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Fiat 500 at CES 2008  (Source: DailyTech/Brandon Hill)
Bosch Start-Stop system reduces fuel consumption and emissions by 8%

Reducing emissions and improving fuel economy is a huge area of investment for many carmakers. Most people equate this type of technology with hybrid or electric vehicles, but Bosch has a system that helps improve fuel economy and reduce emissions on diesel and gasoline motors as well.

The system is called the Bosch Stop-Start System. Bosch and Fiat announced recently that the Fiat 500 would use the systems and Bosch went so far as to claim that 50% of European vehicles would have the Stop-Start system by 2012.

Bosch has been making the system since 2007 and reports it has already delivered 500,000 of the special starters to BMW and Mini. In the Fiat 500, Bosch says the Stop-Start system would be available with the Dualogic automated manual transmission and the 1.2-liter engine. Fiat does say it plans to install the system on other vehicles as early as 2009.

The Fiat 500 will also use a Bosch engine control unit including Bosch software that analyzes the sensor data to start and stop the engine of the vehicle. Stefan Asenkerschbaumer, president of Bosch Starter Motors and Generators division said, "In 2008, roughly five percent of all new vehicles in Europe are equipped with a start/stop system. By 2012, we estimate this will be every second newly registered vehicle—most of them with Bosch technology."

The Bosch Stop-Start system works by turning the motor of the vehicle off when the vehicle is stationary. An example is if a driver pulled up to a stop light, the Stop-Start system would turn the motor off while at rest. When the driver put a foot on the clutch pedal to put the car back in gear, the engine would start back up.

Bosch says that the system reduces fuel consumption and CO2 emissions in the urban component of the New European Driving Cycle (NEDC) by up to 8%. To ensure that the starter lasts with the significantly increased stop/start cycles, critical components of the special starter have been strengthened. Bosch says it increased the service life of starters used in the Stop-Start system compared to a normal starter. The bearings in the new starter were strengthened, the commutator is strengthened, and the planetary gear was improved as well.

The system has other components including control software, a battery sensor, crankshaft sensor, and sensors at the pedals. A high-efficiency alternator and a deep-cycle electric battery are part of the system.

A few specifics on the system remain unclear. For instance, presumably the system won’t function if the driver doesn't place the vehicle in neutral. Bosch isn't specific on that aspect of the system. Another concern is how long the vehicle will be able to remain with the engine cut off in high power usage scenarios like summer with the air conditioner running or in winter with the heater on.

Bosch doesn’t specify if the system would automatically restart the vehicle if it were still stationary if the battery started to get too low on power. Presumably, the system would restart so the driver won’t be left with a dead battery.

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RE: and what about other wear components?
By Solandri on 12/5/2008 5:02:11 PM , Rating: 5
Starts are only bad because the engine parts aren't fully lubricated (oil has dripped down). If the engine is off for about a minute at a red light, the oil won't have dripped significantly, and the start will generate no more wear and tear than keeping it running. Well, maybe the starter motor will get more of a workout, but I assume they account for that in the car's design.

Cold engines are a problem because they're operating at a temperature that's outside the engine's designed operating parameters. So they result in incomplete combustion and wasted fuel. Since the whole point of this is that it saves fuel, it would seem the cooldown at a red light is not enough to waste more fuel than it saves.

RE: and what about other wear components?
By wookie1 on 12/5/2008 6:07:17 PM , Rating: 4
I think you're forgetting about the parts that require oil pressure to keep oil in place, such as main bearings. Residual oil on the bearings without oil pressure is not that helpful due to the loads.

RE: and what about other wear components?
By Samus on 12/6/2008 10:29:58 PM , Rating: 2
I drove a Mini with this system last time I was in London and the start is reasonably efficient. It starts the engine back up in 180 degrese (half a crank cycle) which takes a few tenths of a second, faster than you depress the clutch pedal.

However, it was pretty cold there in November and I wasn't very satisfied with the lack of heat after 20 seconds of the engine being off...for example when I was waiting for a train or a long traffic signal. I also thought it was annoying the headlights dimmed considerably when the vehicle was off. I doubt my Mini had a deep cycle battery or efficient alternator like they are saying it should, because I wouldn't have noticed this otherwise.

On a side note, I was able to trick the system by keeping the car in gear and holding the clutch in. The engine would never turn off. I don't normally drive like this, though. I try to relax at a stop and sometimes even pull the parking brake just to give my feet a rest. London's a bitch to drive in.

RE: and what about other wear components?
By KernD on 12/7/2008 10:43:01 PM , Rating: 3
It's not only the oil that's thicker when it's cold. Here in Canada we get many days with less than -30 degree Celsius, at those temperature the battery itself is less powerful, so at a trafic light how will it do all you need AND restart the enigne. If you have a long way to go in the city, it will drain the battery, and your not talking about a mini's engine here, but a full size V4.

By Fireshade on 12/9/2008 6:50:32 AM , Rating: 3
That's why the Stop-start system has -amongst others- a battery-sensor that goes with some clever electronics logic. It is perfectly possible for Bosch to program measures in diverse situations. They have a solid reputation in low-level car-electronics (ignition, injection, ABS, etc.).

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