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automatic stop start

11K views 36 replies 16 participants last post by  Hillwalker 
#1 ·
Having just sold my freelander after 5 years and a trouble free 140000ks of very enjoyable driving I have just bought an SE Disco Sport.
Very impressed so far especially on dirt roads and corrugations. the suspension is very impressive.
However one thing that is giving me diarrhoea is the stop start.
Any body out there can give me advice on stopping it from working permanently.
I'm in Tasmania by the way.
 
#2 ·
Can't be turned off permanently, as it's included in the calculations of the official emissions numbers. You'll just have to get used to reaching over and pressing the button to temporarily disable it at the start of every journey. In fact, I hated it at first but learned to tolerate it, and now actually miss it when it stops working, which it does every six months or so until the dealer resets it at the service! So you may be lucky and it'll stop working by itself :D
 
#3 ·
You soon get to appreciate it, when it doesn't stop and you're stuck at lights or in traffic and watch the fuel economy numbers drop...

If you have traffic queues. In Tasmania. Perhaps not.
 
#8 ·
It can be disabled by unplugging the brown connector to a sensor under the battery cover to the left of the battery when viewed from the front. I think this is a sensor which monitors brake servo pressure ( depression) and disables stop start if the vacuum is insufficient. I'm not qualified to advise you to do this so its at your own risk of course. I haven't noticed any ill-effects on my car after 9 months.
 
#9 ·
roadster said:
It can be disabled by unplugging the brown connector to a sensor under the battery cover to the left of the battery when viewed from the front. I think this is a sensor which monitors brake servo pressure ( depression) and disables stop start if the vacuum is insufficient. I'm not qualified to advise you to do this so its at your own risk of course. I haven't noticed any ill-effects on my car after 9 months.
I think I will investigate that tomorrow! Automatic stop start does my head in!
 
#10 ·
Likewise. However, it is one of the only signals available tomyou as a driver that a forced regen is taking place (short of putting a bare foot under the drivers door cill and feeling the heat, so at the moment, against my better judgement it is on.

Ps: what is this Eco mode that I keep hearing about? 😂
 
#12 ·
spitstick said:
Can you please explain what a tomyou and a forced regen is to a poor colonial boy
Tomyou was just a typo of 'to you', and 'regens' or 'regenerations' are what clear the soot buildup in the DPF or Diesel Particulate Filter, which is a filter in the exhaust system of diesel cars which traps the particulates (soot) caused by incomplete fuel combustion instead of it going out the tailpipe, as required by recent emissions regulations such as Euro 5 and 6.

There are three types of regeneration:-
1. Passive regeneration, which is happening all the time the DPF is at operating temperature, but can't keep up with soot production so the filter slowly fills requiring...
2. Active regeneration. When the car detects soot in the filter has built up to a certain level (by measuring the pressure difference across the filter) AND certain driving conditions are met, the car injects extra fuel into the cylinders on the exhaust stroke which passes through to the exhaust system where it ignites and burns off the soot in the filter. Unfortunately some of the extra fuel also washes past the piston rings and gets into the sump where it dilutes the engine oil - but that's another story which you can read about at length elsewhere on this forum!
3. Forced regeneration. This is when the driving conditions never meet the requirements for an active regeneration, so a warning appears on the dash, and you need to 'force' a regeneration by driving at a certain speed for a certain time, or take it to the dealer for them to do it for you.

When an active or forced regeneration is under way the car suspends stop/start so it can continue uninterrupted until finished, so that's what Badgerface meant by it being an indicator of a regeneration taking place, although I think he meant active regeneration, not forced.

By the way, there are other conditions where the car will suspend stop/start automatically...

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#14 ·
spitstick said:
Well cheese and rice!!! My mind is boggled.
This has to be the most comprehensive reply ever.
Thank you very much for that info.
Ha - I'm afraid the DS is one of those cars where owners rapidly become experts on the inner workings of their cars - read more around the forum and you'll understand why ;)
 
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#15 ·
Mamil Hi,
If diesel fuel can get past the piston rings on the 'exhaust' stroke, why can it not get past at the'inlet' stroke or even more so during 'compression'. No I don't know how it gets into the oil either. I always thought it happened when the engine was stopped, and residual fuel was able to leak past as the engine cooled and metal parts shrank.
 
