Technical Regeneration DPF, yes, but when??

[Vento]

Concerning a Fiat Croma Dynamic 1,9 Multijet 16V built 2008
For I wanted to know when a regen took place I studied the fuel consumption figures on the dashboard. Unfortunately this figures are very difficult to read due to theire size, especialy during daytime with the lights on (the latter I prefer). Bending forward to decipher the displayed text, is to my humble opinion, a risky undertaking.
Furthermore it's impossible to show the fuel consumption figures when using the navigation system, and in addition, driving with a laptop on your knees is far from comfortable.
To make things better visible and less dangerous I decided to install a thermometer showing the ingreased temperature during a regen. The only one in my possession was a digital in/out home thermometer with a range from minus 50 to plus 60 degrees Celcius. The sensor for the outside temperature was connected to this instrument with a thiny cable from about 2 meter.

The expected temperature during a regen is about 640 degrees C. To prevent the sensor from melting down, it is mounted about 20 cm from the exhaust pipe and 1 meter downstream the DPF housing, in a spare muffler suspension ring (pn 90466668), slided on a free exhaust bracket. A makeshift arrangement was made for I was not convinced of a positive result.

The displayed temperature during driving is 10 degrees Celsius above the ambient temperature, it ingreases a bit with the speed of the car. Driving in town gives about the same result, some 10 till 12 degrees above the environmental temperature, all the readings turns out to be predictable and stable. A higher outside temperature results in a higher thermometer reading.
The previous months the average value of the readings was around 14 degrees, after it went up several times to 20, I expected a regen to be happened. After checking with ECU scan, it proved to be right.

Hope to can lay my hands on a wireless device with acoustic warning signal in the near future.
Regards
Vento

 

[Most Easterly Pandas]

 

[Doofer]

I've never been able to tell when my 1.9 16v is doing it. A few times I've thought it sounded a bit different, looked at the Ic reading and all is normal. I deceived not to care - the few times I've checked with ECUScan, all was well and happy.

I love the mad inventor stuff though. I'm surprised it worked through the bodywork (EDIT: I see, it's wired, not radio). It looks very distracting to keep checking it though - my driving is better with my eyes on the road ahead.

 

[keithglos]

On my 2006 2.4 the first touch on the end of the RH stalk produces an instant MPG readout right in front of me, and large enough to see. Is that Prestigio only?

 

[s130]

I've only once or twice detected a regen whilst the cars is driving along normally. HOWEVER I've a 100% record of detecting a regen when crawling in traffic or at idle at lights.

If when I pull up anywhere and I detect a regen going on I take off again for a short drive to allow the regen cycle to complete. I could let it complete at idle or rev up to 2k rpm whilst stationary but I'm very wary of the huge temperatures welling up just and sitting beneath the car. Forward motion allows the to be blown away and provides additional cooling for the underside of the car.

 

[Most Easterly Pandas]

Forward motion allows the to be blown away and provides additional cooling for the underside of the car.

Fairly pointless, its designed to be capable of doing it standing, and if at the end of your journey why bother to drive some more. Just switch off and it'll sort itself out

 

[Doofer]

Fairly pointless, its designed to be capable of doing it standing, and if at the end of your journey why bother to drive some more. Just switch off and it'll sort itself out

If it was part-way through then it won't complete if you switch off. It will then try again the next time it's warm, which is fine if you generally do long journeys. If you make shorter journeys then you can end up with it permanently trying to regen.

I'd be tempted to let it finish if you know it's doing it, unless you know you're next going on a long journey. I've never noticed it doing it though.

 

[Most Easterly Pandas]

If it was part-way through then it won't complete if you switch off. It will then try again the next time it's warm, which is fine if you generally do long journeys. If you make shorter journeys then you can end up with it permanently trying to regen.

I'd be tempted to let it finish if you know it's doing it, unless you know you're next going on a long journey. I've never noticed it doing it though.

Unless you're someone only doing 3-4 miles a journey every journey it'll be fine. Shut mine off mid cycle loads without any adverse affects.

