Auto stop/start when towing with an automatic
I have a diesel BMW 2L 3 series automatic that has automatic stop/start. It's the first car with this function that I have driven when towing. Should it be switched off when towing
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On both my current and previous Audi Q5, bought in 2013, the stop/start function is disabled automatically when towing.
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Do you know why? I also tow with a Treg and don't bother turning it off unless I am at a difficult junction when it might be a nuisance.
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I turn it off with our Disco when towing as I want to ensure the systems cooling, particularly the auto box's, gets every benefit it can. With the engine stopped so is the gearing's cooling.
I beleve the handbook also states doing so.
Like Mollys we tend in all our vehicles to switch it off when going out solo and only re switch it on when faced with traffic situation it offers us and the plannet any real benefit. Living in a rural area our driving rarely takes us into highly populated areas where it does much good.
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Your choice but why? particularly when not owing? You're just wasting fuel if your stop is longer than about 6 seconds, and of course adding to pollution.
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Is that a fact? There will be the fuel needed to restart the engine and bring it up to speed, plus the extra fuel to replenish the energy taken from the battery to restart.
Clearly there is a time span where one gains but what detailed research indicates this is 6 seconds? A serious question, having worked on diesel engine research and development.[ that, with turbo issues, one where I am reticent to let SS jump in too readily right after a fast or highly loaded run]
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I thought that C, ‘turning it off’, ‘ensure system cooling’, ‘gearing cooling’🤷🏻♂️. Why have something that is called automatic if the user needs to deactivate the auto part & render it manual🤔😕
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Stop start technology is designed to be used in heavy urban traffic, to reduce fuel consumption and reduce emissions. We followed one car down motorway in heavy traffic and couldn’t understand why he was stopping rather than trickling along like the other lanes. Came to conclusion he was using stopstart, so there was a slight but irritating (to those of us behind him) pause every so often. We overtook him eventually along with others, left him to his high tech daydreaming.
You have to hope car designers have got the lubrication right in stopstart cars. Something designed to stop and start x thousands of times, is stopping 10 times x thousands of times instead, wearing on engine if lubricant and components aren’t right. Jury’s out on how much emissions they save overall.
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when I did the sums and experiments (using both simple and differential equations with other factors) it was about between 6 and 7 seconds. Others doing the same got about the same answers. Not saying it was a fact and that was a long time ago now
Very simply from recall on the car we had used about 1.0 to 1.2 cc of fuel on start up, while idling used about 0.1 to 0.2 cc per second. Do the sums, this was based on a 1.6 litre petrol.
Various top gear programmes have shown the stop tart system saves does save fuel.
But as you say there are other factors involved and my car switches it off automatically when towing too but I was just asking why others switched their system off when not towing?
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Here with stop start being automatic is fine up to a point, but it is "dumb" technically. This is because in the simplistic form in our particular vehicles it does not know where or why the vehicle stops or what the immediate future probably holds.
I suspect on all counts I have more idea and can add those important missing details into making a more informed decision if stop start is presently appropriate.
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some interesting stuff on at
https://www.rac.co.uk/drive/advice/emissions/idling/
didn't realise you could get fined for idling?
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Thanks O👍🏻😊. I’m a simple form of Humanoid that struggles away from the black & white world I like, grey confuses me😂😂
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Fuel used wasn't my priority when I bought a 3 litre 2.3 tonne 4x4 with the aerodynamics of an Accrington house brick. I very occasionally let stop/start do its own thing but I find that there's too much delay in restarting when you want to nip into traffic hence mine is almost always switched off.
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It does not say why, but from research, the extra load of the van and the cooling of the engine etc seem to be relevant, and also that all the stop/start can confuse the electrics in the van and you may end up not getting the van battery charged or the fridge running.
We have had enough problems with these, and even getting the lights to work as they used to before we had a "smart" towcar, that we are taking all the suggested precautions!
