DRIVEN
When two component suppliers work closely together, the outcome can be highly impressive – Words by Dave Whyte and Chris Mullett
of AMTs in recent years while Dave concentrated more on what it meant for the driver. We hope you find the outcome interesting. two journalists from the same publication covering the same story can be a bit like putting two sheepdogs in the same paddock. One will sit back and watch, while the other runs in circles making a lot of noise. In the case of this evaluation of the latest Eaton UltraShift PLUS, Dave and I both felt that two heads were better than one. Rather than sitting back and letting Dave do all the work, my view looked at the incredible advances 20 PowerTorque ISSUE 66
If you have negative views about the shift quality of some of the early Automated Manual Transmissions (AMTs), it’s time for a rethink. Admittedly, with some of the first versions the engine rpm seemed to soar between shifts or baulk at selection through the lower part of the ‘box, but with the latest systems so much has changed that you really need a personal update.
THE ART OF INTEGRATION
The intervening years between the first AutoShifts and the latest UltraShift PLUS have resulted in an amazing transformation of performance, efficiency and drivability. Gone is the occasional hesitancy between shifts, replaced by smooth shift patterns and an almost uncanny ability of the engine and transmission to predict and engage the right ratio for any situation. And, as a by-product, there’s every likelihood you’ll be extending your clutch life as well. PowerTorque has always been a supporter of the AMT principle, although admittedly we had our reservations about the early versions, for the reasons already listed. For a while it looked as though the Europeans such as ZF with its AS-Tronic and Volvo with its I-Shift were untouchable in terms of sophistication, even though their North American counterpart, Eaton, had the reputation for longevity and suitability for the Australian market.
As the leading truck manufacturers shift their emphasis to vertical integration, we’ll see specific drivelines becoming available only in particular brands. It may not suit operators that preferred to mix and match their engines and transmissions, but it’s of great appeal to the bean counters that firmly believe a Daimler truck (Freightliner, Western Star, Mercedes-Benz and Fuso), should have a Daimler engine (Detroit 9, 11, 13, 15 and 16-litre), a Daimler DT12 transmission (Detroit 12-speed), and run on Daimler axles (again Detroit branded). Navistar now openly embraces its relationship with Cummins, and there’s every possibility the recently released Cummins 12-litre will take a share of the US market, in consort with the availability of the Navistar MaxxForce 13. PowerTorque ISSUE 66
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DRIVEN It’s a similar story with PACCAR brands Kenworth and Peterbilt. Their future driveline options are becoming focused on the PACCAR MX-13-litre, with the flexibility of larger capacity engines being handled by Cummins. What both PACCAR and Navistar have in common though, is the centralised focus on Eaton as its major supplier for transmissions, except where Allison automatics excel in certain applications. Because on-highway trucks in the North American and Australian markets differ so greatly in terms of weights carried, ambient temperatures and power requirements, there’s a huge disparity when it comes to determining an ideal powertrain solution that fits both markets. So much so, in fact, that the US is now standardising on the sub 500 hp level matched to 10-speed transmissions to handle gross weights of around the 40 tonnes mark.
Sam Abulughod is typical of the new breed of engineers working in the Australian market. As a systems engineer with Eaton Vehicle group, Sam’s background was based in mechatronics, the implementation of robotics in engineering applications. It’s a long way from being on the spanners or twisting a few wires together. Sam and his boss, Graeme Weston, have been instrumental in developing the latest shift protocol for the 18-speed Roadranger UltraShift PLUS transmissions matched to the Kenworth T-Series. A comprehensive test and development programme over 18 months has resulted in Eaton releasing a completely new and more refined computerised shift programme that can be uploaded into any existing UltraShift PLUS transmission coupled to a PACCAR MX-13 engine.
The Australian requirement for higher weights, long distances and high ambient temperatures, puts our market mainly in the 500-600 hp segment, except where singletrailer applications are the norm.
PowerTorque was the first Australian trucking magazine to be invited to evaluate the new programme, and we did so in the company of Eaton’s Sam Abulughod and Jon Penrose, PACCAR’s MX-13 technical specialist.
The introduction of the PACCAR MX-13-litre engine in Kenworth T-Series products brings us back to the original topic of how to get the best driveline matching between engines and transmissions for the B-double, on-highway segment.
Our test bed for the day was a Kenworth T409 6x4 prime mover powered by a PACCAR MX-13-litre producing 510 hp and with 1850 lb-ft of torque. This was coupled to a tri-axle curtainsider carrying concrete blocks as a test weight to gross out at 40 tonnes.
As an example of how fast the powertrain development has moved in terms of engineering, the development team responsible for improving and perfecting the match between engine and transmission has a much broader background in experience than simply being able to select a bunch of different sized cogs and package them in a gearbox.
The PACCAR MX13 engine is returning excellent feedback from operators for good fuel economy and a high acceptance rate amongst drivers. The new shift protocols for the UltraShift Plus transmission enable a complete integration of the driveline.
