I feel I was an expert on our 500TA and SS.
There's a few threads on here about my history and story about it.

After spending £100 or so on a new battery and plugging it into the battery charger each and every time we came home, made it 100% perfect every time, and every time for years. The car was three years old when we bought it and the battery was shot as a SS battery but worked faultlessly in a normal non SS car and continues to do.

Wipers, lights, whatever. Three minutes in stop mode as per design providing that the battery is in tip top condition.

Trouble is, why the heck does it work like that?
If the car would start normally even with an older battery, why can't the SS just remain in stop mode for as long as necessary ...... within reason?

It worked well, but at a cost of money plus hassle. From what I hear, other makes of cars have no issues like this at all. They just work. Full stop.

Regards to all,
Mick.

It’s just a cheap crap design, if the sensing voltage threshold was dropped by a few 100mv it would probably be fine, I guess the intelligent battery sensor is not that intelligent!

Seems likes the ex CEOs lack of investment in many area past decade or so has caused a lot of things like this
No r and d Money to get a good system could have done with lisencing something like the hybrid alternator another manufacturer uses but again that would come down the money

lsgraham_uk said:

Frankly the gearing is too short on the Ta

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Yes and no. For fuel economy it is too short.

The TA makes quite some revs when driving on the motorway. Most competitor cars with turbocharged petrol engines have much longer gearing. However, the short gearing is also what makes the car fun to drive. Accelerating from 80 to 120 km/h (≈ 50 to 75 mph) in highest gear is no problem at all for the TA. Just push the pedal and the TA accelerates. In most competitor cars with turbocharged petrol engines nothing happens when you do so (without shifting down). Those cars will have better fuel economy when driving on the motorway, but they miss the fun.

Mick F said:

I feel I was an expert on our 500TA and SS.
There's a few threads on here about my history and story about it.

After spending £100 or so on a new battery and plugging it into the battery charger each and every time we came home, made it 100% perfect every time, and every time for years. The car was three years old when we bought it and the battery was shot as a SS battery but worked faultlessly in a normal non SS car and continues to do.

Wipers, lights, whatever. Three minutes in stop mode as per design providing that the battery is in tip top condition.

Trouble is, why the heck does it work like that?
If the car would start normally even with an older battery, why can't the SS just remain in stop mode for as long as necessary ...... within reason?

It worked well, but at a cost of money plus hassle. From what I hear, other makes of cars have no issues like this at all. They just work. Full stop.

Regards to all,
Mick.

Click to expand...

It works that way because that’s how it’s designed to work.

Would you want a 500 sitting in the dark in the winter for 5 minutes with its lights and radio on and then failing to start? The battery in my BMW is twice as big plus a little more, but it doesn’t matter as much on a bigger car, adding another 10 kilos to a 500 would make a big difference.

No it wouldn't.

Dunno about you, but I weigh 12st. That's 76Kg.
I could be a bit chunkier at 13st 7lb perhaps?

Would the Fiat500 be too heavy if I weighed 10kg more?

Mick.

Mick F said:

No it wouldn't.

Dunno about you, but I weigh 12st. That's 76Kg.
I could be a bit chunkier at 13st 7lb perhaps?

Would the Fiat500 be too heavy if I weighed 10kg more?

Mick.

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*sigh* You do love to argue don’t you.

If you’d spent as much time at work as we do trying to trim a couple of kilos off a car, you’d realise that trimming 1% off a car is a big thing. 10kg is massive in automotive terms on a sub 1 tonne car.

Two people in a normal small car is too heavy?
10kg is nothing.

I can understand any weight reduction is good in performance cars, but your average bog standard small car 10kg is the difference between a big person driving and a smaller one. Maybe male vs female, but neither of that includes a passenger.

I would say that fitting a bigger battery under the bonnet is a SPACE issue, not a weight issue. If you'd said that, I would have agreed. Weight of only 10kg isn't a problem in the slightest.

Mick.

Mick F said:

Two people in a normal small car is too heavy?
10kg is nothing.

I can understand any weight reduction is good in performance cars, but your average bog standard small car 10kg is the difference between a big person driving and a smaller one. Maybe male vs female, but neither of that includes a passenger.

I would say that fitting a bigger battery under the bonnet is a SPACE issue, not a weight issue. If you'd said that, I would have agreed. Weight of only 10kg isn't a problem in the slightest.

Mick.

