[ds.raikkonen]

The thing is, for city dwellers, DPF can create more headache than SCR system. DEF/AdBlue can be purchased from any decent filling station/service centre and poured into the blue lid underneath the fuel door. Though it has a shelf life of only 1 year, so you can't purchase it in bulk and stow away in a corner, got to purchase a new can every time.

Usage of DEF~2% fuel consumption so you can calculate roughly your requirement. Though vehicles have DEF gauge and warning to warn the driver. Ignoring this warning will lead to 'engine derate' or 'limp mode' (to protect the engine and exhaust components).

DPF has chances of getting blocked and regenerating it can be a bit irritating, and if ignored, cause chances of vehicle going to 'limp mode'. Active regeneration involves flicking a switch and starting the vehicle, in which the ECU maintains revs higher than 2000 rpm and injects fuel in the DOC so that exhaust gas temp increases enough to burn off the accumulated soot. This can happen 'passively' as well, but that requires long stretches of open road. There is also a 'high temp exhaust' warning lamp to show the driver that the vehicle is in 'regen' mode.

[Bibendum90949]

Originally Posted by ds.raikkonen

Active regeneration involves flicking a switch and starting the vehicle, in which the ECU maintains revs higher than 2000 rpm and injects fuel in the DOC so that exhaust gas temp increases enough to burn off the accumulated soot. This can happen 'passively' as well, but that requires long stretches of open road. There is also a 'high temp exhaust' warning lamp to show the driver that the vehicle is in 'regen' mode.

Not all cars come equipped with an active regeneration switch. Guess new Toyota Crysta has it IIRC, where as cars like Seltos, Creta etc doesn't have it. If the engine malfunction light pops up because of DPF clogging, one has to take the car to ASS and do the oxygen sensor cleaning besides carrying out active regeneration, aided by their software and OBD tool. Car is made to idle at higher rpm' s and the process can take anywhere from 20-30 minutes to even an hour in some cases. All the while your fuel is burned.

If it's the DPF warning light that lits up, one can drive the car above 2000 rpm for 25-30 minutes to burn off the accumulated soot (passive regeneration).

The passive regeneration(high exhaust temperature) indication lamp isn't there for all cars too.

[theautoman]

Ad-Blue or other DEF is a solution of 30-35% Urea in water, even before the introduction of BS6 we have been using Ad-Blue in out Trucks, the consumption of Ad-Blue depends on the Load and the driving style of the operator for Commercial Vehicles and Excavators.
it is roughly 5 to 8% of the Diesel being used,

example: if an Excavator consumes 20 liter of diesel per hour, 1 to 1.5 liters of Ad blue will be consumed by the machile. large fleet operators usually used to have a dedicated Bowser and a pump for Ad-Blue. very soon it will be available in most petrol pumps just as easily as other lubricants. it is cheaper than diesel and buying in bulk will cost about Rs 25 to Rs 30 per liter.

[ds.raikkonen]

Originally Posted by Bibendum90949

Not all cars come equipped with an active regeneration switch. Guess new Toyota Crysta has it IIRC, where as cars like Seltos, Creta etc doesn't have it. If the engine malfunction light pops up because of DPF clogging, one has to take the car to ASS and do the oxygen sensor cleaning besides carrying out active regeneration, aided by their software and OBD tool. Car is made to idle at higher rpm' s and the process can take anywhere from 20-30 minutes to even an hour in some cases. All the while your fuel is burned.

If it's the DPF warning light that lits up, one can drive the car above 2000 rpm for 25-30 minutes to burn off the accumulated soot (passive regeneration).

The passive regeneration(high exhaust temperature) indication lamp isn't there for all cars too.

Right, thanks for the info, been trying to gather that for a while.

But the lack of a DPF switch will leave drivers vulnerable and exposed to possibility of vehicle going into limp mode. Doing it on the fly would have been much better, in my opinion.

High exhaust temp lamp should be mandatory as it presents fire hazard to the surroundings, but then if the DPF can’t be regenerated actively, guess it does not make that much sense.

[ds.raikkonen]

Originally Posted by a4anurag

Here's the information from the owner's manual:

Attachment 2032641

Thanks a lot for this info, any idea whether our gasoline vehicles have GPF? I believe it is used only in the European market with Euro 6d norms.

Interesting to note that ARAI specified PM limits only for gasoline direct injection engines in BS6 era. Wonder how PM is being controlled in our gasoline vehicles, if not with a GPF.

