Profile: Western Star Detroit Diesel DD15

By: Cameron Officer, Photography by: Cameron Officer/Supplied

Western Star Detroit Diesel 4800 & 4900 It's clever stuff and also further benefits when it comes to how smooth & quiet the engine operates Western Star Detroit Diesel 4800 & 4900
Western Star Detroit Diesel 4800 & 4900 Western Star Detroit Diesel 4800 & 4900
Western Star Detroit Diesel 4800 & 4900 The roadshow also incorporated a 5864 6x4 boasting the new DD15 engine Western Star Detroit Diesel 4800 & 4900
Western Star Detroit Diesel 4800 & 4900 Cab features supreme comfort in a layout as traditional as Western Star's power and reliability Western Star Detroit Diesel 4800 & 4900
Western Star Detroit Diesel 4800 & 4900 Western Star Detroit Diesel 4800 & 4900
Western Star Detroit Diesel 4800 & 4900 Whakatane-based DPS Haulage's 4884FXC sports a Patchell-built log trailer Western Star Detroit Diesel 4800 & 4900

New engine technology delivering incredible torque and a smoother ride — along with fewer emissions — has arrived in New Zealand. Western Star celebrates the launch of the Detroit Diesel DD15 six-cylinder 4800 and 4900 models with a good old fashioned roadshow.

While Detroit Diesel engines effortlessly evoke heritage and horsepower in equal measure, the new next-generation DD15 power units featuring in Western Star 4800 and 4900 models come with a big twist — and I mean that both in terms of torque and the unexpected.

As for the former, the all new engines boast the ability to provide 90-percent torque in an incredible 1.5 seconds. That's the fat end of 2510Nm (or 1850lb/ft in the old money) available almost instantaneously, as low in the rev range as 1100rpm. I'll get to how that's actually achieved in a second, but as for the latter twist? The new DD15 engines are also smoother, run cleaner, and are more fuel efficient than ever before. Not bad for something with that bad-ass Detroit Diesel badge worn proudly on the block.


The new engine was launched last month with a DD15 Roadshow, which saw two Western Star models sporting the new 560hp straight-six turbo diesel visiting 10 centres across the North Island, letting customers get up close and personal with the latest innovations from both of these famous American brands.

"This is a big developmental win for Western Star and for the New Zealand market as well," Dean Hoverd, national sales manager for local importer Penske Commercial Vehicles New Zealand tells me.

"The DD Series engine meets the new emission regulations that will take effect here from 1 July. But improved emissions compliance is just one part of the puzzle. With the arrival of the new DD15 engines, Western Star will be supplying fully completed 8x4 twinsteer trucks direct from the Portland, Oregon factory."

As Hoverd explains, the resultant cost savings will be beneficial for Kiwi customers. And as I discover, Western Star already has a history of giving both us and the Aussie market some special attention.

"Western Star is a popular brand in this part of the world," Hoverd continues. "Trucks built especially for the New Zealand and Australian markets account for 20 percent of total production, which is a pretty hefty number.

"A key factor is the availability of partially-completed 8x4 twinsteers — a configuration specifically engineered for New Zealand, which started rolling out of the Portland factory in 2010. Prior to that, local modification of 6x4s was required at costs that were higher than the base factory 

build cost."

Hoverd tells me that overall the number of Western Star trucks on the nation's roads has increased significantly of late — between 2005 and 2010 sales averaged around the 30 unit mark. But last year — due largely to the cost-competitiveness of the factory 8x4s — 103 new Western Star trucks joined the national fleet.  The bulk of those sales are for the ever-popular 4800, which accounts for around 95 percent of model take-up,
with 75 percent of 4800s being of the 8x4 configuration.


Aside from the practicalities of a twinsteer setup on New Zealand's sinewy roads, it's not hard to see why the 8x4 configuration is so popular when presented with such a well-dressed example in the form of DPS Haulage's Patchell-trailered 4884FXC 8x4 log hauler. Newly minted in the Whakatane firm's striking livery, the Western Star team had to 'borrow' the new 4800 back for the roadshow. The 8x4 made the grand tour in the company of the white tractor unit you see here — a 5864 6x4 wearing Penske Commercial Vehicles' own colours for the occasion.

The ability to deliver 90-percent peak torque so quickly is due to a newly-developed innovation called the Amplified Common Rail Fuel System (ACRS), matched with low inertia, dual overhead cams, and a robust non-wastegated, non-variable geometry-style turbocharger. The turbo also features a compounding system that recovers normally wasted gases and recycles them into usable power.So, how does the new DD15 engine — which both the roadshow trucks sport — achieve those remarkable power and efficiency headlines? Through a combination of echnologies, actually.

It's clever stuff and also has further benefits when it comes to how smooth and quiet the engine operates, with the ACRS helping to reduce noise and vibration as much as emissions. What's more, the DD15's j-brake system features three levels of braking which not only increases braking power but reduces noise too.
Inside the cab, that long, flat torque curve has further benefits for the driver, eliminating the need for constant gear changes as peak torque stays on the bubble right up the rev range.

"The Detroit Diesel engine incorporates a multitude of clever technologies," says Hoverd. "Up front local customers look set to benefit from our direct line with the factory, and then further down the road, the operating efficiencies of the new DD15 engines in our popular 4800 and 4900 trucks will pay dividends too."

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