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Thread: Fuel Economy Tuning Ideas

  1. #21
    Супер Модератор EC_Tune's Avatar
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    Quote Originally Posted by RoninsDenali
    Hmm what about those who dont use a MAF anymore? Would the corresponding General Airflow table then use Dynamic Air instead of MAF?
    If you use closed loop operation (SD or not) you will be using the o2 crossings tables. I do believe that the Dynamic Airflow will put you into the right Mode though as they are very close except on transitions.

    I created a custom PID to see the % difference between MAF and Dynamic Airflow. Very telling during transitions!

    EC
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  2. #22
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    Do the values need to be changed on the Bank 2 tables as well in the 02 Rich/Lean vs. Airflow Table?

  3. #23
    Senior Tuner S2H's Avatar
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    Quote Originally Posted by MrXerox
    Do the values need to be changed on the Bank 2 tables as well in the 02 Rich/Lean vs. Airflow Table?
    YES
    Bank 1 Drivers side..
    Bank 2 Passenger side
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  4. #24
    Senior Tuner S2H's Avatar
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    on a note about my MPG PID...seems to be close enough..
    I have been getting between 25-26 MPG on each tank of gas...
    and it reported 26.2 on my last hour long drive from home into the city...

    just need to come up with a way to calculate the actual weight of gas per temperature as it changes when its hot or cold...then it would be more accurate....I just used the weight of gas at 80*F for the equation....figured it was in the middle of what it would most likely be
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  5. #25
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    Exclamation

    Quote Originally Posted by EC_Tune
    Here are some settings I used to improve a 2001 Z06 Vette's MPG.

    Attachment 190
    Why does this work? Could you explain more about these tables (what numbers are what)?

    Bill

  6. #26
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    Quote Originally Posted by Billiumss
    Why does this work? Could you explain more about these tables (what numbers are what)?
    Bill,

    No Prob,

    The fuel loop control averages the o2 sensor values to come up with an average o2 sensor value. This value is compared to the B1S1 and B2S1 tables to see if the fuel needs to be increased or decreased to stay at 14.7 AFR.

    By telling the PCM to use a lower average millivolt value (350 instead of 451) it will drive the fuel correction lower and give you a slightly leaner air fuel mixture even though the o2 sensors are only correct at 14.7 AFR.

    Think of it like your thermostat at home. If it's hot, the heater turns off, if it's cold it turns on. No midpoints just On or OFF. If you could average the temperature of your house and have the heater turn on and off "just when you are home" and keep it between 68-70 degrees, your heating bill goes down. These tables work in a similar way.

    If you are in PE mode, the o2 sensors are ignored you just get more fuel period. If you are in Deep DFCO, the o2 sensors are ignored as well it's turning the fuel off instead of on. No feedback corrections just "On & Off" like the heater.

    The General Airflow vs Mode determines which part of the B1S1 (or B2S1) vs Airflow table you are on.
    The B1S1 & B2S1 tables determine how rich or lean the AFR might be biased.

    BTW: If you are monitoring STFT+LTFT, and wideband AFR you will probably notice that the measured AFR in Closed loop moves around a bit with airflow at mild cruise & idle (check in steady state conditions). That's the bias that the B1S1 & B2S1 tables apply to achieve the correct AFR.
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  7. #27
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    Question

    How does this effect lean cruise(open loop) for those that can enable it, ie holden ls1's?

  8. #28
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    Quote Originally Posted by possum22
    How does this effect lean cruise(open loop) for those that can enable it, ie holden ls1's?
    It will not affect Lean Cruise as that condition is open loop as you stated. In open loop (lean cruise) the o2 sensors are ignored.

    EC
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  9. #29
    Quote Originally Posted by EC_Tune
    Here are some settings I used to improve a 2001 Z06 Vette's MPG.

    Attachment 190
    i found the closed loop vrs airflow table but where is the 02 b1 l/r sensor vrs airflow table?
    i found a closeloop proportional base vrs airflow that looks similar

  10. #30
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    What's the vehicle? V-6 doesn't necessarily have all this wonderful stuff.
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  11. #31
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    Any problems with cam surging with this change, EC? Also, what happens if this change is made and I develop an exhaust leak before the O2's?
    1998 NBM Camaro Z28
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  12. #32
    Quote Originally Posted by EC_Tune
    What's the vehicle? V-6 doesn't necessarily have all this wonderful stuff.
    99 transam

  13. #33
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    Jim - It will affect you either way. Just need to fix the leak.

    SmokinHawk - Tables are under FuelControl.Open/Closed Loop.
    Last edited by EC_Tune; 03-28-2006 at 10:30 AM.
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    Well, yeah But I'm wondering if it's any more dangerous to use these swing points with a leaky exhaust than with the stock swing points. I'd like to try it on a 2-3 hour trip Saturday morning, but the exhaust leak won't be fixed for awhile because it's in the center of the collector tubes and it's basically not reachable. Sounds like the 'fix' is new headers.

    What about cam surge while cruising in these airflow modes? I've heard leaning it out can make cam surge worse...?
    1998 NBM Camaro Z28
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  15. #35
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    Quote Originally Posted by EC_Tune
    Here are some settings I used to improve a 2001 Z06 Vette's MPG.

