Mack unveils 10-liter engines; E5 Series offers two mechanical ratings.

In a bid to establish a foothold in the weight-sensitive on-road/off-road medium/heavy construction market, Mack Trucks has introduced two turbocharged, direct-injection 10-liter Maxidynes: the EM5 250 and the EM5 290.The E5 engines, which run in an operating range of 1,150 to 2,000 rpm, weigh 2,133 lb. -- 200 lb. less than the 12-liter E7. Although the E5 is new to this country, according to Mack

In a bid to establish a foothold in the weight-sensitive on-road/off-road medium/heavy construction market, Mack Trucks has introduced two turbocharged, direct-injection 10-liter Maxidynes: the EM5 250 and the EM5 290.

The E5 engines, which run in an operating range of 1,150 to 2,000 rpm, weigh 2,133 lb. -- 200 lb. less than the 12-liter E7. Although the E5 is new to this country, according to Mack it's a highly reliable design that is the most popular heavy-duty diesel propelling Renault V.I. vehicles in Europe.

The E5s that Mack plans to sell in the U.S. won't be identical to the European engines. Renault, Mack's parent, is supplying the engines in "3/4" form to Mack's Hagerstown Powertrain Operations for assembly with U.S.A.-engineered components, including manifolding, accessories and mountings, and cylinder head covers.

First-generation E5s are mechanically fueled (Bosch P7100 pump) and available in horsepower ratings of 250 and 290. Peak torque for the EM5 250 is 975 lb.-ft (50% torque rise); and for the EM5 290, 1,160 lb.-ft. (52% torque rise).

In about a year, the mechanical engines will yield to a second generation of electronically controlled E5s. Some higher horsepower and torque ratings will most likely be introduced at that time, making them appropriate for over-the road vocations such as bulk hauling.

However, since the E5 is not yet available in ratings over 300 hp., the truck maker has elected to restrict its use to medium-duty construction applications, explains Mike Kline, manager-vocational customer focus. He claims that an E5 would be an ideal power source in a Mack RD694 chassis, a lightweight version of its RD600 chassis.

The newest Maxidyne has a 4.72-in. bore, 5.71-in. stroke, and 17:1 compression ratio. Exterior dimensions are 30 in. wide, 52 in. long, and 43 in. high.

Mack's new 10 liter differs in design from the E7. For instance, the E5 has two valves per cylinder rather than four, and one head per cylinder, rather than one head for every three cylinders. However, the E5's warranty is identical to that of the E7, carrying Mack's standard severe-service interval recommendations for off-highway use.

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