Navistar says it is ready to take orders for a severe -duty truck carrying its new 15L MaxxForce 15 engine, a big-bore diesel certified to meet EPA’s 2010 emissions standards without selective catalytic reduction (SCR). Long anticipated, the 15-liter engine uses the same “advanced EGR” approach taken with Navistar’s smaller MaxxForce 11 and MaxxForce 13 diesels.

Initially the new 15-liter will be available only in two heavy-duty vocational trucks – the International PayStar 5900 with either a set-back or set-forward front axle. Availability in Navistar’s on-highway trucks will come later this summer, according to the company.

While the 11L and 13L engines were based on a diesel designed by Germany’s MAN, the new 15L is derived from Caterpillar’s C15, an on-highway engine no longer produced by Cat for the North American market.

The new MaxxForce 15 uses the Cat engine block and crankshaft, but adds new fuel systems, air management and electronic controls to meet 2010 emissions requirements, according to Navistar. It will be available with ratings up to 550 HP and peak torques up to 1,850 lbs. ft.

For its part, Caterpillar has just unveiled a new vocational truck based on the PayStar and built under contract by Navistar. Initially the new Cat CT660 will be offered only with its own branded versions of the Navistar 11L and 13L diesels, but the company said it expects to add the 15L option in the first quarter of 2012.