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Not sure if you’re aware, but if you add 2 70kg people to a 1.2 it weighs 1005kg, if you add another 10kg to the base weight of 865 then that becomes 875 and with two 70kg people onboard it becomes 1015kg.

We spend loads of time trying to trim 100 grams off here and there, to lose 10kg in one instance would be massive.

To deal with that 10kg you’d need a bulkier battery tray, perhaps a chunkier fitting to fasten the battery tray down, adding weight adds more weight, it’s a vivacious circle.

If you can look at a car and remove 5 or 10kg here and there then please PM me your phone number and I’ll get you a job.

306maxi said:

10kg is massive in automotive terms on a sub 1 tonne car.

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:yeahthat:

Sorry Mick; 10kg is massive even to the designers of a 200 tonne airliner.

But actually, I think you're both wrong in this case.

Fiat didn't specify the battery they did to save weight, nor did they specify it to save space - they specified it to save money.

jrkitching said:

:yeahthat:

Sorry Mick; 10kg is massive even to the designers of a 200 tonne airliner.

But actually, I think you're both wrong in this case.

Fiat didn't specify the battery they did to save weight, nor did they specify it to save space - they specified it to save money.

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It will have been a variety of factors, but I can assure you that weight will have been one of them. An extra fiver for a battery for however many 500s they’ve built so far is pretty massive as well..

I don’t think S&S is as bad as people say, just the implementation.

That’s the warning I get in my BMW of many miles when S&S is inhibited, in this case because I’d just reversed into a parking spot. The 500 shouts at you when S&S is inhibited which is a bit stupid tbh.

I'll concede that designers want the weight of the vehicle kept to a minimum, but I'm not arguing about that and 10kg is a worthwhile saving to a designer.

As I said, the difference of 10kg is nothing if you compare the weight of a human being as the driver. 10kg is the difference between what I weighed a few years ago to what I weigh now. Less that two stone.

I'm saying that 10kg is nothing to worry about for a normal road-going car.

Looking at the unladen weight of the various models of 500, the TA is 930kg, the 1.2 is 865kg. Difference of 65kg.

Mick.

to be fair, 10kg may be 'a lot' but in real world situations is the same as 10 litres of fuel or around a third of a tank, how many people only fill their tank to a third to save weight and money? Anyway JR is right - it's all about cost savings for Fiat and SS was only added to enable Fiat to tick a box and not to actually work properly

Mick F said:

I'll concede that designers want the weight of the vehicle kept to a minimum, but I'm not arguing about that and 10kg is a worthwhile saving to a designer.

As I said, the difference of 10kg is nothing if you compare the weight of a human being as the driver. 10kg is the difference between what I weighed a few years ago to what I weigh now. Less that two stone.

I'm saying that 10kg is nothing to worry about for a normal road-going car.

Looking at the unladen weight of the various models of 500, the TA is 930kg, the 1.2 is 865kg. Difference of 65kg.

Mick.

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But me who is actually sitting in the engineering department of a well known brand in the U.K. is saying that we DO care about 10kg, in fact the colleague sitting across from me suggested that on a PHEV version of one of our products, that we reduce the size of the 12v battery on the grounds of weight and cost.

Every kilo you trim off a car comes back to you in increased fuel efficiency and better handling.

This is from actual day to day business in an actual car company, not forum engineering.

To be fair, everyone's correct.

There are stop start systems on the market that add no or very little weight, but they come at a cost, either in development or manufacturing or both.

Fiat tried to balance both, their system didn't add much weight as most of the parts are already needed, but it ended up cheap and doesn't work very well.

It uses the existing starting system with a battery sensor to protect the battery from discharging too far.

In effect it is self defeating as every time the battery discharges (from a start/restart), the engine needs to work harder to recharge it and it needs to do this before the next stop, or there's no next stop!

It takes effort and time to replace the battery's energy, quite often far longer than time between stops, hence it fails to stop the engine.

The battery it's self is prone to aging and the effects of temperature, which limit it's performance, but the battery sensor is static, it does not/cannot compensate for either.

So you end up with an ever decreasing store of energy which requires effort in too short a time to restore to full, if that is even possible (due to battery condition and temp)

Even with a larger more powerful battery, it's still doomed to fail as it would require more effort to return it to a state capable of performing a restart.
You would need to add a more powerful alternator just to match the effects of the smaller battery/alternator.
Turning the bigger alternator would require more engine power and fuel and negate the savings of SS in the first place.


