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Discussion Starter · #1 ·
As I was driving along the motorway at 70mph on Saturday, going down hill I took my foot off the accelerator and the **** engine cut out! It felt to me like the stop/start had activated, as after a few seconds of engine braking I put my foot on the clutch and fortunately it started back up. No error/warning on the dash that I noticed.

I've booked it in for the dealer to check, but they don't sound particularly confident that anything would be recorded if no warning came up. Kind of worrying!
 

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That is not nice; if you search the threads this has def happened to a few others; might help your dealer! I think a software update sorted it.
 

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Could you possibly have been driving in Green Mode at the time? Perhaps you experienced the "coasting" feature?
 

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Could you possibly have been driving in Green Mode at the time? Perhaps you experienced the "coasting" feature?
From what is being described, this is definitely the coasting setting kicking in and is meant to turn off the engine by design to conserve fuel when you are going downhill at speed and neither braking or accelerating. It's meant to happen in Green mode only.
 

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OP says "foot on the clutch", so that means it's a manual trans car. But then they say "started back up", which is an odd descriptor. Can the behavior be repeated? By the way, were you using cruise control? Because it actually uses the friction brakes to maintain contant speed control going down a hill.


That said, the engine uses overrun fuel-cut, however pretty much every car does in the past decade or so. It just feels like engine braking, because it is. From the drivers perspective it should feel reasonably seamless, though IMO the F56 is slightly more abrupt in its transition, as if they're not using progressive cut or return.
 

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Full hybrid cars do this all the time. As a mild hybrid, I'd expect the MINI to do something similar. I don't see this as an issue.
 

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Discussion Starter · #7 ·
I can't remember if it was in green mode, but it's possible, and yes it is manual transmission. I'll have to go look up what this green mode coasting feature is.

I'd exited a built up area at 30mph, accelerated to 70, then later took my foot off as I went down hill and round a bend. At which point it slowed aggressively, as though I'd put my foot on the brake. I didn't have a lot of time to figure out what was going on, and with the engine being so quiet I can't be sure it definitely turned off. But having slowed considerably I changed down and the car came back to life.

Here's the thing though, cruise control was still active and set to 30mph, so my initial thought was maybe it brakes rather than coasts when you exceed the set speed. But I tried to repeat on my return journey and couldn't.
 

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The cruise control is a braking function so if you activated it at 70 and it was set to 30 it would i think brake to slow you fairly firmly down to the set speed; will check this myself as its not something ive done or think would be a good idea-it def did it for me when moving down from 70 to 50 in a road work zone at the weekend though-i think we have solved your problem!
If your foot was on the clutch though should it not deactivate cruise-it would certainly deactivate the auto stop start so it cant be that! or at least shouldnt be!
 

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...snip...
Here's the thing though, cruise control was still active and set to 30mph, so my initial thought was maybe it brakes rather than coasts when you exceed the set speed. But I tried to repeat on my return journey and couldn't.
It sounds probable that you accidentally clicked "RES" on the steering wheel and resumed the cruise control, set for 30. As such, the car would use the friction brakes the quickly decelerate from 70 to the set speed of 30.
 

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Discussion Starter · #12 ·
Yes I think it's exactly that. I tried it out a few times on the way home with cruise set to 30mph, accelerated up to 60 then took my foot off. After a few seconds of normal coasting it started to brake back to 30mph. Typical user error, though not what I'm used to from other cars with cruise control that I've owned.

I think I'll keep the dealer appointment to see if they can fix the annoying rattle from the passenger door.
 

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Glad you figured it out. I was playing with the cruise control today and it seemed to only activate 1mph lower or higher than the speed I was doing (pressing the up and down buttons to set it). Didn't realise you could preset it and make it go straight to that speed. Seems a bit unsafe
 

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Coastng means that the gearbox is disengaged from the engine so it runs on idle to save fuel but as far as I'm informed it's not meant to shut down because with the engine shut down it means you also lose brake power assist and power steering which, in my opinion, can be quite dangerous.

Or am I wrong?
 

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Glad you figured it out. I was playing with the cruise control today and it seemed to only activate 1mph lower or higher than the speed I was doing (pressing the up and down buttons to set it). Didn't realise you could preset it and make it go straight to that speed. Seems a bit unsafe
You're setting it with + or - buttons, of course it'll speed up or slow down. If you want to set the exact speed, use the center "SET" button.

Regarding the preset speed, every cruise control I'm aware of works that way. If you set a speed, then cancel, then click resume, it'll go back to the set speed. That's normal and exactly what the functions are for. Hardly "unsafe", because after all, you have to push those buttons. Nothing happens automatically.

Coastng means that the gearbox is disengaged from the engine so it runs on idle to save fuel but as far as I'm informed it's not meant to shut down because with the engine shut down it means you also lose brake power assist and power steering which, in my opinion, can be quite dangerous.