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DRIVEN
As a bit of background to the development of the UltraShift PLUS, Eaton has taken the basic RTLO-18918A 18-speed transmission and added components such as an Electrical Clutch Actuator (ECA), an XY Shifter for gear selection and an Electronic Control Unit (ECU) that controls all aspects of the transmission. The ECU performs the calculation for the grade of the road and the weight of the vehicle, and it was the further refinement of the ECU protocols that developed new shift points for the Australian market in the MX configuration. The aim of the programme development is to improve the ratio skip-shifting performance of the transmission, and it does so based on its availability with the optional RTLO-18918A version of the Roadranger, rather than the 18918B model. “The ratio spread for the first two gears in the “A” box is 12.9 and 10.41, versus the “B” box of 14.1 and 12.29:1,” said Sam. “That allows us to have a 2nd gear start with a 2nd-3rd gear step of 18 percent, after which it skip-shifts better than in a B-ratio, which has a 2nd-3rd gear step of 44 percent,” added Sam. “By starting in 2nd gear, and with skip-shifting, we get a better launch performance off from rest and better acceleration as it skip-shifts through the gearbox. This choice also extends clutch life. “The ECU is constantly assessing the grade and throttle position to choose the best skip-shift options. It also measures the turning offsets of the steering angle, and by doing so it prevents a skip-shift occurring when negotiating a corner. Holding a ratio during the turn then ensures the best engine performance through the corner. “We wanted to use a mix of performance and economy. We can do that through having grade-based shift files. It’s about understanding how the engine likes to spend time between 1000 and 1400 rpm, and keeping the shift point in the most fuel-efficient zone. The MX engine loves to spend its time where the peak horsepower and peak torque meet, right at 1400 rpm, and every downshift on a hill goes through this zone. “When the transmission is upshifting at full throttle in the first few gears we rev from 1675-1800 rpm. If you are at full throttle you want to keep going, so we skip-shift in the lower part of the box to get it moving. Then we reduce the skip-shifting as you get higher in the box. “It’s all a question of making the engine performance more flexible. If the engine is at 1400 rpm and skip-shifts, you land at about 1100 rpm, and can still pull this weight on level ground at light throttle. When launching downhill, I’ve seen it skip-shift five ratios from 2nd to 7th just to get the truck going. This would be followed by 12th – 14th – 16th, whereas on the flat it would go 14th – 15th – 16th individually,” said Sam.
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The best way to evaluate the new protocols is of course behind the wheel, and both Dave Whyte and I spent the day behind the wheel getting a taste of the new technology. My immediate impression was that at last the driver interested in making a difference can use the technology by varying throttle pedal pressure to promote gear shifts, both up and down through the box. It’s no longer necessary to play with the manual over-ride controls, as the system is so intuitive. The steering-wheel controls for the exhaust brake enable the driver to change the downshift rpm sets and to maximise the additional retardation available. Similarly, upshifting from a launch in 2nd gear depends on throttle pedal pressure, as it selects whether to skip-shift or take ratios on a one-by-one basis. All my driving was completed around the road network to the northeast of Melbourne, and on a light downhill grade it’s not uncommon to see a skip-shift of up to five ratios completed in a split second. In normal driving the combination seems happiest with skip-shifting two ratios at a time, but the outcome is sure to be noticeable in three ways – first, by the reduction in driver fatigue; secondly, by the reduction in driveline stress; and, thirdly, by an improvement in fuel economy. Sam from Eaton used the expression that the new shift programme would “change your mind about changing gears”. Eaton has a lot to show for all the hard work, and, as the company upgrades existing transmissions already in service, it’s not going to be a well-kept secret for much longer. In simple terms, it’s very impressive.
Sam Abulughod Systems Engineer with Eaton Vehicle Group.
THE ART OF INTEGRATION
We’re a clever bunch here in Australia having made an art out of beating other countries at their own game. Cricket, tennis, golf, surfing and a whole swag of other sports make up a list where we have learned from and then beaten other nations at their own game. This is no different in engineering, though it is often overlooked. The latest conquest comes from two very well-known names in the Australian transport industry working together to take on the world with exceptional results. It’s fair to say that the first generation Eaton AMT transmissions were not very well received in this country. There were numerous issues faced by operators at the time, including the dreaded neutralisation and indecisive gearshifts that left many drivers sitting still halfway through a steep climb. These issues can probably be put down to two factors: the installation of American shift programmes, and the higher weights we run here.
That in itself is no mean feat, given the number of systems and sensors on a modern truck, and the engineers at Bayswater knew they had to get it right or risk the same result as Eaton had with their early AMTs. Having sorted the engine fitment, and gained some very favourable customer feedback, it was time for the next challenge. This is where the Eaton UltraShift PLUS comes into the picture. The driveline combination of the PACCAR MX-13 and Eaton UltraShift PLUS has been on sale to American buyers in both Kenworth and Peterbilt products for a little over four years now, so one might think it would be a simple process to fit the same components to an Aussie Kenworth. It turns out the American MX-13 is actually a little different to that on offer here, the most notable difference being that it continues the American tradition of running on a 12-volt system. Another big factor is that more and more American prime movers are running 10-speed transmissions and diff ratios as low as 2.9:1, which would require a very different shift pattern from our standard 18-speed and 3.9:1 or 4.11:1 final drive ratios.
