Stop Start technology? Is it a false economy?

[RuSZ]

Took a new PuntoEVO for a test drive today as a bit of fun and look at the new car.

It had the Stop/Start engine management system on it. Which as we all know stops the engine when the engine thinks the car isnt moving. and restarts it when the clutch/accelerator is pumped. once or twice it cut the engine while i was coasting upto traffic lights, which was a little annoying.

However, my question is, does it waste more petrol than it saves???

a) modern cars use very little when coasting in gear to lights (a lot use non at all) and the Fiat system seems to cut out when coasting...

b) restarting a car uses a lot of petrol compared to leaving it running.. If you a stationary for less than 30seconds the amount of petrol used to restart the engine is MORE than what the engine uses when idling...

so

Stationary for less than 30sec MORE PETROL by STOP START
Stationary for more than 30sec LESS PETROL by STOP START


So have we fallen for a "ECO" gimmick...

 

[RuSZ]

yeah, makes more sense in the Tech section sorry.

 

[alexGS]

I suspect that starting an already-warmed engine doesn't actually use any more petrol with modern (accurate) engine management? So on that basis, any time spent 'off' is a saving except for the amount of electrical power it takes to crank the engine over.

Coasting in gear will still use petrol at really slow speeds, since fuel must be restored below a certain engine speed - otherwise it would die when the clutch is disengaged.

I have a feeling that the starter motor, if it is a conventional type, will come in for a really hard time under this system. My Punto (Mk2 Sporting Speedgear - CVT) had a problem with chewing the teeth off the ring gear. Imagine how much more common that problem will be if the starter is operating 20x more often...

I think ultimately it depends if traffic is stationary for long traffic light cycles, regular hold-ups, etc. - then stop-start will be nice to have. If moving slowly or stopped only briefly, it might be better not to have it unless the car also had some means of moving by electrical power alone.

-Alex

 

[Mrsam21]

I totally agree! I got my Punto Evo a week ago today and the start stop annoys me so much! I normally forget to turn it off then i just cuts out when i need it to accelerate! Mine is a 1.4 and i drive pretty quick in it and i still average 42mpg which i think is good! I think the start stop should be a button where you turn it on if you want where you know you will be stuck in traffic for a while and not automatically on and you have to turn it off! Plus it normally says 'Start stop unavaliable' most times i drive the car!

 

[D4nny8oy]

a) modern cars use very little when coasting in gear to lights (a lot use non at all) and the Fiat system seems to cut out when coasting...

While the engine is in over-run shut-off (above approx 1500rpm) it'll use no fuel whatsoever.

Once the engine speed dips below this, fuelling is gradually brought back in to the idling amount of injector duration.

Stop/Start shouldn't cut out on the over-run, only if the clutch was depressed or if the 'box was in neutral (in which case the engine is on it's, wasteful, idling fuelling). How were you "coasting" to a stop?

 

[D4nny8oy]

I have a feeling that the starter motor, if it is a conventional type, will come in for a really hard time under this system. My Punto (Mk2 Sporting Speedgear - CVT) had a problem with chewing the teeth off the ring gear. Imagine how much more common that problem will be if the starter is operating 20x more often...

All items related to engine start-up (battery, starter and ring-gear to name just a few) are considerably uprated on stop/start vehicles.

 

[custard]

I totally agree! I got my Punto Evo a week ago today and the start stop annoys me so much! I normally forget to turn it off then i just cuts out when i need it to accelerate! Mine is a 1.4 and i drive pretty quick in it and i still average 42mpg which i think is good! I think the start stop should be a button where you turn it on if you want where you know you will be stuck in traffic for a while and not automatically on and you have to turn it off! Plus it normally says 'Start stop unavaliable' most times i drive the car!

I had thought that an overide button on the gearstick would be a good idea?
I seem to recall an old car that had a clutch on the gearstick.

 

[Mrsam21]

I had thought that an overide button on the gearstick would be a good idea?
I seem to recall an old car that had a clutch on the gearstick.

There is a button on the dash but I forget everytime i get into the car and only remember when it cuts out!

 

[custard]

There is a button on the dash but I forget everytime i get into the car and only remember when it cuts out!

yeah,but im thinking of a button where you suspend it as you drive
so if you are at a busy roundabout
you can give it a 1 minute suspend(for example) for that junction

 

[Mrsam21]

yeah,but im thinking of a button where you suspend it as you drive
so if you are at a busy roundabout
you can give it a 1 minute suspend(for example) for that junction

I dont think I can do it with mine all I do when i turn it off is hold the button and a light comes on and the dash says start stop disabled.

 

[RuSZ]

While the engine is in over-run shut-off (above approx 1500rpm) it'll use no fuel whatsoever.

Once the engine speed dips below this, fuelling is gradually brought back in to the idling amount of injector duration.

Stop/Start shouldn't cut out on the over-run, only if the clutch was depressed or if the 'box was in neutral (in which case the engine is on it's, wasteful, idling fuelling). How were you "coasting" to a stop?

I was coasting in gear. slowing for traffic lights from 30mph in 3rd. released clutch at 1100rpm. this is when the engine cut out. I thought i had stalled. but no lights on the dashboard. pushed the clutch and accelrater and the engine kicked back in.

There could have been a system fault on this model..

But the general question is;

"is the ECO Stop/Start really ECO??"

 

[Mrsam21]

I was coasting in gear. slowing for traffic lights from 30mph in 3rd. released clutch at 1100rpm. this is when the engine cut out. I thought i had stalled. but no lights on the dashboard. pushed the clutch and accelrater and the engine kicked back in.

There could have been a system fault on this model..

But the general question is;

"is the ECO Stop/Start really ECO??"

To be honest I think that when the car is just cutting out for a couple of seconds then re starting this will firstly not do the engine any good and will use more fuel than just sitting there on as cars today use hardly if any fuel when standing still.

If the car was going to be off for a 1 min or more then turn back on then yes I feel this will save fuel and not do as much damage to the car.

I just think it depends on how much the car is stopping and starting and how long for.

Sam.

 

[D4nny8oy]

The main benefit (and idea) of stop/start is lower emissions over the course of a journey than an identical car without it, with the resulting lower tax bracket making the car cheaper to own. Any fuel economy benefit will be dependant on the conditions.

 

[alexGS]

All items related to engine start-up (battery, starter and ring-gear to name just a few) are considerably uprated on stop/start vehicles.

Fair call but I've already managed to catch the system out once
Yesterday in 'my' 500 1.2L Lounge with 27 miles on the clock I approached a roundabout. Somehow as I pushed the clutch and selected second (while still moving very slowly) I heard and felt the starter motor engage very briefly with the still-turning engine, making a horrid noise!

This doesn't bode too well regardless of how uprated the items are, though now I have adjusted slightly to how the system works, I select neutral before actually coming to a stop with my foot on the brake and the clutch raised. That way the engine cuts out as soon as possible and as long as I remember not to press the clutch until the last possible moment, the chance of the starter engaging on a still-turning engine are reduced. This is, however, a little unnatural as we've all been told never to coast in neutral, yet that is what you must do if you want the engine to cut out the moment you have stopped.

It helps that in England, your traffic lights change to red and orange before green - in NZ, ours just go straight to green.

russ12, have a look at the 43-page report http://www.fiat.co.uk/uploadedFiles...-DRIVING_UNCOVERED_full_report_2010_EN(1).pdf in which the actual advantage of the Stop-Start system is revealed (report studies 9 million journeys made by 42,000 drivers)...

-Alex

 

[Davren]

i seem to recall an old car that had a clutch on the gearstick.

nsu ro80