ULPower makes horizontally-opposed 4 and 6 cylinder engines.

There is the horizontally opposed 4-cylinder engine with multi-point fuel injection and electronic ignition system with the addition of variable spark gap based on engine speed.

“UL Power 260i”

-The UL-260i is a 4-stroke, 95/100 HP, 2592 cc engine with direct propeller output.

“UL-260i”

-This illustration shows the UL-260i engine in a scaled-down WWI aircraft replica.

From Appendix 9: New, more powerful models have recently been added to the well-known engines for light aircraft, VLAs, ultralights, and homebuilt aircraft.

-The four-cylinder UL390i, giving 140 HP

-The four-cylinder UL390is, giving 160 HP

-And the more powerful UL520i, with 180 HP and six horizontally-opposed cylinders.

-Along with the UL520iS, with 200 HP, a six-cylinder engine derived from the previous model.

“UL520i”

"UL520i dimensions"

"Mobile test bench for the UL"

From Appendix 10: Review of this brand's engine range in mid-2016:

-The 260i, with 82-97 HP depending on the engine speed (2800 or 3300 rpm), with four horizontal cylinders and a four-stroke engine.

-The 260iS, with 95-107 HP at the same rpm as the previous model. The compression ratio has been changed, rising from 8.16:1 to 9.1:1, with the same dimensions and weight (72 kg).

"A UL Power horizontally-opposed four-cylinder engine"

-The new 350i and 350iS with 118 and 130 maximum HP, respectively. They are four-cylinder engines.

-The six-cylinder 390i and 390iS engines that give 140 and 160 HP.

“UL 520 horizontally-opposed six-cylinder engine”

-The 520i and 520iS give 180 and 200 HP respectively.

-All UL Power engines feature dual redundant electronic ignition and FADEC (Full Authority Digital Engine Control) multi-point fuel injection, automatically compensated for altitude and temperature.

-As a curiosity, the firing order for the four-cylinder engines is apparently:
1-3-2-4

-And for the six cylinder engines:
1-4-5-2-3-6

-Of course, you should check the engine or Service Manual for the cylinder numbering. Don't forget or trust it, as each manufacturer has its own standard.

-The main text mentions the four-cylinder 260 and 390 models and the horizontally opposed six-cylinder 520.

"UL Power Logo"

-Recently (circa 2015), the range has been expanded with the 350i and 350is models.