Mazda's Skyactiv system really does work without adding any weight.
It basically stops with a cylinder on compression, then fires that cylinder to restart the engine.
I hear it works pretty much faultlessly, but I'm sure there are large costs behind it and Mazdas are generally more expensive than Fiats.

My Citroen E-HDi uses capacitors and hybrid alternator.
It collects wasted energy from the alternator when it detects the brakes have been applied, stores this energy in the capacitors and then spins up the alternator to restart from the energy in the capacitors, all from free wasted energy.

It doesn't really need the main battery to perform this, so it's not constantly trying to recharge it and the clutch on the alternator disengages once the main battery and capacitors are full, saving further effort from the engine.
It's no heavier than a normal HDi, but there was a small premium to buy it other that model, though I didn't pay it!

It really works well, so well in actually knocks the engine off before it's completely stopped moving.
Restarts are instant, it fires up as soon at the brake is released so there's no hesitation like other systems can suffer from.

306maxi said:

The 500 shouts at you when S&S is inhibited

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I don't know what you do to your car. Mine never shouted at me. :shakehead:

10kg is a big deal when designing a car.

10kg for a battery here 5kg for something else there, saving every gram where you can, can mean the difference between the car meeting emissions requirements, which can make big differences in sales tax, can mean the difference between a car selling or not.

Fiat stopped putting spare wheels in cars a long time ago for the very reason of saving weight, as have many manufacturers. So Maxi is 100% right, 10kg might not seem a lot and yes one driver can weigh considerably more than another, but the carrying capacity of the car can be higher if they save every ounce where ever they can.

Weight costs money as well, every extra nut bolt and screw that’s not needed is wasted money, and for a high volume car like the 500 every extra unnecessary bolt could add Millions to the production costs across the life span of the production run.

So on this point Maxi is spot on.

I still however agree with others, fiats stop-start system is terrible and it does flash big messages up on the dash to tell you when it’s unavailable. Other cars don’t make a big deal of it, and also other systems are not so tetchy, I think the biggest problem is as the battery starts to weaken the fiat system will have the car restarting after a few seconds, other cars get much longer and more reliable life out of the battery, and when it’s no longer up to the job it switches of the system, rather than having the car turn on and off every 5seconds.

At the risk of trying to bring this thread back on topic to the twinair.....


Mrs Bee changes gear about 2/3 up the rev range and gets this for fuel economy on her commute, which is a similar distance to mine:-



I haven't driven the twinair for a while and thought I would give it a spin on a recent two way commute. Keeping up with traffic, no harsh acceleration or braking, using stop/start when stationary, not driving like a nun and not otherwise deliberately eco driving. I got this:-



Less miles than trip A so statistically less representative, but I wasn't trying and easily got that difference in fuel consumption. In comparison, my 118 BMW had a differential of 37mpg versus 41mpg, so not a wide gulf. We had a similar experience of marginal efficiency differences with the 1.2 500 whenever we swapped.

The twinair fuel economy is way more sensitive to how it is driven.

gazz_bee said:

The twinair fuel economy is way more sensitive to how it is driven.

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The same could be said for most downsized engines. The smaller and more heavily boosted it is the more the driving style of a given user matters. You take the old 1.4 for an economy drive and measure it...then razz it and measure it you'll probably get 20% mpg difference in the extreme. Do the same with a TA and you'll easily manage 50% difference because of the design. it has speed or economy not both..you can use one sparingly to get the other on average but it makes them very usage dependent.

gazz_bee said:

At the risk of trying to bring this thread back on topic to the twinair.....


Mrs Bee changes gear about 2/3 up the rev range and gets this for fuel economy on her commute, which is a similar distance to mine:-

View attachment 193321

I haven't driven the twinair for a while and thought I would give it a spin on a recent two way commute. Keeping up with traffic, no harsh acceleration or braking, using stop/start when stationary, not driving like a nun and not otherwise deliberately eco driving. I got this:-

View attachment 193322

Less miles than trip A so statistically less representative, but I wasn't trying and easily got that difference in fuel consumption. In comparison, my 118 BMW had a differential of 37mpg versus 41mpg, so not a wide gulf. We had a similar experience of marginal efficiency differences with the 1.2 500 whenever we swapped.

The twinair fuel economy is way more sensitive to how it is driven.

Click to expand...

It’s almost like the video in the first post of this thread was made by an engineer that knows what he’s talking about!