Isuzu NHR 4J Series Workshop Manual page 138

The 4JB1 Model engine employs a square troidal type
combustion chamber provided with a fence around it.
These designs employed allow a superior fuel
economy over a wide range of driving conditions.
The 4JG2 Model engine employs, for its combustion
chamber, the RECARD
combustion chamber which provides a superior driving
performance, fuel economy and silent combustion over
a wide range of driving conditions.
For the cylinder head gasket steel sheets, laminated
steel sheets are employed.
Three grades of the gaskets according to the piston
head projection measured from the cylinder block are
employed to minimize the fluctuation of the engine
compression ratio.
The Angular Tightening Method is employed to tighten
the cylinder head fixing bolts, connecting rod fixing
bolts and flywheel fixing bolts.
The chrome-plated steel dry type (Chromard) cylinder
liners provide the highest durability.
Auto-thermic pistons with cast steel struts are used to
reduce thermal expansion and resulting engine noise
experienced while the engine is cold.
The tufftrided crankshaft has a long service life.
Because it is tufftrided, it cannot be reground.
The crankshaft main bearings and the connecting rod
bearings are of aluminum alloy. These bearings are
especially vulnerable to foreign materials such as metal
scraps. It is very important to keep the oil ports and
other related surfaces clean and free of foreign
materials.
The tufftriding treatment (nitriding treatment) of the
crankshaft for the increased strength eliminates the
regrinding of crankpins and journals.
An oiling jet device for piston cooling is provided in the
lubricating oil circuit which runs through the check
valve from the cylinder block oil gallery.
Comet V Type swirl
4JB1/4JB1T/4JB1TC/4JG2 – ENGINE 6A1 – 3
Take care not to damage the oiling jet when removing
or installing the piston and the connecting assembly.
The 4JG2 engine use a single spring pintle type
injection nozzle.
The 4JB1 Model employs a direct injection type engine
provided with a nozzle with four holes, which makes it
possible to obtain an excellent mixing ratio of intake air
and fuel spray.
4JB1-TC engine has two springs injection nozzle
system for efficient control.
The turbocharger increase air intake efficiency, the
results in increased engine power, reduced fuel
consumption and minimal engine noise.
Turbocharger rotating parts operate at very high
speeds and temperatures. The parts materials have
been carefully selected and machined to extremely
high precision.
The 4JB1 Model engine employs the QOS II
preheating system which features a quick-on glow to
control the glow time and the afterglow time by the
thermometer.
The 4JG2 engine employs the QOS III system which
allows the most suitable starting conditions for the
glow time to change according to the engine water
temperature, and the optimum for the glow time to
change according to the engine water temperature,
and the optimum changes according to the water
temperature immediately after the start of the engine.
The belt-driven type timing drive belt of the 4JG2
Model engine is a very important functional part, and
requires the specified maintenance.