FAQ: Diesel engines and DPF

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Deleted User 759

Post by Deleted User 759 »

Presently, all MK2 QQs, and some later MK1 QQ's are fitted with a device called with a DPF. There is a good general article regarding DPF's on the AA website. http://www.theaa.com/motoring_advice/fu ... iate=85386 Once I locate specific QQ DPF information and the way they re-generate, I will update this FAQ.

Deleted User 759

Post by Deleted User 759 »


Quick update to this. There have been a number of threads regarding DPF in the 1.5 and 1.6 J11 QQ's reporting problems, or generally trying to understand how it operates to try and avoid future problems. Thanks to several helpful members of this forum, I have been able to compile the following information: The purpose of regeneration is to burn the particulates accumulated in the DPF. In presence of oxygen, the particulates combustion regeneration occurs naturally when the temperature of exhaust gases exceeds 570A°C (1058A°F). In urban driving conditions, the engine barely reaches high temperature, and the exhaust gas temperature consequently varies between 150A°C (302A°F) and 200A°C (392A°F) and requires a system to increase the temperatures in the exhaust. A differential pressure sensor detects filter load status (particulate mass) and triggers the regeneration operation. This takes place by means of a controlled combustion that raises the exhaust gas temperature up between 550A°C (1022A°F) and 650A°C (1202A°F) at the filter intake. The J11 diesel engines use a post fuel injection when the exhaust valve opens to helps to increase exhaust gas temperature to regenerate the DPF. A Nissan bulletin that has been floating around suggests normal regeneration process could increase engine coolant and oil temperature which causes early oil degradation. However it is believed that the true reason for this sensor is because during DPF regeneration, unburnt fuel may pass into the oil causing contamination. The J11 QQ Diesel engines are fitted with an "OCS", or Oil Change Supervisor which monitors the condition of the oil, if your car asks you for an oil change before your normal service interval, it is best to get it changed to prevent excessive ware on the engine. Nissan claim that DPF regeneration system installed on the J11 QQ is superior to previous systems and driving at high engine speed for long periods of time and that regeneration could be activated in town driving. However short trips (read: trips that do not allow the engine to fully come up to temperature) may result in a build up of soot sooner, leading to extra regeneration cycles, or not allowing the regeneration process to start or complete. A number of members however say that they have completed many short trips with long trips "few and far between" and have experienced no problems presently. It is possible to take the car to a garage to run what's called a 'service regeneration', or sometimes known as a forced regeneration. This is where a computer is plugged into the car to enable the service. However, an oil change is required as during a service regeneration, diesel fuel can mix with the engine oil contaminating it. Service regenerations cost approx. £200, however some forum members have reported their dealer allowing the first service regeneration to be done free of charge. The exact parameters of when DPF regeneration is allowed to start, or how it handles interruption/town driving currently remains unclear. Some people have reported DPF problems however:1. Some dealers blame driving style (too many short trips, and not enough long trips....).2. 1 person reported their car suffered a software problem and a fix was applied.3. 1 person reported a sensor problem and in addition had a software fix applied.






SplanK2015-02-22 10:50:19
gvmdaddy
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Post by gvmdaddy »

I'm one of the 3 mile trip brigade. 3 miles to work, 3 miles home, 3 miles to supermarket , 3 miles home a couple of times a week. I get out for an hour or so once a week, sometimes motorway, sometimes country lanes. Driving is my pleasure so its just wind-down time for me. Currently nearing 5000 miles over 9 months. No issues. Stop start works as it should, which is when the engine is warmed up properly. I am taking on board everything that is posted on hear regarding dpf's and regens and am open minded about it all. Some say that regens are a timed event, occurring every 100 miles or so. Some say a late Iinjection of fuel into the cylinder does the job. Others say it may be a 5th injector system. Now the latest info on here mentions this OCS warning. Its such a big issue but I find it strange that none of this info is mentioned in the handbook. Info from Nissan is scarce and sketchy at best. Time will tell if we are making a mountain out of a molehill or not.
Engines have advanced considerably over the last few years, as has the technology used in dpf's, but what about the advance in fuel? Fuels are getting cleaner I would imagine, so could it be that they are more forgiving to the use of dpf's?
I follow this post with interest.
Deleted User 759

Post by Deleted User 759 »

[quote="gvmdaddy"]I'm one of the 3 mile trip brigade. 3 miles to work, 3 miles home, 3 miles to supermarket , 3 miles home a couple of times a week. I get out for an hour or so once a week, sometimes motorway, sometimes country lanes. Driving is my pleasure so its just wind-down time for me. [/QUOTE]
Bit in bold. If you didn't do that, I wonder if the outcome would be much different? We could do with somebody to data log via OBD port. This should give us some clues as to what's standard and maybe even catch a regen event.
gvmdaddy
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Post by gvmdaddy »

No idea SplanK. Its just something that a mechanic friend of mine recommended before I made my purchase. He works primarily on commercial diesels. Is my hours drive helping or is the regen just working during my short commutes and shopping trips? I dont know. Id like too, but I dont. Your last point could yield interesting information if anyone could do it.
duncho
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Post by duncho »

OCS is correct information and should have been provided by each dealer to a new customer byuing a dCi car.
R9M engine uses post fuel injection (when exhaust valve opens) to help increase temperature at DPF regeneration. Information of increased temperature of engine during regen is not correct. Engine has constant temperature (coolant, oil). Oil degrades due to the fact that small amount of fuel leaks to engine oil during each DPF regeneration (increased pressure during regen process).
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Kentishman
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Post by Kentishman »

Every time I think I've got this somebody comes up with a new explanation/theoryOpinion. Sorry fellas I'm confused don't know about anyone else. Probably totally wrong but doesn't seem a major problem in the real world. Nissan don't seem to think it's a major issue nothing in handbook or am I just naive.
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duncho
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Post by duncho »

It's not theory / opinion but genuine information coming from the only reliable source (manufacturer). If you want to know the truth, read the service manual.
duncho2015-02-16 19:15:47
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gvmdaddy
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Post by gvmdaddy »

Thanks duncho...bedtime reading at last!
F1 Bob
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Post by F1 Bob »

If this helps our 1.5 has now done 9500 miles in eight months. Our driving consists of almost daily run of just over 2 miles from cold start and return. We then do a motorway journey once or twice a week of 45 miles round trip at speeds of between 65 -70 mph with occasional cross country drives of 50-60 miles maybe once every two weeks or so. In addition we do a 500 mile motorway trip once every three months.No DPF problems to date and oil change /service indicator still showing as due in 9000 miles, so right on target for a mileage based 18k service.
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