I thought I’d do a series covering less common engine configurations in the US car market, and their availability today (this means no I4s, no V6s, no V8s, and I’m not even sure about I6s). So, let’s start with the 2-cylinder - it’s the lowest cylinder count that can be found in a US car today.
Here’s the one 2-cylinder car available in the US market for model year 2017, the BMW i3 REx, which uses a 647 cc naturally aspirated inline-twin engine originally designed for the C650 family of scooters, and built by Kymco, as a gasoline-fueled range extender, in a serial hybrid arrangement.
Engine output is only 34 hp, but if you plan things right, it won’t even start up - if there’s enough charge in the battery, you’ll get 170 hp of electric power. If you do run the battery down enough to start the engine, it’s not a bad idea to keep the speeds down, though. Otherwise, on the US-spec model, it’s not hard to run out of battery buffer, and end up crawling up a hill - there’s even been a class action lawsuit about this, and plenty of people have hacked the software on their i3s to allow for more battery buffer (as exists in Europe), as well as remove an artificial limitation on fuel capacity meant to get a California credit available to range-extended vehicles where gasoline city range was shorter than electric city range. (The 2017 model doesn’t have the fuel capacity limitation, as its larger battery makes it eligible for the California credits without that limitation.)
EPA mileage in charge sustaining mode (that is, after the battery’s been depleted enough to require the engine to start) is only 36 miles per gallon highway, 33 miles per gallon city, on premium. This is a consequence of a few factors, I’d argue - the tall shape of the i3 compromises aerodynamics, the serial hybrid powertrain compromises efficiency (but gains flexibility, and makes it easier to remove the engine entirely for the BEV model), and the engine likely isn’t optimized for thermal efficiency.
Before anyone asks where the Morgan Three-Wheeler is - it uses an S&S V-twin - I’ve left it off due to it not being a car.
Next time, I’ll be posting the range of three-cylinder cars in the US market, which ranges from one of the cheapest cars on sale in the US, to a legitimate supercar.