The Cx series has the 4.4 in the tier 2 and newer years. I think the biggest difference is the fuel injection system, the MC 115 has a electronic controlled injection pump and the later models have a common rail system I believe

Liking McCormick review, I have chance drive MC with Perkins 6, Cummins 6 6.7lt n our Perkins 4 with auto shift which was loader spec with 130lt/min. Sowing paddock was ok unless you are in hilly country even uncle Cummins 6.7lt struggle unlike MX135 just had that extra boost. Perkins 6 had nice turbo whistle but as you say earlier production had their quality niggles. But great utility tractor for small to medium farms n awesome easy FEL, ours was Trima loader with 3rd n disconnect function.

Mtor