[LONG_TOURER]

I have been hearing a lot of issue pertaining to DPF clogging in high altitude areas like Ladakh, Zanskar and Spiti. Vehicles of various manufacturers like Kia, Mahindra, Hyundai etc have reported issues with DPF and the vehicles had to be towed to workshop.


Been to Leh last month, I myself suffered the Agony of DPF issue with my Hyundai Tucson. Luckily though, i could manage to regen/ Declogg the DPF by driving the car in higher RPMs and completed the trip only to get DPF malfunction when we reached the plains again. Now, to meet the BS6 emission norms in diesel vehicles, there are two configuration in India which are
1) DPF +LNT
2) DPF +SCR

You can read about it here.https://www.team-bhp.com/news/unders...es-diesel-cars


Now, i am a noob in engine working but my basic level of understanding tells me that Diesel engines work by igniting the fuel using high compression in presence of air which is nothing but oxygen.

The main problem driving in high altitudes is the scarcity of oxygen as we go higher up. We know that this take a toll in humans which lead to difficulty in breathing in those places. The lack of oxygen in higher altitude further means less amount of oxygen going through the combustion chamber of a diesel engine resulting in improper combustion. The improper combustion leads to formation of soot through the exhaust system.


For vehicles of pre BS6 era i.e BS4 or earlier, these soot are allowed to come out of the exhaust and discharged into atmosphere, which is why we see diesel vehicles emitting a lot of white/black smokes in higher altitude. However, for a BS6 diesel vehicle, these soot are to be passed through the DPF (Diesel particulate filter) and LNT or SCR as per your vehicle configuration and are mostly trapped by the DPF.

So if we keep driving on high altitudes for considerable amount of time, the soot keeps on getting accumulated in the DPF resulting in clogging / choking of the DPF. The general practise of regenerating/declogging the DPF is to drive the car in higher RPMs preferably above 2k rpm at an speed of 60kmph for atleast 20-25 minutes as per various owners' manual. But these is next to impossible while driving in narrow and windy roads of Manali-Leh highway, Zanskar or Spiti valley for that matter.

So, failure to regen the DPF within the threshold of DPF soot accumulation capacity results in vehicle breaking down in those highways. As per my observation, this DPF clogging issues are happening mostly in Automatic gearbox equipped vehicles where the gearbox tends to keep RPM of the car under 2K RPM for better fuel efficiency resulting in inefficient burning of soot trapped in DPF. Whereas in manual gearbox, we tend to keep the car above 2k rpm while taking a climb.

So, is it safe to assume that BS6 diesel vehicles are not meant to be driven in the terrains like Zanskar, Spiti and Ladakh ?? I would like to have feedback on how BHPians are doing with their BS6 diesel vehicles in those high altitudes. Am i missing out on something ?

"Check Exhaust System" in Tucson


Mahindra Thar had to be towed pertaining to DPF woes

Image courtesy: Rushlane CrashLane Facebook group

[Aditya]

Thread moved out from the Assembly Line. Thanks for sharing!

[shancz]

Good point on hill roads and automatics.

I used to think that this was more of an issue in city focussed driving but the hills use case is valid too

Automatics put you in a catch 22 situation there, sports mode would help at the cost of FE ?

Would also like to add a question that the vehicles with AdBlue are also susceptible ? Doesn't the Thar use AdBlue ?

[rakesh_r]

The new Force Gurkha comes with lean NOX trap system which I believe completely eliminates the need of Ad Blue, please correct me if I am wrong. Getting back to the topic, how did the manufacturers test these vehicles in the hills, since test mules were regularly seen, at least of Mahindra.

[Axe77]

On a related note (and as someone who has very limited understanding of this whole DPF issue) - I believe new emission norms are coming in 2023 which are a significant step up from BS6 as well. Will these make such issues even worse or will that perhaps set right some of the BS6 problems of DPF. Does anyone who understands this technically have a view on this?

I am in the market for a new diesel vehicle either in 2022 / 2023 (I’d like 2022 but can wait till 2023 if the reasons are good enough). I am just not sure whether to ensure I buy it before 2023 when the issues may become even more complex or wait till 2023 so I have a vehicle with the most recent norms.

[Duckdoc]

Originally Posted by LONG_TOURER

The general practise of regenerating/declogging the DPF is to drive the car in higher RPMs preferably above 2k rpm at an speed of 60kmph for atleast 20-25 minutes as per various owners' manual. But these is next to impossible while driving in narrow and windy roads of Manali-Leh highway, Zanskar or Spiti valley for that matter.

