There seems to be an undocumented feature of the 500, at least there is on my 1.4 petrol. The engine management system appears to have an “anti-stall” feature – in 1st gear or reverse you can take your feet right off the accelerator and clutch, and the car will just trickle along at 1,000 rpm like an automatic. Not only will it do this on the flat, but also up a steep gradient. The ECU just seems to adjust the throttle setting to maintain 1,000 rpm whatever the load. The car will even start away from rest with no throttle input, if you are gentle with clutch, which can be really useful for getting away with no wheelspin on mud or snow. Of course, I may be behind the times and perhaps all modern cars do this, but to me this is amazing. Especially as the 1.4 engine has quite a high state of tune with a quite peaky powerband. Presumably the ECU is able to retard the ignition substantially and adjust the throttle in very fine increments while monitoring engine speed and load, without human intervention. Do the 1.2 and the diesel also do this?

Clever stuff, Fiat.

John

I thought all modern cars do this? I forget how it works exactly but the car senses that it's moving and not in gear so it thinks its gonna stall so injects more fuel increasing the revs (or something like that). I assumed therefore it also does it when the car is moving and in gear?

I remember Jeremy Clarkson talking about it on Top Gear when he was driving some ridiculous distance on threppence worth of petrol. In talking about how to use the least amount of fuel, he claimed it used more fuel coasting down hill in neutral than it does in 5th gear for this reason.

Well, this is the first time in my life that I have had electric windows or central locking either, so I am easily pleased

(I learned to drive and passed my test on a 1947 Ford Prefect, so that gives you some idea)

John

yep all fuel injection car have the iddle set at 800-1100 rpm. remember they are no carbs the ecu determines that the revs have to be constant at iddle no matter what thottle position therefore it will compensate if the revs go down on. Add to the fact the car is so light the engine has no probs moving it back or forth, but you mus tbe gentle with the clutch at start.

I notice this a lot with my diesel when I drive it as suggested by ecodrive. If your in gear and slowing down and the revs drop too much the brain thinks your going to stall and revs the car for you and you speed up. It can be quite alarming when your approaching an other car think you slowing and suddenly start speeding up
I thought I was touching the accelerator by accident when applying the brake untill i figured out what it was.

In my 15 yr old (but still Fuel injected) Alfa 155 I manged with 5 people on board to set off and move through the gears up into 5th with out touching the throttle at all. (I was in a funneral proccession at the time) and we topped out at 25 mph in fifth, not tried it in the fiat but will tonight

chrome500 said:

I remember Jeremy Clarkson talking about it on Top Gear when he was driving some ridiculous distance on threppence worth of petrol. In talking about how to use the least amount of fuel, he claimed it used more fuel coasting down hill in neutral than it does in 5th gear for this reason.

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Thats something different. The fuel shuts off completely when on the over run, doesn't matter what gear your in. If you coast in neutral fuel is need to keep the engine going, if you are using the momentum of the car to keep the engine going you need no fuel.

Cheers

SPD

I didn't realise it had this, tried it going into the garage earlier, was great fun cruising into the garage without my feet on the pedals!

This is the hill holder function, it's becoming increasingly common on new cars. It's to help avoid roll backs on hill starts amongst other things. My Civic does it too.

AlexGP said:

This is the hill holder function, it's becoming increasingly common on new cars. It's to help avoid roll backs on hill starts amongst other things. My Civic does it too.

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No it isn't.

Hill-Holder holds the brakes on for 2 secs when you're on a gradient and moving your foot from the brake to the clutch- it's got nowt to do with the engine.

But has been said, it's nothing new- the ECU has a 'target' idle speed and will do what it can to maintain it.

yeah nothing new been around for yonks.

I used to be able to do this on my old E-Reg Peugeot 205 - bring the clutch up slowly and the car moves forward, all feet off the pedal

Lloyd71 said:

I didn't realise it had this, tried it going into the garage earlier, was great fun cruising into the garage without my wheels on the pedals!

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You have wheels on you legs!!!????!!!

OrangeSport said:

You have wheels on you legs!!!????!!!

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That's what happens when you visit forums after being up since 5!

Jake_in_notts said:

I notice this a lot with my diesel when I drive it as suggested by ecodrive.

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That's different, it is to do with how diesels provide an idle in the first place.

Did this the other day in my 1.2 8v 2000 punto and got through to 5th gear without even touching the throttle pedal.

Even easier in dads 1.3Mjet 500

Right. So this is not so much a feature, as a natural property of modern engine management systems. Interesting. I am used to engines where if the revs drop below 2,000 the engine tries to climb off its mounts or just stalls dead. Blimey, drivers are spoilt rotten these days.

Mind you, I seem to remember driving a couple of 1930s Bentleys which had an advance / retard lever on the steering column, and with those you could play a similar trick by fully retarding the ignition - then it was like driving a steam engine and virtually impossible to stall.

John

John R Smith said:

Mind you, I seem to remember driving a couple of 1930s Bentleys which had an advance / retard lever on the steering column, and with those you could play a similar trick by fully retarding the ignition - then it was like driving a steam engine and virtually impossible to stall.

John

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Retarding and advancing the ignition can be dangerous and can lead to detonation/pinging, all done automatically these days. However most manufacturers still haven't fully automated the system for the different fuel qualities and octanes, shame as I believe this would greatly improve bhp and mpg. The needs to be a way of testing the fuel in the tank.

alainmengoli said:

However most manufacturers still haven't fully automated the system for the different fuel qualities and octanes, shame as I believe this would greatly improve bhp and mpg. The needs to be a way of testing the fuel in the tank.

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Well, the ECU in the 500 petrol can compensate for different octane fuels because there is an knock sensor attached to the cylinder block. This is essentially a microphone tuned to the specific frequencies which pre-ignition generates. The Bosch ECU, at least, monitors individual cylinders for pre-ignition and varies the ignition advance accordingly. These values are then written into the ECU maps. So if you use a higher-octane fuel, over time the ECU will adapt the maps accordingly.

John

Does it adapt by % or a remap? I have tweeked bikes before and to compensate for temperature the map was multipied by a percentage i.e. 90% of map to run leaner or 110% of map to run richer. I thought the knock sensor was for extremes i.e. not very precise, correct me I am wrong.