How many cylinders are there in the engine of a semi truck?

Answer 1

4, 6, and 8 are common, a few have 12. ======

I've yet to even hear of a four cylinder semi truck, let alone see one. The 12 cylinder engines, even in their time, were a bit uncommon... the Detroit 12V71, which pretty much went out once the 60 Series was introduced in 1986.

All current production trucks in the US/Canadian market have inline-6 engines.. the last company to offer a V8 was Mack with their EM9 engine, and that went out of production in 2007. Even the 16.1 liter Volvo VE D 16 is an inline six.

V8 engines are more common in European trucks with engine displacements greater than 13 liters, as they're substantially shorter than inline 6 engines, and length limits in Europe and elsewhere are much more stringent than they are in the US and Canada.

Answer 2

Pretty much, in North America, inline six is the normal configuration. The only four cylinder engine available is the 10.5 liter 50 Series Detroit, which is pretty much a 12.7 DD60/DD13 with two cylinders removed. The only other diesel vehicle on the US market I can think of which uses such a configuration is the Isuzu NPR/NQR (also sold as the Chevy/GMC W Series). The 50 Series Detroit might appear in some semi trucks doing lighter work, such as beverage distributors, local P&D, etc., while engines of comparable displacement from other manufacturers are still inline six engines (e.g., the Cummins ISL, Volvo D11, etc). I've personally never seen the 50 Series in a semi truck, although I have seen it used in vocational straight trucks. The last V8 engine on the North American market was the Mack E9, which was discontinued after Volvo acquired Mack through their buyout of Renault. The only V12 engine offered was the 12V72T Detroit, which was effectively phased out by the introduction of the inline six 60 Series Detroit in 1986, although the two stroke Detroit V engines were still used in some buses and motor coaches until about 1992, and continue to be available for industrial, marine, and military applications.

In Europe, due to length restrictions, some manufacturers go to a V8 engine once they get into displacements of more than 13 liters.