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3.9L Isuzu 4BD1T

Isuzu 4BD1T Diesel Specs (1986 - 1991)

The Isuzu 4BD1T is a direct injection, turbocharged diesel engine with a 3.9L displacement. It is found in 1986 to 1991 model year Isuzu NPR and Chevrolet W4500 commercial vehicles in addition to global on-highway, marine, and industrial applications. It is a turbocharged version of the naturally aspirated 4BD1, offering significant more power and less power loss at higher altitudes. Possibly the most common power rating was a 135 horsepower variant rated at a peak 243 lb-ft, although the engine series was produced many varieties depending on application and model year.

3.9L Isuzu 4BD1T Specs


Isuzu 3.9L 4BD1-T (AKA QD100T)


Isuzu Motors Ltd


1986 - 1991 Isuzu NPR/Chevrolet W4500


4 stroke direct injection diesel


Inline 4 cylinder (I-4/L-4)


3.856 liters, 236.08 CID

Firing Order:

1 - 3 - 4 - 2

Engine Block:

Cast iron, dry type cylinder liner

Cylinder Head:

Cast iron

Compression Ratio:

17.5 : 1

Cylinder Bore:

4.02 in (102 mm)

Cylinder Stroke:

4.65 in (118 mm)


OHV, solid lifter camshaft


Mechanical inline injection pump, direct injection


Turbocharged, IHI 6HB6 or Garrett T25 models

Engine Dimensions (approx.):


31.3 in


27.8 in


29.7 in

Engine Weight (approx):

~770 lbs

Peak Horsepower:

up to 135 hp @ 3,000 RPM
(varies by application, 135 hp rating common for Isuzu NPR/Chevrolet W4 applications)

Peak Torque:

up to 243 lb-ft @ 1,800 RPM (varies by application)

Idle Speed:

~ 650 RPM

Max Engine Speed:

~ 3,500 RPM