So, is it safe to assume that BS6 diesel vehicles are not meant to be driven in the terrains like Zanskar, Spiti and Ladakh ??

While I haven't driven my XUV 300 BS6 at high altitude, it is equipped with this park regeneration feature for unclogging the DPF and doesn't need to be driven.

https://youtu.be/iUH3yUW8cPc

[ajmat]

I recall Overdrive, organised a trip to Ladakh in various Audi's, the then new Q7 had major problems and had to be returned on a flat bed. The organisers tried running the cars up and down the highways outside Leh to regenerate the DPF but no joy.

The BSIV Kodiaq's used on the Spiti valley trip suffered no problems at all.

[shancz]

Originally Posted by shancz

Would also like to add a question that the vehicles with AdBlue are also susceptible ? Doesn't the Thar use AdBlue ?

Incorrect question from my side, apologies.
Read through the DPF thread and turns out that the AdBlue works on the SCR(reduce NOx emissions) which is in addition to the DPF and mainly seen on engines above 2000cc. Lower capacity engines use typically use LNT which doesn't require AdBlue but there are some exceptions.

Coming back to OPs question from the looks of it if someone is always stuck in this use case then this issue will be difficult to handle.
Quite likely that the filter was almost full and the driving conditions made it worse generating the messge.

From my understanding in layman terms DPF is essentially a filter which is filled up with soot as you drive. If you drive at higher revs for longer the high exhaust temperature burns it off, clearing the filter. If you don't the system will try to do it by injecting some fuel and raising the idling to burn it off. If that isn't able to sufficiently clear or if the soot generated overwhelms the system then the DPF warning comes up.

I am guessing as the filter fills up these errors will keep coming and the filling up is dependent on the driving conditions(except engine malfunctions releasing more soot). More highways lesser/no occurrences and vice versa.

On the question of BS6 diesels being a concern, if the driving conditions aren't allowing the regen to sufficiently clear the DPF, they are big concern, IMHO.

Ref : audioholic (BS6 Diesel Car owners - Your experience with DPF / SCR / AdBlue here)

[LONG_TOURER]

Originally Posted by shancz

Good point on hill roads and automatics.

I used to think that this was more of an issue in city focussed driving but the hills use case is valid too

Automatics put you in a catch 22 situation there, sports mode would help at the cost of FE ?

Would also like to add a question that the vehicles with AdBlue are also susceptible ? Doesn't the Thar use AdBlue ?

Honestly speaking, i was also of the view that cars with DPF +SCR (which require Adblu addition over certain intervals) would be more robust in terms of DPF clogging. This is true in city drives as i find no DPF+SCR vehicle to have their DPF replaced due to city usage. However things are very different up on hills. I have personally seen DPF issues occuring in kia sonnet which uses DPF+LNT (Lean Nox trap) and also a Mahindra thar which uses (DPF+SCR).

Originally Posted by rakesh_r

The new Force Gurkha comes with lean NOX trap system which I believe completely eliminates the need of Ad Blue, please correct me if I am wrong. Getting back to the topic, how did the manufacturers test these vehicles in the hills, since test mules were regularly seen, at least of Mahindra.

I think this is the very reason why manufacturer now a days choose to test their preproduction vehicles out in the hills. They may want to anticipate how the exhaust system would work at such altitudes and what measures can be taken to prevent a DPF failure in future. So can we assume that the new XUV700 and the Scorpio would be less prone to DPF failure as they were extensively tested on those mountains ? Well, only time will tell.

Originally Posted by Axe77

On a related note (and as someone who has very limited understanding of this whole DPF issue) - I believe new emission norms are coming in 2023 which are a significant step up from BS6 as well. Will these make such issues even worse or will that perhaps set right some of the BS6 problems of DPF. Does anyone who understands this technically have a view on this?

I think emission norms for petrol vehicles are going to be more strict in 2023. BS6 diesel will have little to no impact by 2023 norms as they are very strictly compliant.

Regarding purchase of new vehicle, i would advice you to buy a petrol powered vehicle if you are likely to drive mostly on mountains.

