We basically have 8 engine models from 97-200hp. These ratings are at redline, so realistically the range is more like 85-185hp. We have four 4 cylinder engines; 260i, 260iS, 350i, and 350iS. And four 6 cylinder engines; 390i, 390iS, 520i, and 520iS. These come in different variations (e.g. aerobatic, helicopter, reverse rotating, vertical mount).
The model number reflects the displacement in liters (e.g. 350 is 3.5 liters). The "i" models are a lower compression, and the "iS" models are a higher compression. The only difference is the piston and the fuel mapping.
The 260 and 390 have a shorter stroke and are therefore almost 4 inches narrower than the 350 and 520.
The 350iS and 520iS are the most popular in the United States so we will discuss them in greater detail lower on this page.
Engine Control Unit (ECU)
All of our engines are direct drive, air cooled and FADEC (Full Authority Digital Engine Control), and have multi-point fuel injection and dual electronic ignition.
An ECU, such as the one pictured above, receives information from various sensors and it then controls the mixture and timing from start-up to shut-down.
As a result, in the cockpit, there is no choke, no primer, no carb heat, and no mixture; just a throttle.
As seen in the following video this is a definite bonus on "hot" starts. Normally fuel injected engines are very difficult to start when the engine is warm.
The UL520iS engine is a popular choice in larger or higher performance homebuilt aircraft. It is a common alternative to historic 160-180hp airplane engines because it has more power and less weight.