#16 ·
Bomber209 said:
Mamil Hi,
If diesel fuel can get past the piston rings on the 'exhaust' stroke, why can it not get past at the'inlet' stroke or even more so during 'compression'. No I don't know how it gets into the oil either. I always thought it happened when the engine was stopped, and residual fuel was able to leak past as the engine cooled and metal parts shrank.
It's because during the compression stroke the fuel is injected as an atomised mist at precisely the moment when pressure/temperature is right for it to spontaneously combust as it comes out of the injector, so it doesn't get a chance to seep out anywhere because in normal operation it's never in a liquid form inside the cylinder. Conversely, when the fuel is post injected on the exhaust stroke it doesn't combust, and some of it clings to the cylinder walls in liquid form and gets past the cylinder rings as they rise on the exhaust stroke, and is scraped off (for want of a better term) into the sump as they fall again on the intake stroke.

This process happens in all post injection DPF systems, but the Ingenium equipped DS suffers from more oil dilution because the DPF doesn't get to the correct temperature for passive regeneration to take place, so ALL regeneration is active, it has to happen more often, takes more fuel and longer to complete, so this process is happening for a longer period of time.

So, it's not about failed regens or turning the engine off during a regen, that can happen to any car with post injection DPF regens, but they don't all suffer from such high levels of fuel dilution. In fact, if liquid fuel were sloshing around in the cylinder after it's turned off in order to leak past the piston rings you have a situation called hydrolock, which would destroy the engine within seconds of being turned back on!
 
#17 ·
My automatic stop start also disables when towing our caravan!
 
#19 ·
I've learned a work around on mine for the start/stop. Here it is. If I don't want it to stop, as I brake to a full stop, I keep moving the wheel to either side just a tiny bit. This prevents the engine from stopping. And if I want it to stop I just brake and leave the wheel alone.
 
#20 ·
Mamil Hi (again)
Thanks for the Re-Gen description, that's the best info on the subject I've come across for Oil Dilution. I only meant a small dribble into the cylinder, and if that got passed the 'Rings' there wouldn't be enough left to cause the destructive problem you meant. As for the fuel getting passed during the 'exhaust' stroke, the next stroke being 'inlet' should negate that effect surely. Thanks anyway.
 
#21 ·
Bomber209 said:
I only meant a small dribble into the cylinder, and if that got passed the 'Rings' there wouldn't be enough left to cause the destructive problem you meant.
That was kinda my point, that it's such a small amount of fuel that it couldn't cause hydrolock, but also couldn't result in the amount of fuel dilution people are experiencing, even assuming your theory of how it works is correct.

Lets throw some numbers at it and see what comes out?

A VERY rough calculation of the fuel involved in one post injection can be made.

Fuel consumption 5.3 litres per 100km at a speed of 100 km/h (my actual figures)
1 hr = 5.3 litres
1 minute = 0.08833 litres
1500 engine revolutions per minute, and two injections per revolution (four cylinders) = 3000 injections per minute
0.8833/3000 = 0.00002944 litres of fuel per injection
Post injections are about 30% the volume of main injections (purely my observations), so...
0.00002944 x 30% = 0.0000088333 litres of fuel per post injection.

So, if you turn the engine off during a regen then 0.0000088333 x 2 (assuming two of the four cylinders are in the exhaust stroke at that moment) = 0.000017666 litres of fuel could potentially remain in the cylinders to make its way into the sump.

The oil capacity of the DS is 6.5 litres and some have reported 6% fuel dilution, which is 0.39L.
0.39/0.000017666 = 22083

So, so you'd need to have more than 22,000 interrupted regens to potentially get that amount of fuel dilution, and that's assuming the whole post injection remains in the cylinder AND finds its way into the sump. To put that in perspective, if you have one interrupted regen every day, then that's sixty years of motoring!

So, I think something else is going on. And if you apply the same numbers (which I won't bore you with) to an active regen, you find about half a litre of unburnt fuel washes through the engine on EACH regen! It's well documented that an unfortunate side effect of post injection is that some of this fuel makes its way past the piston rings and into the sump during the regeneration - in any car, not just the DS. Then you add in the fact that LR themselves have stated that because of the "architecture" of the Ingenium in the DS it needs more regens, of longer duration, and injecting more fuel, and you begin to see where the fuel in the oil is coming from....

As for the fuel getting passed during the 'exhaust' stroke, the next stroke being 'inlet' should negate that effect surely
Sorry, don't know what you're getting at there, but if you could explain a bit more fully I can try and reply.
 
#22 ·
Never really sat down and thought about the numbers Mamil....makes perfect sense though.

