Kitfox IV
Speedster
N4JU
 

 

 

The Engine

I decided to investigate the alternative to a Rotax 912. In Spring 1999 we visited the NSI Company in Arlington, WA. After getting an eye full of their manufacturing facilities, I decided to purchase the  EA81-120-TBI including an electrically adjustable 3 bladed prop for 18'800$. Unfortunately, the economy caught up with the NSI Company and they changed hands. The new Company, MPS (Maxwell Propulsion Systems) is no longer manufacturing the engine but does offer limited technical support.

Here are some of the engine specs: 

Engine at unpacking, TOP viewThe engine arrived completely assembled and ready to be mounted. In the picture to the left, one can see the dual ignition going to one single spark plug per cylinder. The air intake with the carburetor is on the left.

Engine Type:             EA81-120-TBI

Serial Number:          # 448807

Engine type:              4 stroke, automotive gas

Ignition:                      single spark plug, dual ignition

Power:                        approx. 110 HP

Carburetor:                ELLISON EFS-2 throttle bony, injector

Cooling:                      Water + oil cooler

Propeller:                    CAP 140 (3 blade, cockpit adjustable)

Engine speeds:        idle :  1500 RPM

                                      norm, 3500 RPM

                                      max    6000 RPM

Propeller reduction gear:           1 : 2.8

Engine at unpacking, from below and leftEngine rearThe muffler with the pre-heater air intake is under the engine. The planetary reduction gear reverses the propeller direction (counter clockwise seen from the cockpit). The gear is equipped with a clutch to allow the propeller to spin freely when the engine quits.

On the rear the V-belt driving the alternator and the water pump can be seen. This engine also has a direct take off shaft from the crankshaft where I attached a vacuum pump for some of the instruments.

The tan colored tank on top is the oil reservoir which in principle,  should assist the cooling of the oil. However, I found that an extra oil cooler was necessary, especially when climbing at higher altitudes.

Installed engine, right sideMounted engine from the lest sideThe picture to the left shows the engine mounted to the fire wall with the power and some of the control cables passing through from the cockpit. Under the engine is the water cooler and under the propeller reduction gear is the oil cooler. As I had felt, the alternator was trapped in the back and could be subject to higher temperatures, so I installed an air duct to direct ram air to the alternator. Since this is a car engine requiring electrical power for producing the spark, a healthy alternator is essential.

The picture on the right shows the fuel line with the strainer and the rising line feeding the carburetor.  In the picture -  below right -  the vacuum pump is visible. All the piping in the engine compartment is of race car quality.

Fuel line with tank shut off valveMounted engine from the left and above

 

The first fuel line installations proved to be inadequate as the automotive fuel had many additives which started to dissolve or disintegrate the hose and seals. Therefore I  replaced most of the material with racecar quality material.

Propeller hub with geared electrical drive forpropeller adjustment Rear part of propeller hub with transmitter-controller Commuter rings for propeller pitch controll

The propeller hub houses a geared electrical servo motor that adjusts the pitch of the propeller. The pitch can be run from +27 degrees to -27 degrees. The option of negative pitch was chosen to have the possibility of operating the Kitfox on floats.

The gear shaft drives a potentiometer which sends a coded signal through the commutator rings to the cockpit control unit.

Aircraft with ainstalled engine and cowling

Finally all the elements belonging to the engine were installed and could be tested!

The next web pages will deal with the cockpit side of the engine and the avionics.

 

Links to various Kitfox related sources:

 

NSI-Subaru Engine Interest  groups: ....................................................

 

 

 

Maxwell Propulsion Systems, Inc.:  successor of NSI .....................

19132 59th Drive NE, Arlington, WA 98223    ph:(360) 474-8118

 

Kitfox Aircraft LLC ......................................................................................

 

Kitfox Mail Browser ....................................................................................

 

 

 

http://groups.yahoo.com/group/airsoob/

nsig@yahoogroups.com

http://sportplanellc.com

 

http://www.maxwellpropulsion.com

 

 

http://www.kitfoxaircraft.com/

 

http://www.matronics.com/browse/kitfox-list/

 

For further information select from the directory at the top right

Contact address is   My.Sky2fly@gmail.com

This page was last maintained 2.9.2008