Or am I wrong?
Coasting IMO can be both freewheeling and also engine braking. When you engine brake, it's more fuel efficient as the fuel is turned off to maximize the engine braking effect. It's literally not firing, but the chassis is forcing it to spin. Hence; engine braking. Since it's still spinning, you still get water and oil circulation and accessories [like the vacuum pump for brakes], but it's the tires driving them instead of gasoline.

If you're freewheeling [transmission in neutral], then the engine should remain idling, which of course burns fuel. If you're in neutral and the engine stops running, then there's an operational problem.

Make sense?
 

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Discussion Starter · #16 ·
Glad you figured it out. I was playing with the cruise control today and it seemed to only activate 1mph lower or higher than the speed I was doing (pressing the up and down buttons to set it). Didn't realise you could preset it and make it go straight to that speed. Seems a bit unsafe
If you have a previously set speed, you can press the RES button and it will accelerate back up to it.

In my case I had been travelling on cruise at 30mph, then accelerated manually up to 70 and didn't disengage cruise. So when I took my foot off the accelerator it coasted for a few seconds before applying the brakes to bring the car back to 30. Previous cars I've owned would have just continued to coast back down to the preset speed with engine braking.

Actually I'm pretty sure our Honda disengages cruise if you manually accelerate over 10mph above the preset speed. Our old VW would have disengaged cruise if you press the clutch, i.e. to change gear. The Mini doesn't seem to do either.
 

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Glad you figured it out. I was playing with the cruise control today and it seemed to only activate 1mph lower or higher than the speed I was doing (pressing the up and down buttons to set it). Didn't realise you could preset it and make it go straight to that speed. Seems a bit unsafe
You're setting it with + or - buttons, of course it'll speed up or slow down. If you want to set the exact speed, use the center "SET" button.

Regarding the preset speed, every cruise control I'm aware of works that way. If you set a speed, then cancel, then click resume, it'll go back to the set speed. That's normal and exactly what the functions are for. Hardly "unsafe", because after all, you have to push those buttons. Nothing happens automatically.

Coastng means that the gearbox is disengaged from the engine so it runs on idle to save fuel but as far as I'm informed it's not meant to shut down because with the engine shut down it means you also lose brake power assist and power steering which, in my opinion, can be quite dangerous.

Or am I wrong?
Coasting IMO can be both freewheeling and also engine braking. When you engine brake, it's more fuel efficient as the fuel is turned off to maximize the engine braking effect. It's literally not firing, but the chassis is forcing it to spin. Hence; engine braking. Since it's still spinning, you still get water and oil circulation and accessories [like the vacuum pump for brakes], but it's the tires driving them instead of gasoline.

If you're freewheeling [transmission in neutral], then the engine should remain idling, which of course burns fuel. If you're in neutral and the engine stops running, then there's an operational problem.

Make sense?
Well surely it is unsafe if you can make it sharply break from 70 to 30 as the OP did? I honestly didn't know you could do that and thought it was a safety feature to only let it start 1mph + or - from the current speed.
 

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Coasting IMO can be both freewheeling and also engine braking. When you engine brake, it's more fuel efficient as the fuel is turned off to maximize the engine braking effect. It's literally not firing, but the chassis is forcing it to spin. Hence; engine braking. Since it's still spinning, you still get water and oil circulation and accessories [like the vacuum pump for brakes], but it's the tires driving them instead of gasoline.

If you're freewheeling [transmission in neutral], then the engine should remain idling, which of course burns fuel. If you're in neutral and the engine stops running, then there's an operational problem.
This is a common belief but it isn't true.

Engine braking is slowing the car down, disposing of kinetic energy that you have just paid a lot of fuel to produce.

In contrast, free-wheeling at idle is using the kinetic energy to keep the car moving, with only a tiny amount of fuel needed to keep the engine running.

Lots of people believe that if fuel is not being supplied that must be 'economical', but it is only half the question. Fuel economy is the result of two factors:
1) minimising the amount of energy needed (eg, a lower cruising speed).
2) getting the required energy on the best possible 'terms'.

The most inefficient thing you can do is apply the brakes as that is just chucking energy away - even though no fuel is being consumed at that moment.
 

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Perhaps a more universal answer regarding overall fuel economy and when you apply free-wheeling versus engine-braking is: "it depends". There absolutely are circumstances where engine-braking is more efficient overall versus burning fuel at idle. Most of those circumstances are in the real world and not idealized situations.

e.g. coasting down a hill where you're approaching a slow car. Engine braking will slow you to a following speed with zero fuel burned and a progressive return from over-run fuel cut, whereas free-wheeling will burn fuel and require the use of brakes and an acceleration enrichment to re-rev the engine to match speed.
 

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Also, I hit the res but by accident today when activating the cruise control that was set to a much lower speed than my current speed and it said cannot activate cruise control, so I'm sure there's a safety feature in there to stop you accidentally effectively slamming the breaks on on the motorway
 
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