Previously, we brought you five examples of the forgotten flat-eight engine. While that led to quite a heated discussion of terminology as to whether “Flat” encompassed both 180-degree-Vee engines and horizontally-opposed Boxer engines, or just one or the other, the consensus was that people liked them. So to that end, we bring you this video covering ten flat-twelve engines.
Whether horizontally-opposed or sharing a crankpin, there’s no denying that engines with cylinders 180-degrees from one another sound amazing. Add in the fact that 12-cylinder engines also have a distinct note, and this video is packed with some amazing mechanical symphonies, a few of which we’ll talk about below.
The Ferrari Berlinetta Boxer with its 180-degree flat-12 wasn’t really a boxer engine at all, but rather an offshoot of the V12 Daytona engine that had its cylinders splayed an additional 120 degrees to lay flat. Originally a 4.4-liter in the 365 GT4, it was eventually upped to a 5.0-liter engine with slightly more compression and a dry-sump oiling system in the BB 512 and the rated power output was bumped to 360 horsepower, before being discontinued in 1984. However the engine would live on for another 13 model-years powering the iconic Ferarri Testarossa.
A slightly more modern 180-degree Flat-12 was the engine from the 1991 Mercedes-Benz LeMans Prototype effort, the M-291. A 3.5-liter engine, it was a significantly underpowered effort, producing an estimated 550-600 horsepower, which was in the neighborhood of 150 horsepower less than the rest of the field. While largely considered a failure by Mercedes-Benz, the M-291 engine did produce one thing in spades – a glorious exhaust note.
Another Ferrari flat-12 effort was the engine which powered the Italian firm’ 1964-1965 Formula 1 effort. A 1.5-liter 180-degree engine, it was quite compact and featured a very unique ignition setup, having 24 plugs, four coils, and four distributors, making in the neighborhood of 220 horsepower at 12,000 rpm.
Porsche was also a player in the flat-12 game, but they actually built their flat-12 as a true horizontal-opposed boxer engine. From 1969-1971 the Porsche Type 912 flat-12 was an air-cooled powerplant that ranged from 4.5 to 5.0 liters. While the 4.5-liter variant started at 520 horsepower, the final 5.0-liter iteration was making 630 horsepower, which was a very significant jump in only three model-years.
Finally, there was Alfa Romeo, who developed their 180-degree flat-12 for Group-5 endurance racing in 1973. Making 500 horsepower out of only 3.0 liters (2995.125 cc, if we’re being exact) it spun to 12,000 rpm and it actually won Alfa the Maker’s Championsip in 1975. For 1976 and 1977, the engine was reworked to make an additional 20 horsepower, leading to another championship in 1977. Alfa then tried to use the engine in their 177 Formula 1 car, where its performance was mediocre.
For information on all ten engines on the list, and to hear the absolutely amazing sounds of the flat-12, make sure to watch the video above… And make sure to have your speakers (or headphones, if you’re at work – we won’t tell) turned up!