DETROIT, Mich. (March 8) — Detroit Diesel is poised to bring a 13.9-liter Series 60 engine in a show-truck chassis to the Mid-America Trucking Show later this month — although first-hand observers might never know it.

Examples of the 13.9-litre engine — up from the 12.7 litres of the current model, an increase obtained with a longer stroke — have surfaced in prototype and near-production trucks, one of which is destined to appear at Mid-America.

However, the company may choose not to formally introduce the new engine at the show, which industry suppliers often use as a public launching pad for new products. All differentiating marks and identification plates have been removed, so if Detroit Diesel decides not to announce the 13.9-liter, the engine will likely be identified as a 12.7.

Detroit Diesel has been testing the 13.9-litre engine in, among other places, the highly sophisticated Rapid Intervention Vehicle chassis Freightliner Corp. is building for Austrian specialty fire appliance manufacturer Rossbauer.

Powered by a 600-horsepower in-line six cylinder, mounted high in the tail, this fire appliance is intended for airport duties where the huge, all-wheel-drive trucks race to a crippled plane on a runway. They have exceptional stability and off-highway performance, with the ability to accelerate to 50 mph in a little over 30 seconds despite weighing in at over 60,000 pounds with their tanks full of water and foam.

The engine in this chassis is a Series 60, and the 600-horsepower rating suggests it is the rumored 13.9-liter version with available torque to 1850 pounds-feet.

The version on display at Mid-America is likely rated 550 horsepower and 1850 pound feet. Some literature suggests the top on-highway rating may be 575 horsepower.