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Thread: Unacceptable vibration/rattle @ 13,000 km SOLVED: loose exhaust hanger

  1. #41
    Moderator Eggman's Avatar
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    Quote Originally Posted by inuvik View Post
    Just a guess though, not sure why Mitsubishi made this change.
    I might be wrong, but I see two benefits to this design:
    1. Placing the catalytic converter closer to the exhaust manifold helps it reach operating temperature quicker.
    2. Placing it up inside the engine compartment makes it more difficult to steal.

    I strongly doubt these thoughts factored in Mitsubishi's decision, but rather it had to be some cost-saving measure.


        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


  2. #42
    Moderator inuvik's Avatar
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    Quote Originally Posted by Eggman View Post
    I might be wrong, but I see two benefits to this design:
    1. Placing the catalytic converter closer to the exhaust manifold helps it reach operating temperature quicker.
    2. Placing it up inside the engine compartment makes it more difficult to steal.

    I strongly doubt these thoughts factored in Mitsubishi's decision, but rather it had to be some cost-saving measure.
    All good points Eggman! You're probably correct it probably saved 50 cents or something like that.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.5 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.6 mpg (Imp)


  3. #43
    Senior Member IchabodCrane's Avatar
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    The change did allow for deletion of the flex joint so a few $$ saved there.. Now there's only the ball/socket style joint behind cat, the rest of the exhaust is one welded assembly from there. Maybe longevity is better with this design?
    Either way this design does little to keep engine vibration from travelling all the way to the back of the car.
    Will weld for beer.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE 1.2 automatic: 45.3 mpg (US) ... 19.3 km/L ... 5.2 L/100 km ... 54.5 mpg (Imp)


  4. #44
    Moderator inuvik's Avatar
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    Quote Originally Posted by IchabodCrane View Post
    The change did allow for deletion of the flex joint so a few $$ saved there.. Now there's only the ball/socket style joint behind cat, the rest of the exhaust is one welded assembly from there. Maybe longevity is better with this design?
    Either way this design does little to keep engine vibration from travelling all the way to the back of the car.
    3 cylinders are inherently unbalanced at low rpm anyway so anytime you create an exhaust with less flexibility it's going to be a candidate to transmit vibration further down the line. Did Mitsubishi change the motor mounts also on the '17's? Just curious if this issue is a sum of multiple changes.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 automatic: 40.5 mpg (US) ... 17.2 km/L ... 5.8 L/100 km ... 48.6 mpg (Imp)


  5. #45
    Quote Originally Posted by inuvik View Post
    3 cylinders are inherently unbalanced at low rpm anyway so anytime you create an exhaust with less flexibility it's going to be a candidate to transmit vibration further down the line. Did Mitsubishi change the motor mounts also on the '17's? Just curious if this issue is a sum of multiple changes.
    The mounts look the same as a 2015, at least to me. Maybe made of different material?

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


  6. #46
    Senior Member IchabodCrane's Avatar
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    Took my Mirage in for an oil change today.
    mileage was 22,789km.
    They asked how things were going with the resonance/rattling issue. Told them no change but I'll let you know when something falls off.
    I guess they called Mitsu corp. again and were told to "reset" everything.. trans parameters, engine parameters etc. ??
    So they did that I guess and they said they loosened the bolts on all the engine mounts exhaust mounts and joints then re-tightened everything to reset that in proper position as well.
    Now I'm supposed to drive it for a few days and report back whether it made a difference or not.
    We'll see I guess ��
    Will weld for beer.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE 1.2 automatic: 45.3 mpg (US) ... 19.3 km/L ... 5.2 L/100 km ... 54.5 mpg (Imp)


  7. #47
    Senior Member MightyMirageMpg's Avatar
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    Out of curiosity why is it assumed the exhaust moving around is causing the vibration? Every car I've owned has used rubber hung exhaust.

    I thought this was a rattle/vibration at a specific RPM non dependant on speed?

  8. #48
    Senior Member IchabodCrane's Avatar
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    it is rpm related as is the exhaust resonance. the resonance is causing an undiagnosed rattle/buzz.
    it's assumed the exhaust not being able to move around due to this more rigid design is causing the resonance/vibration.
    Will weld for beer.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE 1.2 automatic: 45.3 mpg (US) ... 19.3 km/L ... 5.2 L/100 km ... 54.5 mpg (Imp)


  9. #49
    Senior Member MightyMirageMpg's Avatar
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    Interesting theory.

    If you put the car in park and free rev it, it doesn't do it, then this should be ruled out, correct?

  10. #50
    Moderator Eggman's Avatar
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    Quote Originally Posted by MightyMirageMpg View Post
    Interesting theory.

    If you put the car in park and free rev it, it doesn't do it, then this should be ruled out, correct?
    I'm not sure that would be an accurate test. less fuel is used revving the engine while the vehicle is stationary and the engine is not working much. Loading the engine by moving the weight of the vehicle and it will use more fuel at the same given engine RPM. This will change the volume and velocity of exhaust gases moving through the exhaust system, and therefore impact how the exhaust reacts.

    It suppose it could be done on a dynamometer, but that can be expensive.

    It might be helpful to put a camera at various spots along the exhaust to see what's going on. Who will volunteer a camera for this? Haha. Well, there are some small cameras that could be helpful, such as borescope camera, bike camera, surveillance (spy) cam, etcetera.


        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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