Most Long-Eze builders consider fuel economy to be a very important feature of their
unique aircraft. Installation of the Ellison Throttle Body Injector can increase fuel
mileage by as much as 10% over the stock Marvel carburetor. The efficiency of the Ellison
Throttle Body Injector was proven every year that the CAFE 400 comparative aircraft flight
efficiency competition was held. In its last five years, the winning aircraft in the
2 seat experimental category were equipped with Ellison Throttle Body Injectors.
Airbox Design and Airframe Modifications
Careful planning of your throttle body injector installation will result in maximum
performance and economy. The original intake air plumbing called out by the Long Eze plans
is quite restrictive. Dynamometer tests have shown the original intake plumbing to reduce
the 0-235 engine power output by 8 horsepower. Re-designing the air intake system
increases engine power output by reducing flow losses and allows the installation of a
more aerodynamic cowl. Click on inlet airbox for specific
information relating to the design of this important induction system component.
When updating a Marvel Schebler equipped aircraft with the Ellison Throttle Body
Injector a few changes to the airframe are necessary. First, because the throttle
friction of the Throttle Body Injector is substantially higher than that of the Marvel
carburetor, the pull wire and spring type throttle and mixture cables must be replaced
with push pull type cables. Also, the elbow which is normally used on the air inlet
flange of the Marvel carburetor is not compatible with the Throttle Body Injector. This is
because the TBI requires smooth, uniform air, flowing past the fuel metering tube, which
is not available when the air is forced through a right angle turn by the plans specified
elbow. This results in rough engine operation at wide open throttle. The solution to this
problem is to design an airbox which allows air to enter the TBI from all sides.
When the throttle body draws its air from a large volume of still air, good
fuel metering results. Click on inlet airbox for
information on the design of this important induction system component.
If you have a Long Eze with the "male" cooling air intake, there is plenty of
room for a good airbox design. If you have a NACA Scoop for the cooling air intake, there
may be little room for a good air inlet to the throttle body. To gain much needed cowl
clearance, Ellison Fluid Systems, Inc. has designed a
box which mounts to the standard Lycoming updraft sump and allows the TBI to be
mounted in a side draft configuration. This plenum box gives excellent fuel distribution
resulting in maximum fuel economy. The use of the plenum box provides about 3 inches more
cowl clearance than a standard Throttle Body/airbox combination. Also, intake airbox
design is now simplified because the induction air no longer has to make a 90 degree turn
before entering the TBI. The use of the TBI and the plenum box allows for the installation
of a tighter, more aerodynamic, cowl which would not be possible with the standard Marvel
carburetor installed. There are however, disadvantages to using the plenum box which can
be reviewed by clicking
On Long Eze aircraft, TBI
activates the throttle in a spanwise direction will generally yield better performance
than one in which the slide moves fore and aft.
See comments related to fuel filtration
and primer suggestions when planning a TBI installation
on an Long Eze aircraft.
Although it is always important to design the fuel system to minimize the chance of
vapor formation, the Long Eze with its up draft cooling
makes this job very easy because all of the fuel system components in the engine
compartment are surrounded by cold air.
Up draft cooling exacerbates the potential for
and induction ice, making the requirement for a well designed carburetor heat system
even more critical.