There are numerous off-road diesel engine applications. In some applications there is more focus on metrics such as initial cost, packaging and transient response and less emphasis on fuel economy. In this paper a combustion concept is presented that may be well suited to these applications. The novel combustion concept operates in two distinct operation modes: lean operation at light engine loads and stoichiometric operation at intermediate and high engine loads. One advantage to the two mode approach is the ability to simplify the aftertreatment and reduce cost. The simplified aftertreatment system utilizes a non-catalyzed diesel particulate filter (DPF) and a relatively small lean NOx trap (LNT). Under stoichiometric operation the LNT has the ability to act as a three way catalyst (TWC) for excellent control of hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx). The two-mode diesel combustion concept was implemented on a 6.8L medium duty diesel engine and several iterations of the combustion system were evaluated for smoke response and combustion efficiency. The engine was then evaluated over the Non Road Transient Cycle (NRTC) to evaluate performance, emissions and fuel consumption. Results show that this novel combustion concept can meet the Tier 4 final emissions regulations without the use of selective catalytic reduction (SCR).