TDi questions - Regeneration
08-22-2014, 02:43 PM
#1
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TDi questions - Regeneration
I currently own a 2008 Ford F250 Diesel and have owned a Euro spec mid 80's Nissan Patrol diesel, so I have had some experience with diesel engines. We are currently shopping for an A6 3.0 TDi.
My questions have to do with the DPF regeneration cycle (cleaning exhaust filter).
My truck is a pre- Diesel Exhaust Fluid vehicle, but has the DPF. DEF was supposed to make the DPF more efficient and resolve some of the soot and fuel economy issues of the previous generation DPF equipped vehicles. I am curious of what I can expect.
Ford had so many DPF related owner complaints they changed the indication message so it only comes on momentarily at the beginning. However, to prevent DPF clogging or other problems, you need to let the Regen cycle complete (takes 15 minutes approximately). Because the regen cycle initiates based on pressure in the DPF and when the truck is at operating temperature, it seems to enter regen when we are getting close to our destinations. I added a Scan Gauge II with programming so I can monitor the regen status. I am hoping Audi's experience with diesel cars have made their offering a much better owner and operator's experience, especially with regards to the emissions.
Any info is appreciated.
Vincent
My questions have to do with the DPF regeneration cycle (cleaning exhaust filter).
- What indication (if any) do you get when the vehicle enters regeneration?
- How often can one expect the vehicle to enter regeneration? My 6.4 powerstroke enters regen aprox 2 times every tank.
- Are their any common DPF problems?
- Has anyone encountered the need to have their DPF cleaned? I think I read something about a service requirement in a TDi maintenance summary.
My truck is a pre- Diesel Exhaust Fluid vehicle, but has the DPF. DEF was supposed to make the DPF more efficient and resolve some of the soot and fuel economy issues of the previous generation DPF equipped vehicles. I am curious of what I can expect.
Ford had so many DPF related owner complaints they changed the indication message so it only comes on momentarily at the beginning. However, to prevent DPF clogging or other problems, you need to let the Regen cycle complete (takes 15 minutes approximately). Because the regen cycle initiates based on pressure in the DPF and when the truck is at operating temperature, it seems to enter regen when we are getting close to our destinations. I added a Scan Gauge II with programming so I can monitor the regen status. I am hoping Audi's experience with diesel cars have made their offering a much better owner and operator's experience, especially with regards to the emissions.
Any info is appreciated.
Vincent
08-22-2014, 03:45 PM
#2
AudiWorld Member
I can't answer all your questions but here's my early experience with my TDI. In just over 3000 miles of driving, I have noticed 3 regen cycles; all have occurred driving to or from work (a 15 mile drive).
The first time I noticed it was when I got home from work, shut off the car in the garage, but the fan continued to run and there was a slight burning odor. There's no other indication that there is a regen cycle.
A search led me here:VW Touareg DPF and Audi Q7 DPF filter FAQ and Adblue fluid FAQ
Over here, some indicators of a regen cycle are discussed: Any way to know a DPF regeneration is in process? - TDIClub Forums
The first time I noticed it was when I got home from work, shut off the car in the garage, but the fan continued to run and there was a slight burning odor. There's no other indication that there is a regen cycle.
A search led me here:VW Touareg DPF and Audi Q7 DPF filter FAQ and Adblue fluid FAQ
Over here, some indicators of a regen cycle are discussed: Any way to know a DPF regeneration is in process? - TDIClub Forums
08-22-2014, 04:02 PM
#3
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I've got 16k trouble-free miles on mine and only been aware of 3-4 regen cycles during that time - as previous poster noted, I was aware of regen cycles only when car was parked in garage, fan was running and burning smell.
08-22-2014, 04:36 PM
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I did notice that my fuel mileage indicator went down and then when the car seemed to be done it went back up. Also the smell factor after parking the car.
I don't think like the Ford trucks that it will tell you via the DIC when it is going through a regen cycle. Wish it would.
I don't think like the Ford trucks that it will tell you via the DIC when it is going through a regen cycle. Wish it would.
08-22-2014, 06:16 PM
#5
I'll address this in two ways, first with the TDI Self-Study answers -
Active Regeneration
With active regeneration, the carbon soot particles are burned off through a targeted increase in the exhaust gas temperature by the engine management system. In city traffic, which produces low loads on the engine, the exhaust gas temperatures for passive regeneration of the particulate filter are too low. Since the carbon soot particles cannot be broken down, deposits build up in the filter. As soon as a certain level of carbon soot deposits is reached in the filter, active regeneration is initiated by the engine management system. This process lasts for approximately 10 minutes. The carbon soot particles are burned off to carbon dioxide at an exhaust gas temperature of 1110–1200°F (600–650°C).
With active regeneration, the carbon soot particles are burned off by high exhaust gas temperatures. When this happens, the carbon from the soot particles oxidizes with oxygen and forms carbon dioxide. C + O2 reacts to CO2.
Function of Active Regeneration
The carbon soot particles are retained in the inlet channels. The engine control module can detect the level of carbon soot in the particulate filter by evaluating the signals from the mass air flow sensors, the temperature senders before and after the particulate filter, and the exhaust pressure sensors.