(Request mods to kindly merge this post with the previous one, thank you.)

[Bibendum90949]

Originally Posted by ds.raikkonen

But the lack of a DPF switch will leave drivers vulnerable and exposed to possibility of vehicle going into limp mode. Doing it on the fly would have been much better, in my opinion.

Imagine you setting out on a long journey in the night and soon after you hit the highway you get the engine warning light owing to DPF choking, just because your car was being used in city for prolonged periods in the preceding days/weeks/months. That's a situation one needs to be wary of.

Driving long enough with a clogged DPF is detrimental to its life besides loss of power and can even create back pressure to the engine that can cause engine damage or even soot getting to the oil sump through the combustion chamber.

Yes an onboard system that can trigger DPF active regeneration would save the day in such situations, even if it means pulling over the car to carry out the same. If not that, at least a warning light in the instrument cluster that shows the level of DPF/oxygen sensor clog that would make us aware of the impending situation beforehand and take the remedial measures than getting caught unawares during a journey.

Hope manufacturers take note of this and come up with a fool proof solution than leaving us stranded.

[Batfreak]

Originally Posted by ds.raikkonen

Thanks a lot for this info, any idea whether our gasoline vehicles have GPF? I believe it is used only in the European market with Euro 6d norms.

Interesting to note that ARAI specified PM limits only for gasoline direct injection engines in BS6 era. Wonder how PM is being controlled in our gasoline vehicles, if not with a GPF.

GPF is primarily used to tackle Particulate Matter (PM) emissions. Typical MPI petrol engines are programmed to operate very close to the stoichiometric air-fuel ratio (i.e. the air and fuel are in their chemically correct proportions for complete oxidation). The fuel and the air are also pre-mixed to a large extent prior to the injection in the engine and this creates a largely homogenous mixture within the cylinder. In this situation, the engine produces very limited PM emissions anyway since there is just enough air to burn the entire fuel charge.

On the other hand, GPF is often required in GDI engines because the fuel is injected directly into the cylinder, just like a diesel engine and thus, the mixture is not homogenous within the cylinder. This causes the formation of local zones where the air-fuel mixture is actually richer than the stoichiometric value (more fuel than air) while still maintaining an overall lean mixture over the entire cylinder. Though this overall lean condition gives advantages in terms of efficiency, the locally-rich zones within the engine produces much more PM emissions which then need to be trapped using a GPF to ensure that the tailpipe emissions are within the acceptable limits.

Difference between LNT/SCR and DPF

I would also like to clarify some common misconceptions that I can see here. Lean NOx Trap (LNT) and Selective Catalytic Reduction (SCR) cannot be used as a replacement for the Diesel Particulate Filter (DPF) as such. The DPF is used to tackle PM emissions, while the LNT and SCR are techniques to reduce the NOx emissions.

Until Euro 6 (and ergo, BS6), the limitations on NOx were much less stringent and improvements in the engine design/control characteristics could effectively bring the emissions below the legal limits. Since the new norms, however, there has been the need to include an additional device that can specifically target the NOx emissions. Mind you, NOx is an especially major issue for diesel engines, which as I said before, operate with a direct injection (with the subsequent formation of locally rich zones in an otherwise lean mixture) and can produce about 10 times the NOx emissions of even a GDI engine. This is where the Lean NOx Trap (LNT) and the Selective Catalytic Reduction (SCR) come in.

The AdBlue system that was mentioned earlier is just a specific proprietary name of the SCR technology. The basic idea behind SCR is to inject a chemical reducing agent (normally a urea based mixture) in the catalyst to cause a secondary reaction with the exhaust gases that reduces the NO produced by the engine to atmospheric nitrogen. This ammonia mixture is therefore consumed and will need replenishment over time.

There is no hard-and-fast rule as to the choice between SCR and LNT and different manufacturers may adopt different strategies to duck under the emission norms limitations, based also on the engine technology used. As you can imagine, cost is the key decision making parameter here. The Kia Seltos, for example, makes do with just a LNT and thus doesn't need any additional additives from time-to-time.

In modern diesel engines, you will almost always find the DPF to tackle the higher PM emissions. This may often be confused with another catalyst which is ALWAYS present in the system - the Diesel Oxidation Catalyst (DOC) but the key difference is that DOC is for reducing CO, HC and to some extent, the NOx emissions, while the DPF is more specifically targeted towards the soot (PM) emissions. In certain cases (if the SCR/LNT are not present), the DOC and DPF may also be combined into a single composite unit, for operational and cost benefits.

