Cummins X12 engine full review and video

By: Steve Brooks, Photography by: Steve Brooks


As the saying goes, it’s not the size of the dog in the fight but rather the size of the fight in the dog, and therein is the essence of the Cummins X12. Small in stature, it is an engine punching well above its weight. Literally! Yet despite an extensive test program and growing demand, it’s a pocket performer still looking for a truck to call home

 

Sometimes it takes a while to come to grips with a particular piece of hardware. Other times it seems to happen in a heartbeat, and so it was with the Cummins X12.

Almost from the moment the right foot went down and the Kenworth tugged its 56-tonne bulk forward, the 500hp (373kW) X12 revealed itself as something special. Something outside the square.

Sure, there’s no shortage of potent engines in the 12- to 13-litre class and, one way or another, they all have their attributes.

For the most part they are strong, reliable and fuel efficient. No question! 

That said, though, after a day and a half behind the wheel of a Kenworth T408 SAR and quad-dog combination hauled by this livewire lightweight, I’d argue long and loud that none deliver this much punch, this much response, from such a modest lump of metal as the X12.

Again, it truly is something outside the square and it’s increasingly apparent I’m not the only one who thinks so.

Sitting in the shotgun seat of the 408 was the truck’s owner, John Crampton.

A straight-shootin’, quick-witted individual with a larrikin sense of humour, the bloke known simply as Crampo has been in the dirt-moving business in and around the Coffs Harbour district of northern NSW all his working life.

But beware! Lurking just behind the eager smile is a wily thinker with blunt intolerance for apathy and a mind honed sharp by experience and competitive instinct.

 There’s a lot of pride in the Crampton fleet and workloads are diverse. Kenworth and Cummins dominate but under the snout of this classy SAR is a Paccar MX-13. Still, Crampo says he’d prefer an X12 if it was available
There’s a lot of pride in the Crampton fleet and workloads are diverse. Kenworth and Cummins dominate but under the snout of this classy SAR is a Paccar MX-13. Still, mpo says he’d prefer an X12 if it was available

Thirty years ago – and just out of his teens – he bought his first truck, an ’88 Atkinson towing a 2-axle dog trailer.

Thus evolved the company called Crampo’s Tippers, today operating a fleet of 24 units ranging from PBS truck-and-dog combinations to specialist rigid tippers and a handful of concrete agitators.

When it comes to trucks, trailers and anything else to do with his business, he does not suffer mediocrity. Yet while sticking with what works, there’s no hesitation in trying something new if the case stacks up.

Cummins-powered Kenworths dominate the operation but the presence of a couple of Freightliners and Detroit engines, along with a few DAFs, suggest that choices depend largely on needs and opportunity.

An adamant Crampo explains: "One type of truck doesn’t fit all the things we do. Never has and probably never will.

"Some trucks run long distances with grain and fertiliser, others spend most of their time doing quarry and construction work along the coast, some run into and out of farms, others do hot mix and bitumen sealing, and then there are four agitators as well.

"There’s a lot of diversity in the work we do and the trucks reflect that. I guess the engines do, too," he adds. "I figured a long time ago that it doesn’t pay to have all your eggs in one basket."

And it shows. Kenworth and Cummins are the preferred combination for a number of reasons but none more than service, essentially through the local Brown & Hurley dealership.

Still, no one model reigns supreme and you don’t have to look hard to find examples: a T480 with an M11, T408s and 409s with 15-litre ISX and Paccar MX engines, and T3s with the 8.9-litre ISL.

Still doing an honest day’s work, there’s even an old K-series with its original 14-litre Big Cam underneath. 

 John ‘Crampo’ Crampton. Cummins X12 ticks a lot of boxes. The engine’s harmony with Eaton’s Ultrashift-Plus shifter is exceptional
John ‘Crampo’ Crampton. Cummins X12 ticks a lot of boxes. The engine’s harmony with Eaton’s Ultrashift-Plus shifter is exceptional

As for the relatively new installation of the X12 in an eight-year-old and extremely well preserved T408, Crampton is surprisingly quiet for a moment.

"That’s something you probably need to ask Chook," he says with a shrewd grin. "But I do know he was keen to get you up here to drive it."

Funny thing though, I think Crampo was keen to get a second opinion as well. 

‘Chook’ is Mike Fowler, Cummins director of engine business, and I’d talk to him soon enough. For now, and with a bit of urging, Crampo was at least willing to provide some background behind the reasons for replacing the truck’s original 15-litre ISX EGR engine with its 12-litre sibling.

