  6. #26
    Advanced Tuner HartRod's Avatar
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    Quote Originally Posted by lwrs10 View Post
    Wait.....and you are from Oklahoma and a Sooner fan? So am I.
    Boomer Sooner!! That's to funny. Where are you from? PM sent.
    69 Suburban Bagged & Blown: http://67-72chevytrucks.com/vboard/s...d.php?t=200387
    68 Farm Truck build thread-LS3/6L80/TVS1900: http://67-72chevytrucks.com/vboard/s...d.php?t=358692

  7. #27
    Great reading.
    Any more info on how we tackle changing these table to fix a problem we identify?

    I seem to get large lean spikes when lifting off the throttle.

    Cheers
    Benno

  8. #28
    Senior Tuner 5_Liter_Eater's Avatar
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    Good read. Still can't say I have my head around how to change what though. What would be KILLER is developing some histograms that would drive changes to the transient tables. IE: plotting AFR error against the evap factor table or fuel mass impact table filtered to only show data during tip in/out. Just a thought.
    Bill Winters

    Former owner/builder/tuner of the FarmVette
    Out of the LSx tuning game

  9. #29
    Great post sir!

    Thanks

  10. #30
    lwrs10 ,
    Excellent post! Thanks for sharing.

  11. #31
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    Quote Originally Posted by 5_Liter_Eater View Post
    Good read. Still can't say I have my head around how to change what though. What would be KILLER is developing some histograms that would drive changes to the transient tables. IE: plotting AFR error against the evap factor table or fuel mass impact table filtered to only show data during tip in/out. Just a thought.
    When I get time, I will finish my how to tune transients. Takes a ton of time I do not have right now though....

  12. #32
    I'd like to get this figured out, but it seems we've got some conflicting opinions on this.

    I'm a bit skeptical of both opinions seeing that both are off an order of magnitude when converting from seconds to milliseconds...
    03 Avalanche Z66
    5.3L, Vortech supercharger, water/meth injection, circle D 3200 stall converter, truetrac diff, shorty JBA headers
    Replaced 5.3 with ATK 6.0 460 hp crate motor - haven't put sc and w/m on it yet

    00 vert vette
    Rebuilt LS1 with large cam, injectors, ported and slightly milled 243 heads, Weiand/Lingenfelter Intake Manifold, Vararam Ram Air Intake, LT headers, no cats, Corsa Indy exhaust, higher stall converter

  13. #33
    Advanced Tuner JamesLinder's Avatar
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    Fuel Injector Computations - As exact as possible!

    Computations to dial in fuel injectors attached; essential 1st step to tuning.

  14. #34
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    I'd like to try those transient settings in my '98 tune. Are any of those changes parts or configuration specific?
    1998 NBM Camaro Z28
    LS3 motor
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  15. #35
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    Sounds like I'm going to need Calibrated Success Advanced and not just Basic to figure out the specific workflow. Basic is enroute now.
    1998 NBM Camaro Z28
    LS3 motor
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  16. #36
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    Sigh.....it really sucks that these transient tables aren't in the 2004 Z06 pcm. I've been trying to get my 36 lbrs perfect for the longest time. :/

  17. #37
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    Quote Originally Posted by JamesLinder View Post
    I plan to log AFR verses mass airflow (MAF) with TPS closed during deceleration tonight to see how much the gain on the evaporation table needs to be reduced in areas that are now lean with the stock 2000 Camaro setting. I will also log AFR verses mass airflow with wheel acceleration > 100 (or some meaningful number determined by trial and error) with TPS open more than say say 1% to determine if any changes are
    needed to the Z06 impact factor gain table to make it fit my set up perfectly.

    Bottom line, if you modified your motor from stock, then there is going to be room for improvement in your transient
    fueling gains. The more you modified from stock, the greater the magnitude of the changes you will need to make.
    As always, logging the key parameters with filters that ensure the data logged is applicable to what you are intending
    to tune, should be your goal. Here is what GM used for the Z06 Vette (2002).

    The difference when you get enough acceleration enrichment by using the impact factor gain (decreasing where needed)
    is amazing!!!!!!!!!!!!!!! Good luck Jim.
    I'd like to work on this today, are you able to provide specific config files or specific steps to optimize the transient fuel settings? I guess for now I'll just use the Z06 Impact Factor Gain table and use the same Min Fuel Milligrams that you used (0.0012). However, comparing my factory transient tables to the 408 tune you posted earlier, my stock transient tables are also different here:

    Warmup Transient Fuel:
    Delta Min Incr
    Initial time
    time decay
    previous

    Transient Fuel Mass:
    Fuel Boiling
    Fuel from wall Stabil.

    Transient Fuel Mass Gain:
    Fuel to Wall

    Should I leave those additional settings as original factory, update them to values used in a later model, calibrate them somehow...?

