Author Topic: Start Stop on New Jazz  (Read 21122 times)

Rory

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Re: Start Stop on New Jazz
« Reply #15 on: December 31, 2015, 02:02:07 PM »
… one of the many criticisms of this testing is that the official cycle is so old (1970) that no-one had thought of stop-start at the time so the test doesn't permit it.
It’s not that it doesn’t permit it, it simply doesn’t mention it, and the criticism is that something which isn’t mentioned makes quite a big impact to the results.   The test also doesn’t take account of hybrids – so you get wacky results from some cars which can do most of the test under electric power but are hopeless under electric power on the road (Mitsubishi PHEV is noted for this).

Even if it is permitted, the test specifies that the engine is started from cold so the stop-start wouldn't kick in anyway during the short urban test cycle.
The test is done from cold but in an ambient of at least 20C.  I’ve heard of lots of cars where stop/start is very uncertain in the way it works, but I can tell you on the VW Tiguan which replaced our 2009 Jazz, I can back it out of the drive from overnight stop, go 200yds to the end of the road and the engine will stop,  It does it every time I forget to de-activate it. Manufacturers do a lot of pre-test work on vehicles that they (yes, they test them themselves) test so you can be sure that stop/start where fitted will be working perfectly.


This is the best I can find in terms of confirmation that stop/start is used - like I said above, the issue is that it's simply not mentioned:
"Deficiencies in the test cycle contribute to the widening gap – but cannot account for the entire variation. Notably the test cycle hasn’t changed in the last decade although the gap with real-world driving is getting wider. Part of the reason for the widening gap seems to be that manufacturers are increasingly deploying technology to improve the efficiency of cars that produce a big improvement in official tests but much smaller difference when the car is used on the road (such as stop-start technologies that switch off the engine when the vehicle is stationary). During the official NEDC test the vehicle is actually stationary for around 4 minutes or 20% of the test. Stop-start technology therefore has a considerable benefit in the test, but much less in average driving."

Source, page 17: http://www.transportenvironment.org/sites/te/files/publications/Real%20World%20Fuel%20Consumption%20v15_final.pdf 
« Last Edit: December 31, 2015, 02:21:05 PM by Rory »

culzean

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Re: Start Stop on New Jazz
« Reply #16 on: December 31, 2015, 02:32:01 PM »
It’s not that it doesn’t permit it, it simply doesn’t mention it, and the criticism is that something which isn’t mentioned makes quite a big impact to the results.   The test also doesn’t take account of hybrids – so you get wacky results from some cars which can do most of the test under electric power but are hopeless under electric power on the road (Mitsubishi PHEV is noted for this).

The most glaring example must be the BMW i8 which is quotes as 135mpg and congestion charge and road tax exempt,  but battery only lasts 18miles on a good day (probably half that if you want either the heater,  aircon or lights on LOL).  How can a car that can reach 155mph and 0-60mph in 4.5 sec ever achieve 135mpg  it has a relatively tiny 5kw/h battery,    I bet in real life average journey you would get about 30mpg if you were careful but the testings regulations are so shiite and skewed that it has been classified as a 'clean' car that does 135mpg and emits hardly any CO2.


Rory , that was a great article in your link,  who would have thought carmakers would go as far as disconnecting the alternator to reduce engine load and taping over bodywork gaps to reduce drag ?  all the tests seem to be run with all electrical equipment and aircon turned off as well,  probably under quite a high ambient temperature with high humidity to improve mpg as well. 
« Last Edit: December 31, 2015, 02:43:48 PM by culzean »
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Rory

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Re: Start Stop on New Jazz
« Reply #17 on: December 31, 2015, 04:01:58 PM »
Rory , that was a great article in your link,  who would have thought carmakers would go as far as disconnecting the alternator to reduce engine load and taping over bodywork gaps to reduce drag ?  all the tests seem to be run with all electrical equipment and aircon turned off as well,  probably under quite a high ambient temperature with high humidity to improve mpg as well. 

Thanks - I didn't read it all to be honest, but was struggling to find evidence that stop/start is used.

It's the fact that it defaults to "on" that makes it a certainty for me as the car has to run as started.  As you say, AC, lights and radio etc are all turned off for the test, but they will remain off if the ignition is turned off and back on again.  Stop/start won't - it defaults to on.

Downsizer

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Re: Start Stop on New Jazz
« Reply #18 on: December 31, 2015, 04:17:48 PM »
I don't believe stop/start would have been widely introduced if it didn't affect test results, thereby perhaps reducing the tax band, and giving a marketing advantage.  I don't think motorists generally value it very highly for its own sake.