The short version of the story is that Chook and Crampo have known each other for a good while.

With Cummins wanting to add another dimension to its long-running X12 trial program, and Crampo more than willing to operate an engine which even on paper appeared to tick a lot of boxes, arrangements were promptly put in place.

Essentially, the truck went to the pilot centre at Cummins headquarters in Melbourne, the 550hp (410kW) 15-litre ISX which had notched more than 17,500 hours pulling dog trailers through the hills and hollows of northern NSW was removed, and over the next few months a highly detailed transplant was performed.

It wasn’t just the engine, though. With John Crampton firmly convinced that time and technology are now right, the Eaton 18-speed manual gearbox was replaced with its automated Ultrashift-Plus counterpart. The automated Eaton is, in fact, now the Crampo standard.

 Strong, light and compact. X12 fits easily under the SAR hood and dramatically reduces weight over the front axle
Strong, light and compact. X12 fits easily under the SAR hood and dramatically reduces weight over the front axle

"You have to keep moving forward," he comments, "and from what I see, they’ve absolutely got the auto box right."

Indeed they have. In fact, it took little time behind the wheel to form the firm opinion that the relationship between engine and transmission in this installation is without doubt the best I’ve ever found in US equipment, and that includes the formidable engine and automated transmission pairing in various Mack models.

Whatever shift program Eaton wrote for this particular truck with this particular engine in this particular application, it should be set in stone. It was that good, with levels of intuition and shift quality simply second to none.

The transmission’s capacity for making huge skip-shifts and the engine’s willingness to pull away without moan or groan from as low as 1000rpm was nothing short of extraordinary. This truly is a big engine in a small package.

What’s more, this transmission also featured a ‘dual mode’ function, reading suspension air pressure to instantly adjust shift sequences between loaded and unloaded conditions. Clever!

Report Card                                                  

Now, with more than 10,000km under its belt since the truck’s return to Coffs Harbour, there are no regrets.

None at all, and it’s a serious Crampo who explains: "Look, truck combinations in Australia are for the most part constrained by dimensions, so for a high-gross application like a PBS truck-and-quad dog, you need a truck with a short BBC [bumper to back of cab] like the SAR.

"But with a big bore engine, a short BBC puts restrictions on space and weight, so there’s a negative impact on payload.

"That’s where an engine like the X12 is such a viable alternative if it can deliver the right levels of performance and fuel economy. And, as far as I’m concerned, it’s delivering both."

"It’s definitely not shy when it comes to work. It might be a small engine but there’s nothing small about the way it pulls.

"Like I said, it ticks a lot of boxes for this sort of work."

Arguably the biggest tick of all, though, is in the box marked ‘tare weight’.

 Cummins engine chief Mike Fowler and John Crampton. X12 installation in a well preserved T408 was a good move for both. Performance of the 12-litre is surprisingly strong
Cummins engine chief Mike Fowler and John Crampton. X12 installation in a well preserved T408 was a good move for both. Performance of the 12-litre is surprisingly strong

With a dry weight of just 860kg in its current Euro 5 form, the X12 is around 540kg lighter than its 15-litre brother.

However, the big news in the Crampo installation is that, along with a number of significant changes to the cooling system and front suspension, Cummins has stripped more than 820kg off the weight over the front axle compared to the 15-litre layout.

For the record, the standard multi-leaf front suspension was replaced with parabolic springs, while the original copper and brass radiator made way for an aluminium assembly based on the cooling package used with Paccar’s MX engine and in Kenworth’s new T610 range.

The payload improvement is obviously significant but, according to Crampton, there’s still more work needed to maximise the engine’s full payload potential.

At the moment, the truck struggles to reach six tonnes over the steer but, as Fowler explains, there are ways and means of increasing weight over the front axle.

For example, the X12 is an extremely compact package – in fact, it’s now also being trialled under the short snout of a Kenworth T359 in a weight-sensitive fuel haulage application – and simply locating the engine further forward will result in a notable increase over the steer, which, in turn, will allow more payload over the drive axles.

As for fuel, the average is 1.93km/litre, or 5.5mpg in the old scale, measured over the engine’s first 4000km since returning to Coffs Harbour. AdBlue consumption is typically around 3.5 per cent of fuel consumption.

Crampton admits to being satisfied with the early figures. As he is quick to point out, the engine is still new, the hills are many in and around Coffs, and loaded weight is always around 56 tonnes.

"Anyone who reckons that’s not reasonable fuel consumption for a new engine hasn’t spent much time pulling quad dogs around here," he says abruptly. "Besides, it’ll only get better as it goes along."

