The Saito FA-40a Golden Knight.

Well, they've done it again! As expansive as the Saito line of engines is, the folks at Horizon are constantly working to fill any gaps in the engine-displacement lineup. Their new .40 4-stroke fills the slot between the .30 and the .50-size engines and provides an additional option for .30 to .50-size planes. In addition to offering a complete line of 4-stroke engines, the Horizon engineers also raise the power-to-weight ratios of each new engine. They did it well with the FA-100 that I reviewed in March 2003 in Model Airplane News, and they now have a similar power-to-weight-ratio success with the new FA-40a.

The FA-40a has nearly the same mounting dimensions as the FA-30, so the larger engine can easily replace a .30 in an existing model with a little rework. This isn't a bored-out .30; the dimensions and specs of this new design fall between those of the .30 and .50. With a power increase of 30 percent more than the .30, but a weight increase of only 15 percent, the 40a boasts quite a power-to-weight-ratio improvement!

I was curious what the "a" in 40a represents, so I asked. Horizon says it's just a revision letter from the development process and doesn't have any real significance for the modeler.

NOT JUST ANOTHER PRETTY FACE
I tested the FA-40a GK (Golden Knight) version for this review and wanted to know what the difference (if any) in engine performance would be with a black finish. After intensive research (one phone call to one of Horizon's helpful specialists), I confirmed my suspicion: the pretty black and gold finish gives an aesthetic advantage only. It's nice that Horizon continues to offer modelers a choice.

FEATURES OF NOTE
The engine incorporates the new cam housing design of other recent releases, such as the FA-100. Horizon says this weight savings contributes to the improved power-to-weight ratio. In addition, the crankcase vent is now in the side of the cam housing. This change increases lubrication of the cam, bearings, shaft and the valve lifters. Saito uses bronze bushings riding on a steel shaft for cam support as a general feature, whereas other brands, to my knowledge, use ball bearings. Both designs require good lubrication.

The muffler elbow joint can be adjusted to a variety of positions to match your engine-compartment space. Notice that the muffler pressure fitting is now at the muffler's outlet end. This allows easy access to the vent line when you want to remove it to refuel.

Another feature I've noticed in recently released engines is the location of the muffler pressure fitting near the outlet end of the muffler. That isn't a big deal, but the pressure hose is now visibly exposed and out in the airstream. I suspect that the designers used the pressure fitting to help retain the end plug and to take advantage of the muffler's extra thickness near the outlet to help secure the fitting. One advantage of this location for the pressure fitting is that the modeler has easy access for removing the vent line during refueling. I would consider moving it near the inlet and then installing a screw plug in the vacant hole or replacing the fitting with one of a right-angle design. Modelers just have to mess with things, you know!

The FA-40a muffler elbow is interesting. You can use it in a variety of positions and angles depending on engine-compartment space. I would have liked to see wrenching flats on the muffler body to aid in tightening the muffler to the elbow or engine. To prevent gouging, I used pliers with a soft piece of aluminum flashing wrapped around the muffler end.

The 1.4-inch prop shaft on the FA-40a; its diameter fits most props in the .40 range, and this eliminates the need to ream out the prop holes. The double-locking nuts are a great safety feature (usually found on the larger engines).

Most props in this size range will fit the 1.4-inch prop shaft, and that eliminates the need for reaming out or shimming props. The double-locking prop nut, usually found on larger 4-strokers, is a great safety feature on the FA-40a.

Other high-value design features include the AAC construction (aluminum piston, aluminum cylinder, chromed cylinder) and the one-piece head/cylinder.