I leave it on when not towing, but OH hates the system and always turns it off in both our vehicles. She also turns off the handbrake auto hold, never uses the cruise control, and prefers to drive with the radio off, so I am not surprised she does not like the stop/start!
Son in law has a 4 year old VW Polo and his stop/start function has recently failed, need to ask him what the problem was.
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I leave the stop start on all the time in my Kia Sorento; when towing and solo.
The car uses an algorithm to decide if the oil is the correct temp, the battery charge sufficient, the engines temp right etc before the stop start kicks in.
If there is a problem with the system the car has a 7 year warranty so Kia can sort it out!
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I don't understand that at all?
On my manual runaround, I have to have the car in neutral and the clutch depressed for the auto stop to engage, so simply keeping the car in first at a busy junction means it doesn't engage.
On the auto only when it's at a complete stop and brake pedal pressed does it engage, press the accelerator and a split second later (certainly not a second) I'm moving,
I've never been caught out like you suggest even in in busy city centres, and the auto hold will hold the car stationary while I'm moving my foot.
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actually I'm wrong, just checked and just taking my foot off the brake restarts the engine so completely ready to go by the time I've moved my foot over.
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No idea about manual cars .... I don't drive them.
My auto will do the same as yours .... but I choose to switch the stop/start off. I use my left foot to hold though the car does have 'hold' if I give the brake pedal an extra shove to engage it. Stop/start will probably save a gallon over the life of the car vs a new £300/£400 starter motor.
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I just press the auto hold button and it's done, happens automatically on the manual for some reason , sounds as if your car isn't that modern?
I think that starter motor wearing out on cars with stop start is now a myth, google it. Also the latest cars with it don't even use a starter motor at all, amazing eh?
Automotive engineers don't use 'traditional' starter motors in these situations," he explained. "The starter used for start-stop systems combines several technologies
...does not use a starter for restarts at all. It uses engine combustion. As a driver releases the brake pedal, the fuel injector in one cylinder fires, and the spark plug ignites, allowing the engine to start with combustion
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yes I know! but it does happen every decade or so, even to me
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It's a 14 plate ML350 ..... modern & expensive enough for me ... hold is achieved by using the foot brake, no other buttons to press.
I don't need to ask Google to tell me that if I use something more often it'll wear out sooner. Yes, some cars effectively use their alternator as as starter motor so it's always spinning whether starting the car or not. Google Smarts mhd Fortwo ..... not Merc's best idea.
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On both our automatics it restarts when you either take your foot off the brake (if using foot brake) or on the Touareg, press accelerator if auto hold is in use, so there is a slight delay, which I must say often annoys me in the same way as it annoys MM.
SIL has a manual VW Polo and his stop/start operates when he comes to a halt with clutch depressed and foot on brake, car does not need to be in neutral. Seems to be a few different ways of doing things.
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".does not use a starter for restarts at all. It uses engine combustion. As a driver releases the brake pedal, the fuel injector in one cylinder fires, and the spark plug ignites, allowing the engine to start with combustion"
Somehow I think that with our diesels that spark plug based technology is a "non starter"
So probably restarting our diesels will still be dependant on a starter motor being used?
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No.
The ability to get out of the way of a big wagon is called driver anticipation and ensuring that the driver is aware of what is going on around him/her at all times!
Some information about the Mazda i-stop system (I used to have a CX5):
i-stop and Clean Diesel Engines
Unlike gasoline engines, which use a spark plug to ignite the air-fuel mixture, diesel engines compress the mixture until it spontaneously combusts. Therefore, to restart a diesel engine, sufficient compression is required.
While conventional diesel engine idling stop systems require two engine cycles to restart, Mazda's unique i-stop needs just one cycle, thanks to its precise control of the piston positions. As a result, i-stop achieves the world's fastest diesel engine restart time of approximately 0.40 seconds (internal measurement on vehicles with automatic transmission) and its operation is barely noticeable.
i-stop offers a quick engine restart and a natural operation with little vibration and noise.
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