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Automotive Science or Voodoo?



  • user777user777 Posts: 3,341
    i've got nothing against a dyno-pull (?) but when you start talking about read-out the tailpipe, i'm thinking you're thinking emissions... but you might be thinking combustion efficiency.

    i was merely wondering if SW could categorize a more narrow acceptability band on transmitters which might be causing the unit to run excessively rich, or on a sub-optimal schedule.

    we might be talking the same thing, i don't know.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 44,427
    I guess I meant that what could you learn that wouldn't already be throwing a code at you with the normal diagnostic scanning?

    If you are experiencing very poor fuel mileage, below EPA, but no codes are being thrown, then I think maybe you need to be looking at say a conspicuous drop in horsepower...where the engine has lost power/efficiency but not due to a defect that the computer will recognize.

    For instance, (and I don't know the answer to this, so....) how would a dyno react if you let 20 lbs of air out of the tires?

    Or throwing it another way, could software tell you that your alignment is way out and that you are literally dragging your tires along? Probably not.


  • user777user777 Posts: 3,341
    hmmm. let me try this: in my domain, there are mathematical models for unit operation, and the transducers that monitor and thus also control unit operation have an expected range of values at various operation points. we know for example by a particular transducer reading low, that there is a problem with unit efficiency, and we can validate the sensor, based on the other sensor readings.

    without such a model, how do you know if a sensor is drifting, or out of calibration or "clogged"? it might not be tossing a diagnostic code, and yet it's not operating properly either. therefore, the engine may be running to a sub-optimal condition.

    for example the MAF or O2 sensors or the EGR valve.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 44,427
    But could something that subtle affect fuel mileage so noticeably? I mean, are these automotive sensors working so sensitively as that?


  • user777user777 Posts: 3,341
    this isn't my domain, but yeah, when someone says they are getting 17HWY, and the vehicle is supposed to be getting 25 (and everyone else is), and there are no codes, yeah, i think the sensor is "bad", but still providing a within-range measurement that is being acted upon to the detriment of the combustion cycle.

    really, i don't think sensor validation is as critical in a vehicle, nor do they want tight tolerances, because of the false positives and desire for running reliability...this then comes at the detriment to detecting loss of efficiency due to the transducer measurement itself.

    am i totally duped? i don't know...this isn't my domain of expertise, but I got a sneaky suspicion that the car makers are using adaptive control within limits, and are diagnosing transducer failures within limits, but in the realm of possibility are vehicles runnning needlessly derated. they ain't tossing codes (till something like the CAT is fully gone), or the wires are falling off the 02 sensor. ;) meanwhile, the person is just burning gas faster than necessary.

    can you catch this during emissions testing time? i don't know - can you and have the vehicle not pass?
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 44,427
    Well I don't know, except to say that gas mileage is subject to SO MANY variables that have nothing to do with the engine management system per se.


  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 44,427
    Hey, this looks small enough to put in a car! Let's all buy one...oh wait, you can't says FAQ....


  • Yes in fact I distribute the product. I have used BlueSky in every car I own every time I fill up. I have been doing this for the past six years. I have spent thousands of dollars testing BlueSky here in California and in Mexico, Japan, Europe and Sri Lanka. It was originally developed for diesel fuel and we found it to work very well in gasoline as well as bio-diesel, ethanol & methanol.

    It is not a device but a liquid fuel additive one adds to your fuel every time you fill up. Use about 1-ounce for every ten gallons of fuel. It will clean your fuel system & combustion chamber. The theory behind all this is that you will have an even dispersement of fuel in the combustion chamber which has been cleaned. This clean combustion chamber, free of carbon build-up will provide the best environment for a 'complete burn' of the fuel. This means the more fuel gets burned=less pollution and more power! If you have a dirty fuel system or combustion chamber this will maximize your fuel consumption and may improve it substantially. Thank you for the opportunity. If you have any more questions please feel free to contact me.
  • isellhondasisellhondas Issaquah WashingtonPosts: 17,611
    Sounds like you really believe that stuff makes a difference.

    Blue Sky? I think I would find another product line!
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 44,427
    This seems counter-intuitive, since a light carbonization of the fuel chamber would increase compression and hence power. I don't see the relationship of carbon to a "complete burn" one way or the other.

    I could see where a fuel injector CLEANER would give a better spray pattern but this has nothing to do with the combustion chamber.

    If the claim is that the additive changes the chemical composition of gasoline itself, I'd like to see the science behind that claim and what molecular changes have occurred.


  • Hello, I am having idle problems with my 1998 Chevy Cavalier Z24. The car runs great when I first start the vehicle but after it warms up it will start running poorly. It is most noticable after it warms up and then I shut it down for a few minutes (like running into the store), after I re-start the car it accelerates terrible. Idles fine but won't accelerate.
    I borrowed a Actron Autoscanner from a buddy of mine and ran diagnostics on the vehicle, this is what I got:

    Trouble codes, ignition on, engine off:


    Diagnostic codes, Engine running:

    ABSLT TPS(%) 0.0
    RPM 920
    CALC LOAD(%) 19.2
    MAP ("HG) 8.9
    IAT (F) 63
    IGN ADV(DEG) 17 TO 26
    LT FTRM1(%) 21.9
    ST FTRM1(%) -9.4 TO -14.8
    O2S11(V) .195/.760
    ST FTRM11(%) -10.9 TO -14.1
    O2S12(V) .000 TO .005

    From what I've been able to read into this is that my map sensor isn't working correctly and my downstream O2 sensor is faulty. I'm clueless regarding the other information. Are they normal or not?

    Thanks in advance! :sick:
  • srs_49srs_49 Posts: 1,394
    I don't think the P0171 code means that the downstream O2 sensor is bad. Just that it's detecting an excess of oxygen on the exhaust flow. Which could be caused by a bad MAF sensor.

    All the rest of the codes could be a result of the excess oxygen in the exhaust.
  • Mr_ShiftrightMr_Shiftright CaliforniaPosts: 44,427
    yep P0171 is tricky. Many a good 02 sensor has been replaced because of that code.

    MAF sensor is a good guess; also coolant temp. sensor can throw this code; perhaps even a vacuum or exhaust leak.


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