Ps: it's well past your bedtime down there 😊
 
#23 ·
Badgerface said:
Never really sat down and thought about the numbers Mamil....makes perfect sense though.

Ps: it's well past your bedtime down there 😊
Watching "Le Tour" keeps me up into the wee hours, but I get the hint, time for me to get off my soapbox :lol:
 
#24 ·
An excellent post Mamil thanks a lot. As Bf says it certainly makes sense.

Interesting developments in Le Tour with an in-team fight for Sky. Reminds me of the Wiggins/Froome situation when Wiggins finally "won"
 
#25 ·
I have read Mamil's post with its calculations.

One thing that I think is relevant is that piston rings in IC engines have been designed from day one to keep oil in the sump and combustion gases "up top". By introducing liquid fuel above the piston rings then there is a massive challenge. The liquid fuel is very dense (relative to gas) and has to be accelerated by the piston and its rings against gravity as well. The piston rings are normally geometrically shaped to maximise the retention of oil in the sump, (acting as a non-return device). This works against fuel above the piston and in practice would be unlikely to offer much resistance to liquid fuel passing into the sump. Of course the Ingenium piston rings may be designed try to overcome this, or maybe not.
 
#26 ·
Good point Hotfrog, and just another example of emissions legislation pushing engine design in directions that have unwanted side effects, and I'm thinking EGR here as well as DPF!

Meanwhile, I think these have been posted before in the oil dilution thread, but worth repeating here to clarify the precise source of the oil dilution...

Firstly, an article in Biodeisel magazine called "Understanding the post-injection problem" explains how the fuel gets into the oil during a regen :-

Post-injection of fuel into the cylinders is intended to vaporize in the cylinder but not combust, exiting then through the exhaust valves and traveling downstream where the introduction of the unburned fuel to the catalyst creates an exothermic reaction incinerating the collected soot. Inevitably the heavier fractions of fuel will not vaporize during post-injection and in liquid form can adhere to the cylinder walls. Through the slapping motion of the pistons and oil rings, the unburned fuel from post-injection can make its way through the tight, hot quarters between the piston, rings and cylinder walls. The fuel accumulates in the crankcase and dilutes the oil, which is a major concern regarding engine wear and longevity.
Then an excerpt from the DS workshop manual confirming the link between this and the fuel dilution calculation:-

Diesel Particulate Filter Side Effects
Engine Oil Dilution
Engine oil dilution can occur due to small amounts of fuel entering the engine crankcase during the post-injection phases. This has made it necessary to introduce a calculation based on driving style to reduce oil service intervals if necessary. The driver is alerted to the oil service by a message in the instrument cluster.
The DPF software monitors the driving style and the frequency of the active regeneration and duration. Using this information a calculation can be made on the engine oil dilution. When the DPF software calculates the engine oil dilution has reached a predetermined threshold (fuel being 7% of engine oil volume) a service message is displayed in the IC.
And finally, the infamous JLR service bulletin on oil dilution ( JLRP00100) explains why the problem is particularly bad on the DS :-

Early service due to oil dilution
The "Service Required" message is being displayed early due to oil dilution, caused by a higher than expected number of DPF regeneration cycles.
- Duration/distance to complete a full regeneration on (some models) is longer than (other models) increasing the likelihood of an interrupted regeneration when a customer ends their journey. {I think this is where the theory of oil dilution being a result of excess fuel being "dumped" into the sump when a regen is interrupted came from. Whereas actually the reason interrupted regens mean more oil dilution is because if one is interrupted then next time the engine is switched on it will start one all over again, so the total number/duration of regens increases.}
- Due to hardware and architecture differences between model lines, the amount of post injection required to achieve a similar burn rate is much higher on (some models) compared to (other models).
- This combines to significantly increase the Fuel In Oil (FIO) contribution for each successful regeneration event.
- Combined with the increased post injection requirement and increased impact of interrupted regeneration on oil dilution, FIO increases at a much faster rate on the Land Rover models.
{If you translate the manufacturer speak into plain language, what they're saying here is that the DPF on the Ingenium equipped DS is too far away from the engine to maintain the high temperatures needed for effective DPF regeneration. So, passive regeneration doesn't happen at all, and active regenerations are more often, longer, need more fuel injected, and are more likely to be interrupted and require to be repeated, so the oil dilution problem is exacerbated}
Chippy, yes an interesting battle within Team Sky developing, and being half Welsh you can guess who I'm cheering for ;)
 
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