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Engines on test: Isuzu 4JK-1E5-TC
The latest engine on test by Engine Technology International is the Isuzu 4JK-1E5-TC; a 2.5-liter, twin-turbo four-cylinder diesel that delivers 400Nm of torque, as fitted to the special edition Isuzu D-Max AT35
Admittedly, whilst it was Engine Technology International’s first ever commercial vehicle on test, there was something exceptionally refreshing and honest about the Isuzu D-Max AT35. Taken in direct comparison to the typical cars we get in on test, the 160hp 2.5-liter could be seen as an outdated solution by some, but in situ in the big truck, it makes an awful lot of sense. Whilst this particular model is somewhat of an anomaly for the UK (the AT standing for Arctic Trucks, whose conversion adds caricatured 35” Nokian off-road tires, blistered arches, and expensive Fox Racing off-road dampers) there is a purposeful, workhorse of a machine beneath it all. Think farmer, in a Nomex race suit.
The standard D-Max has, perhaps unsurprisingly, been described by Isuzu as a tool rather than an emotional purchase which, when firing up the 2.5-liter inline four cylinder turbo-diesel engine, becomes immediately apparent. A direct carry over to the AT35, the European-specific CRDi common-rail unit doesn’t gain any additional power or refinement despite the new ‘lifestyle’ derived exterior potentially opening up the range to new demographics.
As mentioned, the underlying agricultural thrum of the diesel engine exudes a reassuring feeling of good old-fashioned reliability and dependability, if not refinement; you get the impression that if you lived in the remote North Icelandic village of Kópasker that the AT35 wouldn’t let you down. In the UK, this can come across as something of an overkill, but its nice to know that should the weather take an unexpected snap for the worse, you’ve got it covered.
Its purpose as primarily an off-road tool also directly translates to the general driving experience when on road. The engine’s colossal 400Nm of torque (some 43% more than its predecessor) is available across a 600rpm band that tapers off at 2,000rpm, allowing for solid progress across a number of different surfaces. Shift lock, and a selectable two-high, four-high, and four-low ratio differential allows the AT35 the ability to genuinely stroll across pretty much any terrain the UK may throw at it. And despite having to haul over 2,100kg of chassis and cab around, the engine never felt underpowered and managed to return respectable economy of over 32mpg, which was surprisingly close to the manufacturers claims.
On road, the NVH of the drivetrain is more than apparent in the cabin, however it is almost to be expected of such a vehicle. But the swell of torque low down in the rev range means that ‘around town’ speeds can be achieved rather rapidly for what is a behemoth of a car; all in all, the modifications make the AT35 some 125mm taller than the standard D-Max. This rapid progress surprisingly continues when taking it above town speeds; highway on-ramp’s can be dispatched with ease and when at speed, ambient noise and tire drone drop to be almost inaudible; surprising, given the large footprint of the Nokians.
A hidden gem in the AT35, however, was the exceptionally smooth and well-judged Aisin automatic five-speed transmission. Whilst unlikely to appear in any premium branded product any time soon, its pairing to the Isuzu engine has to be applauded as it made for a rather enjoyable driving experience. Well matched to the torque curve of the engine, the unit quickly slips between gears with little interruption to progress. The optional manual mode is also worthy of praise; in that it truly is a manual, staying in gear until the lever is pushed or pulled forwards or backwards – again, adding to the truck’s off-road prowess.
The AT35 is an extremely niche purchase for most markets that aren’t subjected to frequent blizzards, and in all honesty the regular D-Max is more than capable of dispatching the varied fields of the UK. That said, short of the Lamborghini Huracán we tested around eight months ago, I’m struggling to think of a car that has turned heads and made people smile as much as the AT35. As I say, it’s an interesting anomaly but an honest and purposeful one that I’ve grown really rather fond of.
6 February 2017