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kwhelan

hard to argue with this ie stop/start use

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@kwhelan be careful, referencing scientific tests like that will get you banned from the internets!!

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If I was interested enough I would want to see the original test data and methodology used. That guy is just a youtuber who makes a living out of presenting basic science to uncritical audiences. He did not make the actual tests. 

For example, every time the starter cranks the engine it draws energy from the battery. That energy is restored by the alternator putting extra load on the engine, and that requires extra fuel to be burned. Was this factored into the original test data ? Small four cylinder engines can be expected to be more fuel efficient that larger 6 or 8-cylinder engines. How would this affect the results ?

Until proven otherwise, youtube videos are not worth the paper they are written on :) 

Cheers...

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2 hours ago, jon dee said:

If I was interested enough I would want to see the original test data and methodology used. That guy is just a youtuber who makes a living out of presenting basic science to uncritical audiences. He did not make the actual tests. 

For example, every time the starter cranks the engine it draws energy from the battery. That energy is restored by the alternator putting extra load on the engine, and that requires extra fuel to be burned. Was this factored into the original test data ? Small four cylinder engines can be expected to be more fuel efficient that larger 6 or 8-cylinder engines. How would this affect the results ?

Until proven otherwise, youtube videos are not worth the paper they are written on :) 

Cheers...

wow,

just wow

I can see why they want to give the vote to 16 yr olds now

you must be hanging out for booster #4 by now

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3 hours ago, E30 325i Rag-Top said:

@kwhelan be careful, referencing scientific tests like that will get you banned from the internets!!

Ive always believed stop start was a waste of time , may have to reconsider now, its interesting that i think most people quietly agreed but I guess manufacturers would hardly have bothered with all the expense if they didn't know something we didn't

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1 hour ago, kwhelan said:

wow,

just wow

I can see why they want to give the vote to 16 yr olds now

you must be hanging out for booster #4 by now

It's only physics son... nothing to be frightened of :)

This is what real research looks like... https://www.e3s-conferences.org/articles/e3sconf/pdf/2021/44/e3sconf_vesep2020_01030.pdf 

Cheers...

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@jon dee that looks like some 16 year old’s homework. I wrote longer, more detailed, reports when I was an under-grad on industrial placement. Mind you, that was when you had to do some work to get an academic qualification rather than open a box of corn flakes.

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1 hour ago, E30 325i Rag-Top said:

@jon dee that looks like some 16 year old’s homework. I wrote longer, more detailed, reports when I was an under-grad on industrial placement. Mind you, that was when you had to do some work to get an academic qualification rather than open a box of corn flakes.

That is a stunningly dismissive statement of what appears to be a genuine effort to document the effects of stop-start operation on various engine operating parameters. Quite frankly it sounds like something a Chinaphobe would say, but sobeit. If a 16yo can produce something like that then the world is in better shape than I thought :)

Cheers...

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That is a stunningly dismissive statement of what appears to be a genuine effort to document the effects of stop-start operation on various engine operating parameters. Quite frankly it sounds like something a Chinaphobe would say, but sobeit

 

pot kettle

you were obviously interested enough to comment

first you gave us your expert opinion, completely write off the video with smarmy comments that because he didnt do the tests,( its invalid etc

you rave on for a whole paragraph with a personal theory about starters and whether they allowed for that, FFS just watch it and save yourself the embarrassment next time

all without, by your omission, watching it

you make a weak joke about all of youtube being crap,

then trying to defend your obvious smuggness in the first post actually find and give a counter arguement, (good thats how its supposed to be done)

yes the video was dummed down to make it watchable in todays 15sec attention span audience and it was done with humour.

unlike yours where 90% would just say TLDR

then when someone dismisses your argument mostly in jest but just probably trying to point out to you your smugness ,

like a typical lefty you make it personal, start calling someone names, Chinaphobe  (FFS how embarrasing for you and you should apologise)

make it personal because thats how any lefty wins an arguement, hint that the person is RACIST and bang I win.

I don't know why I'm even writing this because I know it all just flying past your head, God help my grandkids with the state of NZers critical thinking now

Trying to discuss anything with a lefty is like banging your head against a wall, unopen to anything that might contradict your preconformed science

if it doesn't come from the podium of truth, the single source, it must be burned to the ground.

 

 

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Calm down fellas. Pack of lefty-righty sandal wearing keyboard smashers 🤦‍♂️ 

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My thoughts exactly, how did this devolve into personal insults and then political ones?!

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16 hours ago, jon dee said:

If I was interested enough I would want to see the original test data and methodology used. That guy is just a youtuber who makes a living out of presenting basic science to uncritical audiences. He did not make the actual tests. 

For example, every time the starter cranks the engine it draws energy from the battery. That energy is restored by the alternator putting extra load on the engine, and that requires extra fuel to be burned. Was this factored into the original test data ? Small four cylinder engines can be expected to be more fuel efficient that larger 6 or 8-cylinder engines. How would this affect the results ?

Until proven otherwise, youtube videos are not worth the paper they are written on :) 

Cheers...

The load from the alternator is not really an issue. 

