HAC4 Pwr Algorithm = JUNK????

Discussion in 'Cycling Training' started by allanw, Sep 10, 2004.

  1. allanw

    allanw New Member

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    I've been using my HAC4 for 4-6wks now and it seemed that my power output was low (avg ~100watts) even though my performance was med/high (21-23mph avg on flat @ 240lbs rider+bike+equipment). I went to the analytic cycling page and based on my numbers I should be registering ~300 watts, far from the ~100 the HAC4 is telling me about.



    So then I opened this poll to see if I was alone

    http://www.cyclingforums.com/t175831.html

    turns out there looks to be two groups. One group down around 100ish and the second up around 2-300. Very weird...



    I blame the HAC4 algorithm's dependency on altitude gain, it seems if your not gaining altitude you can't exceed 100 watts easily even at 21mph @ 240lbs on the flat/slight incline (<2%).



    Anybody else???
     
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  2. ric_stern/RST

    ric_stern/RST New Member

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    it won't be anywhere near accurate for level ground cycling or even going uphill if you're going quite fast (probably need to be going uphill at less than 20 km/hr for it to approach reasonable accuracy)

    ric
     
  3. EricN

    EricN New Member

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    Yep mine is not even close to accurate and I know for a fact that I have all my info entered in correctly. If you want to use power to train I'd suggest getting a real power meter, however the HAC4 is an awesome cyclocomputer aside from the power estimation.
     
  4. franco1

    franco1 New Member

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    I've compared mine to a SRM and it gave me the same values as what he had.
    We rode next to each other with the same gears and speed.
     
  5. ric_stern/RST

    ric_stern/RST New Member

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    it must've been pure luck then as it's highly unlikely the HAC4 can be accurate (especially on flat roads)

    ric
     
  6. franco1

    franco1 New Member

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    Yes it was on a climb when we compared it, and never again.
    But if you train using your hac read out and you see improvement on it say in 2 weeks time then I guess its ok using it as a guide line. Obviously if you want accurate reading then you will have to spend that extra money.

    I just thought it was good value for money.
     
  7. ric_stern/RST

    ric_stern/RST New Member

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    it's likely to be reasonably accurate on climbs, however, it's possible to calculate power to about the same accuracy with a calculator for hills when you get home.

    ric
     
  8. xbgs351

    xbgs351 New Member

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    I blame the HAC4 algorithm's dependency on altitude gain, it seems if your not gaining altitude you can't exceed 100 watts easily even at 21mph @ 240lbs on the flat/slight incline (<2%).

    Don't blame the algorith, just understand how it works.
     
  9. vitiris

    vitiris New Member

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    I live in a fairly (read very) hilly area in SW England. I find the HAC4 power reading to be great and ride with it on most of the time (cadence on the flat). The reading is very consistent on grades of 3-4% upwards but there is a time lag involved. It certainly lets you know if you are slacking! If it rains forget it, I have achieved some amazing power outputs when rain gets into the little sensor holes on the side :D

    Sean
     
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