Just out of curiosity, do many people use a carb setup on their
 aviation Wankel's

 Figured I'd ask since I've seen a few questions
 regarding the standalone ecu for fi and not much regarding getting
 a carb on the 13B (assuming most people use 13B's.)

 Vlad

 Not many. There may be one or two. The fact is an aviation carb
 is as much money as a fuel injection system. I think Ken Welter
 uses a 48 mm Weber carb. Webers cost over $1000 and are not easily leaned.
 Two 48 mm Mikunis might be had for less than about $750 total.

 Paul Lamar


 This is going to sound ignorant but I have to ask anyway.
 Why not use auto carbs? Last I checked Edelbrocks were
 about $300 shipped from Summit/Jegs.
 Vlad

 Well you can but they cannot be leaned at altitude.
 That is essential for low fuel burn.
 For awhile there there was a remote leaning kit available for
 Holly  four barrel carbs. I don't know if that is still
 available.

 Paul Lamar

 Hi Paul,
 Just an off-the-wall thought for your comments. Can a standard
 auto carb sit atop a pipe with an adjustable window downstream
 of the carb? Similar to the way a propane oven burner or bar-b-que
 burner mixes air with the propane gas. At sea level the window
 is closed, and all air goes into the engine thru the carb and the
 venturi does it's thing. At altitude, the window in the pipe
 downstream of the carb is progressively opened allowing air to
 enter, thus less air thru the carb. Less air thru the carb would
 equal less gasoline sucked in by the venturi and a leaner mixture
 arrives at the engine. This approach would "lean" the mixture by
 admitting more air rather than less gasoline. I'm probably missing
 something obvious, if this were so simple it would have been done
 years ago by aeroengine manufacturers  : )  Any thoughts?   Dave M


 ------------------------------------------
 Yes that might work but you might also loose fuel through the window
 as the pressure in the intake pipe goes below and above atmospheric
 pressure
 on a regular basis per rev.

 Ken Welter was fooling around with dynamic pressure effect
 leaning. I never really figured out how his idea worked.

 Unlike a car an airplane is always going at least 100 MPH so dynamic
 pressure will be above static atmospheric pressure. If you feed
 that from a forward facing scoop through a pipe and some sort of
 valve into the intake pipe below the carbs that MIGHT work with
 no loss of fuel. At 100 MPH at sea level dynamic pressure is
 .18 psi. Not much compared to the pressure variations in the intake
 manifold that are probably on the order of  +/- several psi above and below
 atmos.. You would need a rather long pipe from the scoop to retain the
 fuel vapor on average. It might also screw up the tuning if it were
 beyond a certain size. A very short non tuned manifold like Ken was
 using may have helped.

 Another possibility is to just bypass the carb to the carefully designed
 and sealed ram air box so any accumulated raw fuel drains
 back through the the carb into the engine. That may or may not lean the
 engine. It would be interesting to fool around with this.

 Unfortunately our main man doing R&D making automotive carbs
 work in aircraft was Don Dunbar. Recently deceased God rest his soul.
 His plan was to copy Revmaster and remove the float bowl from the
 bottom of a Mikuni carb and control the pressure of the fuel at the needle
 valve orifice with a manual valve. It works for Revmaster. Dave McCandless
 might be taking up the quest for his Rotec radial in his Funk.

 RevMaster/Mikuni 40 mm carbs are a bit small for a rotary so the larger
 motor cycle 48 mm Mikuni could be modified in the same way.

 Paul Lamar

I think a much easier way to do mixture control on a holley (or any similar
downdraft carb) is to mess around with the float level in the carb..
Lowering the level of fuel in the float chamber causes leaner mixture while
raising it enriches.  How about a device which raises or lowers the height
of the float valve seat via a cockpit actuated control lever?


Matt-

Well yes and no. Some are easier than others. Here are some ideas.
I guess one could make an entirely new float bowl for the Mikuni.
It might have some market besides aircraft like Harley for better
mpg :)

Paul Lamar