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Unintended Acceleration - Find the Cause

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Comments

  • wwestwwest Posts: 10,706
    "..The answer is obvious..."

    No, it isn't...!

    How would YOU go about designing a brake over-ride system that does not interfere with those times the driver might well intend to closely overlap braking and throttle? Then there is the company that claims to have had brake over-ride for many years. I don't remember the exact design wording but I do seem to remember they made provisions in the design for intentional use of the brakes and throttle simultaneously.
  • busirisbusiris Posts: 3,442
    The Brake Override System operates when these conditions are met:

    a) The throttle opening is greater than 1/3

    b) Vehicle speed is above 5 mph

    c) Brakes are applied firmly

    d) The accelerator pedal is applied before the brake pedal


    So, in the Edmunds test, we have checkmarks beside A,B,C & D. If the brake over-ride feature was installed in the vehicle, why would the test results under full throttle show a 25%+ longer braking distance?

    Also, when you read reports that Toyota purchased suspect vehicles, and along with the floor mat official recall delays and refusal of access to EDR data at first - just makes you wonder.

    I agree, and you do make a valid point... in that Toyota's resistance to issue recalls/repairs initially suggests a company that is more concerned with profits than its customers and their safety.

    And, there are many other issues besides UA that just haven't gotten the same publicity.... Corolla electronic steering issues, Prius HID headlamp failures, etc.

    IMO, there's little question that Toyota's image is tarnished due to these mis-steps, but unless the company is run by complete idiots, management would certainly be able to figure out the test could be easily duplicated....cheaply.

    All one needs to do is find a used late model Toyota without the over-ride feature , install new rotors/pads, and off to a flat stretch of road he goes...

    Invest $20K or less , demonstrate Toyotas are death traps, and sell your story/test results to the highest bidder.

    A great way to make a living, if one can get the work...
  • busirisbusiris Posts: 3,442
    You're grabbing at straws....

    Neither you nor I am designing anything. Its already designed and implemented, and the specifications were shown a couple of posts back.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,626
    We can always blame the brake-override system for future UAs, too. :P
  • wwestwwest Posts: 10,706
    What is the comparative stopping distance starting at 60 MPH for the same car with and without cruise control engaged previous to the beginning of brake application..?

    With CC engaged the engine might still be operating at WOT right up to the instant the brake light switch circuit closes. Without CC the throttle will likely be fully closed once your foot reaches the brake.
  • wwestwwest Posts: 10,706
    As currently implemented we can certainly blame it for not preventing UA.
  • wwestwwest Posts: 10,706
    edited March 2011
    Listen to the engine NOISE at the 36-38 second point in the clip.

    Now listen for the expected level of engine noise at the 45-47 second mark.

    http://www.insideline.com/toyota/camry/2010/2010-toyota-camry-stuck-throttle-bra- - ke-test.html

    In the first case we must assume that the gas pedal is fully depressed but it is likely the throttle is far from wide open, maybe as little as 10%. Yet we hear LOTS of engine NOISE.

    The engine is operating totally without load so the rev limiter would be preventing the engine from WOT, probably via the DBW system.

    In the second case absent some sort of BOS the throttle would have been WIDE OPEN with the engine RPM being limited only by the transaxle torque converter stall point, 2,000 to 3,000 RPM. No induction noise even...?

    This 2010 Camry had a BOS system installed, puzzling part is why Dan Edmunds did not note same.
  • busirisbusiris Posts: 3,442
    It would appear that some folks simply don't know when to stop beating a dead horse.
  • frankok1frankok1 Posts: 56
    Wow if you are correct the others who did tests on braking (remember others - but not sure) then you have a hit on your hands. I would send a separate note suggesting a retest
    http://support.edmunds.com/contactus.aspx?type=error&altref=http%3A%2F%2Fwww.edm- unds.com%2F
    https://www.ideas.edmunds.com/Page/Home

    As for busiris replying to me:
    "Invest $20K or less , demonstrate Toyotas are death traps, and sell your story/test results to the highest bidder. "

    I was hoping NASA would do that for RARE UA cases with at least 200 times $20k - but it appears to be a poor job just on the basis of the vehicles and pedals they selected - and not using MISRA for computer code checks.
  • wwestwwest Posts: 10,706
    If that statement is meant to be somehow a rebuttal of my position on the UA stopping distance (no engine noise = no WOT) then you missed your target by a wide margin.
  • MrShift@EdmundsMrShift@Edmunds Posts: 43,626
    edited March 2011
    After careful consideration of everything I've read here and elsewhere, I'm pretty much satisfied that the case is closed, and no electronic malfunction is at fault for the UA incidents.

    I suspect the floor mats + driver inability to cope with the emergency is the reason, and in some cases, pure driver error.

    I do however, think that malfunctioning cruise control does happen in cars, but that it is easily shut off by tapping the brakes in all cases.

    So I guess I'm done with hashing this around personally. It's been most enjoyable sparring with everyone and exploring all the possibilities.

    Naturally I know that some of you are not satisfied, so carry on. Should I see anything that re-opens the case I will let you all know!

    Shifty, Visiting Host
  • wwestwwest Posts: 10,706
    edited March 2011
    "..easily shut off by tapping the brakes in all cases.."

    And if the brake light switch malfunctions, then what...?

