PowerTorque tested the lates TG3 MAN B-double prime mover over a typical test route for this kind of truck to ask the question, can the new MAN really cut the mustard?
The truck tested in this run, up and over the Cunningham Gap out of Brisbane, followed by a descent down the old Toowoomba Range crossing, is fitted with the D38 engine which meets the Euro6e emission regulations.
Power comes out at 640hp (477kW) from the 15.2L engine and it produces 3000Nm (2213 ft lb) of torque. Emissions are controlled using SCR and EGR, and the engine is fitted with a two-stage turbo.
With a loaded B-double set the truck began climbing Cunningham’s Gap after coming out of Brisbane and kept up a good pace, around 44km/h at 1650rpm. The quality of the torque available is clear and the truck settles down quickly to get the job done, with minimum fuss, it never rushes anything. The driver can just let it lug its way up the grade and it just continues to pull. Because the control systems are precisely monitoring everything all of the time.
Listening to the engine note, a driver could be feeling the engine is lugging too low, but the system knows what it’s doing and can pull up from this rpm level. The driver has to leave old perceptions behind and learn to trust it.
It does not feel like the D38 engine is overworking itself at all. It’s clearly got more capacity available. The engines are built to cope with a control system, which will keep it below 1600rpm, at the point where horsepower will match torque. Watching the truck haul itself up the varying gradient on the Gap, it obviously likes a point around 1600rpm and changes to get into its comfort zone.
This change to running trucks at lower rpm ranges has two factors behind it. One is the fact that the extremely sophisticated control of diesel engines has reached a point where it can cope with the strain put on an engine hauling 60 tonnes up a climb in high temperatures. The second factor is that after many decades of talking about fuel economy the trucking community in Australia is genuinely looking for frugal fuel use.
There is now an expectation that a B-double prime mover will achieve 2km/L all of the time. Whereas, in the past, they were happy with 1.65km/L.
The engine meets Euro6 emission limits and the control system which help the engine meet them also give it the flexibility to meet the challenge of a climb like the Gap. This is illustrated at the very top of the grade when the trailers are still hanging down the hill and the final kick of the climb tests even the best truck. This MAN lets the truck drop down to 33km/h and it just hangs on over the top in eighth.
Once over the top another strength of this latest design comes into play, the excellent retardation from the engine brake, the EVBec, which MAN claim generates 840hp of stopping power. This is a very high number for a compression brake to offer, but in the drop off the top of the Gap and then the steep descent of the old Toowoomba Range, the Brakematic, as it is known, showed just how much control it offers to the driver in a situation where control is paramount.
The engine brake has the exhaust flap positioned upstream of the turbo, allowing it to generate more back pressure when activated. The airflow creates an increased turbine speed on the exhaust side, which, in turn, ups the intake side speed. Pressure level overall increases and the effect of the braking increases correspondingly.
That’s the theory, and the practice bears this out. The engine brake doesn’t have to be finessed to avoid over-braking when on a descent. It’s not a matter of full engine brake and see if it holds, it’s more about modulating the brake to maximise speed down the grade while retaining full control and the ability to pull up if required.
At the top of the old Toowoomba Range the driver just has to apply the brake, and the system knows that they don’t want to go any faster than that. The driver is setting their speed at the crest of the hill and for 5km it is able to hold that speed going down the grade.
There is no need for driver intervention to help maintain the speed, no riding the brakes. The sensation is different, the driver presses the brake to signal the speed and then the trucks overruns a little bit and then pulls it back to a km/h that they’ve set.
The descent of the Toowoomba Range saw the truck passing most of the other trucks heading down the grade but able slow down or speed up, at will, just using the control switch. The service brakes were not needed even when having to slow behind another truck before being able to overtake.
After the experience of the first descent the driver starts to feel comfortable, knowing that it’s going to use the engine brake and the service brakes, and do what it needs to keep to the correct safe speed.
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