Kenworth MX-13 engine test

Can a Euro engine make itself at home in a Kenworth? Matt Wood went to Mount Cotton to drive a few examples of this new engine/chassis combination and reckons it works.

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Someone from Cummins is trying to kill me. I know this sounds a bit paranoid but just remember not so many decades ago the CIA tried to kill Fidel Castro with a pair of poisoned underpants.

Just recently, I was presented with a rather innocuous looking hoodie on a Cummins test drive. It looks pretty much the same as those used to terrify convenience store attendants the world over, except of course for a cool looking Cummins logo on the front.


It turns out this garment was cunningly designed to hurry my departure from this mortal coil.

Oblivious to the lurking danger within, I was wearing this rather comfy jacket recently as I parked my car on a dark single lane suburban street. I hopped out of my chariot, locked the driver’s door and turned to walk away and found that the cartoons were indeed right; people really do make a ‘gakk’ sound, when unexpectedly grabbed around the neck.

The cleverly designed drawstring around the neck of the hoodie was just long enough to be jammed in the locked door of my car.

Just then, headlights appeared at the end of the street and were heading my way. I was trapped. I flapped and jiggled in an effort to get off the roadway looking pretty much like a seagull in gumboots trying to steal a watermelon.

Something had to give and the drawstring finally slid out of the hoodie leaving me just enough time to roll over my car bonnet and out of danger.

As I lay panting on the nature strip, the bright Cummins red drawstring still hung from my car door, flapping in the breeze like a piece of raw flesh just torn from the carcass of a dead animal.

You may wonder what motive Cummins may have for this assassination attempt. Maybe, I’ve been too critical of Cummins exhaust gas recirculation (EGR) in the past?

No, I think it’s because I’ve been writing too many positive things about the Paccar MX-13 engine, which has just been officially launched in the Kenworth T409 and now competes with the Cummins power plant in lower horsepower applications.

Either that or I’m completely mistaken and I’m just really very clumsy. I’m going to join Reporters Without Borders just in case. I will not be silenced.

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Since the end of 2010, Cummins has been the sole choice of engine for the Kenworth brand. The days of speccing a Detroit or Cat in a Kenworth have been consigned to Austalian trucking history and are well and truly over.

Detroit became a part of the Daimler empire early on and Caterpillar decided to pull out of on-highway truck engines before ADR80/03 emissions regulations hit.

With the introduction of the MX, Kenworth now has its own engine. Now Kenworth buyers have the option of the traditional red engine or the silver in-house power plant.

When I say ‘own engine’ I mean Paccar and the MX has come to the Kenworth stable from the other Paccar brand DAF. The engine itself is nothing new and 1,000 units have been sold in Australia since 2007 in the DAF brand.

The Australian launch of the DAF flagship, the XF105, two years ago certainly raised the profile of the MX-13 and no doubt paved the way somewhat for wider acceptance of the engine.


The MX-13 is a 13-litre engine that uses selective catalytic reduction (SCR) for emissions control.

It’s available in two different power ratings; 460hp (343kW) and 1,700ft-lb (2,305Nm), or 510hp (380Kw) and 1,850ft-lb (2,508Nm).

Clearly none of this is going to set the world on fire horsepower wise and when I first  got wind of this project I was initially quite sceptical.

To be honest, I initially felt this engine was going to suck a lot of the driveability and character out of a uniquely Australian truck — a travesty akin to sticking a Nissan engine into a Holden Commodore … oh wait, sorry. They actually did do that, didn’t they?

I got to drive some prototype T409s around the Mount Cotton test track in Queensland last year near the beginning of the MX testing program, and to my surprise I had to admit in the T409, the little MX actually promised to be quite a handy little unit.

Nearly 2 million test kilometres later the power plant has now been officially launched as an option in the Kenworth T409, while the initial test group consisted of eight trucks in varying applications, a further five have gone on to cover another half a million clicks.

The MX is being launched on a platform of lightweight, driveability and economy. It uses a compacted graphite iron (CGI) block that makes it very light (about 1,200kg) very strong and surprisingly quiet.

CGI is becoming quite popular as the material of choice in high performance car engines as well and is often used for exotic European ‘V’ configuration engines.

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The MX-13 is also sold in the United States and has been offered as an engine option in both Kenworth and Peterbilt products. The Aussie Kenworth MX however, is based on the Dutch-built Euro spec MX, though it does share some castings with the American version.

These castings are to help the 13-litre nestle between the chassis rails of a conventional prime mover rather than the European cab-over configuration of the DAF product.

The US experience has seen some interest in the MX as a Paccar engine option. There are now according to Paccar more than 51,000 MX engines operating throughout North America.

In fact, the MX has just had a record sales year in the US in 2013. With mandated fuel economy regulations on the way for Class 8 (heavy-duty) prime movers there could be even more take up on the way for the little silver engine.

The addition of the MX engine to the Kenworth line-up now means for the first time a 24-volt truck will be rolling off the Bayswater assembly line. Past experience with the DAF XF105 and the MX engine has indeed backed up the fuel economy claims.

