stop/start - great eco function or downright dangerous?
Discussion
Having lived with my new car for a month I'm suggesting it's the latter.
Its an auto, and every time you come to a standstill the engine cuts out even whilst in drive, lift your foot off the brake pedal and it restarts.
So, you're approaching a roundabout, you've slowed to a stop and are looking for a gap, you see one but it's tight and your engine isn't even running, do you floor the loud pedal hoping the engine will restart quick enough to allow you to accelerate into the space, or hold up traffic and wait for the next gap?
The other option is to roll forward very, very slowly so that the car is still moving and the start/stop doesn't activate, but then you get up to the give way point, you can't stop now as the engine will cut out, so you roll a little into the road you're joining to keep moving, then a little more, then you HAVE to fully stop for an oncoming car, then the engine cuts out but now you're actually halfway into the road you're trying to join, you're in the way now.
Handily, there's a button to disable it, you have to press it every time you get into the car, which I'll be doing from now on.
/rant over.
Its an auto, and every time you come to a standstill the engine cuts out even whilst in drive, lift your foot off the brake pedal and it restarts.
So, you're approaching a roundabout, you've slowed to a stop and are looking for a gap, you see one but it's tight and your engine isn't even running, do you floor the loud pedal hoping the engine will restart quick enough to allow you to accelerate into the space, or hold up traffic and wait for the next gap?
The other option is to roll forward very, very slowly so that the car is still moving and the start/stop doesn't activate, but then you get up to the give way point, you can't stop now as the engine will cut out, so you roll a little into the road you're joining to keep moving, then a little more, then you HAVE to fully stop for an oncoming car, then the engine cuts out but now you're actually halfway into the road you're trying to join, you're in the way now.
Handily, there's a button to disable it, you have to press it every time you get into the car, which I'll be doing from now on.
/rant over.
Wouldn't hitting the accelerator and hoping for the best work pretty well? The engine should start as you back off the brake pedal, and rev just like normal? Test it out at an empty roundabout and see what it does. My guess, it will work just as though the car has been on the entire time.
StottyZr said:
Wouldn't hitting the accelerator and hoping for the best work pretty well? The engine should start as you back off the brake pedal, and rev just like normal? Test it out at an empty roundabout and see what it does. My guess, it will work just as though the car has been on the entire time.
Exactly what I was thinking.The OP is asking the question almost from the perspective of someone who doesn't drive a stop start and wants to understand how they work. Surely as an owner he can test this?
SWoll said:
StottyZr said:
Wouldn't hitting the accelerator and hoping for the best work pretty well? The engine should start as you back off the brake pedal, and rev just like normal? Test it out at an empty roundabout and see what it does. My guess, it will work just as though the car has been on the entire time.
Exactly what I was thinking.The OP is asking the question almost from the perspective of someone who doesn't drive a stop start and wants to understand how they work. Surely as an owner he can test this?
Although I do understand his problem. You need confidence in the system and this could be hard to find when pulling onto a busy roundabout!
Crusoe said:
cold should kill the stop start soon (most don't work under 4 deg or similar.)
yep. I thought mine had broken! It was quite embarrasing and I don't know why I'm sharing it online. But I kept stopping at lights, looking at my revs, scratching my head and saying "Ehhhhh" until I realised 
StottyZr said:
Wouldn't hitting the accelerator and hoping for the best work pretty well? The engine should start as you back off the brake pedal, and rev just like normal? Test it out at an empty roundabout and see what it does. My guess, it will work just as though the car has been on the entire time.
Rhetorical, the post is the thoughts that go through my mind rather than me actually asking you all the questions.So, to answer, no, it doesn't work as well as if the engine has been on, that's impossible. It does restart pretty quickly, but restarting quickly and pulling away will never make as quick a getaway as just sitting in drive ready to go.
My point is that the system creates a poor style of driving. You're either rolling/creeping to keep the engine from cutting out or sitting still waiting to take your chances at junctions and roundabouts wondering if you have enough time to restart and pull out..
yellowbentines said:
Rhetorical, the post is the thoughts that go through my mind rather than me actually asking you all the questions.
So, to answer, no, it doesn't work as well as if the engine has been on, that's impossible. It does restart pretty quickly, but restarting quickly and pulling away will never make as quick a getaway as just sitting in drive ready to go.
My point is that the system creates a poor style of driving. You're either rolling/creeping to keep the engine from cutting out or sitting still waiting to take your chances at junctions and roundabouts wondering if you have enough time to restart and pull out..
So you've posted a rhetorical question on a discussion forum? OK...So, to answer, no, it doesn't work as well as if the engine has been on, that's impossible. It does restart pretty quickly, but restarting quickly and pulling away will never make as quick a getaway as just sitting in drive ready to go.
My point is that the system creates a poor style of driving. You're either rolling/creeping to keep the engine from cutting out or sitting still waiting to take your chances at junctions and roundabouts wondering if you have enough time to restart and pull out..
I've mentioned this on here before, but a mate works for a company who have a fleet of Corsas which are fitted with stop-start and he's demonstrated on more than one occasion that it's potentially dangerous.
He does a trick whereby he arrives at a 'stop line' quickly, brakes hard but stops braking JUST before the car completely halts and then tries to pull-away again (usually in 2nd).
The car will, at least half the time, stall/cut out - and as it's still moving, you roll out into the junction with no power (and I assume no brake or steering assist either or are they separate?)