Still, there’s one box the engine doesn’t tick. At least not yet. Given its modest displacement, engine brake performance of the X12 is marginal at best, an opinion no doubt accentuated by the formidable braking power of the 15-litre engine it replaced.

And there’s the thing: Cummins set the bar exceptionally high with its 15-litre engine dispensing up to 600 braking horsepower.

 Crampton is a big believer in ‘horses for courses’ and MX-powered DAF CF does a good job in a particular application
Crampton is a big believer in ‘horses for courses’ and MX-powered DAF CF does a good job in a particular application

So given the X12’s peak braking output around 375hp, it’s easy to be disappointed in a high weight application running over steep hills.

Even unloaded it’s surprisingly unimpressive, struggling to pull road speed back when running from, say, an 80km/h zone into 60. It needs to be better.

Fortunately, Fowler says there are several ways to improve the 12-litre’s braking performance – but again, given its relatively modest displacement, improvements may be similarly modest.

Meantime, back behind the wheel, everything Crampo was saying was quickly becoming obvious. In terms of pulling power, the X12 was full of surprises.

There’s a deep rumble reminiscent of its bigger brother as it digs towards a torque peak of 1700lb-ft at 1100rpm, matched by a level of gritty determination across the rev range belying the engine’s humble 11.8-litre displacement.

Again, though, in this instance it’s a performance unequivocally enhanced by a superb affinity with the Eaton shifter.

Yet marry this inherent tenacity with a level of throttle response, which I’m prepared to suggest is unmatched in any installation of similar proportions, and you can be quickly left wondering about the vast array of workloads applicable to something so light yet offering such solid performance.

As Crampton puts it: "It’s always horses for courses and I probably wouldn’t use it for pulling a 5-axle dog, but other than that I can’t see why it wouldn’t handle most other jobs. I expected it to be a reasonably good thing but it’s definitely better than I thought it’d be.

"Think about the payload you’d get if it was in a T350 pulling a 3-axle or even 4-axle dog. That’d be awesome, I reckon."

Crampo pauses for a moment. "There’s never really been any engine like this since Cat’s C12 and C13."

He’s right, but the difference is the X12 does it with considerably more grunt. Then again, the Cummins currently lacks something the Cats didn’t. A truck to call home!

Homeless or Homely?

They may not like to admit it, but it’s a fair bet Cummins insiders have long known it wouldn’t be easy finding a home for the X12.

Simply explained, the giant diesel engine specialist missed the boat badly almost a decade ago when it found itself largely empty handed in the wake of Cat’s 2008 departure from the on-highway engine business.

Sure, Cummins had its 15-litre Signature engine to supplant the yellow company’s C15 but what it didn’t have was something to step into the void left by the sudden departure of Cat’s super-successful C12 and its C13 successor.

 Snapped during a driver change in Lindsay Transport’s Coffs Harbour depot, this Western Star is punched by an X12, notching more than a million kilometres in less than two years. All on Brisbane to Sydney B-double work. Fuel consumption rates highly
Snapped during a driver change in Lindsay Transport’s Coffs Harbour depot, this Western Star is punched by an X12, notching more than a million kilometres in less than two years. All on Brisbane to Sydney B-double work. Fuel consumption rates highly

It’s no secret, of course, that in our part of the world Cat’s little big boys carved a huge following, never more than in Kenworth’s T4 range.

Before then, Cummins had reasonable success with its M11 and ISM engines but, as Fowler admits: "Once the C12 arrived, we were out of the picture between 400 and 450hp.

"The C12 kicked a lot of goals and Kenworth was quick to capitalise with the T4, particularly as 50-tonne truck and dogs entered the market."

Of course, Cat’s departure also created a massive void at Kenworth. It, too, had nothing to fill the hole and it would take a long and tedious development program before the Paccar MX-13 was ready to start life under the snout of a T4. 

However, with the MX now on stream, why would Kenworth consider adding the X12 to the portfolio and potentially risk sales of Paccar’s own engine?

An answer depends on who you talk to.

Ask some Kenworth dealers and salesmen, and they will quietly and very unofficially admit they’d like the X12 because the Cummins reputation for service is second to none and reports about the engine’s attributes are starting to filter deep into customer ranks.

Fair enough, but what Kenworth’s corporate masters in Seattle would have to say about the X12’s inclusion is open to speculation.

From the outside looking in, it won’t be an easy sell. Then again, Kenworth and Cummins are both exceptionally good at keeping the customer satisfied.

