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The Ecomatic Golf is entirely conventional in ap­pearance & is available in Europe in two & four-door forms. It’s what’s under the skin that makes this car so interesting. By JULIAN EDGAR Volkswagen’s Ecomatic: a whole new meaning to stop/start driv­ing Recently, Volkswagen brought a uniquely-specified demon­stration model to Australia. Called the Golf Ecomatic, it has a lot of relevance to future cars – especially those which spend most of their time in cities. At first glance, the specifications of the Ecomatic Golf don’t look very exciting – a Diesel engine with just 47kW (but 124Nm), a 0-100km/h time of 18 seconds, and a top speed (even with the car’s good aerodynamics) of only 156km/h. But it’s the fuel economy – and how VW obtains it – which is the intriguing aspect. Diesels always have good economy but with a city cycle of 4.6 litres/100km (about 62mpg) this car’s something else again! Emission levels January 1995  53 The drivetrain is based on the standard Golf Diesel, with a few additions. On the right is the huge battery which powers the heater water flow, vacuum & power steering when the engine is off, & just to the left of that is the bellows which controls the clutch movement. are also greatly reduced over a conventional diesel engine. So how do they do it? The basic approach is that the engine is switched off whenever it’s not needed. In urban use, that can amount to as much as 60% of the time. The resultant fuel saving is about 40% over a conventional car of the same type, with obvious reductions in pollution and noise emissions. The Ecomatic Golf uses a conventional Golf Diesel power­ train, from its 4-cylinder 1896cc engine to its single-disc dry-plate clutch and five speed manual gearbox. However, the car is driven in a way that’s quite different compared to a conven­tional Dash warning lights are used to indicate aspects such as the need to change gear for best fuel economy & to warn if the wrong gear is selected (for example “second” when the car is station­ary). The button on the end of the right-hand stalk switches the Ecomatic system off. 54  Silicon Chip car. For a start there’s no clutch pedal. The clutch is operated pneumatically, being triggered by a micro-switch in the (conventional looking) gear lever knob and activated only when the throttle is released. To move off, first gear is selected and the accelerator is depressed. The car drives off with a slight jerk and as revs rise the gear lever can be moved into second and so on. At the first throttle liftoff – eg, when ap­proaching a red light – the engine dies completely and the clutch automatically disconnects the engine and transmission. Changing back down through the gears is pointless – the engine is switched off and there’s no connection between it and the wheels anyway. While sitting at the lights the car is quiet and still, although all of the usual electric and engine-operated equipment, such as the brakes, heater and radio, continue to work normally. When the lights turn green, pressing on the accelerator immediately starts the engine and the car moves off – if you’ve selected first gear, that is. If you’re in the wrong gear, a warning light glows. Another warning light is used to indicate when a gear change should be made if best fuel economy is to be realised. When driving around in first gear, the engine takes five seconds of zero throttle application before it dies. This means that, for example, if you’re leaving the driveway of a petrol station and you’ve waited more than five seconds for traffic to clear, the engine will have switched off by the time you wish to join the flow. In order to maintain engine-dependent functions when the engine is off, the Golf uses a huge 92 amp/ hour battery and a 90-amp alternator. Electric motors are used to circulate coolant for the heater when the engine is stopped, while vacuum for the brakes is supplied by an electric pump. The power steering also uses electrics rather than an engine-driven pump. The electric power steering system is also more fuel-efficient than a conven­ tional hydraulic system, saving 0.1 litres/100km. A potential problem with this system is that voltage-dependent devices could be upset by the large drop in battery voltage each time the engine is started. These ancillaries include the headlights and the airbag trigger This diagram shows the layout of the control system. Note the electrical operation of the power steering, coolant & vacuum pumps. control unit. VW solved this problem by using a second, much smaller, battery to supply these ancillaries during the actual starting process. Since this typically takes less than half a second (according to VW), this battery needs only a very small capacity and in fact looks like a motorcycle battery. Electronic control system The Ecomatic electronic control system (horribly dubbed by VW the Digi-Swing) uses 13 input sensors. Coolant temperature, load, gearbox speed, road speed, gear position, brake operation and Ecomatic switch position are just some of the inputs. The amount of torque being applied to the steering wheel, whether or not the driver’s hand is in contact with the gear lever knob, and whether the bonnet is open or closed is also monitored. The latter input is necessary to avoid the possibility of automati­cally running over a mechanic working under the bonnet! The control system decides when to start and stop the en­gine, engage and disengage the clutch, switch on the pumps for power steering and vacuum, and when to switch to the auxiliary battery during engine starting. A dedicated ECU controls the Ecomatic functions. Input sensors include load, coolant temperature, gear lever movement, road speed & nine others! A range of control behaviour is built into the system. If the coolant temperature is below 40°C, the engine will not au­tomatically switch itself off, nor will it do so when the car is in reverse gear. Before the clutch is (automatically) engaged, the electronic control unit checks engine speed against output shaft speed and waits until the two are identical. VW claims that this allows the fully-laden car to move off up a one-in-five incline with no problems. Driving the Ecomatic Once you get over the shock of the engine constantly switching itself off, it takes only a short time to adapt to this car. In city use, apart from the problem of inattentive pedes­ trians who can’t hear you coasting up to them, the car works well. On open roads, the fact that the engine switches off the moment you lift the accelerator could cause a few problems when it comes to ensuring smooth cornering lines. However, this prob­lem is easily overcome by activating the override button. This disables the system so that the engine runs constantly as in a conventional car. The car is on sale in Europe now and, given the positive reaction to the demonstration car, it’s probably only a matter of time before it’s on SC sale here. January 1995  55