Sorry if I wasn't very clear. I tried to stay away from the technical aspects as much as I could to keep it simple and understandable but please let me know if it wasn't.

[sv97]

Even after reading the whole thread, I have one doubt whether the DPF filter will get clogged or not if one does only city driving in a BS-6 diesel engine even after using BS-6 diesel as fuel?

[Batfreak]

Originally Posted by sv97

Even after reading the whole thread, I have one doubt whether the DPF filter will get clogged or not if one does only city driving in a BS-6 diesel engine even after using BS-6 diesel as fuel?

Absolutely. As a matter of fact, the low load, low engine-speed condition that is typical of the urban environment is generally the worst use case in terms of soot emissions. PM emissions tend to decrease as the speed or the load on the engine increases.

The DPF would, thus, be in-charge of reducing the tailpipe soot emissions (even with BS6 compatible fuel) and would need regeneration.

[Bibendum90949]

Originally Posted by sv97

Even after reading the whole thread, I have one doubt whether the DPF filter will get clogged or not if one does only city driving in a BS-6 diesel engine even after using BS-6 diesel as fuel?

Yes even with BS6 fuel, DPF can get clogged for cars that are used in city for prolonged periods. Same was indicated in my previous post. It's a precarious situation we should be wary of especially if you've an out station trip in the offing and if you plan to drive in the night.

On the other hand, petrol particulate filters are less prone to clogging.

[ashvek3141]

Originally Posted by Bibendum90949

Yes even with BS6 fuel, DPF can get clogged for cars that are used in city for prolonged periods. Same was indicated in my previous post. It's a precarious situation we should be wary of especially if you've an out station trip in the offing and if you plan to drive in the night.

Pardon my noob question. So does this mean that one should avoid going for a diesel vehicle if his running is like around 70-80% in city traffic conditions? I don't literally mean 'city' here; but a similar condition wherein there is a slow moving traffic for substantial distance, wherein one can hardly take his car beyond the 2-2.5K rpm mark.

[Bibendum90949]

Originally Posted by ashvek3141

Pardon my noob question. So does this mean that one should avoid going for a diesel vehicle if his running is like around 70-80% in city traffic conditions? I don't literally mean 'city' here; but a similar condition wherein there is a slow moving traffic for substantial distance, wherein one can hardly take his car beyond the 2-2.5K rpm mark.

It's certainly not such a big enough reason to warrant staying away from buying a diesel car. It's just that one needs to be mindful of the consequences. In fact it's not just the kms covered in city limits that should count, instead the number of hours one spends in city limits. To log 500 kms in city, one could take 35-40 hours or even more depending on the traffic, means more quantity of fuel is burned without passive regeneration.

It's a different matter that city roads are not as choked as before, thanks to the pandemic. Even then, it's still not conducive for passive DPF regeneration. Considering service intervals are set at 10000 km or 12 months, it's a matter of time cars running predominantly in city gets this warning light. My friend in his Seltos has got DPF warning twice even after BS6 fuel came in the picture, that car is used mainly in city.

[chaudh2s]

Originally Posted by sv97

Even after reading the whole thread, I have one doubt whether the DPF filter will get clogged or not if one does only city driving in a BS-6 diesel engine even after using BS-6 diesel as fuel?

If everyday you continue to drive for 15-20 minutes more after engine temperature gauge reaches its fully hot position, your dpf would get regenerated by itself.
If your driving is less than that everyday, but once a week you drive 15-20 minutes at 2500rpm after reaching fully hot position, your dpf shall be ok.
Don’t use non dpf approved engine oils and never over fill engine oil.
Follow these 4 measures and forget about dpf.

[chaudh2s]

Also, 1 more thing I forgot. Keep your fuel tank above quarter level (preferably above half) all the time when driving in city. This is because dpf uses diesel to burn off soot when you are drving less kilometers everyday or running cold, and if fuel is low, the ecu instructs dpf to stop using diesel for regeneration.

[ds.raikkonen]

Originally Posted by Bibendum90949

My friend in his Seltos has got DPF warning twice even after BS6 fuel came in the picture, that car is used mainly in city.

An idea what was the distance covered between the two DPF tell tale lamp illuminations? Thanks