 

[keithglos]

MEP, do you have a Croma? They were one of the first with DPF in 2005, and most later DPF's were very different. Fiat had all sorts of problems with the 2008/9 DPF's mainly because the dealers didn't have a clue. The Croma system is complex and full of potential problems, if you don't complete the regen you can dilute the engine oil with fuel, and that can cause the engine to run on till it has no sump oil left. How do you stop an auto when it's running on its engine oil?
I prefer to know when the regen is on, the instant MPG just about halves, usually for about 5 milles. It doesn't start till the exhaust temperature is high enough.

 

[Most Easterly Pandas]

Engine oil dilution is a common problem with any early DPF, and is due to how the DPF operates. Shutting of mid cycle shouldn't make any difference to this.

If oil is regularly maintained and you keep an eye on it you shouldn't have an issue with oil level raising high enough to cause 'Over Run'.

 

[s130]

Fairly pointless, its designed to be capable of doing it standing, and if at the end of your journey why bother to drive some more. Just switch off and it'll sort itself out

I doubt the car was designed to tolerate numberous stationary regens. Whilst the odds one won't really hurt I prefer to avoid them.

Early shut-ff during the regenration cycle leaves the cylinder bores extreamly rich with unburnt fuel. This leads to oil dilution and eventual engine seizure in worst cases. This is fact, not a rumour and not scare mongering.

These worst case are cars driven on regular shortish runs where a DPF regen is started and then the engine is shut off. Day after day this repeats.

When the engine is shut off the last major squirt of diesel is not combusted so lies in the bore to drain down into the sump.

On a normal regeneration termination the last squirt of fuel is burnt by the normal running of the engine.

Now whilst a small number of prematurely terminated regens can be tolertated by the car & engine oil I see no reason in adding to the stress if I know a regen is in process and I can wait a short while for it to complete.

 

[Most Easterly Pandas]

When the engine is shut off the last major squirt of diesel is not combusted so lies in the bore to drain down into the sump.

On a normal regeneration termination the last squirt of fuel is burnt by the normal running of the engine.

Do actually know what your talking about? Or is this what you've read online?

A DERV is a compression ignition engine. No unburnt fuel is likely to be left in any cylinder, shut off of a modern diesel comprises of fuel being cut to all cylinders and then it runs out of ignition and the engine stops. If there is fuel there it'll still run.

Again, if the car is correctly looked after there should be no adverse affect with oil levels rising, just change the oil when it is supposed to be changed, and with the correct stuff - this is where most go wrong.

 

[s130]

Sadly I do know what I'm talking about and don't dispute DERV is a compression ignition engine. No diesel engine is 100% complete combustion. This is why diesels, when laboured at low RPM produce clouds of smoke, soot, etc. All signs of incomplete combustion. If the engine is kept running then fuel which was not completely combusted on the previous cycle will normally be scavenged on the subsequent cycles. So a few cycles later, long before there is any chance of the unburnt fuel draining away into the sump, the process catches up with itself and the excess/uncombusted fuel is combusted/burnt over the next few cycles.

The reason petrol engines do not suffer from incomplete combustion is that the combustion process is a slow 'flame front' burn. Once the burn has been initiated by the spark plug it naturally completes. As long as their is the initiating spark then the combustion process will complete (unless there are major other issues).

Stepping back, as you said yourself and is supported by all automotive tech gurus, early DPF systems based on heavy fueling led to oil dilution.

Whilst I've read a lot I also tend to trust Service Managers closer to the real life experience. One such Fiat Service Manager who defected from GM/Vauxhaul quite openly told me about the major problems GM were having with (especially Zafiras 1.9s) of siezed engines due to oil dilution. These school & supermarket run cars were constantly failing to complete regeneration before the engines were shut down.

The added factor explained was that very few people check their oil levels and in these cases the oil levels were rising but as the cars have no "over level" indicator so the users are oblivious to the problem till it is too late. I have/had no reason to doubt him.

Also on the rare occassion I've shut the engine off in the middle of a regen cycle the smell of unburnt diesel fumes is blatently obvious if you hang around the car for a few mintues to give them a chance to waft out of the exhaust.