Cars without stop-start don't do it (lets be honest, it's pretty hard to stall a modern car thanks to digital idle control and lighter-than-air clutches) so it's clearly the stop-start stepping-in. I assumed it was one dodgy car but he's done it in at least 3 different cars and one of their staff had a T junction shunt and said that roughly the same thing had happened to them.
Their fleet manager went back to Vauxhall who denied any issues but said they'd look at the cars in question for 'isolated faults' - not heard back since they arranged that tho.
Clearly you have to be driving aggressively, which doesn't really match the 'eco' credentials of the cars in question - but it's the sort of thing I don't like cars taking control over and unless you live in a busy city, it's got to be fairly pointless?
He does a trick whereby he arrives at a 'stop line' quickly, brakes hard but stops braking JUST before the car completely halts and then tries to pull-away again (usually in 2nd).
The car will, at least half the time, stall/cut out - and as it's still moving, you roll out into the junction with no power (and I assume no brake or steering assist either or are they separate?)
Cars without stop-start don't do it (lets be honest, it's pretty hard to stall a modern car thanks to digital idle control and lighter-than-air clutches) so it's clearly the stop-start stepping-in. I assumed it was one dodgy car but he's done it in at least 3 different cars and one of their staff had a T junction shunt and said that roughly the same thing had happened to them.
Their fleet manager went back to Vauxhall who denied any issues but said they'd look at the cars in question for 'isolated faults' - not heard back since they arranged that tho.
Clearly you have to be driving aggressively, which doesn't really match the 'eco' credentials of the cars in question - but it's the sort of thing I don't like cars taking control over and unless you live in a busy city, it's got to be fairly pointless?
johnpeat said:
He does a trick whereby he arrives at a 'stop line' quickly, brakes hard but stops braking JUST before the car completely halts and then tries to pull-away again (usually in 2nd).
That shouldn't happen. Unless GM have some weird system, SS should only engage when the car is stationary, car is in neutral and clutch up. Surely he can't be doing all those things whilst trying to pull away quickly?I like my SS system, but it's on a manual. I can understand the OP's post about it being disconcerting in an automatic. At least on a manual the driver makes it engage.
I wouldn't buy a car with stop start. Indeed, it's a selling point if it hasn't. I'd rather sit at the lights in an huge american auto doing that slight rev, straining at the leash thing, dumping hydrocarbons onto the Prius behind.
Ideally, I'd like the fuel feed/spark plug option to shoot flames from the exhaust too.
Ideally, I'd like the fuel feed/spark plug option to shoot flames from the exhaust too.
The BMW system is actually quite good. Its automatically on, but only engages when you are out of gear and you have your foot off the clutch. Therefore, its a simple system to work around, but if you are stopped for a period of time, its dead simple to have the engine stop.
Oh, and its clever enough to know when to NOT stop - i.e. when its hot (aircon), very cold (to keep the heater running) or when you have a large drain on the battery (or its low). Not had a problem and works well...
Oh, and its clever enough to know when to NOT stop - i.e. when its hot (aircon), very cold (to keep the heater running) or when you have a large drain on the battery (or its low). Not had a problem and works well...
LuS1fer said:
I wouldn't buy a car with stop start.
I didn't realise it had stop start when I agreed to buy, being an auto I didn't think it was possible to have stop start so didn't bother asking or checking If it's disabled the light goes out on the dash rather than on, so if the engine is running and it's disabled before you get in the drivers seat for a test drive, you might never notice until it's too late!
off_again said:
The BMW system is actually quite good. Its automatically on, but only engages when you are out of gear and you have your foot off the clutch. Therefore, its a simple system to work around, but if you are stopped for a period of time, its dead simple to have the engine stop.
Oh, and its clever enough to know when to NOT stop - i.e. when its hot (aircon), very cold (to keep the heater running) or when you have a large drain on the battery (or its low). Not had a problem and works well...
I've found the system on my BMW quirky. Sometimes the engine will cut out if the car is still rolling at low speed in neutral - leaving you without power steering. Nice. Also, it can be fooled if you are coming to a stop but then have to quickly get going again, and only dip the clutch. Then it will cut out but not restart. Oh, and its clever enough to know when to NOT stop - i.e. when its hot (aircon), very cold (to keep the heater running) or when you have a large drain on the battery (or its low). Not had a problem and works well...
So if I understand this correctly, with an auto box the car engine will stop with the gear selector in D then start again when foot is removed from brake pedal with the selector still in D?.
Doesn't sound safe, or at the very least good for autobox longevity.
What is the car?. Might be worth looking into getting the feature disabled.
Doesn't sound safe, or at the very least good for autobox longevity.
What is the car?. Might be worth looking into getting the feature disabled.
RicksAlfas said:
That shouldn't happen. Unless GM have some weird system, SS should only engage when the car is stationary, car is in neutral and clutch up. Surely he can't be doing all those things whilst trying to pull away quickly?
I like my SS system, but it's on a manual. I can understand the OP's post about it being disconcerting in an automatic. At least on a manual the driver makes it engage.
It's hard to know exactly what's happening - he could even be slightly locking the wheels (fooling the car into thinking it's stopped as ABS doesn't work below certain speeds?) or whatever - but he had worked-out how to make an SS equipped Corsa stall (and demonstrated it to a dealer, who said that his driving was 'unsuitable for the car' I like my SS system, but it's on a manual. I can understand the OP's post about it being disconcerting in an automatic. At least on a manual the driver makes it engage.
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