Technical Why does the Dualogic sometimes creep in traffic?

[44sunsets]

The other day I was driving in peak hour stop-and-go traffic on a definite uphill gradient, and I noticed that when I let go of the brake pedal, the car would sometimes move forwards on its own, without touching the gas pedal (like the "creep" function of conventional torque-converter automatic transmissions).

It really surprised me, because I was expecting the car to slowly roll backwards when letting go of the brake, which is what would normally happen in this kind of situation.

Does anyone know why the car sometimes creeps forwards?
As I understand it, the Dualogic gearbox does not have a creep function.

 

[UFI]

I don't know if it's normal operation for assisting the car on hill starts, but since the DL has the same clutch as a manual, it's definitely not a good idea to let the car creep. My theory is that the DL preloads the clutch once you let off the brake on hills to prevent rollback. If that's the case, hold the brake until you're ready to go.

Otherwise, it might mean the clutch actuator is out of adjustment.

 

[44sunsets]

Thanks UFI, that makes sense. I'll be sure not to let the car creep in future.

 

[Most Easterly Pandas]

OP your dualogic shouldn't be doing this and has a fault!

The mat isn't trapped on the gas pedal pushing it down slightly is it? If not get this looked at ASAP as it'll be wrecking your clutch!

 

[44sunsets]

Nope the floormat is fixed via the screw so it's definitely not trapping the gas pedal or anything.

The creeping thing only happened that one time for a couple of metres uphill, so it hasn't happened again since then. If it happens again I'll get the service centre to look at it, though I'm not sure how I'd reproduce the problem.

 

[Melanabb]

Probably not relevant to you but my 1.4 turbo petrol in GPA creeps in first gear with no pressing of pedals going on. Not sure if its normal but I appreciate it in stop-start situations

 

[Most Easterly Pandas]

Probably not relevant to you but my 1.4 turbo petrol in GPA creeps in first gear with no pressing of pedals going on. Not sure if its normal but I appreciate it in stop-start situations

I believe the AGP uses the Selespeed system also, if so then again no it isn't normal and you should get it looked at unless you fancy splashing out for a replacement clutch prematurely

 

[keiron99]

My theory is that the DL preloads the clutch once you let off the brake on hills to prevent rollback. If that's the case, hold the brake until you're ready to go.

I have only had my dualogic a couple of days, but I don't think your theory is correct.

In my (again, admittedly extremely limited) experience, the "hill hold" feature, which is supposed to prevent roll back on inclines, does not work at all. Even on very steep hills, it doesn't work at all. I've read that to get it to work effectively you need to disable the ASR and possibly even the "stop start" feature. I've experimented with this, to no avail.

I sort of understand why they didn't implement a "full" auto box (I think to keep weight and cost down?) but surely it wouldn't have taken much engineering to implement an effective hold feature? This is, after all, one of the key benefits of an auto.

 

[Boodajuda]

I thought hill hold uses the brakes? Using the throttle seems idiotic.

The hill hold on my A500c SS seems ok but only works if the car has rolled back a fraction before applying the brakes, or the weight of the car is obviously leaning backwards. It was the same on my old 159Ti.

 

[Most Easterly Pandas]

My theory is that the DL preloads the clutch once you let off the brake on hills to prevent rollback.

Not how it works, its no different to a manual clutch in how it works.

In my (again, admittedly extremely limited) experience, the "hill hold" feature, which is supposed to prevent roll back on inclines, does not work at all.

Care to expand on how it doesn't work?

The hill hold on my A500c SS seems ok but only works if the car has rolled back a fraction before applying the brakes, or the weight of the car is obviously leaning backwards.

Car shouldn't roll back, should hold the brakes on for 2 seconds after removing your foot off of the brake before it releases meaning you'll then roll away, or it should release when you get to biting point.

 

[keiron99]

Care to expand on how it doesn't work?

It, err...rolls back!