I'm more than happy with my position/opinion so I'll stick to my original practices

1) try not to let regens uncessarily take place when station if you can
2) try no to abort a regen if it it taking place when you come to an end of a journey

Of course the occasional inability to try and avoid 1) & 2) is going to happen but I personally see no point in NOT trying to reduce the occurances if you can.

Each to their own.

 

[keithglos]

We have also during regen the extra alternate fuel pulses which do not burn in the combustion chamber, but pass through unburnt to effect the regen. If my oil was not changed for the official 18000 miles it would have been through about 45 regens.

 

[buster]

From my understanding the dpf regen doesnt work like what is expressed here any way.My understanding is that no 4 or no 5 cylinder injector,injects a quantity of fuel whilst the exhaust valve(s) is open.This then finds its way into the trap and increases the internal temperature and burns the deposits away.Either way still a pain,the big stuff that my company works on has now resorted to fitting them too.Serious money when a turbo fails.

 

[s130]

For the early Cromas the eLearn offical blurb is as follows:

Therefore the particulate needs to be removed on a regular basis, regenerating the filter following a procedure that makes use of multiple injections to increase the temperature of the exhaust gases (about 600°C) and burn the particulate. The regeneration procedure is controlled by the injection control unit which acts: on the metering of the fuel (up to five injections in the same engine cycle per cylinder) and on the control of the air (E.G.R. and supercharging pressure).

All 4 cylinders are used with up to 5 injections per cycle. Also the extra injections take place AFTER TDC so the excess fuel is not part of the initial compression combustion but it is pumped in to add fuel to the exisitng fire. Details on the exact timings after TDC are a little more difficult to come but the early pulses are delivered whilst the exhaust valves are still closed and the power stroke is in procress as if left too late the combustion flame and heat will have already most died out by the time the exhaust stroke starts and the exhaust valve opens. The rest of the excess fuel injection does occur during the exhaust stroke thus keeping the fire going for longer during the exhaust stroke.

DPF regeneration technology is evolving and certainly becoming much more efficent and less dangerous to the engine.

 

[Vento]

On my 2006 2.4 the first touch on the end of the RH stalk produces an instant MPG readout right in front of me, and large enough to see. Is that Prestigio only?

No, it's not Prestigio only, but stil, by no way as clear as the temporary reading created. And, what's more, many times the navigation system is in use, by which MPG readout is impossible.
Was several times warned, just before a intended stop, a regen is going on. Could finish this regens by driving on.
Looking forward to install a wireless unit with a adjustable buzzer.
Regards
Vento

 

[Marsupilami]

Hi@all,

I've just passed the 200'km milestone with my 2.4 Croma. Still smooth driving because of fantastic 5 cyl engine and ZF automatic gear.
It took me years until I understood the regen rhythm of my car, till then shocked by the temporary high fuel throughput (and the blue exhaust in the rear window). Worst is when standing so ventilation may bring gases and bad smell into interior.
Fact is that after every (!) approx. 150km - resp. 100 miles - DPF regen cycle takes place. It just depends of the situation if you notice (standing or urban), barely (countryside) or not at all (Autobahn resp. Motorway).
When driving consumption increases for the next <10 km between 50-100% in city, about 40-50% (outside) and about 20% on Autobahn. If it started before reaching destination I mostly continue driving until regen ended, since it is always better to stop engine without greasy fuel deposite, wherever.
A bigger problem is the increasing percentage of "biological fuel", creating hard deposits and leading to noticable power loss up to 50 hp!! I twice had parts exchanged because of that. Best way to reduce the unavoidable problem is to use special additive. Since doing that the problem may still occur sooner or later, but really much later.
Hope to drive this technically best ever built FIAT up to 300' km or more: Nothing is perfect - also for this car - but it is very safe, very quiet for that power and even at higher speed (can talk or listen to music normally at 190 km/h), it has the lowest oil consumption I've ever had (half liter on 20' km), reasonable diesel consumption for its weight (certainly at high speed, compared to petrol engines) and supports me if I'm in a real hurry (up to 235km/h chrono, 220 true speed, in Germany (sorry to make you jealous for the sometimes opportunity to speed legally).

Good evening @all