I’m not renowned for having a light right foot at the best of times and I was still able to average 2km per litre in the XF as a heavy B-double on an interstate run. The only real issue I have with the DAF isn’t really that much of an issue, I just find it a bit boring, and not very engaging to drive.

Behind the MX there’s the option of the time honoured Eaton manual or the two-pedal Eaton UltraShift automated manual transmission (AMT). Apart from the diesel exhaust fluid (DEF) tank and the distinctive shape of the exhaust after-treatment box hanging from the chassis, there’s little else to distinguish the MX-powered T4 from a Cummins-powered rig.

However, coinciding with the arrival of the MX is the arrival of a new interior for Kenworth’s conventional models.

The Kenworth crew have decided to take the fun out of guessing what certain switches do by standardising switch gear across the bonneted range. New grab rails, more seat travel, a smart steering wheel, a curved dash and overhead console all make an appearance in the K200.

The driver’s seat gets more adjustment, travel and sleeper cab models get wrap around curtains and all fuses and relays have been moved to a spot behind the passenger side dash panel.


Unfortunately on the examples I looked at, the overhead storage netting that replaces the old door and latch set-up is only made up of two strands of elastic, which isn’t going to stop small items bouncing out on rough roads and landing on the driver’s head.

At 2am, there’s nothing like a sudden avalanche of CD cases, pens and paper clips raining on your head to get your attention.

At the end of the MX testing regime we finally got the chance to take the production spec finished products for a spin at the Australian Automotive Research Centre (AARC) near Anglesea in Victoria.

The assembled rigs were set up in both single trailer and B-double guise and weights were up from the last Queensland drive to between 35 tonne and 62 tonne gross. The vehicles included the T409 and the T409 SAR, and for good effect the DAF product was also well represented.

My first spin was in an UltraShift AMT equipped B-double. I climbed into the driver’s seat and glared at the AMT shifter, and if it could glare, I’m sure it would have glared right back at me.

I’ve never been a big fan of Eaton’s AMT, not through any dislike of the brand, just because I’ve wanted it to be so much better. There are some excellent AMTs out there, but the Eaton ‘box has never really performed at 100 per cent to my mind and it constantly loses marks for clutch engagement and low speed manoeurvring.

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Programming an AMT to take orders from a different engine is no small task. The MX has a typically European torque curve that gives peak torque from 1,000rpm to 1,400rpm and peak horsepower from 1,500rpm to 1,900rpm. The 16-speed ZF AMT used in the DAF performs admirably behind the MX, but I was dubious about how the 18-speed Eaton would perform behind the MX.

As it turns out, I was pleasantly surprised.

While I didn’t have the chance to drive it bobtail or to hook up and drop trailers with it, which is generally a big area of weakness with the Eaton ‘box. I did get to play with it at low speed, forward and backwards.

The ceramic clutch of the Eaton, while durable and cost effective, has made it hard to get slippage in delicate low speed situations.

The MX’s high pressure common-rail fuel injection gives impressive fuel delivery control at low rpm and there’s now some slippage possible in the clutch, making it much more controllable at low speed.

Going forward at normal road speeds the AMT behaved beautifully making the most of the low down torque in bottom box and skip shifting, where possible.

At higher speeds the AMT and MX wound out higher in the rev range picking up some of the 13-litre’s oomph. The marriage of the UltraShift Plus AMT and MX-13 engine is by far the best performing Eaton AMT application that I’ve driven to date.

To get a bit of a performance balance, I jumped into a B-double DAF XF105 and then promptly fell asleep. Luckily the bloke in the passenger seat woke me up and I got to drive around in circles for a bit until I lost the will to live. And it was then I climbed aboard a T409 SAR B-double with an old school manual shifter in it.


This was a bit more like it and gave me a chance to get a real feel for the engine and how it performs. I knew from past experience the MX was quite torquey and very forgiving on the gear changing front. But with a bit of extra pudding on it back, I was still impressed with its performance.

A short shuffle through bottom ‘box was easily done before making the jump up to high range and interestingly in top ‘box the engine was happy to change whole gears on flat ground, even at this weight.

I was basically driving it as a 9-speed progressively upshifting and leaving the splitter button alone. With each gear change the tacho needle would drop and then the engine would dig in, shouldering the load and lugging it along with impressive tenacity.

At one stage on a climb, against all instincts, I let the silver donk lug down to 850rpm and to my surprise it actually clawed its way back up the rev range without needing me to grab a lower ratio.

Out of the nicely insulated DAF, the MX actually has a bit of a note to it, especially in a day cab T4, but the lack of resonance from the CGI engine block makes it strangely muted and not intrusive.

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MAKE/MODEL: Paccar MX-13/Kenworth T409

ENGINE: 12.9 litre Paccar MX-13 with high pressure common-rail fuel injection

CONSTRUCTION: Compacted graphite iron (CGI)

EMISSIONS CONTROL: Selective catalytic reduction (SCR)

POWER: 460hp (340Kw) @ 1,400rpm to 1,900rpm or 510hp (375Kw) @ 1,500rpm to 1,900rpm

TORQUE: MX-13 460hp, 1,700ft-lb (2,305Nm). MX-13 510hp, 1,850ft-lb (2,508Nm)

GCM: 70,000kg 


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