THE CT13 performance characteristics and drivability are unlike any previous Cat engine. It's much quieter than the C13 and this is really noticeable in the cabin of the CT610.
The lack of engine noise requires new drivers to keep an eye on the tacho in order to get the gearchanges working smoothly. The engine sounds much the same at 1300 rpm as it does at 1700 rpm and it takes a little time to adjust your senses.
The CT13 engine's fuel maps show greatest economy between 1200 and 1400 rpm but fuel economy doesn't change dramatically between 1400 rpm and 1600 rpm and the engine can easily rev to 1900 rpm if needed.
In fact, the performance mode of the optional Eaton Ultra Shift Plus automated gearbox uses 1900 rpm as an upshift point. Throttle action is very different to the C13 and C15 engines and the fuel delivery is much more responsive to throttle position. For example, 85% throttle is 85% fuel to the engine, so any lack of attention to throttle position will affect road speed.
This incremental throttle response could be a big plus for operators looking for improving their fuel economy.
The CT610 will come with 3.9:1, 4.1:1 or 4.3:1 diff ratios and operators will have to carefully choose which ratio suits the truck's operating environment. The standard 18-speed Eaton Roadranger gearbox has 0.83 and 0.76 overdrive ratios. It follows that a CT610 with 3.9 diffs won't suit hilly terrain but will get great economy on the relatively flat highways in most parts of Australia.
I managed to maintain better top-end road speed by downshifting half a gear at 1400 rpm (100 km/h is at 1450 rpm) and mostly making full shifts the rest of the time. The CT13 has better torque than the C13 and therefore has greater lugging characteristics.
Maximum torque is spread evenly from around 1100 rpm to 1300 rpm and it's surprising how long the CT13 will hang on to a gear.
I timed a 4.1:1 C13 and a 3.9:1 CT13 (both at 42 tonnes) on the long climb up the Pentland Hills near Ballarat in Victoria and the CT13 was only 6 seconds slower, despite the disadvantage of a lower diff ratio.
So despite the different driving styles and different performance traits of the two engines the trip times were essentially the same.
It's surprising how quiet the new engine brake is at all rpm levels.
It's actually unbelievably quiet. In fact, many drivers doubt it's working because they can't hear it, so you really have to tune in to its sound.
In terms of retardation, the new CT13 engine brake is more powerful than the C13 engine brake and its lack of noise makes it an engine brake that you don't have to switch off in built-up areas.
All of these new aspects of the CT13 will add to the perspective operators have about Cat engines.
- René Bueman