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  1. #1
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    Default Alternator freewheel pulley - faster gear changes

    A freewheel pulley allows the alternator to continue spinning on its own inertia whilst engine is slowing down in preparation for a gear change. This results in less load on auxiliary drive belt and faster gear changes. Some claim they also improve fuel consumption.


    Pulley on the left is original pulley from my 2002 Smart 450 Cabrio Cdi and now very much worn. Pulley on the right came from a Renault, unsure which model and year. This pulley is a freewheel pulley made by INA. Original pulley has 5 grooves. This INA pulley has 6 grooves. No real problem, only have to ensure belt is in right grooves and correctly aligned.
    Diameters measured over top of ridges: Original pulley when new 54.2 mm. This INA freewheel pulley 55.7 mm.
    I had to machine the new pulley to make it align crank shaft pulley. Removed 1.1 mm where pulley faces alternator.
    Nowhere in WIS could I find any torque specification for alternator pulleys. Google also no good for same so I checked Renault Dialogys and found specified torque is 8.2 daNm.


    Freewheel pulley fitted on alternator. Protective cap fitted. Existing belt was in a poor state so I fitted an older used belt in a slightly better condition.

    Road test:

    Noticably faster gear changes shifting up. No change shifting down.


    Why faster gear changes shifting up?
    The high inertia of a fast spinning alternator with standard pulley will slow down (resist) speed changes of the wee Smart engine.
    A freewheel pulley allows alternator to continue spinning on its own inertia because decoupled from engine when engine slows down. Engine can therefore reduce its rotational speed faster.

  2. #2
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    Default Re: Alternator freewheel pulley - faster gear changes

    God, that alternator is nearly rotted away

    Have you spotted a marked difference when the alternator has a heavy load on it vs fully charged and no ancillaries on?

    I've not got any figures on how fast a fully loaded alternator will shed its revs when suddenly allowed to freewheel? , would it beat the engine back down to lower revs loaded or not loaded? I wonder
    fq101.co.uk

  3. #3
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    Default Re: Alternator freewheel pulley - faster gear changes

    Alternator is in good condition.

    Alternator is only fully loaded for short time after start up when engine is cold and outside temperature is below 8 C.
    For normal running alternator loading is nil.
    These engines are tiny, yet they are outfitted with standard size alternators, same size as 8 litre engines and larger.

  4. #4
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    Default Re: Alternator freewheel pulley - faster gear changes

    Quote Originally Posted by tolsen123 View Post
    For normal running alternator loading is nil.
    Don't exaggerate
    There'll always be an electrical load to some extent and therefore some physical load on the alternator (ok slightly less so on your rusty old diesel ).

    I meant by fully loaded doing some night driving , headlights, hifi etc etc .. ok, yes the main load is right after starting to replenish starting current, but nighttime is the next highest load of course.
    fq101.co.uk

  5. #5
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    Default Re: Alternator freewheel pulley - faster gear changes

    I did my test drive with headlights on, fan on second speed, and radio on. Alternator is rated at 85 amps. I guess i was drawing no more than 20 amps.
    That is pretty much standard on most cars.
    You should make a trip north for a test drive.

  6. #6
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    Default Re: Alternator freewheel pulley - faster gear changes

    You just want me for my DCT lol

    Sounds like a good plan though Tolly , beers on you ?
    fq101.co.uk

  7. #7
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    Default Re: Alternator freewheel pulley - faster gear changes

    Pub is nearby but only sour beer.

  8. #8
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    Default Re: Alternator freewheel pulley - faster gear changes

    INA 535005910 is a perfect fit for any Smart 450 Cdi with Bosch alternator. No machining is required.



    Spacer under existing pulley is reused. Tightening torque 8.2 daNm. Outer groove on pulley is not used.

    Above pulley can be sourced for about 28.

  9. #9
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    Default Re: Alternator freewheel pulley - faster gear changes

    Quote Originally Posted by tolsen123 View Post
    A freewheel pulley allows the alternator to continue spinning on its own inertia whilst engine is slowing down in preparation for a gear change. This results in less load on auxiliary drive belt and faster gear changes. Some claim they also improve fuel consumption.
    Hmm. Sceptic.
    The problem here is the engine has to pick up the alternator wether it has been freewheeling or not. This means the overall energy used to run the alternator is the same, wich voids any claimed fuel savings. The gear change bit of the car does not care one bit about the speed of the alternator.
    How this freewheel thingymabob can result in faster gearchange is beyond me. What an alternator does is it makes electricity. Thats all.

    Please come back with proper numbers and some valid customer reports as you sound like JK: "some say..." and then some rubbish comes out of his mouth.


    Some things are fun. Others are not

    Frodie fancies fun over not

  10. #10
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    Default Re: Alternator freewheel pulley - faster gear changes

    I also am not convinced there is much fuel saving but will soon find out.

    As for speed of gear changes shifting up, I now have firm evidence there is an improvement. 10% increase in acceleration time going from a standstill to 80 km/h.
    Try for yourself rather than argue the opposite. Surely your alternator pulley will be years overdue for replacement so why not fit a freewheeling pulley and see for yourself?

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