My New MK3 Jazz

[guest7642]

It's a bit of both. There have been several independent studies that suggest idle stop typically reduces overall fuel consumption between 5% and 10% depending on the vehicle and the type of driving. As far as the cost of recharging the battery is concerned that is minimal. Don't forget that the engine starts within a quarter of a second so the starter motor barely nudges the engine. The same studies typically suggest that the engine only has to be off for two to three seconds for stopping it to be worthwhile. Or put another way - three seconds of idling burns as much fuel as it takes to replace the battery charge lost by idle restart.

I'm not sure about it being fair to be harsh with manufacturers. I've now found a few articles that suggest that idling and stopping aren't that big a part of the testing so an I/S system doesn't sound like it would have much effect. But either way I wouldn't call it gaming the system since it's a pretty obvious feature. Overall is I/S worth it to us as drivers? I dunno. Given the extra cost of R&D and manufacturing costs I bet there's not a lot in it. But having bought a car with I/S it seems silly not to utilise it. Even if the end result is a greater cost to us at least using it will reduce that cost.

I was not trying to be harsh to the manufacturers.  It is in their interest to put their product in the best light - look how far many have been prepared to go though.  Not running the engine when you have are stationary for an extended period makes sense but I doubt many would see a saving of 5-10% in the real world.  In a test like this one https://en.wikipedia.org/wiki/New_European_Driving_Cycle it is not that surprising as more than 10% of the ECE-15 (urban) test is spent at idle (i.e. stopped).

You make some very good points I just think we have a slightly different opinion on this one 

[andruec]

Some good responses. Grateful for the advice about coming to a stop - obvious really! I agree that, as you get used to the system, you can finesse your pressure on the brake pedal especially at roundabouts and, in time, get quite good at not triggering the idle stop in these situations.

Yeah, I quite like it for that reason. I enjoy driving and for me controlling I/S is another skill to develop. I'm also very much into efficient driving so it adds to the challenge. Stopping only when absolutely necessary and never for less than five seconds

But for someone just wanting to get from A to B I can imagine it being a nuisance. On those rare occasions when it has switched the engine off just when I want to accelerate it's very shocking and frustrating. In a more powerful car it could be dangerous as well if you are trying to leap into a gap. Luckily the Jazz CVT doesn't do jack rabbit starts anyway (presumably protecting the belt) so if the car refuses to move when you jab the accelerator it's unlikely to leave you stranded.

As regards engine wear, I realise these systems are relatively new but is there any evidence of premature wear. The battery and the starter are uprated and not all the oil will have drained back down into the sump - there will still be a protective covering - it's not like starting from cold every time.

No idea. I will say that I can't see any difference in the battery after two years either.

For me, the CO2 stuff is secondary (we need to reduce CO2 but these systems are not a game changer), the real impact is in emissions at pavement level so I think they have a role to play in improving air quality.

Agreed. A few %ge points less fuel consumption ain't going to change the world but if cars didn't run their engines while stationary in queues the air in towns would be a bit cleaner. Although I believe that even when I/S starts it still emits a little puff of extra pollution so it's not perfect.

[andruec]

I was not trying to be harsh to the manufacturers.  It is in their interest to put their product in the best light - look how far many have been prepared to go though.  Not running the engine when you have are stationary for an extended period makes sense but I doubt many would see a saving of 5-10% in the real world.  In a test like this one https://en.wikipedia.org/wiki/New_European_Driving_Cycle it is not that surprising as more than 10% of the ECE-15 (urban) test is spent at idle (i.e. stopped).

That's true although I note this from the article:
"The cycle must be performed on a cold vehicle at 20–30 °C (typically run at 25 °C)"
and
" Total duration is 780 s (13 minutes)" for Urban and "6 minutes" for Extra Urban.

So the I/S won't be working for probably the first half of the first test and likely not at all for the second test. Even yesterday with my car sat in the sun all day with 24 degrees when I drove home the I/S wasn't working for the first ~5m.

You make some very good points I just think we have a slightly different opinion on this one 

Oh aye, no offence meant

[dogbiscuit]

Hmmm....... Thanks for the resume. And, the final, no confidence line.