That said, maybe I haven't been courageous enough to just leave it and see how far it does roll. As soon as it does start rolling, I naturally put my foot on the break.

I will go and find a quiet hill and test it out!

 

[Most Easterly Pandas]

It, err...rolls back!

Take a chill pill!

That said, maybe I haven't been courageous enough to just leave it and see how far it does roll. As soon as it does start rolling, I naturally put my foot on the break.

I will go and find a quiet hill and test it out!

Doesn't sound like it's kicking in at all then, like you say have a play somewhere quiet.

Are you sure you have got it?

You shouldn't be having to deactivate anything to get it to work though btw

 

[keiron99]

Take a chill pill!

Sorry to have upset you, I didn't know how else to answer your question.

Are you sure you have got it?

It is referred to in the manual.

 

[Most Easterly Pandas]

It is referred to in the manual.

But don't forget the manual will show how everything works, even if not fitted to your car (such as optional extras etc).

Get a fairly steep hill and it should kick in if fitted.

 

[keiron99]

OK here are my findings after a couple of hours thorough testing in my 500c Dualogic Start Stop. And I need to eat my words...a bit.

There is indeed a hill hold facility. On any hill - as far as I can tell, you are given a slight period of grace between moving your foot from the brake to the throttle. To activate it, it *seems* like you need to press the brake a little firmer than usual - I may be wrong on that.

But it definitely does hold the car - but not for long. My wife and I took turns familiarising ourselves with it, just to get a feel of how quickly you need to move your foot. You do need to be quite quick. I have no idea how the technology works behind it but it's a shame that Fiat didn't make it hold the car longer.

Now, there is a proviso here. It does NOT work when the Start-Stop system is activated, and on my car, this is activated by default. To me, the hill hold function is much more important than saving a few mpg with SS (which I don't like anyway).

So I need to get in the habit of deactivating SS each time I start the car. I really wish the car would remember the last setting - I read that with the latest cars, this is indeed the case.

 

[Most Easterly Pandas]

To activate it, it *seems* like you need to press the brake a little firmer than usual - I may be wrong on that.

Officially you don't have to press it harder, I know I don't in my Bravo, but a few have reported similar to you, so might be more of a 'how it feels' if that makes sense?

it's a shame that Fiat didn't make it hold the car longer.

Not really, it's only supposed to be used for the transition from brake to gas/accelerator tbh, I personally think it holds long enough (assuming the timings are the same as my Bravo).

Now, there is a proviso here. It does NOT work when the Start-Stop system is activated,

Interesting. Although when SS kicks in for me I apply the handbrake, so I wouldn't find that an issue.

So I need to get in the habit of deactivating SS each time I start the car. I really wish the car would remember the last setting - I read that with the latest cars, this is indeed the case.

At the next service ask the dealer to do a software update (they should do this anyway as standard) and your SS should then remember your preference

 

[D4nny8oy]

Or use the handbrake.

 

[keiron99]

At the next service ask the dealer to do a software update (they should do this anyway as standard) and your SS should then remember your preference

According to this thread here:

https://www.fiatforum.com/500/329488-fiat-500-twinair-turn-start-stop-off-permanently.html

unfortunately my car is too old according to the chassis number to benefit from the software update.

(And apologies again for being a bit rude earlier.)

 

[keiron99]

Or use the handbrake.

Which sort of defeats the point of an auto and makes what is supposed to be a "semi auto " a "quarter auto"!

 

[D4nny8oy]

Which sort of defeats the point of an auto and makes what is supposed to be a "semi auto " a "quarter auto"!

It's not an Auto, it's a "Robotised manual" with all the traits of a manual gearbox- clutch and H-pattern gearbox components, all operated by hydraulics which provide a semi-auto action.

The 500 Dualogic Owner's guide even states the handbrake should be used where necessary on steeper gradients. Many people complain that the Hill Holder 2 sec delay is too long already, so extending it would cause Fiat Technical/Bosch more grief.