Cummins 3.9 Turbo Diesel Engine Specifications

by Joanna Swanson
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The Cummins 3.9-liter turbo diesel engine is part of the B-series of engines created by Cummins. Its trade name is the Cummins 4BT, a reference to its four cylinders, position as a B-series engine and the addition of a turbocharger. It is manufactured for use in commercial step vans, marine applications and agriculture, among other applications.

Type and Configuration

The 3.9-liter Cummins turbo diesel is an inline four-cylinder engine with four cycles. It features turbocharged aspiration that is not intercooled. The bore is 4.02 inches and the stroke is 4.72 inches. The first cylinder to fire is number one, followed by three, four and two.


The Cummins 4BT is 37.7 inches high, 30.6 inches long and 24.6 inches wide. It weighs between 745 and 782 pounds and has a gross vehicle weight rating of 16,000 pounds. It consumes 7.6 gallons of diesel per hour and the fuel pump operates at between 0.5 psi and 10 psi.

Cooling and Lubrication

The cooling system on the Cummins 3.9-liter engine can hold 8.8 quarts when allowing space for the coolant to expand. The engine thermostat allows temperatures between 181 and 203 degrees Fahrenheit. The oil pressure ranges from 10 psi while idling to 30 to 65 psi at normal operation. The engine can carry up to 10.4 quarts of oil and it can reach a maximum temperature of 250 degrees Fahrenheit.

Intake and Exhaust

The air intake system on the 4BT can pull in 270 cubic feet per minute. The exhaust gas flow is 700 cubic feet per minute at 900 degrees Fahrenheit.


The 3.9-liter turbocharged engine can produce 150 horsepower at 2,800 rpm and 265 foot-pounds of torque at 1,600 rpm. Its compression ratio is 17.5-to-1. The pistons operate at 2,205 feet per minute and the brake mean effective pressure is 177 psi.

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