[AlanHo]

A few days ago I drove into the centre of Birmingham with my wife. The journey is mainly along the main A34 road which is populated by a number of road island and traffic light junctions and quite a few traffic light controlled pedestrian crossings. We were driving just after the morning rush hour and traffic was heavy. It is a main route for several bus services and there are few opportunities to get past buses when they stop for passengers.  The overall length of the journey was 8.3 miles (13 km) and it took us 35 minutes.

It was an ideal opportunity to check how often and for how long the ISG would operate.

My wife kept a note for me of each time the car came to a halt and the number of seconds the Auto stop activated each time. Where a zero is recorded the car stopped - but the ISG did not activate because the car had not reached 6 mph since the previous stop.

The engine stop times were as follows :-

3, 8, 19, 11, 18, 5, 0, 0, 7, 16, 22, 7, 28, 2, 0, 0, 0, 12, 16, 21, 6,0,0,0, 4, 0,0, 18, 43, 12, 24, 3,0,0, 18, 22, 6, 31, 9, 5,0,0, 7, end of journey.

Total number of stops                  : 44
Number of times ISG activated     : 29
Total time engine was off             :  403 seconds (6 minutes 43 seconds)
Average speed for journey           : 14.3 mph (23 kph)

I should add that this happens to be just about the worst conditions to use a diesel – it was a cold morning start with an air temperature of 7°C and the engine temperature gauge was still not at its normal maximum when we reached the destination. Surely a recipe for premature DPF regeneration if done too often (which I don’t - For such journeys we usually use my wife’s petrol i10 – but I wanted to carry out this experiment).

Whilst it might be argued that on this journey the ISG may have saved a cup of fuel – the downside is the fact that the engine never reached normal running temperature. My conclusion – for a diesel car switch the ISG off when undertaking short town journeys – I have a feeling in my water that the fuel saving is not worth the extra engine wear and the effect on the DPF.

[Shambles]

Very useful experiment Mr AlanHo - thanks for taking the time to do it


Might make a useful front-page portal article... hint hint

[Phil №❶]

I  to your wife for getting involved and assisting you, I love to see working partnerships. 

[Dazzler]

I  to your wife for getting involved and assisting you, I love to see working partnerships. 

  and thanks to you as well, of course, for coercing her into it 

[Phil №❶]

and thanks to you as well, of course, for coercing her into it 

 

[eye30]

Thanks for the report.

Do you happen to have the £££ of the trip?
I say this because next time it would more cost effective to use your free bus pass given the regen which will probable kick in soon due to the low speed/temp for the trip.

ps
Also, no worries about parking at other end.

[AlanHo]

Thanks for the report.

Do you happen to have the £££ of the trip?
I say this because next time it would more cost effective to use your free bus pass given the regen which will probable kick in soon due to the low speed/temp for the trip.

ps
Also, no worries about parking at other end.

We do normally use our pensioners free travel passes and go into Birmingham by train from Solihull rather than the bus. We don't use the bus because it goes via Grottsville - they are usually full and trouble on the buses is far from rare.  This trip we were collecting some furniture - hence using my car rather than management's i10.

[peon2t]

I've recently read that - on an average - ISG stops save fuel if they last 18 seconds or longer. If they last only a few seconds you waste more fuel on restarting the engine than you save. So your experiment indicates that the ISG in your case probably wasted more fuel than it saved.

But I must say that  when I drive  the ISG usually only comes to action for stops between 30 seconds and two minutes. This is because I never go to neutral gear in stop-and-go-traffic. I only go to neutral when I come to a traffic light where I can assume that it won't turn green during the next ten, twenty seconds.

[Mike SX]

Very useful, and excellent information

Thanks.

[eye30]

go into Birmingham by train from Solihull

Had to use Solihull station a few years ago when I was going to a seminar held at a Hotel, can't recall name but was on what looked like an industrial park, a few miles from the station.

Seemed a good service to Birmingham ??? but then had to hike across the city centre to get too new street

[Mike SX]

ISG may have saved a cup of fuel.

At full working temperature, at tickover, it would consume 6 milli litres of fuel per second, ie. slightly more than a 5 milli litre medicine spoon; just over 1.5 cups

[Asterix]

Thanks Alan.

I am amazed to see that you can get your wife to help you with your various experiments.

If I asked my wife to help with something like that, she would call me silly and the test unnecessary.. 

[AlanHo]

Thanks Alan.

I am amazed to see that you can get your wife to help you with your various experiments.

If I asked my wife to help with something like that, she would call me silly and the test unnecessary.. 

You youngsters have yet to learn the psychological chicanery skills needed to get the best out of people - including your wife.................

She knows all too well the advantages of keeping me happy and indulging in my foibles................

[Asterix]

Thanks Alan.

I am amazed to see that you can get your wife to help you with your various experiments.

If I asked my wife to help with something like that, she would call me silly and the test unnecessary.. 

You youngsters have yet to learn the psychological chicanery skills needed to get the best out of people - including your wife.................

She knows all too well the advantages of keeping me happy and indulging in my foibles................

Women of your generation was taught to obey their husband.

Things have changed.....they even get to vote now...

[Phil №❶]

@Asterix,

What's the world coming to, eh.

[marti30]

This sort of driving is different to mine. Since the car's 100,000 mile service/first MoT it has been used 18 days during which it clocked up 2,269 miles and the engine has been started 26 times. Given my indicated average fuel consumption and speed it uses a litre of diesel approximately every 20 minutes (64.9mpg 43 mph). I don't think ISG is for me.

[eye30]

has been used 18 days
the engine has been started 26 times.

 
Hardly at rest then

[marti30]

I'd be interested to know how much fuel an engine uses at idle. It can't be much if mine uses about a litre every 20 minutes in normal use (normal for me, anyway). There are times when mine ticks over for several minutes at a time when for example I arrive at a campsite and am paying for and selecting a pitch. I dislike stopping and starting the engine for short periods thinking that the wear and tear on some components outweighs the really quite small saving of fuel and pollution.

[AlanHo]

I would estimate that the average 1.6 litre diesel would use 0.9 litres per hour when idling once the engine is warm and without the aircon calling for power.

Hence .015 litres per minute.(15 millilitres per minute)

At 60 mph on a flat road my car averages 60 mpg which equates to a fuel consumption of .076 litres per minute. (76 millilitres per minute)


So what are you going to do with that info?