Hi all and seasons greetings,

I got my self one of those cheap copy tiny tachs off ebay a few weeks ago...tested it out on my DCDI 503 fitted to my trike a few days ago....I was surprised that it indicates that my small Westach analogue gauge is under reading around 160rpm,

What worries me is that I thought my trike tach was over reading by around 5%....indicating a take off RPM of 6900rpm...so it may accentually be hitting 7000rpm + on take-off, if this new digi tack is to be believed,

I also did a quick reading with my hand held laser tach which is what I originally set my RPM with...and the reading I got from that agrees with the digi tach....I tried the same duel test with my wife car...both gauges inc within 10rpm of each other on that so I think they are both accurate,

Only been able to test my trike RPM to 3000rpm at the moment...I will try a full power test over the w/e if it stops rain here in the UK,

This engine has only run for 30 from new...bought it last summer...one of the last available here in the UK,

So if it was hitting 7000rpm could I have done any harm...and what max RPM should I set it to....the Rotax manual stating 6800 take off max 5 mins...but all my buddy's say 6500rpm max,

What do you guys think it should be.

  • Re: What should I set my max RPM to 503.

    by » 11 years ago

    Well Nick,

    I assume you've had a drink or two to ask for a jolly chap's off the cuff opinion when the free and easy to find Rotax Manual is gospel.

    Rotax 503 = 6,800 rpm for 5 min's then you're permitted 6,500 for the rest of the day.

    [Perhaps what you want is someone's O.K. to carry on, having apparently found out you busted the rpm speed limit. If the prop is the correct one I have always thought WOT was held to max permitted rev's.]

    Happy New Year,

    mike hallam also wondering when the field will ever turn from a muddy bog back into an airstrip !

  • Re: What should I set my max RPM to 503.

    by » 11 years ago

    Hi Mike...I suppose I'm just wondering what other folk set there's to....as you say Rotx say take off speed 6800 for 5 mins...but everybody I asked when I first set the motor up last summer say aim for 6500 max,

    P.S. I got around to testing the static RPM on the ground today...the tiny tach and the a/c tach both ind 6400rpm...so fingers crossed I may not have over revved it,

    So my next move is to see what I get in flight...if it ever stops raining....

  • Re: What should I set my max RPM to 503.

    by » 11 years ago

    Hi Nick - 6800 is your never exceed WOT (in level flight) RPM, max duration is 5 minutes. 6500 is your maximum sustained RPM. In my plane 6250 static gives me 6550 on climb out and just under 6800 WOT in level flight. Cruise RPM for fuel economy and engine longevity is at about 80% power which on the 503 is 5700 RPM if your WOT is set properly. What you describe sounds like your pitch is a little fine.


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