GPF’s v DPF’s all you need to know?

Engine, Exhaust, Drivetrain, ECU Issues and Fixes
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MikeM
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Post by MikeM »

Read of some horrendous failures with Euro 6 DPF setups, with LR’s ingenium engine probably one of the worst. I think likely due to the way they programmed the regen sequence as it doesn’t allow you to just run hot for 20 minutes independently. It automatically goes into sequence without driver’s awareness, on a short journey it doesn’t complete leading to soot buildup and a large swig of unburnt diesel seeping through to the engine sump ( hence frequent oil change requests). A petrol engine runs hotter so hopefully not an issue, but thought to share this extract taken from a Which Car article re Subject

“Do petrol particulate filters need maintenance?”

According to manufacturers, cars with petrol particulate filters shouldn’t need to regularly be driven at higher speeds for short periods to stop them getting clogged up with soot, unlike with diesels.
Petrol particulate filters aren’t prone to getting blocked up like diesel particulate filters because petrol engines heat up quicker and run hotter than diesel engines, so more of the soot that’s collected in the filter is burnt off. Additionally, Porsche says that the electronic control units in its cars will detect when soot particles occasionally need to be burned off and increase the exhaust gas temperature to do this.
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bobajob
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Post by bobajob »

I think the issues is with only some Jaguars and is down to positioning of the DPF. On the transvers engined E-Pace the DPF is further from than the engine than in the longitudinally mounted F-Pace. As a result the DPF takes longer to heat up causing regen issues. Unburnt fuel is dumped into the sump diluting the engine oil.

Not that this answers you question!
gasgas1
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Post by gasgas1 »

can't see how fuel would seep down into sump, unless piston rings faulty, then car would be pumping out black smoke all the time?
bobajob
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Post by bobajob »

One of many articles out there - I assume it's seeping down the bores but happy to be educated!

The transverse engine installation leaves insufficient room between the engine and the bulkhead for a close-coupled DPF in the exhaust manifold. Instead, it is positioned after the oxidation cat converter under the car about 1 metre from the exhaust manifold. That means that in normal driving (typical school run) it can never get hot enough to enable passive regeneration of cold start soot. It has to actively regenerate using diesel fuel introduced via the engine. We know there is warm-up period for active regeneration of between 10 and 15 minutes before the HC/PM starts to burn. It then takes a further 15 to 20 minutes to complete the active regeneration giving a total time of up to 35 minutes for the whole process. Lots of drivers switch off mid-regeneration long before this has completed. So 35 minutes of post-injection every 150-200 miles is the real reason why sump oil is being contaminated by diesel in these vehicles so quickly and why some of them need an oil change in as little as 5,000 miles. In a letter of 24-10-2017 JLR provided a definition of 'typical driving style' to prevent the problem. "Typical driving style as an average across customers is journeys of 15-30 minutes with a speed between 50 km/h and 100 km/h, which includes some drives of over an hour. The exhaust temperature achieved in normal driving is low and as such there is no passive regeneration and soot must be cleared through active regeneration." This makes Discovery Sport and Evoque Ingenium diesels unsuitable for the purposes for which a significant percentage of owners bought them.
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Nuclear Nick
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Post by Nuclear Nick »

gasgas1 wrote: Sat Jul 25, 2020 6:55 pm can't see how fuel would seep down into sump, unless piston rings faulty, then car would be pumping out black smoke all the time?
This is the usual route for chronic sump oil contamination with diesel. Piston rings are not a perfect seal for fluids and diesel is a very good penetrant. Excess diesel fuel in the combustion chambers can be due to a number of reasons but these days is often as a result of regen cycles being interrupted or when sufficient temperatures are not achieved to burn off the extra fuel during a regen.
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On-Track
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Post by On-Track »

gasgas1 wrote: Sat Jul 25, 2020 6:55 pm can't see how fuel would seep down into sump, unless piston rings faulty, then car would be pumping out black smoke all the time?
Black smoke in the exhaust is a sign of incomplete combustion. If (and it's a massive if) the piston rings provided a perfect seal then in the event of excess fuel lying in the combustion chamber being partially burnt there would be a massive cloud of black smoke on start up.

Black smoke in cars is almost always caused by faulty injectors (injecting streams of fuel instead of sprays).

If you ever went trainspotting in the mid sixties you'd have noticed massive clouds of black smoke from diesel locomotives both on start up and when accelerating away from a standstill. This was because they had massive turbochargers. Inertia meant that for a few seconds after a call for more power the turbocharger provided insufficient charge air and not all the fuel was burnt in the combustion chamber. My knowledge comes not from trainspotting (I gave it up with the demise of steam :D ) but a working lifetime in the railway industry.
Peter

Current: 2020 Carmine Red GTS http://www.porsche-code.com/PMST9ZI9
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MikeM
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Post by MikeM »

Now I understand where the signature “on track” originates 🚂. Also re modern powered engines, a few puffs of black smoke on start up can signal an imminent turbo failure. 😳
Previous Porsche’s
2008. 987 Boxster S Sport basalt
2012. 991 Carrera S aqua
2016. Macan Turbo volcano
Current
2020. Macan GTS crayon
2024. Macan GTS gentian sometime this year https://configurator.porsche.com/porsche-code/PR8H7WC6
On-Track
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Post by On-Track »

MikeM wrote: Sun Jul 26, 2020 1:18 pm Now I understand where the signature “on track” originates 🚂.
Well spotted. The last eleven years of my working life were spent with the largest manufacturer of On Track Machines in the world. Great firm.
Peter

Current: 2020 Carmine Red GTS http://www.porsche-code.com/PMST9ZI9
Gone- 2015 Sapphire Blue Diesel
Gone -2013 Cayenne Diesel
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