Paul

I see a lot of manifolds online that will fit the 13b that are for carburetor use.
 Is it a good or bad idea to use say an ellison TB or (Marvell Shebler?) carb?
My thinking is less fuel preassure less plumbing everything seems

easier from

what I understand the fuel burn difference is only .5 in favor of F/I. I really
think I could've had my motor running months ago if I didn't have to fight with
the F/I manifold and fuel rails and injectors. Lets say I where to go that rout
would I not simply need a good ignition system and a redrive? what about boiling
the fuel in the bowl or do aircraft style carbs not work that way?

Tony

There is a lot to be said for using an aircraft carb that can be

leaned

at altitude on a rotary. You have mentioned several of those

factors.

We were having lunch up in Bishop with the bunch that showed up
to help Dave get the wings off. One person asked me what was the
most reliable rotary system one could install. I said an aircraft

carb

and a couple of magnetos :)

Ken Welter has been flying Weber carbs for years.

Hans

    Yes I have been flying for over 1300 hrs on Weber and I fly
regularly at high altitude as I live in the Northwest where there are
lot on mountain.
   The reason I like a carb is that it is simple, just hook up a
fuel line and a throttle cable and go fly.
   There are a couple of ways to lean the mixture on a carb. What you
need to do is create a pressure differential between the float bowl
and the Venturi. There is a way that is used on snowmobiles that uses
bleed air from intake vacuum to do this.  The way I did it is with
a controllable air ram. When the air ram is closed all the air is
drawn through the air cleaner shown in this photo. When the air ram
is opened it creates a higher pressure on the Venturi then on the
float
bowl as the float bowl vents are on the side of the velocity stacks
and the air ram shoves the air strait into them as the ram tubes are
positioned about an inch from the velocity stacks.
   Also note that I flew for about 400 hrs without any
mixture control on the Weber. With a high tech carb such as a Weber
with multiple air correction circuits compared to a crude antique
carb such as an aircraft carb the Weber can sense the thinner air and
deliver less fuel so less manual adjustment is needed.
   Also I don't think there is any way an aircraft carb will deliver
the airflow needed with a smooth power band. I have used a 51mm Weber
for about 100 hrs but am now running a 48mm. For all out power the 51
is best but the 48 has a smother power band and is less altitude
sensitive so I would probably suggest it for most applications.
   Ken Welter


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OK,  All this time I've been heading toward EFI, Now I'm hearing EFI is
perhaps not a good choice.  So here is my question to all.  What are the
major problems with the plumbing?  Should a certain material be used for
the plumbing?  Paul why is it you stated the homebuilder probably can't
make a reliable plumbing system for the high pressure EFI system?  T.W.


----------------------------------------------------------
He can make it all right. It is designing it seems to be
a problem. In other words making decision on where to put what
seems to be the problem. Fuel pumps, selector valves, vents, etc.. If you
are installing a Lycoming those decisions are made for you. Each type
of airplane is different so therein lies the problem. High pressure
EFI fuel systems are not as easy as they look. People make big mistakes.
The other thing is high pressure pumps suck a lot of amps.
Too bad they are not as good on sucking fuel :)
So now the electrical system becomes slightly more important.

On the other hand low pressure none return carburetor fuel
systems are pretty straight forward. The low pressure electric
pumps are not finicky and have been around for decades. It
is also possible to get a mechanical fuel pump without too much
trouble. The old diaphragm mechanical pumps were positive
displacement and would suck the chrome off a bumper.

In effect the carb float bowl acts like a small fuel sump and
covers a few sins.

Now what kind of airplane are you building?

BTW one of the reasons the crash rate is higher for low wing
airplanes is fuel management by the pilot is more complicated
in low wing airplanes.

Paul Lamar ...No rotor no motor.

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