The 4J diesel engine family has been the bedrock of Isuzu’s light trucks and utes for many years, and we are now seeing the opening of a new chapter in Australia.
The 2021 Isuzu D-Max will get an all-new 3.0-litre turbo diesel engine under the bonnet, replacing the long-serving and much-loved 4JJ1.
This new engine is called the 4JJ3-TCX, and although it has evolved from the previous engine (with an unchanged bore and stroke), it’s effectively all-new: new cylinder block, new pistons, new cylinder head and new fuel injection system. Only the conrods are carryover.
In addition to countless bench testing, the new engine also clocked up more than 4 million kilometres of durability driving.
Isuzu knows that Australians, who make up the second-biggest export market for the D-Max in the world, love the 3.0-litre engine that has been powering the Isuzu D-Max for many years. It has built up a strong reputation for durability and reliability, two elements that off-roaders and commercial operators hold dear.
While the outgoing D-Max gradually fell behind the pack in terms of refinement, technology and general modernity, it has stayed popular with increasingly discerning buyers in an increasingly competitive segment. Most of that success can be pinned against the gruff but likeable engine.
This new 4JJ3 engine looks to build on that strength and reputation, while also touted to be quieter, smoother and more thermally efficient. And it’s mostly here because of Australian demands and feedback. Only Australia and Thailand will receive this new 3.0-litre engine.
Power and torque
There is more power and torque available for the new D-Max, with the new 4JJ3 rated at 140KW @ 3600rpm and and 450Nm @ 1600-2600rpm. That’s a modest improvement of 10kW and 20Nm over the outgoing 4JJ1, but the new engine promises to be more flexible with its torque delivery.
Firstly, that peak torque range is much lower and five times wider than the outgoing model.
Putting that peak torque aside, 400Nm is available from 1400-3250rpm, virtually all of your operating range. Isuzu says 300Nm comes on tap from just above idle at 1000rpm.
This is difficult to compare with others in the segment, because the figures aren’t always readily available. However, it’s an undeniable improvement over the outgoing engine.
New metal bits
Perhaps most important to those figures above is the new variable geometry turbocharger, designed to improve torque and throttle response. Isuzu’s diesel particulate diffuser (DPD, Isuzu talk for a DPF) is mounted in the engine bay directly behind the turbocharger, further away from tall grass and potential damage.
This gets bolted to new engine castings for the 4JJ3-TCX, which comprises of an Isuzu-patented aluminum alloy cylinder head, and a cylinder block made from two materials: a cast iron upper (with induction-hardened, melt-in cylinder liners), while the lower section is cast alloy.
These materials are similar to the 4JJ1, as is the dual overhead camshafts and roller rockers. Inside the engine lives new aluminium pistons, lightweight and redesigned for better combustion.
The 4JJ3 crankshaft is new as well, which means the only real major carryover parts for this new engine are the connecting rods. On the front of the engine, the Isuzu 4JJ3-TCX retains a timing chain, made from stainless steel and using a double-scissor idle gear between crank and timing gears.
New fuel system
Pumping fuel at an impressive 250mpa (36,260psi), the new Denso-sourced fuel injection system uses a cam-driven high-pressure fuel pump that delivers 25 per cent more fuel pressure than the old pump, and is 20 per cent more energy-efficient.
The injectors are also new, mounted vertically above the piston and fed through a common rail. The new injector design does away with the command piston for less internal moving parts, and uses multiple injections per combustion cycle for smoother and more efficient running.
It’s cutting-edge stuff, and the D-Max is one of the first to use this new Denso injection system.
Without any selective catalytic reduction through diesel exhaust fluid (AdBlue), the new engine meets Euro V emission standards. Isuzu’s smaller 1.9-litre twin-turbo diesel is Euro VI compliant, however Isuzu has chosen to stick with the bigger engine for the Australian line-up.
Only Thailand and Australia receive this new 3.0-litre diesel engine, with the 1.9-litre used in markets with more stringent emission requirements. The 1.9-litre diesel engine makes 110kW and 350Nm.
The outputs of 140kW and 450Nm are the same, whether the engine is paired to either Isuzu’s own manual or an Aisin-sourced automatic gearbox (both six-speed). This is different to many other utes, who often have reduced peak torque figures in manual configuration.
2021 Isuzu D-Max servicing and warranty
Servicing for the new D-max is covered by a seven-year capped-price program, which totals $3373 after seven years or 105,000 kilometres.
With servicing intervals of 15,000 kilometres or 12 months, Isuzu estimates the new D-Max will be 10 per cent cheaper to maintain, in comparison to the old D-Max. Isuzu tells us this comes courtesy of redesigned components (such as electric power steering and sealed wheel bearings), yielding longer service for maintenance items.