Benefit of start/stop

[Pieisgood999]

Hi guys,
It would appear that more and more cars are equipped with start/stop (more's the pity)
I was wondering if anyone knew of a study which worked out how long you needed to stop at the lights before the stopping of the engine became beneficial to consumption.
By that I mean that the energy needed to operate the starter would have to come from the battery, and there's a loss in efficiency due to the weight of all the beefed up starter equipment needed for start/stop.
Also, has anyone used vag-comm to turn it off automatically on startup?
Does the start/stop use the same starter as on cold start, or is it a separate mechanism like the older versions?

 

[speed12]

This isn't from VWs, but from having tested a LOT of other vehicles with stop/start at work, the system is worth around 2-3% CO2 saving over the NEDC emissions cycle - each stop (with engine off) in the cycle is 16s (with a 7s stop at the end).

I appreciate the NEDC is not really a good reflection of 'real' driving; but a stop is a stop and 2-3% of fuel saved over 20ish mins is reasonably good.

The extra weight from the starter is essentially negligble in the grand scheme of things. Most vehicles will also have some very mild regenerative braking, so you aren't completely wasting starting cranking power either.

 

[Stripey]

This isn't from VWs, but from having tested a LOT of other vehicles with stop/start at work, the system is worth around 2-3% CO2 saving over the NEDC emissions cycle - each stop (with engine off) in the cycle is 16s (with a 7s stop at the end).

I appreciate the NEDC is not really a good reflection of 'real' driving; but a stop is a stop and 2-3% of fuel saved over 20ish mins is reasonably good.

The extra weight from the starter is essentially negligble in the grand scheme of things. Most vehicles will also have some very mild regenerative braking, so you aren't completely wasting starting cranking power either.

Which is it...2-3% saving in CO2 emissions or fuel consumption? Or both?!

 

[speed12]

Apologies, slip of nomenclature - for the NEDC it's 2-3% CO2 saving, but the two are directly linked so you'll see essentially the same savings in fuel consumption (probably nearer 1-2% to be honest). Still a good figure for such a minimal impact on driving style -
I.e doesn't have any effect on driven vehicle performance.

 

[Chr15b]

My thinking is start stop, and DPF (for diesel) both help with the testing phase for determining a cars emissions output. i've no idea how long the testing phase is, but if the car isnt running for a percentage of it, can only lower the figure.

DPF my thinking is, if for the testing phase you can capture some of the crap, you can gain better figures, ignore that the car will use more fuel later for the regeneration cycle, and that it will ultimately dump it out the exhaust anyway - just not during the testing cycle.

cynic, moi?

 

[Russkiya]

Stop/start may not seem to benefit you directly, but in the overall scheme of things with millions of cars that are in use at any one time but in the 'stop' stage is a massive saving in global fuel and CO2 emissions.
There are other benefits;

1. Quieter streets = friendlier people (less shouting)
2. Less smell= healthier people
3. Less smog= less polishing your car

These points won't happen overnight, but they will come.

In building passenger aircraft, a few kg/pounds of weight saving make a huge fuel saving in the life of the aircraft. Billions are spent just for a few KGs.

 

[Stripey]

I think it makes sense to cut the engine when stationary. Not so good if you need the air con on to cool you down but 30 seconds with no air con may not make a massive difference to temperature...... Not in the UK anyway! And 2% savings in CO2 and fuel may not seem like much but it's better than nothing.

 

[mikef4uk]

I would like to be able to go forward 5 years and see how many stop/start systems require new starter motors and/or ring gear

 

[marvin1]

I would like to be able to go forward 5 years and see how many stop/start systems require new starter motors and/or ring gear

Be careful what you say! I have been castigated here by suggesting increased wear and tear on appropriate associated components. Down the line however there are many parts of today's cars that may not seem so clever an idea after 5/10 years. But there again I'm a cynical old bugger who knows sweet FA.

 

[Genegenie]

I would like to be able to go forward 5 years and see how many stop/start systems require new starter motors and/or ring gear

Also one of my concerns, though my car is on PCP and in any case will belong to someone else in 3 years time. The handbook of my last car, Seat Leon petrol, reccomended stopping the engine to save fuel if stationary for longer than 20 seconds....

 

[nauend]

I would like to be able to go forward 5 years and see how many stop/start systems require new starter motors and/or ring gear

Did a google search, and VW first introduced a version of stop-start back in 1983 (Polo Formel E). Stop-start became standard in the Mk6 Bluemotion in 2008'ish, so there will be cars that have had it for around 5 years, so there may be people who can answer your question.

I did a search on GolfMK6.com but could not find any threads raising a concern about this. The few that discussed it also thought that VW would design the components to handle any wear that additional stop-starts might cause.

 

[mikef4uk]

Also one of my concerns, though my car is on PCP and in any case will belong to someone else in 3 years time. The handbook of my last car, Seat Leon petrol, reccomended stopping the engine to save fuel if stationary for longer than 20 seconds....

So a case of ''I'm on the Bus ring the bell'' eh?

 

[Chr15b]

Be careful what you say! I have been castigated here by suggesting increased wear and tear on appropriate associated components. Down the line however there are many parts of today's cars that may not seem so clever an idea after 5/10 years. But there again I'm a cynical old bugger who knows sweet FA.

friend had a 2008 bmw mini, in time he had it, a little under two years, it had four timing chains and work done to or replacements of tensioner components. the general opinion from all involved was the start stop didnt help.

 

[Geomets]

friend had a 2008 bmw mini, in time he had it, a little under two years, it had four timing chains and work done to or replacements of tensioner components. the general opinion from all involved was the start stop didnt help.

The S/S system had nothing to do with these problems. I had a Peugeot 207 RC, BMW powered. These engines were for less reliable than the classic TU. My car didn't have S/S, but I changed 3 chain tensioners in 2 years and calibrated the phase of the cam-shafts twice. The chain needed changing but I finally changed the car! Lucky me! The 1.4lt Saxo I had before was a reliable, honest little fun-car. I missed it (it's features to be exact) for as long as I had the Peugeot (it had good points of course). BMW got its finger and screwed (further) the PGA group. TU engines were reliable, rev-hungry (the 16-valve ones) and fuel-efficient. What BMW were thinking? Rubbish engine, but S/S had nothing to do with it. Just check the Peugeot-Mini forums. S/S had nothing to do with the problems these problematic engines had.

 

[Finepics]

Honda have used this since 1999 and Citroen since 2006, but Toyota had a car with S/S in the early '70's! I think it's been around long enough to be proven technology. But battery life might be compromised! This is an interesting read:

http://en.wikipedia.org/wiki/Start-stop_system