BSFC help needed

Discussion in '4x4's, SUV's and P/U Trucks' started by Die2self, Apr 17, 2009.

  1. CarlD

    CarlD Well-Known Member

    Depends on how the manufacturer chose to interpret the definition of load. OBD-II defines it as airflow relative to maximum. But that could mean relative to the maximum possible at that RPM, or relative to the maximum the engine is capable of at that RPM (volumetric efficiency.) Or, it could mean airflow relative to the absolute maximum the engine is capable of at some high RPM. It is obvious from the readings I see on my Ford, GMs, and Toyota that they have all interpreted it differently.
  2. Die2self

    Die2self Saving more by using less!

    I think you are right on this CarlD. I tried a little something different on the way home as I had 20 MPH wind with me (tailwind). :) To get on highway 249 (PSL 70) there is an elevated ram on to the highway, so I would also get a little help from gravity, I punched the gas in 4th and just let it go with WOT (the peddle to the metal as it were). by the time it was at 3350 RPM I had hit 73 MPH and cresting the hill to go to the valley floor, the TSP was at 75 and the LOD value was around 63. I guess at the lower RPMs the LOD is a function of how much air is being moved in to the engine because I can have the peddal down at low RPM's but the LOD will NEVER go over 30 until the RPM's build up over 2000.

    However with WOT for that time didn't hurt the MPG to much as I ended at home with 21.7. :eek: I was put a little more gas in it than I normally do and it got back up to speed faster for the pulse. I am thinking I have not been giving it enough gas in the pulses. I will now try and keep the TPS value at 40-45(which is not the max that I thought it was.) I would also guess that the max LOD value is above 63 as well but I just didn't want to take the RPM's up to the max of 4275 to find out, I may have to do that another time.;) There seemed to little difference in the gas comsumption from the TSP of 35 and 40. I will keep you updated on the ongoing experiment. Thanks for the comments and the advise so far.
  3. Taliesin

    Taliesin Well-Known Member

    Some interesting info about LOD there. Mine (and most everyone's by the way they write here) reports it as a percentage at current RPM. My pulses are normally at about 75-80 LOD (sometimes a little higher. It goes Closed loop at 95%).

    You might need to do some checking to see when it goes closed loop compared to TPS and go for a target TPS?
  4. Die2self

    Die2self Saving more by using less!

    So, does this mean you can get LOD values of 75-80 at around 2000 RPM? I can't seem to get mine above 30 until I break 2000 and that is with the pedal on the floor.
  5. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    I can get 100 lod at any rpm, by flooring the pedal.
  6. Taliesin

    Taliesin Well-Known Member

    Same here.
  7. JusBringIt

    JusBringIt Be Inspired

    SEems like you may have some Ecu issues, that or something else. Either ways, it may be hampering your fuel economy.
  8. Damionk

    Damionk DWL Lover

    Could these odd values for LOD be because of incorrect settings on the SG? I don't know but That would be the first thing I would check.
  9. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    I just had an idea. Watch your MAP gauge. It should read something low at idle, maybe 4 or 5 psi. That's a vacuum compared to 14 psi atmosphere. At full throttle it should read at or very close to 14 psi - no vacuum because of no throttle restriction.

    75-80 lod pulses on mine are about 12 psi MAP.
  10. Die2self

    Die2self Saving more by using less!

    pale, I will see what it says on the way home tonight and let you know.

    The SG setup is pretty standard, with the fuel setup as hybrid so that it will not keep going off every time I turn the vehile off at the stop lights.

    I can go through the setup if you all want to wade through it here.:)

    Funny you should mention a vacuum issue. there has always been and issue with the HVAC system when under heavy load from the engine (going up Mountians and steep slopes for extented times) the HVAC changes from the position is on (Air with main vents and lower vents on) and then just cycles through the different positions (main vents/defrost/nothing) until it just shuts off completely, but the dealers that I have had look at it say that is normal. NORMAL, this is the only vechile if have owned that doesn't stay where I put the HVAC knob. I wonder if there is design flaw in this system with the vacuum lines.