    How many of us are so inured to "tapping" the brake to shut down CC that in a panic situation if it didn't work would we know to resort to the CC stalk...?
  • houdini1houdini1 Kansas City areaPosts: 5,768
    I guess we all assumed that you would be completely up to date on "toe tapping". :P

    2013 LX 570 2010 LS 460

  • wwestwwest Posts: 10,706
    I'm so up to date I have a CC patent application pending.

    On I90 in ID I would often shut CC off as I was a bit nervous about entering those mountainous terrain curves with the CC set at a fairly HIGH speed.

    Lack of being in control, if you will.

    So I modified the system in my Porsche C4 (DBW) such that if I put foot pressure on the gas pedal the CC goes into "neutral" mode. Once I release foot pressure the CC automatically returns to normal operation.

    So now "I" can drive those curves even above the set speed if I wish but be much more comfortable that if I want/need to let off the gas slightly the car will instantly respond.
  • busirisbusiris Posts: 3,442
    After careful consideration of everything I've read here and elsewhere, I'm pretty much satisfied that the case is closed, and no electronic malfunction is at fault for the UA incidents.

    I suspect the floor mats + driver inability to cope with the emergency is the reason, and in some cases, pure driver error.

    I do however, think that malfunctioning cruise control does happen in cars, but that it is easily shut off by tapping the brakes in all cases.

    So I guess I'm done with hashing this around personally. It's been most enjoyable sparring with everyone and exploring all the possibilities.

    Naturally I know that some of you are not satisfied, so carry on.


    I'm it total agreement.

    More and more, at least for most rational examinations, it appears that the UA ship has sailed...
  • All existing sudden unintended acceleration (SUA) investigations focus on the question of how the throttle is opened when drivers do not press the gas pedal. They fail to reveal a convincing cause of SUA. This submission here reports a novel investigation, in which we explored and confirmed a new possibility that the sudden unintended acceleration can be trigged when the throttle is closed. We find that the Evaporative Emission Control System (EVAP) can cause the sudden unintended acceleration when the throttle is closed.

    The nature
    There are two fuel-air supply paths in a modern vehicle. One is the main path including the throttle and fuel injectors, which are controlled by the vehicle computer and gas pedal, and the other is the Evaporative Emission Control System (EVAP), which is controlled solely by vehicle computer. The second fuel-air supply path is ignored by industry so far in investigating the reason of SUA. The EVAP system deserves a careful examination as a possible cause of the SUA, because existing vehicles lack an effective system to monitor the functioning of the EVAP system.

    In a typical existing EVAP system showed in Figure 1, the gas vapor is temporarily trapped in the Charcoal Canister, when the vehicle stops or works in a condition that is different from the predetermined criteria. When the vehicle is running in a ‘good’ condition that fits the criteria stored in the vehicle computer (PCM), the PCM actuates the Purge Solenoid Valve, and then the trapped gas vapor is sucked by the vacuum of the intake manifold into the engine and is burned there. By design, the EVAP system has serious potential safety problem, That is, if the liquid gas in the gas tank enters in the Charcoal Canister for whatever reason, the EVAP system will automatically supply the engine with highly dense gas-air mixture once the Purge Solenoid Valve is actuated, and then the vehicle will suddenly experience unintended acceleration, ineffective brake and other unwanted consequences.

    The nature of the unintended acceleration problems is the defective design of the Evaporative Emission Control System (EVAP) shared by the vehicles of all automakers. All vehicles have been required of equipping with the EVAP system since 1971. Therefore the SUA is a common problem for all automakers.

    The Plausibility

    It is plausible in realistic vehicle running environments for the liquid gas in the gas tank to enter the charcoal canister of the EVAP system. Following is a partial list of possible scenarios:
    • People over-refill the gas tank, either intentionally or accidently;
    • Vehicle experiences heavy bump;
    • Gas tank is squeezed by accidents;
    • Fuel in the tank expands due to the temperature effects, because there is big temperature difference between the outside air and the underground storage of gas station in some days and some places.
    • The valves supposed to prevent liquid gas from entering into charcoal canister are broken, like the fuel shut-off valve.
    • Other cases.
    Both the vehicle computer and the driver do not know whether the liquid gas enters into the charcoal canister of the EVAP until the vehicle experiences the unintended acceleration. Since the unintended acceleration is so violent that many drivers cannot deal with it appropriately and promptly.

    BY Zhongkui Wang
    PHD in Syracuse University
  • wwestwwest Posts: 10,706
    Okay, you have a good case for how fuel might enter the intake manifold, but from where does the air/oxygen come to run the engine at such great torque levels....?
  • wwestwwest Posts: 10,706
    edited March 2011
    "..The EVAP system will automatically supply the engine with a highly dense gas-air mixture once the PURGE solenoid valve is actuated..."

    Where does the air come from if the throttle plate isn't WIDE open...?

    And with the throttle closed how do we produce enough heat via compression to ignite a DENSE mixture...?

    Pour all the liquid fuel you wish into the intake manifold and thereby into the cylinders but absent enough air/oxygen the spark plug will not be able to ignite the COLD fuel.

    Inject fuel into a diesel engine without the "throttle" FULLY open and you get NO "ignition".
  • frankok1frankok1 Posts: 56
    Did you submit it to Edmund's million dollar contest that required proof with test data that they would then confirm? (they must have relied on Mr. Shiftright's opinion to take a chance with the 1-million)

    Did you send the idea to NASA? - they reviewed a few others' ideas

    If not contact the other group investigation of all UA causes
    http://www.trb.org/PolicyStudies/UnintendedAccelerationStudy.aspx

    They just had meetings last week but there is contact info
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