Likewise, it’d be a brave individual who’d suggest that Volvo Group would allow Mack to add the X12 to a family stable already endowed with a hugely popular 13-litre engine. Simply put, there’s a better chance of winning Lotto.

Maybe Freightliner! Maybe so, except that Freightliner is part of Daimler. So, too, is Detroit Diesel, and it has an engine of similar displacement called a DD13.

Sure, DD13 in Australia sells little better than square marbles but, nonetheless, it’s still part of a large and powerful corporate collective with its own agendas.

Then again, corporations can be strange creatures at times and the recent appearance at a major US commercial vehicle show of a Freightliner with an X12 under the snout did not go unnoticed.

Make of that what you will but it certainly fires the thought that Daimler’s other dependant, Western Star, could also be a candidate for an X12.

It’s a big ‘maybe’ though, particularly in our neck of the woods where Western Star and Detroit Diesel both operate under the Penske banner, and the consistent feedback from the mogul’s men is that X12 and Star won’t be co-habiting anytime soon.

However, as you’ll read soon enough, the X12 is already on trial in a couple of Western Stars and, from all reports, doing a great job.

Meanwhile, what about International’s ProStar?

With no viable alternative to the X12 from within its own ranks, surely ProStar’s appeal for short-haul truck-and-dog applications would be enhanced by adding the light and lively 12-litre Cummins to a portfolio already equipped with the X15 engine.

Besides, it’d certainly be something of a coup to be the first to offer an engine with so much apparent potential.

 It’s a fair bet Cummins insiders have long known it wouldn’t be easy finding a home for the X12
It’s a fair bet Cummins insiders have long known it wouldn’t be easy finding a home for the X12

But don’t hold your breath. Given the debilitating delays in bringing ProStar to market, you’re probably better going for another Lotto win than wait for anything resembling an International initiative.

Looking outside the square, perhaps X12 could be a candidate for a nationality other than American. Japanese, for instance.

Market leader Isuzu doesn’t lack for much except an effective prime mover model, and it’s no great secret that some of its local leaders would dearly like a strong, efficient, advanced engine around the 12- or 13-litre size for its flagship Giga.

Again, though, it’s hard to see a way through the corporate complexities. 

On all these scenarios and suggestions, Fowler just shrugs and says: "We’ll keep doing what we’ve been doing, and that’s building a case for the X12 by showing the market what it’s capable of.

"We already know it’s capable of so much and so do a lot of others. Word is getting around."

Building a Case

On a quiet Saturday afternoon in the latter part of 2012 I was given an unofficial and definitely ‘off the record’ steer of a Kenworth T609 in the industrial backblocks of south-east Melbourne.

Underneath the drooping snout was a Cummins 13-litre engine, secretly installed at the company’s Scoresby pilot centre.

Yep, that’s right, 13 litres! The engine was a test unit built at a state-of-the-art Cummins manufacturing plant in China.

With Australia becoming a global field test site for Cummins, it was sent here for a two-year trial to validate reliability, performance and fuel economy in a B-double shuttle operation. Horsepower was said to be ‘something above 500hp’.

Known internally as the ISZ13, the engine was essentially built for the burgeoning Chinese market where Cummins has established large operations in joint ventures with the massive Dong Feng and Foton brands.

In this case, the 13-litre was part of the Dong Feng business, and for Cummins South Pacific it was an ideal opportunity to assess the engine’s merits for the Australian market.

After all, there remained a yawning gap in the Cummins product range between the 11-litre ISM and the 15-litre ISX.

 It’s all about energy productivity and by that I mean maximum payload and minimum fuel. The X12 ticks that box probably better than any.
It’s all about energy productivity and by that I mean maximum payload and minimum fuel. The X12 ticks that box probably better than any.

However, little more than a year later, in September 2013 to be exact, something occurred that would take the local focus off the 13-litre and shove it square in the face of an entirely new engine project called the G-series.

Not to be confused with the existing ISX12 engine designed and built in the US for the US, the G-series would come in 10.5- and 11.8-litre displacements, with the bigger of the two ultimately known as the ISG12.

While design and development would be led by a team in the US, the G-series was created in a joint venture with Foton – the Beijing Foton Cummins Engine Co. – and would be built in China in a high-tech plant described as the showpiece of Cummins manufacturing facilities around the world.  

Indeed, at the announcement of the new engine family, its importance was ideally described by Cummins vice-president and chairman of Cummins China, Steve Chapman, when he said: "The G-series global design approach is a vivid demonstration of how Cummins is transforming from a multi-national to a truly global company."

