Brainy Benzes eke out fuel savings

If you want to optimise fuel savings then trust your Mercedes-Benz to do more of the driving.

That’s the message from Benz’s plug-in hybrid guru Jochen Strenkert, who says some tricky tech can cut fuel consumption by five per cent if the driver takes the hints being offered by the car and allow it to recapture the maximum amount of energy while cruising.

“We did some experience and we figured out about five per cent that we can drive more efficiently if we inform the driver to move his feet from the throttle and the car makes the recuperation algorithms by itself,” Strenkert explained.

Stenkert was speaking at a future drivetrains media briefing in Stuttgart last week, where the headline items were Benz’s EV attack and its confirmation of a modular inline six-cylinder engine strategy.

But there were also a variety of more detailed initiatives revealed as engineers and researchers emerged from their workshops and labs to share technology advances that will soon be soon be making it into production.

Plug-ins are an important part of that story for Benz, with four models launching in Australia in July and 10 due to be launched globally by the end of 2017.

It was officially confirmed at the briefing that the facelifted S-Class plug-in due toward the end of 2017 will be the to use a new generation lithium-ion battery developed and manufactured by Benz that will lift electric operating range from today’s 30km to beyond 50km.

But Strenkert also revealed two operating system optimisation measures the new S-Class will introduce that will aid that range improvement – if the driver is willing to let the car take over.

One uses the sat-nav system to calculate the optimum coasting cornering speed to harvest the maximum amount of energy, while the other boosts battery charge when it receives instruction there is a traffic jam ahead.

“What we will do for the new S-Class is get the information from curves ahead of the driver and calculate how fast we can cruise the curve and recuperate (energy) on that velocity automatically without braking needs from the driver,” Strenkert confirmed.

“In the next S-Class we also use traffic jam information to calculate the best operating conditions because we want to drive traffic jams in fully electrical mode because it is more efficient.

“So we charge the battery first when you drive on a highway. We calculate there is a traffic jam in seven to eight kilometres and we increase the state of charge of the battery on low power management of the engine.”

Strenkert made it clear that S-Class’ cornering harvest would only apply when the car was in Eco mode, rather than one of the more sporting set-ups the driver can opt for.

“We calibrate the system for the start in the economy program so we think the driver would like the best efficiency in economy mode,” he said.

“In Sport+ mode we do not cut the engine off so the recuperation is not as interesting as in the mode where the driver lifts the pedal and we cut the engine.”

The functions are also designed to operate mostly transparently to the driver.

Apart from the new I6 family and the upgraded plug-in hybrid system, the next S-class will also debut Benz’s new 48-volt onboard power supply and integrated starter generator (ISG) with the I6 that will operate like a mild hybrid system.

Four-cylinder engines will also get the 48-volt battery system combined with a belt-driven starter generator dubbed RSG.

These initiatives will follow on from updates for the E 350e plug-in, which is expected on Australian sale late in the year, that include analysis of the planned route so the electric driving, recharging and cooling strategies are optimised.

For instance, if the navigation systems warns a steep hill is upcoming on the route the electrical and powertrain components are cooled more than normal.

“Then we have more possibility to have the maximum performance if you creep up the hill,” Strenkert explained.

The E-Class also uses speed sign identification to recommend to the driver when to ease of the throttle so harvesting can be maximised. However, because speed sign identification is not yet available in Australia, we won’t be getting that feature any time soon.

The E-Class plug-in will debut the use of Benz’s new 9G-TRONIC nine-speed auto as part of a plug-in drivetrain.

It will also debut the latest-generation electric motor which pushes power up from 60 to 65kW and torque from 350Nm to 440Nm. Curiously, however, the E 350e’s overall torque limit is 550Nm compared 600Nm offered by the C 350e, which uses the previous generation electric motor.