Rotax’s new 912S

Rotax’s new 912S produces more horses per dollar than its 80-hp 912 (no “S”). One of the big success stories in light aviation powerplants is the Rotax 912. The four-stroke engine evolved from Rotax’s two-stroke line and offered a strong 80 horses. Still, some planes need a little more.
MORE GET UP AND GO
“An airplane that climbs well on the (regular) 912 won’t see much improvement from the 912S,” said one of the leading importers, Phil Lockwood of Lockwood Aviation Supply.
“But if your plane climbs a bit marginally with the 912, the 25% power increase in the 912S will make a world of difference.”
More power usually means more weight; however, the 912S adds a mere 3.5 pounds over the standard 912.
Rotax Aircraft Engines – a division of world aviation leader Bombardier – also offers the 914, a turbocharged version of the 912. The 914 brought power from 80 horses to 115 (with 100 continuous), but comes with a substantial price increase. Now, those who need a little more have perhaps a better choice, and with a much more modest price increase.
The standard 912 goes for just over $9,000, while the new 912S runs $1,700 more. “However, it is the best value per horsepower,” said Lockwood Marketing Representative John Hunter, who compares the 912 at $112 per horsepower to the $107-per-horsepower 912S. Any way you cut it, that’s improved value in a powerplant – with few penalties.
HOW DOES IT PRODUCE EXTRA POWER?
Two factors account for this pleasant turn of events (more power; roughly the same weight).
First, the 912S uses a few more cubes. Displacement has increased from 1,211 cubic centimeters (74 cubic inches) in the 80-horse 912 to 1,352 cubic centimeters (82.6 cubic inches) in the 100-horse 912S.
Second, Rotax raised the compression ratio from 9.0:1 on the standard 912 and the 914 turbo to 10.5 on the 912S. “That’s all the difference,” said a smiling Hunter.
A simple solution to gain a bunch of extra oomph, it’s a tried-and-true method from the world of automobiles.
About all a user needs to do differently with this engine is use more octane (to handle the higher compression ratio). Rotax recommends 91-octane fuel for the regular 912 and 95-octane for the new 912S.
You have your choice of leaded or unleaded for either engine. Most ultralight enthusiasts will use perfectly acceptable (and cheaper) auto gas, while kit builders based at airports may select 100LL avgas. Rotax confirms that either is okay.
Insofar as installations go, the bolt patterns remain identical with the older models of Rotax four-stroke engines, so designs in progress can go with the new model without redesign efforts.
Owners of larger ultralights (or ultralight-like aircraft) and builders of somewhat larger kit planes can find something to like in the new engine. Service, long a strength of Rotax service centers, remains one of the compelling reasons to buy the brand.
The new 912S was in action at EAA AirVenture ’98 in Oshkosh. The first advance examples of the new engine were seen on the Air Cam. While the twin-engine “ultralight” has always been most impressive, it’s more so now.
For further information, contact your local Rotax dealer.