    I found this on another site:

    ---
    So I screwed with it by decreasing the Transient Fuel Mass Gain-Fuel to Wall Impact Factor AND the Impact Factor-Gain. The problem got worse. COOL, go the other way then! So I took it back to stock, added 10% to both those tables and started my drive home from work. WOW! A ton better. I pulled over half way half, added another 10%. HOT DAMN!!! Pulled over again, added another 5%. WOO HOO!!! I figured I was getting greedy so I thought I'd leave it alone for awhile. Let's see how that works for a couple days. Well, the rest of the way home I couldn't help but notice, I didn't have lean spikes as bad anymore.
    ---
    Last edited by JimMueller; 09-14-2014 at 09:44 AM.
    1998 NBM Camaro Z28
    LS3 motor
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  18. #38
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    Quote Originally Posted by JamesLinder View Post
    I'm really surprised. The only table I had to mess with is the gain on the impact factor to get more acceleration enrichment.
    I would think that your GM setting on the 2004 is adequate unless your motor was not supercharged from factory and you
    added one, or added a turbocharger. In my case, switching to the gain in the 2002 Z06 instead of what GM put in all the
    LS1 and LS6 motors that were not Z06 version took care of what I needed. Maybe your VE's and/or MAF is not as dialed
    in as you thought they were? That is what I found out when I started trying to tune transient fuel. When we do not have
    access to a load bearing dyno we are at a huge disadvantage because we cannot achieve perfect steady state on the road.
    At some point in time I plan to see if I can rent an hour or two of dyno time to fine tune mine, realizing that they say this
    usually results in tunes that error on the lean side when you go onto the street.
    Yeah, the MAF/VE are dialed in. I made a couple changes to the 02 sensor values to help with gas mileage(lower values) when I originally tuned it. I just changed them back to stock along with lowering the min inj pulse and default inj pulse from 1200 - 2400 rpm from 1.2xx to .927 and that seemed to make a substantial difference in part throttle and decel rich swings are gone now.

    I'm happy for now. I think that lowering the 02 sensor values screwed up my part throttle. Perhaps it was too lean on tip in. Much better now with stock values.
    Last edited by SVT_Z06; 09-18-2014 at 09:31 AM.

  19. #39
    Advanced Tuner JamesLinder's Avatar
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    Recent Learnings about Transient Fuel Tables - MODELING TAU (Wall Film)

    Recent tuning work resulted in a better understanding of how the transient fueling tables work, and I thought I would share this
    simple summarization of what I learned tuning these tables on my 408 stroker motor. While reading this summary please keep
    in mind that the purpose of the transient fueling tables is to correctly predict the impact MAP changes during throttle position
    changes have upon intake port wall fuel film by formulating a model to accurately predict the rates at which fuel is deposited upon
    and evaporates from the intake port walls. To maintain proper fueling, injector pulse width must be modified during throttle
    position changes to maintain a consistent film of fuel on the intake port walls at all times. When tuned properly, the transient
    fuel tables will ensure that evaporation and deposition of fuel on the walls are occuring at the same rates so that wall film
    remains relatively constant.

    IMPACT FACTOR - During acceleration I found that LESS fuel was being deposited on the intake port walls than predicted by the
    factory GM settings. This created a rich condition because the fuel injectors were attempting to compensate for more fuel building
    up on the intake port walls than was actually taking place for the modified motor. This means the numbers in the Impact Factor
    table were too LARGE and needed to be reduced to eliminate transient rich fueling. Multiplying by lambda error in this case moved
    transient AFR in the right direction (except for 60 MAP which had to be increased).

    BOILING RATE (EVAPORATION) - During de-acceleration I found that fuel was evaporating from the intake port walls SLOWER than
    predicted by the factory GM settings. This also created a rich condition because the fuel injectors were attempting to
    compensate for more fuel boiling off the intake port walls than was actually taking place for the modified motor. This means
    the numbers in the Boiling Rate table were too SMALL and needed to be increased to eliminate transient rich fueling. Dividing
    by lambda error in this case moved transient AFR in the right direction (except for 60 MAP which had to be decreased).

    TUNING TRANSIENT FUELING - The purpose of tuning these tables is to maintain stochiometric fueling during changes in throttle
    position; tuning in this case effectively removes the rich and lean spikes that would otherwise occur even though the MAF and
    VE tables have been properly calibrated. Transient fueling is crazy difficult to tune because these "spikes" occur so quickly and
    because an error in either table affects the operation of both tables for the specific MAP and ECT region impacted. Tuning two
    tables simultaneously which have opposite impacts on non-steady state fueling is considerably more difficult than the more common
    chore of tuning a single table during steady state conditions.

    The GAIN tables for EVAP and IMPACT can be used to modify the values in the base tables for various MAF rates, since the velocity
    of the air flowing through the intake ports during transient conditions can necessitate adjustments to the base table values to
    maintain proper fueling. The higher the MAF the higher the velocity of air through the intake ports, and the less fuel that can
    hang onto and build up on intake port walls as compared to that for lower air velocities. As air velocity increases, GM decreases
    the Impact Factor gain values to account for this and prevents the rich transients that would otherwise occur at higher air
    flow rates. GM set the gain for EVAP RATE at unity (1.0) for all MAF rates. Evidently, evaporation/boiling rate has the most
    impact on fuel wall film as the throttle is being closed (de-acceleration), and air flow rates/velocities when the throttle
    butterfly is nearly closed do not impact boiling rates that much.
    Last edited by JamesLinder; 01-07-2015 at 07:30 AM. Reason: REVISED FOR ACCURACY 1-5-2014

  20. #40
    Tuner Stuffs's Avatar
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    thanks for sharing James