The phrase "litre version" refers to a variation or variant of a product that is measured in liters. It means there is a specific size or quantity of the product available, usually measured in liters. Full definition
This is undoubtedly the best 4 - litre version of the current engine architecture. (evo.co.uk)
This is a 2002 Focus (UK spec) the 2 litre version with the MTX75 transmission. (mechanics.stackexchange.com)
The wide wheel arches that have been squared out and the chequered flag livery on this standard 1 - litre version does look quite cool in its own way and so does the upright stance. (auto.ndtv.com)