John Ratsey

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Re: Start Stop on New Jazz
« Reply #19 on: December 31, 2015, 08:43:58 PM »
I have noticed, on the occasions that auto stop has failed to activate, that the indicated trip mpg can visibly drop as fuel gets used and the increase in miles is very small. And that's after, say, 50 miles of open road motoring with a reported mpg of around 60. So the auto stop can give some benefit to mpg in real life particularly if in a long queue for traffic lights where there are significant stop periods.

However, traffic snarl-ups are often in the form of slowly crawling traffic, such as the queue for a roundabout, when the auto stop doesn't get a chance to work. I wonder whether the proposed improved emissions testing will include some of this.

culzean

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Re: Start Stop on New Jazz
« Reply #20 on: January 01, 2016, 11:22:35 AM »
quote from traffic management website technical section about stop-start vehicle emissions............

 “Once at operational temperature, a modern engine’s three-way catalytic converter at idle will reduce oxides of nitrogen, while oxidizing CO and HC compounds effectively to zero. But stopping the engine causes the catalytic converter to cool. At restart, a burst of air-polluting emissions is generated before the converter reattains operational temperature.”


Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

zzaj

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Re: Start Stop on New Jazz
« Reply #21 on: January 01, 2016, 12:34:08 PM »

BMW say it saves fuel is the engine is stopped for 2 seconds.


Not those German car manufacturers again?

culzean

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Re: Start Stop on New Jazz
« Reply #22 on: January 01, 2016, 12:55:17 PM »

BMW say it saves fuel is the engine is stopped for 2 seconds.


Not those German car manufacturers again?

Yes the very same German car makers who have the EU legislators in their pockets (and maybe even employ them as 'consultants') when they write the Euro vehicle emission laws LOL - no wonder Americans think European car makers and legislators are the same people and the laws are framed accordingly (with so many loopholes and get-out clauses that it is virtually impossible to break EU emission laws )
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

Downsizer

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Re: Start Stop on New Jazz
« Reply #23 on: January 01, 2016, 02:27:13 PM »
Regarding the effectiveness of the catalytic converter when idling, it does not of course remove carbon dioxide, which is what the tax band is based on.  So it seems that stop start may reduce the tax liability while at the same time increasing emissions of toxic NO and CO!

artjet

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Re: Start Stop on New Jazz
« Reply #24 on: January 01, 2016, 02:31:52 PM »
I just wish I could permanently disable this annoying, useless feature  >:(

Paulwhitt20

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Re: Start Stop on New Jazz
« Reply #25 on: January 01, 2016, 02:54:56 PM »
My wife likes to disable the stop start when she remembers. I don't think she trusts it to start up again in time. I am used to a hybrid so the engine just does its own thing and I don't worry about it.

Skyrider

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Re: Start Stop on New Jazz
« Reply #26 on: August 11, 2016, 10:41:03 AM »
The thing I like about the stop start system is it tells you why it is not working. My previous car with this system gave no indication and if it did not activate for a while it left you wondering if it was actually working.
« Last Edit: August 12, 2016, 10:07:17 PM by Deeps »

Skyrider

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Re: Start Stop on New Jazz
« Reply #27 on: August 11, 2016, 10:44:49 AM »
I just wish I could permanently disable this annoying, useless feature  >:(

There must be something wrong with mine, it is completely unobtrusive.

Skyrider

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Re: Start Stop on New Jazz
« Reply #28 on: August 11, 2016, 02:48:20 PM »
I've always thought the stop-start thing has more to do with reducing pollution than improving fuel consumption.

I have always thought it is more to do with reducing the manufacturers total product Co2 output and their tax liability. The punters fuel consumption is not their priority, much like the tiny petrol engines turbo charged to within an inch of their lives.

Things will change next year with the new VED rates. The manufacturers will soon start their advertising campaigns for beat the tax increase sales.
« Last Edit: August 11, 2016, 02:58:58 PM by Deeps »

ColinS

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Re: Start Stop on New Jazz
« Reply #29 on: August 11, 2016, 04:13:02 PM »
Back on topic.  The manual will cut the engine if the car comes to a halt and is in neutral irrespective of the foot brake or handbrake being engaged.  So no need to dazzle drivers behind (my pet hate).

It will start again if you depress the clutch, move the steering wheel or the car starts rolling away.

As John says, there are several reasons that it will not activate, engine cold, demand from aircon etc.  But the cleaver one is that if you are stop start in traffic, it eventually recognises that and keeps the engine running.  Obviously Honda don't share BMW's theory.

I like this feature but did'n realise it operated in a different way on the CVT.  That really is a bad design fault that it will not stay cut out with the handbrake on in park.

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