REFLECTOR: It's been really quiet this week

Tue Feb 18 09:54:40 CST 2014

I'm with you John... Aerosparks never recommends more then 25 degrees BTDC , below 12,000 ft.

Steve 

Date: Tue, 18 Feb 2014 08:51:13 -0600
From: aminetech at bluefrog.com
To: reflector at tvbf.org
Subject: Re: REFLECTOR: It's been really quiet this week

    On 2/17/2014 11:44 AM, Brian Michalk
      wrote:

      I've been flight testing.  It's a
        slow process for me, since my engine design while Franklin
        based, has EFI and EI.

        I have been battling high CHT's even in the cooler weather, and
        am seeing positive results as the engine breaks in.

    Sorry for repeating myself, but I really think you need to reduce
    the timing advance to 24-25 degrees.  My anecdotal experience has
    been that any departure from the mag/massive electrode combination
    increases the detonation tendency for the Franklin engine.  Further,
    multiple changes compound the problem.  When I bought my plane it
    had one mag and one EI, both using massive electrode plugs.  I
    experienced minor detonation symptoms such as an occasional plug
    fouled with metal and an occasional high CHT.  When I switched to
    auto plugs for the EI, the symptoms worsened with more frequent plug
    fouling, erosion of the electrode and an occasional engine stumble
    right after takeoff, a real attention getter.  When I switched the
    mag plugs to fine wire, the engine stumbling became more frequent
    and I had to replace a cylinder and piston due to severe pitting.  I
    have eliminated the symptoms by reducing the timing advance.  I
    manually increase the EI advance once I'm above 9k for max power. 
    Maybe Mike W will comment also.

    John

        Specifically, I've been testing the forward CG limits, and have
        decided that my decision to move equipment as far forward as
        possible was a bad one.  I was intending to have Juanita be able
        to fly the airplane without ballast, but with my weight, I can't
        really carry much in the copilot seat.  I mounted a big Optima
        Red Top at a 15 inch arm location.  This weekend I relocated it
        temporarily to just forward of the whales tail, but for a
        permanent solution, I am looking at some of the really
        lightweight batteries that are out there, and am having a hard
        time making up my mind.

        Option 1: some lightweight lead/acid battery

        Option 2: an alternative chemistry

        For option 1, John mentioned the Braille batteries.  I looked
        online, and people seem to think that Braille is stretching
        their performance numbers, but if Velocity is using them, then
        that's a pretty good endorsement.  There are also Odyssey
        batteries that look pretty good as well.

        Option 2 for me would be the new LiFe (Lithium Iron) batteries
        that are used in some motorcycles, snowmobiles and jet skis. 
        Those are all pretty high vibration environments, which was my
        first concern.  Next, they are really incredibly lightweight.

        Now, when these batteries reach 13 volts, they are basically
        dead, with 30% capacity remaining.  They are fully charged at
        14.3 volts, and appear to take a charging voltage up to 15
        volts.  For me, I'd need to convert my internal regulated
        alternator to external, and bump up the voltage to accommodate
        these new batteries.

        Another down side is, like the LiPo batteries, these need to
        have the cells balanced.  There is a special connector that
        ensures all of the cells are charged to their proper voltage,
        but balancing a battery doesn't have to be performed for every
        charge.  I also think that rather than charging through the
        balancing port, a person could use a hobby grade balancer that
        places a load on cells to draw down their voltage, achieving the
        same goal.  Bulk charge through the terminals, then balance by
        discharging excess capacity.

        And another downside is that they like to be stored at something
        like 80% capacity.  This may be fine for our needs.  As long as
        they can start the plane, they can be charged at high currents,
        so within a few minutes after starting they would be at 100%.

        Okay.  For one final upside:  The higher operating voltage will
        spin a prop faster, and will have smaller voltage drop in your
        cables.  I'm solid state switching, losing a couple of tenths of
        volts across each solid state relay.  This bump up in voltage
        would really be nice for my electric gyros, which are always
        complaining about low voltage until I bring up the engine RPM's.

        LFX19A4-BS12MSRP:
            $199.95 
        SHORAI LFX Lithium-ion Powersports battery,19AH 12V, "A"
        polarity, Case Type 4

        Length 5.83" 

        Width 3.39"

        Height 3.46"

        Weight 2.32lbs

        CCA 285amps

        I would need two of those, which would put me at the lower end
        of my CCA requirements.

        www.shoraipower.com

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