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Prime Mover Magazine

Isuzu heralds first ever factory-built two pedal 4x4

A significant part of Isuzu’s recent N Series upgrade, the new NPS 4x4 AMT promises agile offroad capabilities in a package that’s easier than ever to drive. 

With increasing competition in the 4x4 light-duty segment, particularly since arch-rival Hino released its 300 Series 4x4 last year, Isuzu has hit back with an updated NPS 4x4 featuring a specifically calibrated version of the proven five-speed automated manual transmission (AMT) available in the N Series range.

Isuzu heralds it as the first-ever factory-built two-pedal 4x4 light truck on the Australian market and is pitching the vehicle as an ideal candidate for entities such as mine sites and the rural fire service.

The theory is that people who are not adept at manual truck driving will be significantly safer and more comfortable when driving the AMT equipped units under demanding conditions.

Importantly, the NPS 4x4 is still available with a conventional five-speed manual transmission, as has been the norm since the model was introduced in 1992.

More importantly though, whether in AMT or manual guise, this is a seriously capable off-roader featuring a high/ low range transfer case and manually engaged free-wheeling front hubs to maximise fuel economy and reduce tyre and driveline wear when operating on the black top. 

It is available in four configurations – single or crew cab with either 4.5 or 7.5 tonne gross vehicle mass (GVM) and respective gross combination masses (GCM) of 8.0 and 11 tonnes.

The 4.5 tonne GVM versions can be driven on a car licence. 

Power is delivered by a 5.2 litre turbocharged and air-to-air intercooled four-cylinder diesel producing 155hp at 2,600rpm and 419Nm of torque between 1,600 and 2,600 rpm. This is delivered to the AMT via a fluid coupling and ‘wet’ clutch, meaning the clutch plate runs in transmission fluid, which provide the benefits of a smooth take-off and reduced clutch plate wear and heat buildup in extreme operating conditions.

During steep descents, Isuzu says engine braking is enhanced by improved exhaust braking effect, courtesy of a redesigned butterfly valve that creates higher exhaust back pressure.

The vehicle is fitted with a diesel oxidation catalyst (DOC) exhaust emissions reduction system which Isuzu says is a robust, low-maintenance arrangement that copes well with high idle time applications.

It enables the vehicle to meet current Euro 5 standards without requiring AdBlue or particulate filter regenerations.

This is an important consideration given the cost of AdBlue at around $1.00 per litre must be added to the cost of fuel for a true indication of fuel running costs of vehicles equipped with selective catalytic reduction (SCR) emissions control systems.  

On the topic of fuel consumption, Isuzu says operators can expect an average of five per cent reduction across all models in the latest N Series range compared to their predecessors. 

Speaking at the N Series launch, Simon Humphries, Isuzu Australia Limited (IAL) Chief Engineer, Product Strategy, said the NPS AMT has been meticulously designed to provide operators with take-all-comers reliability and easy manoeuvrability.

“Because the NPS with AMT is the only factory-built two-pedal light truck available on the market today, we invested the time and resources into taking a literal ground-up approach to developing a superior product for all operators looking for a 4x4 light truck that’s easier than ever to drive,” said Humphries.

“The product available today was created from over three years of ongoing development and testing, much of which was conducted in Australia with teams of engineers from Isuzu Japan. Many changes were made to both hardware and software specifications to ensure the best possible on- and off-road driving experience in Australian conditions.”

Inevitably there are bound to be purists who will be skeptical of the AMT’s abilities in arduous off-road conditions, particularly when ascending or descending steep inclines.

One such concern might involve the transmission shifting to an inappropriate gear at an inopportune time, leaving the operator stranded in a precarious position.

However, Isuzu engineers have made sure this can’t happen because once 4x4 low range is selected the AMT reverts to clutch-less manual operation meaning the driver has complete control over the gear selection process.

Another important feature is necessary due to the elevated transmission fluid temperatures developed during high ambient temperature off-road operation. To counter this the transmission fluid cooler is now a stand-alone unit where previously it was integrated with the radiator.

In addition, a larger charge air cooler is said to provide a boost to engine power in extreme conditions.  

“These improvements radiate from local condition testing and customer feedback,” said Humphries. “They are further evidence of Isuzu constantly analysing the market to deliver fit-for-purpose products in direct response to customer needs in this country.”

The NPS 4x4 AMT has also received an upgrade where rubber meets road.

It is shod with Bridgestone L330 225/80R17.5 tyres with off-road tread pattern for improved results in mud and sand. In addition, the higher load capacity of this tyre enables full utilisation of the 3,100kg steer axle limit, 200kg higher than with the previous tyres. This change was in direct response to requests by rural fire service operators for a higher GVM.

At the recent 2018 N Series launch event Isuzu had a number of NPS 4x4 AMT units, comprising a mix of single and crew cab variants, lined up for testing at a reasonably challenging 4x4 track.

Each had a realistic payload of around two tonnes and there was also one manual shift version for comparison purposes.

During the test drive there were opportunities to ascend and descend a steep and moderately rough slope, typical of what a rural fire service vehicle would be expected to tackle in the line of duty.

In 4x4 low range and second gear there was ample power for the climb with the prodigious low-end torque combining with the torque multiplication effect of the AMT to make light work of the hill.

Similarly, when descending in the same gear with exhaust brake engaged there was no requirement for any foot brake intervention.

In both cases it felt as though the vehicle would be quite capable hauling at least double the payload, particularly given first gear was still available.

Another impressive feature was the surefooted stability of the vehicle over rocky terrain.
The multi-leaf spring suspension managed to strike an ideal balance between compliance and load bearing, soaking up the undulations to give occupants a reasonable ride while maintaining vehicle stability and composure over the rough stuff.

At the end of the day, the general consensus was that Isuzu has well and truly achieved its objectives with this vehicle.

As a light truck able to be driven on a car licence, the NPS 4x4 AMT exhibits the qualities that fire service crews, mine site managers and the like are looking for: Simplicity of operation combined with a bullet-proof engine and driveline, with the added bonus of a DOC emissions system requiring no AdBlue or regeneration.

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