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Reverse Engineering the Algorithm


Flex727

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Perhaps I'm the only one, but I suspect not - everytime with any gadget or situation with software running I am always trying to figure out the algorithm. For example, I've been driving a rental car this week. It's the first car I've driven that has that horrible auto-shutoff of the engine when stopped at a light. Personally, I think it's a really stupid feature and it's unnerving. However, I noticed it didn't shut off right away so I started to try and figure out what conditions caused it to shut off. It seemed to be a timer at first, but then the timer seemed to vary. Everytime I collected a new piece of data it seemed to contradict what I had already figured out. Then once it re-started all by itself while I still had my foot on the brake and hadn't moved. This algorithm was starting to look very complicated and I knew it couldn't be right.
Then it hit me! It was indeed extraordinarily simple, there was just a single added piece that I didn't take into account at first. The whole thing is one line of code, as follows:

image.png.8b7520c30bdca4e3cf2e57200fcf9d67.png

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You are not alone..... :)

In engine START-STOP automatic  algorithm present battery voltage comparator, time from engine start and even driver seatbelt switch.

In fact, I keep asking myself about the logic of everything that contains a program in the controller.

However, I am surprised when instead of a simple and clear algorithm they use something strange and a very excessively advanced controller that does not cope with the task.

In my opinion, the main thing for the driver is that the brake algorithm does not start to be updated remotely when the driver needs to brake ... ... :(

 It's good that they still haven't mechanically disconnected the driver's steering wheel from the wheels ... Although they are constantly trying to put this task on algorithms and electronics.

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Tested and approved:

When battery is discharged to some predefined level, than engine does not stop at red traffic light.

Even if battery is charged - very slow motion prevent engine stop.

For me engine stop is very annoying, especially at short traffic light, when my car is not first, and other cars has similar behavior.

So it will take 2-3 times more to pass junction with a short traffic light.

 

 

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On 7/5/2021 at 4:11 PM, AlexUT said:

So it will take 2-3 times more to pass junction with a short traffic light

In my part of Orstralia this phenomenon is caused by people playing with their mobile phones.  Grrrr  Especially annoying at Turn arrows, where the culprit is the only car to get through.  😠

As for stop/start engines, it is another area where I'd love to see the actual result in an overall vehicle environmental impact study.  To save some fuel it actually severely impacts life expectancy of many other components, yet all we hear is the improvement in fuel consumption.  

Here's another little doozie on that concept!  My local volunteer fire brigade I'm in had a brand new truck a while back, that had a "save the environment" engine computer restriction in place.  It would limit the engine to half power until about 15 minutes elapsed.  All in the name of reducing pollution by not letting the engine work hard until totally warmed up.  Meanwhile, the house, car, forest, burning thing we were hugely delayed in getting to because of going so slowly, played merry hell with the Design Rules initial aim as it sent vastly more plumes skywards!  Sometimes the time delay on site was the difference between a breakaway fire and a quickly controlled one.  Could our whole Organisation get an exemption for every truck like it in their fleet?  No..."Design Rules must be implemented in all applications".  Much time went by until common sense prevailed.  Meantime we would "rocket" up the freeway at a leisurely 60km per hour like a mobile chicane, with huge numbers of vehicles building up behind us wondering why we weren't going faster.   Ohh ohhh, here's a hill....everyone push.  Ohh yeah, we've got lots of them!   I kid you not.  

cheers, Aus

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I have a truck with that "feature"...

there is a whole myriad of things that inhibit the auto-stop function

engine not up to temp
low fuel
off road/sport driving mode
uphill/downhill stops
taking foot off brake and re-applying a couple times with in several seconds
steering wheel turned more than X degrees
trailer or dummy plug connected to trailer light socket
and others........

I personally find the function annoying....
and maybe it works good when the vehicle is new, but what happens with age and it gets hard to start?
you can press the button to turn it off, but it is not a persistent setting, every time you start the vehicle it turns on.

I have a friend who is a dealer mechanic, he tried to connect to it with the OEM service computer, but could not disable it.

I did some research and found a site called Forscan, that has software, I purchased a USB to OBD-II adapter and was able to make a change where at least Auto-Stop OFF is the default mode.

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