This gizmo wot turns the engine off when stuck at lights...

[thismonkeyhere]

'Bluemotion' is, I believe, what VW call it. Other manufacturers offer the same thing. Turns the engine off when stopped at lights or otherwise in stationary traffic. I know a couple of people who swear by it and claim big savings.

Worthwhile? I have done some research and calculations around this, upping the figures for both the fuel used at idle and the time spent stationary for a stty commute (so I can't be accused of a fudge in favour of my argument), and as far as I can work out, I might save about £75 a year. Fair enough, £75 is £75, but what price the gizmo in the first place?

Thoughts? Dodgy maths on my part or 'emporer's new bluemotion'?

[Coldfuse]

Blue motion is VW's name for efficient cars. I think your referring to stop start technology.

[McSam]

doogz said:

Doesn't the lower emissions as a result of the car turning itself off in traffic, result in lower road tax/VED/whatever you want to call it?

Yes. It's not really designed for fuel savings in the real world, though it will give some small saving I don't think it'll be anywhere near what the OP calculated - not with a typical modern diesel consuming about 0.3l per hour at idle!

[Amateurish]

It's for the benefit of the European Driving Cycle fuel economy tests. For the urban cycle, the vehicle spends a relatively long time at idle. These stop start systems give manufacturers an appreciable benefit in terms of fuel economy results e.g. reduction in 5-10 grams of CO2.

[Crusoe]

bluemotion covers more than stop start, they tend to have slightly more aerodynamic bodywork, a slightly lower ride height and longer gearing all to help economy. Main benefit of the stop start is the reduction in emissions on the urban cycle tests I believe so you probably save some road tax. Other things included on other similar models from other manufacturers as well as VAG include things like disengaging the alternator under certain circumstances, brake regeneration, disengaging aircon, flaps to close the engine vents to help warm up etc.

[MysteryLemon]

Saving the world or not, it wont save anything when that little gadget fails leaving you with a car that wont restart at the lights, or when the car gets older and starts getting compression issues and can't be restarted easily when warm.

I often worry about the stop/start button in my partners Scenic. yes, it's kinda cool, if not totally pointless, but what if, one day, something somewhere between the button and the ECU eats itself and there's no way of starting it?

What's wrong with a key that connects 2 wires together and tells a relay to start the engine instead of a button that tells the ECU you want to start the engine, which has a thing about it then tells the starter motor to turn...

Modern cars are stupid.

[HustleRussell]

OP- I expect you can put the £75 you've saved towards a new starter motor for when your original one fails prematurely due to starting the engine several times more per journey than a non stop-start engine.
I may be wrong though, manufacturers may have beefed up their starters so they last just as long...

[thiscocks]

save your breath http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[SuperchargedVR6]

Certainly with petrol engines the amount of fuel required to get the engine started (even when hot) can be quite significant. Probably why you don't see it on big V6s & V8s etc. I can't really see much of a benefit tbh.

It's a marketing gimmick to get the tree-huggers on side.

[8vFTW]

Always thought it seemed like a great way to wear out the components your ignition system much quicker than usual.

[Ben Magoo]

All of my cars have stop/start technology although I only use it at the beginning and end of a journey and sometimes when waiting at level crossings etc.

You could save yourself the same amount of money (and the cost of buying a new car!) using your existing stop/start technology

[Chicane-UK]

8vFTW said:

Always thought it seemed like a great way to wear out the components your ignition system much quicker than usual.

Because of course they would just bolt the technology onto existing engines without even thinking about such things, and uprating them accordingly..

It's clear a whole lot of work has gone into stop start and in my experience, the technology worked really well. I didn't find it intrusive, or annoying.

[cptsideways]

Some of them do not use the starter motor - eg Mazda's i-stop system

In 3500 miles of driving the stopped readout was on 3+ hours after lots of town driving. Fuel saving is not the issue though its the annual tax/BIK reduction that is worth far more.

[Superhoop]

cptsideways said:

Some of them do not use the starter motor - eg Mazda's i-stop system

What do you think it uses to start the initial engine rotation then?

[sleep envy]

Superhoop said:

cptsideways said:

Some of them do not use the starter motor - eg Mazda's i-stop system

What do you think it uses to start the initial engine rotation then?

A squirt of fuel into the cyclinder which is still under compression and is then ignited.

[cptsideways]

Superhoop said:

cptsideways said:

Some of them do not use the starter motor - eg Mazda's i-stop system

What do you think it uses to start the initial engine rotation then?

It fires one cylinder near TDC to get it going again. Clever stuff indeed, it will use the starter motor for backup occasionally though.


http://www.mazda.com/mazdaspirit/env/engine/siss2....

[Superhoop]

cptsideways said:

Superhoop said:

cptsideways said:

Some of them do not use the starter motor - eg Mazda's i-stop system

What do you think it uses to start the initial engine rotation then?

It fires one cylinder near TDC to get it going again. Clever stuff indeed, it will use the starter motor for backup occasionally though.


http://www.mazda.com/mazdaspirit/env/engine/siss2....

Nope, it uses the starter every single restart. It's only used to promote initial engine rotation (between 45 and 90 degrees of crank movement) and then the firing of a cylinder does the rest

That's why the PCM counts engine restarts, with the starter motor requiring replacement after 250,000. If you read the article you posted, it actually shows the starter motor operation.

[GroundEffect]

doogz said:

Doesn't the lower emissions as a result of the car turning itself off in traffic, result in lower road tax/VED/whatever you want to call it?

That's one of the only ways for us to meet Stage VI emissions...

Also, this isn't really a 'gizmo', it's just a function in the ECU. From the engines I've seen, many can get away with no changes at all.

Edited by GroundEffect on Tuesday 29th January 17:58

[EDLT]

MysteryLemon said:

Saving the world or not, it wont save anything when that little gadget fails leaving you with a car that wont restart at the lights, or when the car gets older and starts getting compression issues and can't be restarted easily when warm.

I often worry about the stop/start button in my partners Scenic. yes, it's kinda cool, if not totally pointless, but what if, one day, something somewhere between the button and the ECU eats itself and there's no way of starting it?

What's wrong with a key that connects 2 wires together and tells a relay to start the engine instead of a button that tells the ECU you want to start the engine, which has a thing about it then tells the starter motor to turn...

Modern cars are stupid.

I wouldn't use the word modern, ECUs have been involved in starting most cars for at least 20 years.

EDIT:
And stop start disables if you have the climate control/AC on - which is on permanently in my car.

Edited by EDLT on Tuesday 29th January 18:02