DIsabling start-stop

[MagicMark]

I've had some bad experiences with automatic stop-start features, and it's just through pure luck that I've not been in an accident. However it seems to have proliferated like a virus. There should be a way to disable this nasty feature permanently, however most cars that support it only have a temporary disable button.

Do any of the modern (2010 and later) French estate cars provide a way to disable it permanently? I may have to replace my beloved Citroen C5 Exclusive Estate shortly, but don't want a car that'll switch off when I need it to work.

Mark

[RichardW]

You might be able to turn it off using diagbox. However, you don't really need to worry too much - Citroen have made it so sensitive that it only works for about 5 minutes after a new battery is fitted!

[MagicMark]

Thank you, Richard. It would be good if it can be turned off. Some of these "green" features introduce significant safety risks, and safety ought to take priority.

[GiveMeABreak]

Never had an issue when it does work - what sort of safety issues are you talking about. Most situations have been factored in to prevent any issues.

I don't believe there is an option to disable it directly though and looking at the BSI there are component settings that are set specifically for certain types of equipment - so changing any of these may have an adverse effect on vehicle operation (starter / air conditioning, voltage retention device, BCSU etc.

I think, as Richard mentioned, if you are getting a vehicle with this system (most nowadays) is to just temporarily disable it or leave it alone and it will eventually stop working as the battery capacity falls below 80% in any case.

[MagicMark]

To explain...
I was in a hire car, waiting to pull into a moving line of traffic. Spotted a gap, pressed the accelerator, and the startup delay was enough that I had to hit the brakes to avoid a collision. I then pressed the magic button to disable the start-stop. Later, in the (many miles long) queue of traffic, I stalled the car. No problem, restart, keep going. On leaving the queue, and getting to a junction, went to pull forward, and the delay caused a repeat of the first issue. When I had stalled the engine, the start-stop had reset, so I got caught twice in the same journey. I'm used to driving my C5 turbo diesel, where I get instant response, but my employer make us drive hire cars, with this dangerous behaviour. Hence my concern.

[GiveMeABreak]

Interesting, as there are anti-stall measures incorporated into the system. For general information on later Stop Start systems (and here I'm specifically referring to manual or auto models of the system only with reinforced starter and not reversible alternator or network maintaining devices:

Manual gearbox (*)
For a manual gearbox, automatic stopping and restart of the internal combustion engine depend on how the clutch pedal is depressed.

"D" Clutch pedal pressed down fully.
"E" Automatic restart point of the internal combustion engine.
"F" Depression direction of the clutch pedal.
"G" Intermediate point.
"H" Torque transmission area.
"J" Automatic stopping point of the internal combustion engine.
"K" Clutch pedal fully released.

The Stop and Start system with starter authorises the automatic stopping of the internal combustion engine when:

• The gearbox is in the neutral position
• The clutch pedal is released as far as the automatic stopping point of the internal combustion engine "J"
• The speed of the vehicle is less than or equal to 3 km/h
• The Stop and Start with starter function requests an automatic restart of the internal combustion engine if the clutch pedal is depressed beyond position "E".

Automatic gearbox (*)

For an automatic gearbox, the Stop and Start with starter function authorises the automatic stopping of the internal combustion engine when.
First case:

• The brake pedal is pressed when the gear selector is in position "D"
• The speed of the vehicle is less than or equal to 3 km/h

Second case:

• The neutral position is activated for 0,5 seconds
• The vehicle speed is equal to 0 km/h

N.B.: The Stop and Start function authorises the automatic stopping of the internal combustion engine if the vehicle is on a gradient of between -12 and +8%.

The Stop and Start with starter function requests the automatic restart of the internal combustion engine when.
First case:

• The brake pedal is released
• The gear lever is in the "D" or "R" position

Second case:

• The gear lever is in the "D", "R" or "M" position (Coming out of the neutral position).

N.B.: The Stop and Start with starter function deactivates the automatic stopping of the internal combustion engine 10 seconds after reverse gear is engaged, unless the neutral position is maintained (0,5 seconds) or if the vehicle speed reaches 10 km/h.

Specific strategies of the Stop and Start function (Note, I've not included all the other strategies here for passenger compartment requirements (heating / power consumables etc. only the ones concerning road conditions)

Reinforced starter activation time monitoring strategy
The Stop and Start system with starter deactivates the automatic stopping if the reinforced starter is operated excessively, to prevent heat build-up.

Anti-stall strategy
The "Stop and Start" system with starter calculates a risk of stalling following a lack of torque in the restarting phase. The "Stop and Start" system with starter deactivates the automatic stopping when this risk is above a prescribed threshold.

Strategy for heavy traffic (Automatic gearbox)
After an automatic restart, the Stop and Start function authorises the internal combustion engine to stop at 2 km/h if:

• Vehicle speed is less than 13 km/h
• The accelerator pedal is not pressed

N.B.: Following an automatic restart in heavy traffic, the internal combustion engine is prevented from stopping.

[MagicMark]

Interesting. That certainly wasn't the behaviour that I experienced - with that algorithm, the engine should not have stopped. I guess it's possible that the hire car was faulty.

[myglaren]

Could a 'fault' be introduced that doesn't impact on anything else but disables the stop-start nonsense?

[MagicMark]

That's an interesting plan. I guess it would depend on the system architecture. If the start-stop system used sensors of its own, then it's possible, but it's much more likely that it simply takes data from the engine control unit.
Mark

[CitroJim]

I regularly see significant delays in some very modern cars getting moving after say, when traffic lights turn green or a suitable gap appears at a junction.

I know, from being queued up behind them on my bike, that many are the result of Start/Stop and not a dozy driver with poor reaction times.

Several times, such cars have been in significant danger of being rear-ended.

I'm of the opinion that Start/Stop systems are dangerous.

[MagicMark]

Thank you, Jim. That suggests that it's not just me! I wonder whether anyone has carried out a risk assessment.
Mark

[GiveMeABreak]

The systems use sensors from all over the car and not just the engine ECU. It's actually quite complex, as it monitors seat belt status (restarting the engine if it's in stop mode if you unbuckle your seat belt) - which is easy to do if say pulling in for petrol - you don't want the car starting when not in the driver's seat! Then there's the monitoring of the Climate control system ECU, which will start the engine or prevent it from stopping if the temperature request by passengers requires engine to be running or for the A/C to be running, or if there's power consuming devices being activated (USB chargers and the like), heated rear windscreens, outside temperature, number of stop start cycles since the ignition was switched off, battery condition, battery charge status module status, etc. etc., but you get the picture.

[MagicMark]

Wow! So disabling the system may be as simple as plugging in a USB charger! Interesting.
Mark

[GiveMeABreak]

Indeed!

But like I've said, I really don't have to worry about it (moreso if you don't use the vehicle everyday on a reasonable trip) as the battery in my case dips below the threshold so is almost on permanent deactivation. I had my battery replaced under warranty for the Stop Start not working - but again after a few weeks of this it stopped working, so I don't bother with it now.

If I go on a longer trip (motorway) it will be enough to replenish the charge and so may start working again for a few times until the car is only used once or twice a week and then it stops working again. Mine is a later system, which does not have all the extra gubbins like the ultra capacitor, network voltage maintaining system that they used on earlier versions.. They stripped all that out to save on costs, and thought they could do it with just the enhanced battery, but it really is pathetic. But doesn't bother me as I can save the wear on the reinforced starter instead which suits me better in that it will last a lot longer.

[MagicMark]

OK, thank you, Marc. It certainly seems like I won't have to worry about it for very long.
Always good to get advice from the Tomorrow People.
Mark