O.S. Engines FS-91 II FI - Manual (Page 5)

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This is the FS-91S -FI (fuel injection) engine equipped with a
revolutionary fuel supply system that was jointly developed by Futaba, a
manufacturer of Radio control equipment, and O.S. Engines, a
manufacturer of model engines.
This system detects engine speed with a sensor based on throttle
signals transmitted from a transmitter. It then determines the fuel
injection volume based on the required amount of fuel to be supplied for
that engine speed as calculated by an electronic control unit (EC-291S -FI>) referred to as the "EC-2", after which fuel is injected into the
engine from an injector. In addition, adjustments can also be made using
dial on the transmitter. The result is an engine for sport models that
features excellent engine speed linearity relative to throttle operation
under all types of flight conditions.
INTRODUCTION
FEATURES
Supplies the Proper Amount of Fuel at all Times
Easier starting
Greater stability during idling
Excellent linearity and response relative to stick operation.
Simple Adjustment Using Dials on the Transmitter
Air-fuel mixture at medium and high speeds can be safety and easily adjusted
from the transmitter.
Adjustments can be made while on the ground and during flight.
Stable Supply of Fuel at all Times
Pressurized fuel is controlled at a constant pressure with respect to all types of
movement during flight allowing stable engine performance at all times.
Light Weight and Easy Installation
The sensor and injector mounted on the engine are both compact and
lightweight, while the electronic control unit (EC-2) is also lightweight, enabling
various connections to be made easily the same as plugging in a servo.