Saito Fg-90R3

Despite the rapid development of electric motors, which are increasingly becoming powerful counterparts, internal combustion engines that closely mimic the sound of their full-scale inspirations continue to hold an overwhelming fascination for model enthusiasts. This is particularly true for radial engines, which impress with their unmistakable sound.

The FG90 R3 from Saito has been available from aero-naut for some time and is currently one of Saito’s most powerful radial engines. Therefore, we would like to put this engine to the test and write a short report about it here.

According to Saito, the FG 90R3, similar to the FG 60, is also derived from the FA-220 glow engine. Among other things, a petrol-compatible carburettor has been installed, and the cylinders and cylinder heads are manufactured from a single piece. The crankshaft features double ball bearings. As with the FG84 R3, large heat sinks are mounted on the housing, intended to be positioned in the propeller’s airflow to ensure optimal heat dissipation from the crankcase. The magnetic sensor appears to be the same type as on the FG60 and is mounted at an angle to the side. The exhaust outlet is directed to the rear, which means the CM6 type spark plug sits well-protected at an angle. It is almost a little too hidden, because when a ring silencer is fitted—which must be purchased separately—it becomes quite tight when attaching and locking the spark plug connector. The carburettor is again located behind the mounting plate, though this time the throttle lever has moved to the left side. However, Saito seems to have learned from the ‘grumbling’ about the FG 60 radial engine’s carburettor: this time there is the option to choke the engine from the outside. When installed, it was more than cumbersome to prime the engine with fuel on the 60 and also the 84.

For the most recent model, the FG90 R3 being tested here, Saito has also come up with a practical solution: in the centre of the throttle lever, there is a connection to the internal choke flap, which can be operated via the enclosed ‘choke stick’. To do this, a 4mm hole must be provided in the cowl and possibly the front of the engine mount when installed. To ensure the carburettor can be primed without a second person holding the choke stick in position, a collar or similar should be installed in the cowl so that the stick remains in the required position. After priming, the choke stick can be removed again. Unfortunately, servo-controlled priming is not provided. The main needle valve is located at the top right of the throttle lever, and the idle needle is arranged within the throttle lever. Choking does not, of course, adjust the idle needle, as the fitting for the choke stick is a thread directly on the throttle lever. Therefore, when readjusting the needle, the stick must be unscrewed so that the carburettor adjustment tool can be used.
In addition to the previously mentioned stick for choking, the engine also comes with the carburettor adjustment tool. Due to the wealth of information regarding the engine construction on the aero-naut website, it is not necessary to explain these points again here.