The combination of these two factors, along with little or no operator training on how to get the best results from an AMT, meant the uptake of Eaton’s first-generation AMT was very short lived. It also left a bad taste in the mouths of some operators, who are still hesitant about buying an American AMT. Times have changed though, and so has the Eaton AMT. There is another part to this story, which also involves some Australian engineering that leads the way. The recent introduction of the PACCAR MX-13 engine under the bonnets of Kenworth trucks was not as simple as it may seem. Alongside all the engineering required to fit the engine into the chassis rails of a Kenworth T409, there was also a lot of electrical engineering needed to make it run.
Jon Penrose, PACCAR’s resident MX 13 engine technical specialist.
For a long time now, Kenworth, like most Americanbased models, have run on a 12-volt electrical system. The PACCAR MX engine fitted to Australian Kenworths runs on a 24-volt system, so a lot of work went on in the background to ensure that all of the systems on a truck would work together seamlessly.
There is also the communication between the engine and transmission to take into account, and, as these two components had never been paired up before, a good translator would be required to enable this to happen.
Andrew Mills, PACCAR marketing brand specialist for Kenworth.
This translation needs to work between three different control modules, which, to make matters difficult, are shared between PACCAR and Eaton. Firstly, PACCAR’s MX-13 Engine Control Module (ECM) needs to communicate with Eaton’s Electronic Control Unit (ECU).
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DRIVEN While the MX-13 passed Eaton’s certification test (which tests to see how an engine responds to requests from the transmission) with flying colours, there were some glitches to be sorted. These were mostly related to gear changes while the cruise control was activated, and were resolved using a separate MX integration control unit. The result is clear communication between the engine and gearbox control modules, and perfect co-operation between the two. The integration goes well beyond electronics, though. The gear ratios have been optimised to suit the MX-13, delivering improved launch characteristics with the bonus of reduced clutch wear. The use of slightly taller ratios in the bottom end of the gearbox also allows for better skip shifting while still keeping engine rpm in the sweet spot for horsepower and torque. This in turn contributes to good fuel economy, something every operator is seeking, while still giving the feeling that the engine is performing. Gear shift points, and the actual gear chosen, are determined by a combination of factors. These include the grade on which the vehicle is operating, the weight of the combination (as determined by the Eaton ECU) and, most importantly, throttle position. The transmission is programmed with grade-based shift files, and will make more aggressive changes on steeper climbs while skip-shifting on level ground. This programme also has different parameters for various stages of shifting, with the lower range gears working higher in the rev range to maximise horsepower, while the higher gears utilise the lower rpm torque band to maintain momentum. The MX also benefits from a turning offset programme, which restricts skip-shifting during turning manoeuvres. This eliminates the chances of finding the truck in the wrong gear half way around a corner – another shortcoming of early model AMTs. In order to find out if all of this technology works, PowerTorque took the first T409 with the optimised shift programme for a drive in the hilly country to the east of Melbourne. After only a short while, it was obvious that there had been a lot of work put into this programme. The shift quality was seriously smooth, with the Roadranger skip-shifting flawlessly, and the MX-13 providing plenty of power to get the single-trailer combination motivated. From a standstill, the combination worked well on a 5% grade, providing fast, smooth and accurate gear changes without over revving the engine. On the downhill side, with only a light foot on the accelerator, at one stage the transmission jumped four gears. The shift from 4th to 8th seemed like a big one, but with gravity doing its thing and plenty of torque on tap at low revs there was no need for a gear in between. 26 PowerTorque ISSUE 66
Mr. Whyte at the wheel - never happier than when he’s driving someone else’s new truck and using their fuel.
The market for 13-litre engines between 424 hp and 524 hp is a big one, considering it takes in single-trailer, B-double, truck and dog combinations and vocational units. It is also a market that sees 85 percent of new units sold being fitted with AMT transmissions, which may explain why Kenworth has invested so heavily in the MX-13 and Eaton UltraShift PLUS combination. What it means, though, is that Kenworth now has a genuine contender for this segment, where it has fallen short in previous years due to engine supply issues and the stigma associated with Eaton AMTs. But here’s the clincher – in typical Aussie style, they have taken an idea from overseas and made it better. Having driven the American version of this driveline, I can honestly say that the Australian-engineered version is better in terms of shift quality and timing. What’s more, in a real stroke of genius, they have given the Europeans, the leaders in AMT technology, something to worry about. Without overstating it, this is the smoothest driveline I’ve ever experienced in an American-style prime mover. Not only have the engineers from Eaton and Kenworth achieved what they set out to do, they have shown the rest of the world how it’s done. Aussie Aussie Aussie, Oi Oi Oi!