With a diesel engine, the fuel-saving-effect is accordingly, somewhat lower.
This invention is not new, VW as a manufacturer, and Hella as a refitter already offered them in the 1980's or 90's. Indeed, in these systems one had to shut down the engine by pressing a button. The VW-engine was restarted by depressing the clutch, the Hella system had to be started by pressing the button again.
Unfortunately, a number of fuel saving innovations over the past few decades, have not been able to assert themselves, among others, e.g., was also the so-called 3+E or 4+E regulation of longer gear-ratios in the gearbox. Drivers were too unfamiliar with the situation of down-shifting, when necessary, on the motorways. Whether the start-stop-automatic, which is found in almost all new cars nowadays, actually saves fuel, depends entirely on the type of driving conditions, certainly not on the free-flowing motorway from Hamburg to Munich, without tail-backs.
Nowadays, one is always quick to quote percentages, even though they are - with the exception of driving under precisely pre-determined conditions - absolutely pointless. However, apart from a definite fuel-saving effect, the environment also benefits. Can one also achieve this in ones standard, run-of-the-mill car ? Certainly, but no-one knows whether the older starter-motors can stand the extra strain or not. In any event, it is interesting to know that these starters are re-engaged the minute the engine is shut down and that they wait for the terminal 50. This is something that your older starter cannot manage.
The conditions for the shutting down of the engines are also checked more carefully. The engine will not switch off, if ...
- the required engine-oil temperature has not yet been reached, - it is too hot or distinctly too cold outside, - the interior temperature is still too low, - the vacuum for the power-brake support is too low, - the battery charge is too low, - it can be recognised that passengers wish to alight (e.g., door open).
The various manufacturers interpret the system differently. E.g., at BMW, below a certain temperature there is fundamentally no start-stop activity. Unfortunately, sometimes one is not even informed as to why the start-stop is not functioning. And this is not at all rare. Also taking this aspect into consideration, the savings percentage is to be taken with a pinch of salt.
One can even assume a certain, sometimes senseless self-authority of the system. The engine is shut off, after a short time it starts again, however, without the traffic lights changing to green or the driver having done anything at all to cause it to do so. Why does the engine shut down, if it can't guarantee at least 1- or 2 minutes of down-time?
Let's go back to the normal case. Start-stop is only possible when the car is stationary and, if there is a manual gearbox, it may not be in gear, and the clutch may not be pressed. If one would, e.g., let the car roll downhill by releasing the brake, it would restart by itself. In automatic vehicles, the engine cut-off occurs whe one changes from the gas- to the brake pedal. The starter kicks in automatically, when the clutch is pressed or one changes from the brake- to the gas pedal.
It becomes particularly interesting, if the car is stalled when pulling off, which can still happen, e.g., if the clutch is let in too quickly. In this case, two systems may try to restart the engine. Thereby, it's actually all quite simple. If the car is still in motion, it can be started manually. If the car is stationary, then by pressing the clutch it will start automatically. One should keep calm, and try not to get nervous.
Various manufacturers install the start-stop system without the buyer even having a choice. In the future, the control device will analyse the situation in the individual cylinders more precisely. Together with the petrol-direct-injection the preparation for the engine restart is so efficient that to start the engine, the starter needs only to turn one stroke further. In comparison to previous systems, the starter will be protected more. Apparently, there are engines running in laboratories, which can be started completely without using the starter … 03/12