Today after a long time i am posting on this blog. The reason is simple...I just noticed that the number of visits to the technical blog have been far more compared to the other "time pass" blog that i write even though the technical one has had just 30 odd blog posts. I thought, let me rekindle the technical fire and write a few things about software, automotive and sorts.
I also thought that it would be quite a joke if i re-write what is already written in numerous websites and re-iterate the same story again. However, i would still do it if i think i can explain things in a simpler or shorter way. In the meanwhile, for those of who who do not follow my other "timepass" blog, i just moved to Germany, the land of innovation. This would also give me with some more additional time to do stuff which i would have missed because of lack of time and interest when i was in India. However, there are also quite a big bunch of new responsiblities that one has to take into consideration when he moves to a new country. This is not just doing all kinds of registrations and getting your papers in order but also adjusting to the culture and lifestyle of the place.
Today, i would be talking a bit about engine start-stop or MSS as Merc's would call it. In India most of us would have experienced that the bus drivers and the auto-rickshaw drivers turn of the engine at the red traffic lights when they have to wait. Normally this is done in order to save fuel and get better milage figures. In Europe most premium cars do offer start-stop as a default fitting. At BMW all cars come with an automatic start stop. How does this work?
In a manual transmission you would stop the car, switch to neutral and brake. This would be then used by the software as the trigger to cut off the engine. In an auto transmission though you would have to keep the brake depressed while the transmission is still set to "D" position. Although to the user this would seem quite a simple function because even an uneducated indian autodriver can do this, for the software it is quite a challenge.
The challenge poses itself as two questions:
1. When should the engine be cut off ?
2. When should the engine be started again ?
The first question translates to a list of sub questions the answers of which are evaluated by the software to decide if the engine can really be switched off. Some of them are here...you could think of some more and leave them in the comments.
Please leave your comment if you have one. You can subscribe to this blog by using the links under "Subscribe to"
I also thought that it would be quite a joke if i re-write what is already written in numerous websites and re-iterate the same story again. However, i would still do it if i think i can explain things in a simpler or shorter way. In the meanwhile, for those of who who do not follow my other "timepass" blog, i just moved to Germany, the land of innovation. This would also give me with some more additional time to do stuff which i would have missed because of lack of time and interest when i was in India. However, there are also quite a big bunch of new responsiblities that one has to take into consideration when he moves to a new country. This is not just doing all kinds of registrations and getting your papers in order but also adjusting to the culture and lifestyle of the place.
Today, i would be talking a bit about engine start-stop or MSS as Merc's would call it. In India most of us would have experienced that the bus drivers and the auto-rickshaw drivers turn of the engine at the red traffic lights when they have to wait. Normally this is done in order to save fuel and get better milage figures. In Europe most premium cars do offer start-stop as a default fitting. At BMW all cars come with an automatic start stop. How does this work?
In a manual transmission you would stop the car, switch to neutral and brake. This would be then used by the software as the trigger to cut off the engine. In an auto transmission though you would have to keep the brake depressed while the transmission is still set to "D" position. Although to the user this would seem quite a simple function because even an uneducated indian autodriver can do this, for the software it is quite a challenge.
The challenge poses itself as two questions:
1. When should the engine be cut off ?
2. When should the engine be started again ?
The first question translates to a list of sub questions the answers of which are evaluated by the software to decide if the engine can really be switched off. Some of them are here...you could think of some more and leave them in the comments.
- In an automatic, is the brake depressed above a threshold?
- Is the gear still in "D" when the driver stopped the car. i.e. He stopped it when it was running.
- Is the door closed? . If the door is opened, mostly the driver wants to get out and in that case it is better to turn on the engine and let him know that he should safely lock the vehicle before he exits.
- Is the engine too warm or too cold? In which case it would either need the coolant pump to cool the engine and if too cold would need to run to reach operational temperature. Especially with turbocharged engines, it would still make sense to run the oil pump a couple of more seconds to ensure that the bearings are still lubricated as the turbo charger speed drops down. Note that unlike the engine, the turbocharger may quickly reach rpm's in 30,000 and above range. Some of the high end turbo's may be spinning at 60,000 and above at higher loads.
The second question is not just the opposite of the first one though in some cases it is . Again, this translates into its set of sub questions.
- Has the passenger compartment temperature dropped too low or is it too high, in which case the air conditioning might need to be turned on which would need the engine to run in some cases.
- Is the brake booster pressure too low, in which case the engine needs to be turned on to generate the pressure.
- Has the driver changed the gear lever position from "D" to say " R". In which case the engine needs to be started to change the solenoid positions in the gearbox.
- Has the brake been released?
- Is there a demand by the battery with a charging request.
In the end what looks like a very simple functionality to the driver and most likely for which he isn't going to pay a lot...the software really has to work a lot to be able to give the right kind of user experience. You wouldn't want the car to start when you honk for example and at the same time, you would want the car to start as soon as possible when you step on the gas after the red goes orange.
Please leave your comment if you have one. You can subscribe to this blog by using the links under "Subscribe to"
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