It's reasonably easy to figure out having an engine turn of for a certain period of time leads to small fuel savings  

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WOW..... just WOW :)

Kevin, I suggest you take a few hours to calm down and then read what you just wrote. You are indulging in the very behavior that you are ranting about. Classic example of the Straw Man Fallacy... you make assumptions and unfounded assertions and then attack them :) 

All good. But to get back on topic, the fundamental justification for stop-start is that it reduces fuel use by turning the engine off when the vehicle is stationary. And the yardstick used is the urban driving cycle which conveniently contains a significant number of periods of idling. This is the target for the stop-start technology, and where the fuel savings are made. 

But if a vehicle's daily commute does not involve driving in heavy city traffic, but follows a flowing suburban route with few stop signs or traffic lights, the results will be very different from the standardised urban cycle. Taking this argument to its logical conclusion, driving town to town on the open road, the stop-start system will have saved zero fuel. So, as the saying goes.... results may vary. 

Cheers...

 

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23 minutes ago, dirtydoogle said:

The load from the alternator is not really an issue. 

It's reasonably easy to figure out having an engine turn of for a certain period of time leads to small fuel savings  

Fair comment. Delving into some of the more informed descriptions of how stop-start technology is controlled, I see that one of the safeguards is that the system will be deactivated if battery voltage drops too low or if the engine temperature is too low. So while the amount of energy required for each engine start may be small, it still has to be restored, and regenerative braking is probably the only way to get that energy without using fuel.

Yes... turning the engine off does save fuel, but as was shown in the research paper I referenced above, turning it back on again does use a little bit of extra fuel. A hot engine requires a richer mixture to ensure smooth starting and this can be seen by the dip in lambda. The net gain in fuel saving depends on how long the engine is turned off before being restarted. 

Cheers...

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Let's not overlook any congestion effects, stop/start faffing around getting off the lights slowing up the car behind, surely that's a net increase in fuel being used?

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1 hour ago, tawa said:

stop/start faffing around getting off the lights slowing up the car behind, surely that's a net increase in fuel being used?

Stop / start doesn’t make it any slower to get away, you lift off the brake and by the time your foot is on the gas the engine is running, it’s that quick (well it is in a new bimmer anyways).

If it’s Auckland traffic, the car behind will be either texting, looking at Facebook, watching a movie, doing their make-up or eating breakfast anyway. Normally takes them ten seconds to realise the car in front has moved, it’s why the traffic is so sh*t.

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Yeah it's a pretty seamless transition in my G20. However lately it's rarely worked. Come to to think of it, didn't work pretty much all winter last year too. Assuming due to battery voltage from short trips in Akl traffic and the cold etc but I'm not complaining

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17 hours ago, Navin said:

Yeah it's a pretty seamless transition in my G20. However lately it's rarely worked. Come to to think of it, didn't work pretty much all winter last year too. Assuming due to battery voltage from short trips in Akl traffic and the cold etc but I'm not complaining

sales guy told us it learns your route and then overrides it at certain stop signs etc, it certainly appears to know every morning where you are going  just like your phone so I guess its not beyond the realms.

we have noticed it not working lately on very familiar streets and even when we pull up to open our gates to property but kicks in if your going somewhere different, its not great in an f40 there's a definite shake or vibration as the 3 cyl fires up which gets tiring really fast, the fours seem much better and in the big ones you'd struggle to hear it had even stopped. wish they gave you the choice or it remembering your on/off state and not resetting everytime you start the car though

an f40 at idle is not exactly thirsty

 

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22 hours ago, kwhelan said:

 wish they gave you the choice or it remembering your on/off state and not resetting everytime you start the car though

 

 

You can thank vw for that.

Personally I don't think fuel economy is the main purpose behind stop/start but more emissions. If the car isn't running then it's not producing emissions and that helps car manufacturers meet the super tough regulations. Joe public doesn't give two hoots about emissions but rather fuel economy which is a handy byproduct and selling tool.

Half the duration of the emissions and fuel economy tests are measured whilst the car is at a stop

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The starter motors must be beefed up to cope with all the extra work, I haven’t really heard much at all on early failures in bimmers with stop/start tech.

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uddsdds.gif

The vehicle is "stationary" for 18.9% of the 1369 second test duration.. Now you know :)

Cheers...

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there are / were more than one testing cycle. That looks to be an ancient USofA EPA one for urban cycle, there will be a joined extra-urban (or highway in US speak). All slightly different to reflect different traffic characteristics of various countries and areas. Hundreds of different EU ones. But yeah, pretty sure none of them have anything near 50% idling time. 
Would be interesting to know how it works under WLTP when no two journeys can be exactly the same..?

@Gaz not sure that was directly VWs fault, more the risk-averse reaction of most other manufacturers in the hope of not being fined.

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4 hours ago, Gaz said:

You can thank vw for that.

Personally I don't think fuel economy is the main purpose behind stop/start but more emissions.

yeah couldn't agree more, they were forced into it rather than it being a natural progression. I guess it all comes done to pure numbers or quantities,I think killing cylinders would be easier and probably a better outcome, not sure why bmw havn't done that

my 7 km drive to work has one stop sign and one set of lights,if its stops its for less than 45 seconds ever unless a train happens to come through town as its scheduled to do at 5.15pm every night but I guess in Auckland it all adds up,

it can be coded to remember the last settings at turn off with software too

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