What is intelligent energy management?

In fulfilling its primary charter of getting us from A to B, our car's engine finds itself loaded up with all sorts of other incidental jobs. Each of which saps a little of the energy from that primary task, putting more pressure on engine, fuel supplies and environment alike.

For example, an engine keeps cool by powering an internal coolant pump -- and keeps us cool by powering an air-conditioning compressor.

A vehicle's engine finds further distraction in powering the hydraulic steering system, relieving us of most of the effort involved in turning the steering wheel. Ditto the braking hydraulics that amplify a relatively light push on the brake pedal into the power to decelerate a ton and a half of car from 60km/h to zero in less than a hundred metres.

It's also responsible, via the alternator, for generating power for all those lights, audio and navigation systems, 12-volt outlets, fuel pumps, washer pumps, engine management and ignition systems, electrically powered door- and bootlocks, windows and sunshades, exterior mirrors, seats, safety gizmos like seatbelt pretensioners, airbag triggers, folding headrests and pop-up roll protection, sunroofs, moonroofs, folding roofs... there's no doubt the average 21st Century car asks a lot of its engine.

More than it needs to, in fact. The simplest way to get all this happening has always been mechanically -- by connecting the water pump with cogs, the air-conditioning compressor and alternator by external belts and so on. Which means from the moment we start the car at Point A, those devices are always on and diverting engine power away from the drivetrain, until we arrive at Point B and switch the engine off.

Lightening the engine's workload
But with the help of sensor devices and intelligent engine management systems, today's mill can be made to run much more efficiently than its pre-electronic, pre-computerisation ancestors.

An example: with a substantial reserve of power always on hand in its battery, why does it need to spin an alternator constantly to fulfil all those electrical needs? Wouldn't it take a load off the engine to keep the alternator on only when the battery needs topping up? And while the battery's fully charged, it makes sense to convert other functions from mechanical to electrical, relieving the engine of other power-saps.

Enter a raft of new technologies, all aimed at lightening the load placed on the engine by peripheral devices, both directly and indirectly. For example, braking is totally dependent on friction. Friction can be used to generate electricity. Hence the advent of regenerative braking systems like that in the Hybrid Synergy Drive systems Toyota uses in its Prius and Lexus hybrids.

Touching the brake pedal puts the car's motor-generators into generator mode, converting internal friction into braking force and electrical energy with which it tops up the battery. Mercedes-Benz takes this a step further -- all you have to do to activate these regenerative forces in its upcoming S400 BlueHybrid is take your foot off the accelerator.

BMW takes the notion further again, co-opting other peripheral devices to assist by staying out of the way when the engine is applying power to the road, and stepping in to do their job only during deceleration. With or without braking, deceleration uses forces of resistance inside the engine and transmission.

BMW's clutch-driven alternator disengages to lighten the engine's load, engaging only when it detects deceleration. This adds modestly to engine resistance when it's needed and tops up the car's absorptive glass mat (AGM) battery at the same time (although it will activate at any time it detects an urgent need for a top-up). The result: greater efficiency both when accelerating and slowing.

The extra electrical energy opens up all manner of opportunity to lighten the load elsewhere, too. Electric power steering boxes, for example, save the engine from having to provide a constant supply of hydraulic power in anticipation of the driver turning the wheel. Instead, the car activates the electric motor/s on demand. The same goes for electrically powered coolant pumps. This means these devices place no direct demand on the engine, drawing their power from the battery instead.

Auto start-stop systems
Refusal to start has always been the internal combustion engine's favourite way of annoying its owner. Firing it up as the most stressful part of its operation. Especially petrol burners. Diesels have always been easier to keep running, without the need for spark plugs and therefore no requirement for a constant roll of perfectly timed, perfectly placed electrical charges.

But now, with the evolution of better plugs and improved ways of channelling the charge to them, and the advent of computerised engine management systems, those cries for roadside help have become fewer and farther between. Engines are now reliable enough to take to the next level: auto stop-starting when there's no call for them to be wasting fuel and fouling the atmosphere while they're stationary, even for a moment.

Stop-start systems are appearing in different forms through all manner of drivetrains. Full hybrid systems like Toyota's Hybrid Synergy Drive simply turn their petrol engines on and off as they need them. Mild hybrids like the Smart Fortwo 'mhd' can cut the engine every time they detect deceleration, using a heavy-duty starter-cum-generator -- a kind of oversized starter motor -- to give it a stronger than normal kick in the pants as soon as it's needed.

BMW has been able to deploy the technology in some of its standalone internal combustion engines. Deceleration and shifting to neutral switches the engine to sleep mode until it's put back in gear, and the accelerator is pressed, at which point it restarts instantly.

An important part of the technology is the capacity to tell itself when not to deploy -- for example not stopping before the engine has reached optimum running temperature, or not starting if it detects open doors or undone belts, automatically restarting the engine if it detects motion, or if the battery charge drops too low.

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