    Attachment 190
    well i am going to try some of this i guess but my O2 voltages are completely different
    365.67467 435.79289 435.79289 435.79289 456.85554 490.89549 500.91723 456.85554 456.85554. should i just plug the ones in from what you showed or how should i go about changing these? and also the other table you posted up what exactly does that do? thanks
    nick

  16. #36
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    Quote Originally Posted by soundengineer
    for a MPG PID
    something like this might do the trick...not 100% sure..perhaps I'll play with it today some..
    [SENS.20]/(([PID.6210]*0.132276)*[SENS.112]*[SENS.70]*8/6175)

    then just make a histo that the x axis is the MPG PID..and select the MPG PID to log as well..
    result should give you 1 box on the histo...and it will average as you drive....
    would be nice to have better resolution on the MPH sensor like I talkek to chris about at one time
    Scott:

    I tried using the above formula and the histogram always read zero. I was looking over the formula and could not figure out what [SENS.112] was used for. The injector flow rate is shown by [PID.6210] and converted to Imperial. I deleted the [SENS.112] and the histogram is updating.
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  17. #37
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    Quote Originally Posted by Blacker
    Scott:

    I tried using the above formula and the histogram always read zero. I was looking over the formula and could not figure out what [SENS.112] was used for. The injector flow rate is shown by [PID.6210] and converted to Imperial. I deleted the [SENS.112] and the histogram is updating.
    sens.112 is extremely important....Injector Pulse Width in milleseconds

    if its not working then you are missing something while logging
    must log all of those parameters...

    I have an updated one now too..takes into account IAT and ECT..

    [SENS.20]/(([PID.6210]*0.132276)*[SENS.112]*[SENS.70]*8/(6175*(((([SENS.11]+[sens.10])/2)+273.15)/299.8167)))

    this should get you MPG..and should compensate a little for fuel temperature a little bit..cause fuel weighs different amounts at different temperatures

    seems to be accurate in my car...
    works perfect..last 4 tanks have been all within .5 of dead on for me...

    basically its
    [MPH]/(([Injector Flow Rate]*0.132276)*[InjectorPulse Width]*[RPM]*8/(6175*(((([IAT]+[ECT])/2)+273.15)/299.8167)))

    with everything converted so that the units match appropriately

    You Must Log:
    Vehicle SPEED
    Injector Flow Rate
    Injector Pulse Width
    Engine SPEED
    IAT
    ECT
    Last edited by S2H; 03-28-2006 at 03:02 PM.
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  18. #38
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    Excellent work Scott! I knew there was a reason we kept you around.

    As for the "Lean Cruise", I am going to take it a step further (maybe others can as well) and use my wideband to log the AFR and see where my O2 voltages end up with a leaner mixture. Add those values where EC mentioned or where my light cruise transitions are. I may have to learn how to stay out of the throttle or not lean into it as hard.

  19. #39
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    Quote Originally Posted by SUTTERERMAN85
    well i am going to try some of this i guess but my O2 voltages are completely different
    365.67467 435.79289 435.79289 435.79289 456.85554 490.89549 500.91723 456.85554 456.85554. should i just plug the ones in from what you showed or how should i go about changing these? and also the other table you posted up what exactly does that do? thanks
    nick
    You need to look at the General Airflow vs Mode & determine where you are currently vs MAF airflow in g/sec.

    I like to leave the top points where they are (Mode 12,14, & 16) or richen them (~526) to keep the AFR around 14.4 in closed loop at higher airflows. You don't need it really rich just slightly richer there.

    If you are idling in closed loop and see the AFR is in the 15's or greater you need to adjust the lowest mode values. I find with cammed cars that roughly ~526 works nice. There are upper & lower limits (not accessed in HPT) that will prevent you from GTF'ing it (Gone TOO Far) so if you keep changing the value & nothing happens you've GTF'd it.

    The General Airflow vs Mode values I have there should be OK for your application. They are just guidelines though. If you have a heavy truck with 44's on it, nothing will help .

    EC
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  20. #40
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    Quote Originally Posted by JimMueller
    Well, yeah But I'm wondering if it's any more dangerous to use these swing points with a leaky exhaust than with the stock swing points. I'd like to try it on a 2-3 hour trip Saturday morning, but the exhaust leak won't be fixed for awhile because it's in the center of the collector tubes and it's basically not reachable. Sounds like the 'fix' is new headers.

    What about cam surge while cruising in these airflow modes? I've heard leaning it out can make cam surge worse...?
    I haven't run into cam surge issues yet but you will end up in the higher airflow ranges pretty quick with a cam, especially the bigger ones.

    As to the header leak, it probably won't hurt you to "check out" the values & see what they do for you.

    Here's a quick test you can do with your wideband & the scanner.

    At light throttle cruise disable Closed Loop & Fuel Control Enable and command 15-16 AFR at cruise. If you are using SoundEngineer's MPG PID you can see the instant MPG & changes. Observe the wideband & see if it follows properly.

    It hasn't bothered any of the engines I've worked on at all. Remember, you are only at ~30-50 HP utilized to maintain cruise speed in a car. With proper engine cooling (factory is fine for most NA applications) you will be fine at cruise MPH. Trucks require more HP at cruise because of drivetrain, weight, and frontal area though.

    EC
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