It's a no need!
Regards Gert
Gert Dalgaard Soerensen
Stabelvej 9, Haarby
DK 8660 Skanderborg
Denmark
Europa builder No. 151
Europa Classic / Rotax 914
AC reg.: OY-GDS
Phone.: +45 8695 0595
E mail: lgds@post6.tele.dk
http://home19.inet.tele.dk/dalgaard/oygds.jpeg
http://www.oy-reg.dk/billeder/l613.jpg
Den 24/05/2005 kl. 18.29 skrev Ronald J. Parigoris:
> <rparigor@suffolk.lib.ny.us>
>
> Is anyone flying with a mixture control for 914? How are you doing
> it, how
> does it perform?
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> I am about done for a while studying up on 914. Unless someone
> convinces
> me otherwise, I will install a mixture control of sorts.
>
> Instruments I have:
> 2 UMA EGTs, one for left side and 1 for right
> 1 CHT but with switch to measure left and right
> Split Second O2 monitor, pretty slick readout with a number of LEDs at
> center is Lambda of 1. They mapped the O2 sensor they use quite
> extensive,
> so i am pretty certain it will give more information than just being a
> switch, like most 3 wire O2 sensors are used on cars.
>
> OK Mixture control. simple, change pressure going to the float bowl! 1
> switch, 1 knob, 3 LEDs.
>
> The 914 is turbocharged. When operated with MP under ambient, you
> could
> vent the float bowl to atmosphere. OK until you raise the MP over
> ambient.
> At that point you would begin to spew out the overflow and no fuel
> would
> be flowing into the manifold, it would go the other way. Rotax
> engineers
> most of the time connect the float bowls to airbox pressure. The
> carbs
> are adjusted to work using airbox pressure as a constant.
>
> Side Note, it is absolute critical that you have a good no leak
> free flow
> connection to this connection, as well as the airbox to fuel pressure
> regulator OR ELSE!!
>
> Now when you go over approx. 100% power, the ECU looks for combo of
> certain RPM and MP to determine that in fact you are making some heat.
> Once it determines this, it then switches the plumbing from airbox
> pressure to above airbox pressure. The way it does this is there is
> a 12
> volt 3 connection switch/solonoid. Output goes to float bowls,
> there are 2
> inputs, 1 from airbox normal pressure, 1 from a portion of airbox that
> gets hit with impact air and is in fact over airbox normal.
>
> First off i will have a 2 position DPDT switch. 1 position will be
> Auto
> Rich where in fact ECU controls Rich, and the second position will be
> Rich, where in fact it will be rich all the time. First off Rich
> Mixture
> is much more desirable than lean. So manual rich can be used to
> determine
> if rich of peak EGT, can probably be used to help cool down a hot
> motor
> and can be used in conjunction with choke to get you to a safe
> place if
> any number of things happens that causes a lean mixture. Also if
> for any
> reason my Lean control fails for any reason, by selecting Rich it will
> take it out of the circuit. The Lambda display wants things when
> making
> some heat at full scale rich, or 1 LED less.
>
> Will have a Blue LED come on when ECU is asking Solenoid to come
> on, and
> will have another flashing Blue come on when Rich is selected.
>
> Now for lean. Even though the Bing type 64 is somewhat altitude
> compensating, and does even a little better if turbocharged, none
> the less
> when you fly in thin air, the thinner the air gets, the richer
> things run.
> OK. Concept is since when you increase pressure to float bowl it gets
> richer, then if you decrease, it will get leaner. Now this is a
> turbo, so
> to have a chance at some sort of linear control, you need to have some
> means of a lower than airbox pressure that is constant changing
> with the
> airbox pressure. Not just vent or intake from atmosphere. I will plumb
> into the balance tubes between the cylinders. This is MP, that from
> what i
> am told (I have yet to test) is about 1 inch below airbox pressure. So
> concept is to T the airbox line going to the Airbox normal side of
> the 3
> way solenoid/switch. Connect the extra nipple to a pilot controlled
> valve
> that then goes to the MP Balance tube. In other words leak some
> pressure
> to the Manifold (Which BTW also leans things out, will be limited
> volume
> though). Now if you hit Rich button it bypasses this in event of a
> problem. I have all stuff to do a ground test, and after test can
> determine what size of restrictor to install on MP leak so just
> enough can
> be allowed to leak. I will have a blinking Red LED situated so the
> knob
> extension will cover the LED when it is in Normal (richest position
> it can
> get). This way if Auto Rich or Rich is asking for rich, then the
> red LED
> will begin to get bright and flash. If not in Normal it will get your
> attention. Other times the Red LED will glow dimly.
>
> There you have it.
>
> 1 switch, 1 knob, 3 LEDs.
>
> Testing before I install lean control in panel will determine just how
> well it works, and if leak serious affects my MP gauge reading, and
> just
> how much the leak leans out due to pushing extra air downwind of
> carbs.
>
> No matter what will install Rich button. I scratch built a ~ 7,500HP
> Carburetor (A 30,000,000 BTU) hot air balloon burner in 1985 that
> is still
> flyin my machine, making this smaller task pay attention
> superficial seems
> to be a PIECE OF CAKE.
>
> (famous last words, overheated cylinders, melted/broken pistons,
> trashed
> gearbox, warped exhaust, seized turbo and bent connecting rods with
> extra
> venting in the crankcase on a new motor that didn't even fly yet.)
>
> Ron Parigoris
>
>
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