My brand new, EX Navi, arrived today........ 

I wouldn’t worry unduly as I think I have just been unlucky and have a car with a difficult to diagnose electrical fault(s) and that is bound to reflect on my assessment of the car. The only fault that I have that appears to have been reported by others is the starting issue. I’m hoping my electrical fault has been cured with a new fuse box (time will tell). I hope you have many miles of enjoyable driving in your new Jazz and don’t ever need to contact Honda UK for help.

[dogbiscuit]

Hmmm....... Thanks for the resume. And, the final, no confidence line.

My brand new, EX Navi, arrived today........ 

I wouldn’t worry unduly as I think I have just been unlucky and have a car with a difficult to diagnose electrical fault(s) and that is bound to reflect on my assessment of the car. The only fault that I have that appears to have been reported by others is the starting issue. I’m hoping my electrical fault has been cured with a new fuse box (time will tell). I hope you have many miles of enjoyable driving in your new Jazz and don’t ever need to contact Honda UK for help.

[dogbiscuit]

But what don't you like about the idle stop feature? It seems a shame for you to be constantly disabling it. It almost never causes me any problems and whilst it probably isn't saving fuel or reducing pollution by huge amounts it is helping. My only gripe with it is one you won't have in that on the CVT version you have to keep the foot brake pressed at all times to keep the engine off.

Regarding the stop start feature there are a couple of reasons I don’t use it that often. The first one is that I’m sceptical about the amount of fuel saved vs the wear and tear on the starter and associated components. I agree that my fears may be totally unfounded and I am open to persuasion with some facts and figures. Also I have a car that is reluctant to start sometimes so this has some bearing on my decision not to use it. However I do use it in long traffic queues at roadworks etc. where I may be stopped for extended periods of time.

[culzean]

But what don't you like about the idle stop feature? It seems a shame for you to be constantly disabling it. It almost never causes me any problems and whilst it probably isn't saving fuel or reducing pollution by huge amounts it is helping. My only gripe with it is one you won't have in that on the CVT version you have to keep the foot brake pressed at all times to keep the engine off.

Regarding the stop start feature there are a couple of reasons I don’t use it that often. The first one is that I’m sceptical about the amount of fuel saved vs the wear and tear on the starter and associated components. I agree that my fears may be totally unfounded and I am open to persuasion with some facts and figures. Also I have a car that is reluctant to start sometimes so this has some bearing on my decision not to use it. However I do use it in long traffic queues at roadworks etc. where I may be stopped for extended periods of time.

I don't think longevity of engine etc is taken into account with things like 0W-20 oil and stop-start - the makers are just happy to put a tick in a box that satisfies latest climate change regulations and gets them a small claimed gain in mpg.  They will worry about engines wearing out prematurely at some later date,  but for now - another box ticked.........

How many original buyers of new cars keep them long enough to notice any downside anyway ? And car companies are more concerned with new vehicle buyers and legislation than people who buy secondhand.   I never use less than   5W30 oil in our cars and if I had stop-start I would turn it off.

As a case in point the regular failure of rear wheel bearings on MK1 Jazz (and other car brands BTW) was down to changing tried and tested taper roller bearings for ball bearings with less 'friction' but also less longevity,  Taper rollers would often last life of vehicle, ball bearings about 40K on average - all the rear bearings on our MK1's had to be changed,  some were changed twice.

[dogbiscuit]

Re Dogbuiscuits unfixable faults, there has been lengthy discussion elsewhere about starting difficulty, which is sometimes attributed to fuel flooding following repeated starts in a short time with the engine still cold.  The answer seems to be to floor the accelerator and use the starter once, which clears the flooding.  Someone who has experienced this may like to comment with more authority than me.

When the parking sensors fail to function, is the light on the sensor switch lit (to the right of the steering column, low down)?

Thank you for the suggestion of flooring the accelerator but mine is a cold starting issue. A problem that never existed on my previous cars and shouldn’t exist on this one. Totally unacceptable for a brand new Jazz. Regarding the parking sensor switch, it fails to illuminate and refuses to do so until the ignition is recycled. The current diagnoses is a faulty fuse box.