>>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


----------------------------------

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

In my last e-mail to you I asked about motorcycle fuel injection systems
these are very compact and are being used on bikes with as much as 180hp.
would these be any better or worse than the current injection system we
have now? I think we can simply use our injectors for the Mazda. But why
would you? these already handle N/A 13b horsepower does it use the same
type pumps and the same psi? I know your not a motorcycle mechanic so
I'm only asking if all injection is created equal.

Tony

I think it is. That plumbing is an accident waiting to happen
on an aircraft engine.

Paul Lamar ...No rotor no motor.


Tony
Looks to me that it is no different then what is on the Mazda, except it
appears that there is only a single injector per intake as compared to the
Mazda which has two per rotor. It also looks like there is a pressure
regulator on the fuel rail. Why would you want to go to a carb with the
potential for carburetor icing when you can use FI, which is pretty much
immune from it.

Lets look at facts:
Auto:             single fuel tank and single pump (Carb or FI)
Airplane:             two or more tanks and dual pumps (Carb or
FI)
                With two tanks, the pilot has to manage the
fuel.
High Wing Airplane:     Fuel can gravity feed from either wing (still have
engine pump and boost pump).
Low wing airplane:     Fuel must be able to gravity feed from either wing
to fuel selector and pump/s.
Filter:             Before pumps to protect pumps from water and
debris                 (Carb or FI)
FI:                 Requires high pressure fuel to atomize in
injectors
                Requires return line to take excess fuel
back to                 tank. It is strongly suggested that
it is the same                 tank as the feed tank.
                Requires a small bleed line between fuel
rail intake                 and the return line to allow the
high pressure pump                 to purge air from the system
if you run a tank dry.

I was flying a Piper Comanche 250 to the First Flight celebration at Kitty
Hawk NC and wondered why my airspeed was getting lower and lower in cruise.
Weather was overcast, with visibility of 15 miles. Finally woke up and
applied carburetor heat and, guess what, the airspeed returned. The engine
was a Lycoming 0-540 with no carburetor temperature gauge. Would much prefer
a IO-540, but that came later in production.

So you can see there is not much difference between the two systems. As Paul
has stated, the problem is in the execution of the design. Even if you had
just one tank, there would still be people who would run out of fuel. You
have a lot of support out here, if you have a question, put it on the list
and sort through the suggestions you get back. It is your airplane and your
engine and systems. Just make sure that it is properly executed.

Giff Marr
L-IVP/20B 45%
    

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