Originally Posted by Duckdoc

While I haven't driven my XUV 300 BS6 at high altitude, it is equipped with this park regeneration feature for unclogging the DPF and doesn't need to be driven.
https://Youtu.be/iUH3yUW8cPc

Yes, this self regeneration is only being offered in Toyota vehicles. I have seen toyota innova doing self regeneration while the vehicle is idling. Other manufacturers should also follow this path.

Originally Posted by ajmat

I recall Overdrive, organised a trip to Ladakh in various Audi's, the then new Q7 had major problems and had to be returned on a flat bed. The organisers tried running the cars up and down the highways outside Leh to regenerate the DPF but no joy.

The BSIV Kodiaq's used on the Spiti valley trip suffered no problems at all.

I believe it the end of era for fuel efficient diesel vehicle to be driven on mountains. Atleast i will think 100 times before taking my Tucson to mountains again.

[Bibendum90949]

Another relevant thread on DPF.

https://www.team-bhp.com/forum/techn...te-filter.html (FAQs about DPF (Diesel Particulate Filter))

[88_TANK_88]

While travelling in the region, especially approaching the higher passes, I could clearly see my car bellowing smoke when accelerating after the bends. I had to drop a gear and raise rpm to stop that from happening frequently. I can imagine the amount of soot that would be trapped in DPF of BS6 cars. The lean air and low oxygen levels result in incomplete combustion. ECU can ajdust fuelling based on O² sensor but those have their own limitations. Even the turbos need to work harder and boost comes at higher than normal RPMs.

[LONG_TOURER]

Originally Posted by 88_TANK_88

While travelling in the region, especially approaching the higher passes, I could clearly see my car bellowing smoke when accelerating after the bends. I had to drop a gear and raise rpm to stop that from happening frequently. I can imagine the amount of soot that would be trapped in DPF of BS6 cars. The lean air and low oxygen levels result in incomplete combustion. ECU can ajdust fuelling based on O² sensor but those have their own limitations. Even the turbos need to work harder and boost comes at higher than normal RPMs.

I agree with the turbo boost part, the turbo would kick in late and is more aggresive (non linear) in mountains. But we all can live with that and drive on. But this DPF clogging issue is quite concerning. Imagine you are at 15ft above MSL and suddenly your vehicle breaks down. How are people going to survive who get AMS in those altitudes.

[abhishek46]

Originally Posted by Duckdoc

While I haven't driven my XUV 300 BS6 at high altitude, it is equipped with this park regeneration feature for unclogging the DPF and doesn't need to be driven.
https://Youtu.be/iUH3yUW8cPc

This feature is available in the Creta Diesel as well.
However, in my view, this a wastage of fuel.

For cars with Manual Transmission, one can simple head out to an open road, and drive at good speed for 15-20minutes.
This will clear the DPF error, and it will be a refreshing drive as well.

For cars with Auto Transmission, I am sure there would be some way to manually engage specific lower gears to achieve 2000+ Rpms.


Now coming to the SCR or LNT Debate,
My opinion is that either presence or the absence of LNT/SCR will NOT have any Impact on the DPF's performance.

That is because, the LNT/SCR stage is performed after the DPF stage.

To elaborate, the SCR System or LNT hardware are fitted downstream (after) the DPF filter.

In Summary,
If there is Soot, the DPF will get clogged.
If the exhaust gas temperatures are low, the Soot will not get cleared.
If the Soot does not get Cleared, the DPF warning will appear.

Coming back to the original problem, i.e. the Soot.
The generation of soot is hardly in the user's control.
It is the engine design, the usage conditions, the quality of the fuel, which affect the Soot Generation.

[shancz]

For the drives like the OP mentioned diesels will always run a risk of potential DPF issues at the worst place/time. IMO petrol is the safer option here.
I hope the DPF issues find a resolution which doesn't involve getting rid of the DPF altogether.

This is slightly OT but since the issue of DPF getting choked with soot from the diesel engines is being discussed.
I would like to remind fellow BHPians that without the DPF the soot was being shot out in the open ruining the surroundings for the people behind, unless they are themselves windowed up, behind the windscreen of their cars, probably belching out similar amounts for the ones behind them and finally resting on the face of some poor biker like me

Without the F, we feel the DP hitting out faces while you guys are accelerating out of those turns.

And before someone asks why isn't your visor down, IMHO what's the point of riding through the hills with your visor down

[Big Smoke]

Won't parking the car and idling at higher RPMs for about 30 mins solve the issue? I believe that's what the system essentially is in any car with the self-regeneration feature.