After that, nothing much was heard of the ISG12 in our neck of the woods until its appearance at the 2015 Brisbane Truck Show, accompanied by a press release announcing the start of Australian field trials.

Cummins was excited, and rightly so.

Finally, here was an engine with the apparent attributes to fill a seemingly interminable void in the Cummins catalogue.

What’s more, Cummins was quick to point out that ‘the field test program is solely a Cummins project, with engine installation carried out at the brand’s Scoresby pilot centre.’ In other words, it was totally a Cummins initiative.

Still, looking small and spindly alongside its 15-litre brother at the Brisbane Truck Show, and with no immediate sign of an eager truck partner, the future was undeniably uncertain.

Nonetheless, Cummins was determined to push forward, citing a long list of features starting with the ‘innovative architecture’ of a sculptured block design and extensive use of composite materials to bring the engine’s dry weight down to just 862kg.

What’s more, with 500hp and 1700lb-ft of torque, and torque rise said to be as high as 60 per cent, the ISG12 could claim title to the highest power-to-weight ratio of any engine in the 10- to 16-litre class.

Then there was the XPI common-rail fuel system derived from the 15-litre engine, generating injection pressures over 30,000psi to achieve high levels of fuel efficiency and engine response.

 The Cummins reputation for service is second to none and reports about the engine’s attributes are starting to filter deep into customer ranks
The Cummins reputation for service is second to none and reports about the engine’s attributes are starting to filter deep into customer ranks

Plus, the relative simplicity of a wastegate turbocharger, a single-cam in-head design, and a rear geartrain to keep vibration and noise down.

By the time the 2017 Brisbane Truck Show rolled around, Cummins had more big news.

For starters, in a clever marketing initiative, both the ISG12 and the 15-litre ISXe5 were rebranded the X12 and X15 respectively.

The really important news, however, was that both engines would be able to meet the proposed Euro 6 emissions standard without any EGR input.

Given the depth of difficulties with its ISX EGR engine, it was welcome news that went way beyond the Cummins camp.

On those 12-litre field trials, the first unit actually went on the road a month before the 2015 truck show, again in a Kenworth T609 running top-weight B-double shuttles between Melbourne and Tarcutta.

Yet despite the prospect of filling an obvious gap in the Cummins range, Fowler admits he was nervous about the 12-litre engine’s ability to withstand the pressures of an intense B-double workload.

"I honestly wanted to see if we could break it," he confides, "but in two years and 400,000km it has done everything asked of it and then some.

"I suppose you could say I’ve been surprised but when you take a long, hard look at it, I think the real technological breakthrough with the X12 has been the creation of an engine with such strong power density in a lightweight cast iron block."

Four more X12s are now on trial in various applications.

There’s one in a Lindsay Transport Western Star hauling non-stop B-doubles between Sydney and Brisbane, which has now notched an astonishing 1 million kilometres in less than two years.

Word has it that fuel consumption of this unit is consistently around 2.3km/litre (6.5 mpg), which is incredibly impressive given the workload. It’s worth noting, however, that AdBlue consumption is relatively high at around 7 per cent of fuel consumption.

There’s another engine in a B-double fuel tanker operation with Toll Liquids, again in a Western Star. Still in the Toll operation, there’s also an X12 in a Kenworth T359 pulling a single fuel tanker which has apparently set a new benchmark for tare weight.

Most recent in the ranks is John Crampton’s T408 tipper and quad-dog combination.

"There have been the occasional issues," Fowler remarks, "but seriously, we’re more than happy with the results in reliability, performance and fuel. We’re particularly excited about some of the fuel figures that are coming through."

As for the future, it’s a cautious and perhaps even evasive Fowler who says simply: "There are many options on the table but the potential for the X12 is obvious to most people who know anything about it.

"All I can really say right now is that Cummins will continue to pursue all opportunities and there are definitely many applications where a lightweight, fuel-efficient, high-performance engine would be welcome.

"It’s all about energy productivity and by that I mean maximum payload and minimum fuel. The X12 ticks that box probably better than any, so it’s more a case of when rather than if it will be offered in a truck.

"Perhaps the biggest question is whether a Euro 5 or Euro 6 version will be the first X12 on the books of a truck supplier. I reckon we’ll know soon enough."

Cummins X12 Specs

Displacement:   11.8 litres

Power:               350-500hp (261-373kW)

Torque:              1800-2300Nm (1328-1696lb-ft)

Length:              1295mm         

Width:                938mm

Height:               1050mm

Weight (Dry):    860kg

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