    Any way I will look at the MAP on the way home under WOT (you know if i didn't know better I would think you trying to reduce my over all MPG for the spring challange, has someone paid you off;))
  11. Damionk

    Damionk DWL Lover

    As far as the settings on the SG, I believe all you would need to check is the engine size and cutoff setting. I have only had mine for a few months so I am still learning. I am sure others here would be able to give you much better advice in that regard.
  12. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    Funny. I've seen that same AC position shifting on a ~1990 Dodge Dynasty and a similar year Dodge Caravan. They must be cousins.

    Who do you think paid me? ;) Bwa-hahaha! :D
  13. Taliesin

    Taliesin Well-Known Member

    I used to get the same thing in the Ranger (back when WOT wasn't avoided like the plague).
  14. Die2self

    Die2self Saving more by using less!

    Then I can tell you now,
    3.9 L for the engine size as that is what I have.
    Cut off setting is 16 because idle TPS is 12 (12+4=16)
  15. Die2self

    Die2self Saving more by using less!

    MR PANCAKE??? (no he wouldn't, would he:confused:)
  16. Die2self

    Die2self Saving more by using less!

    Ok here are the results from the ride home:

    Turned on MAP, LOD and TPS wth MPG on the SG

    MAP sits at 14.4 or 14.5 with engine off (no vacuum)

    At idle:
    MAP = 4.5
    TPS = 12
    LOD - 4

    At WOT
    MAP - 14.2-14.3
    TPS = 75 (pedal on the floor)
    LOD = 63 at 3K RPM at 72 MPH (4th gear)

    Pulsing trials
    MAP = 13.9
    TPS = 40-48 (MAP stayed about the same throuhout that range in the pulse)
    LOD = 30-34 (if RPM is over 2K in 5th gear)

    It felt like a much quicker pulse and was up to 21.0 MPG at the end of the highway section:)

    So what does this information tell you or would you like some more informaiton to work from??

    I think I have been babing the Pulse to much, if I go off of MAP and TPS I should be able to get closer to the bulls eye for efficent fuel usage. I am thinking TPS at 40-48 and keep the MAP up neer 13.8 since LOD does not seem to be working out to well for my vechile.

    I may try a 2nd gear WOT to see if I can get the LOD to the top.
  17. Die2self

    Die2self Saving more by using less!

    Ok, this moring I almost forgot to add LOD back to the guage before I did the next WOT experiment in 3rd gear to see what I can get for LOD Value. Man is it hard to keep an eye on the tach, SG, MPH and traffic while merging from an on ramp (downramp):eyebrow:

    So in thrid I was able to take the RPMs higher to about 4K while the LOD value steadly climbed to 73 at about 62MPH when I shut it down because there was a truck in the left lane and a car in front that I didn't want to plow into (I just know that I wouldn't like that done to me :)) The MAX HP from the facotry is said to be at 4275 so I think if LOD values are suppose to be related to that then I would think that I am getting closer to the top values of the LOD. However, these values don't seem to help to try and get to the 75% LOD value becuase it will not get there in 5th gear under pulse appliction.

    Does anyone have any suggestions? Should I just keep MAP up in the 13.6-13.9 range and TPS 40-50? Just from the seat of the pants feel it seems to be better than before (TPS 30-36).

    Any other data that you want me to get for you?
    Last edited: Apr 22, 2009
  18. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    2nd gear WOT? :eek: :D

    It looks like your LOD reading is off. I think your idea of using MAP instead is a good one. I think your target might be a little high. I'd aim for the low 13s or high 12s instead. Test it and see what gives you better results.

    Just watch out for the LOOP gauge - if it goes to "open", your mileage goes to "crap". At WOT, the computer gives up trying to match the air/fuel ratio, and just dumps extra fuel in there to be sure things don't go boom. Find out where the cutoff is for that, and then don't go past that.

    Another thought in all of this: Much of the magic of P&G is from the Glide part. Aim for the trip mpg at the end of each glide to be higher than the one before. Make whatever pulse you need to, but if it's a heavy one, then you need a longer glide to balance it out. Hold out the glide until you see that trip mpg tick up one more 0.1 than last time, and then pulse it.
  19. JusBringIt

    JusBringIt Be Inspired

    say what??
  20. Die2self

    Die2self Saving more by using less!

    Yup your right I just looked it up and Horsepower @RPM 175@4800 it is the torque that come on at 225 Ib-ft torque @ 3200. It must be the allergy meds. :p

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