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Stop-start, does it actually cost you more?

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    #32
    [Deleted User]
    Posts: 21,179 ✭✭✭✭ [Deleted User]


    MuppetCheck wrote: »
    The Leon has the auto hold kicking in when it restarts. You get a jolt when you go to move off - it's very irritating in traffic and makes the car easy to stall. On the plus site it restarts itself if it does happen.

    My big fear of stop start systems is oil starvation to the turbo when the engine cuts out. Probably accounted for on modern cars but I wouldn't just switch the engine off myself like stop start does.

    I thought a lot of modern turbos have water cooling ? I thought vag had it ? if so it would be easy to keep an electric pump going.


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    #33
    The Dagda
    Closed Accounts Posts: 1,345 ✭✭✭The Dagda


    jameshayes wrote: »
    I think I read somewhere, could have been the F30 brochure- that when the car is off for more than 3 seconds it starts saving fuel

    Once the engine is off it stops using fuel!


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    #34
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    The Dagda wrote: »
    Once the engine is off it stops using fuel!

    It uses extra fuel to re-start it though so there is a trade off.


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    #35
    The Dagda
    Closed Accounts Posts: 1,345 ✭✭✭The Dagda


    Rivka Long Pick wrote: »
    It uses extra fuel to re-start it though so there is a trade off.

    How much extra fuel? 3 seconds worth? A hair's breadth? A modicum?


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    #36
    corkgsxr
    Registered Users Posts: 3,404 ✭✭✭corkgsxr


    The Dagda wrote: »
    How much extra fuel? 3 seconds worth? A hair's breadth? A modicum?

    How long does it take to regain the power used to restart.

    Thats were the 30 seconds for petrol and 50 for diesel came from.

    so if your going to be stopped at lights for more than 30 seconds it was worth it. If it was 25 seconds it wasnt.


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    #37
    pippip
    Registered Users Posts: 2,249 ✭✭✭pippip


    corkgsxr wrote: »
    How long does it take to regain the power used to restart.

    Thats were the 30 seconds for petrol and 50 for diesel came from.

    so if your going to be stopped at lights for more than 30 seconds it was worth it. If it was 25 seconds it wasnt.

    I assume those figures are based on a standard car switching off and on its engine versus running idle. Then the 3 seconds quoted by BMW F30 must be on an adapted engine designed for stop/start or else you would be using more fuel than saving on short stops under 30secs.


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    #38
    The Dagda
    Closed Accounts Posts: 1,345 ✭✭✭The Dagda


    corkgsxr wrote: »
    How long does it take to regain the power used to restart.

    Thats were the 30 seconds for petrol and 50 for diesel came from.

    so if your going to be stopped at lights for more than 30 seconds it was worth it. If it was 25 seconds it wasnt.

    What about 26-29 seconds?! lol

    These systems are getting more efficient and cleverer all the time. They're beginning using regenerative braking and capacitors to restart the engines so the power being used is "free". Even the first generation systems were far more efficient then you're claiming...


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    #39
    corkgsxr
    Registered Users Posts: 3,404 ✭✭✭corkgsxr


    Yes standard car. Study was done for hypermileing. But was modern enough cars.

    as regards capacitors or like power still has to be made.

    5th gear done a test with stop start vs not saved 10% but half way through the test the stop start disabled itself because the batterys got too low. Pottering about town wasnt enough to recharge itself with repeated stop starts.


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    #40
    Chimaera
    Registered Users Posts: 1,652 ✭✭✭Chimaera


    The benefit of capacitors is they can be charged very quickly using regenerative braking i.e. the energy released by slowing down the car is recovered and stored in the capacitor instead of being wasted as heat in the pads/disks. This can be used to restart the engine rather than drawing from the battery.


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    #41
    sunnysoutheast
    Registered Users Posts: 2,072 ✭✭✭sunnysoutheast


    R.O.R wrote: »
    BMW have it sorted better on their Auto's - it goes off the accelerator, so you can sit there, not using fuel and not pressing any pedals, until you need to head off again.

    The engine stays stopped as long as you have your foot on the brake in D. Lift it off and the engine starts. Unless mine is not working right!!

    In the US you can get the car coded to remember the start/stop setting when the engine is turned off but they don't seem to allow this in the UK as policy so I assume Ireland would be the same. Might be something an indy can do though.

    I disliked s/s at first but wouldn't be without it now.


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    #42
    sunnysoutheast
    Registered Users Posts: 2,072 ✭✭✭sunnysoutheast


    Chimaera wrote: »
    The benefit of capacitors is they can be charged very quickly using regenerative braking i.e. the energy released by slowing down the car is recovered and stored in the capacitor instead of being wasted as heat in the pads/disks. This can be used to restart the engine rather than drawing from the battery.

    I think the Mazda system uses capacitors and is meant to be very good.


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