When the carbon soot level reaches a predetermined limit, the engine management system initiates active regeneration.
From the flow resistance of the particulate filter, the engine control module can detect the level of carbon soot deposit in the filter. A high flow resistance indicates that the filter is in danger of becoming blocked. The engine control module initiates an active regeneration process. To do this:
– Exhaust gas recirculation is switched off to raise the combustion temperature
– An extended injection period is initiated after a period of main injection with reduced quantity at 35° crankshaft angle after TDC, in order to increase the exhaust gas temperature
– The intake air supply is regulated by the throttle valve
– The charge air pressure is adapted so that the torque during regeneration does not change noticeably by the driver
These measures lead to a targeted, brief increase in the exhaust gas temperature to approximately 1150°F – 1200°F (600°C – 650°C). In this temperature range, the collective carbon soot oxidizes to carbon dioxide. After this active regeneration period, the particulate filter is ready for operation again and can begin filtering carbon soot out of the exhaust gas.
In the 7,500 miles I've covered with my TDI, I can only tell that regeneration is taking place by (1) auto start/stop will not function and (2) cooling fans running after the engine is shut off. Haven't had a strong odor associated with that though...could be my nose is shot after Iraq and AFG. During normal driving you can't really tell when the motor is actively in regeneration mode.
The self-study says the active regeneration will occur roughly every 600-800 miles, depending on usage. There are multiple pressure sensors monitoring the exhaust system. Once there is a sufficient build-up of carbon in the particulate filter this will trigger ECU to enter active regeneration.
For the DPF question and issues, there are none which I've heard of. It's a fairly stout design and functions very well! There are no requirements outlined for servicing the particulate filter.
Shoot me an e-mail and I'll forward the self-study guide to you, or search Google using the above program number. It's a short read and is VERY detailed!
Originally Posted by Audi 3.0-Liter V6 TDI w/ Clean Diesel System - Self-Study Program 941803 - Page 73-74
Active Regeneration
With active regeneration, the carbon soot particles are burned off through a targeted increase in the exhaust gas temperature by the engine management system. In city traffic, which produces low loads on the engine, the exhaust gas temperatures for passive regeneration of the particulate filter are too low. Since the carbon soot particles cannot be broken down, deposits build up in the filter. As soon as a certain level of carbon soot deposits is reached in the filter, active regeneration is initiated by the engine management system. This process lasts for approximately 10 minutes. The carbon soot particles are burned off to carbon dioxide at an exhaust gas temperature of 1110–1200°F (600–650°C).
With active regeneration, the carbon soot particles are burned off by high exhaust gas temperatures. When this happens, the carbon from the soot particles oxidizes with oxygen and forms carbon dioxide. C + O2 reacts to CO2.
Function of Active Regeneration
The carbon soot particles are retained in the inlet channels. The engine control module can detect the level of carbon soot in the particulate filter by evaluating the signals from the mass air flow sensors, the temperature senders before and after the particulate filter, and the exhaust pressure sensors.
When the carbon soot level reaches a predetermined limit, the engine management system initiates active regeneration.
From the flow resistance of the particulate filter, the engine control module can detect the level of carbon soot deposit in the filter. A high flow resistance indicates that the filter is in danger of becoming blocked. The engine control module initiates an active regeneration process. To do this:
– Exhaust gas recirculation is switched off to raise the combustion temperature
– An extended injection period is initiated after a period of main injection with reduced quantity at 35° crankshaft angle after TDC, in order to increase the exhaust gas temperature
– The intake air supply is regulated by the throttle valve
– The charge air pressure is adapted so that the torque during regeneration does not change noticeably by the driver
These measures lead to a targeted, brief increase in the exhaust gas temperature to approximately 1150°F – 1200°F (600°C – 650°C). In this temperature range, the collective carbon soot oxidizes to carbon dioxide. After this active regeneration period, the particulate filter is ready for operation again and can begin filtering carbon soot out of the exhaust gas.
The self-study says the active regeneration will occur roughly every 600-800 miles, depending on usage. There are multiple pressure sensors monitoring the exhaust system. Once there is a sufficient build-up of carbon in the particulate filter this will trigger ECU to enter active regeneration.
For the DPF question and issues, there are none which I've heard of. It's a fairly stout design and functions very well! There are no requirements outlined for servicing the particulate filter.
Shoot me an e-mail and I'll forward the self-study guide to you, or search Google using the above program number. It's a short read and is VERY detailed!
08-23-2014, 06:36 AM
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Many thanks for the info and the document reference. I will read through it as well.
I suspect the owners' experiences with the Audi TDi are much better than some of the Ford Diesel owner experiences. I haven't had problems with my DPF, but I make extra efforts to avoid conditions that might cause operational issues (like interrupted regen, shutting down during high EGT's, etc).
After reading the TDi forum, I might want to consider an aftermarket monitoring device like another Scan Gauge II (I have 2) or a Banks IQ if I find I need to track the regen cycles or DPF & EGT temps.
Thanks again,
Vincent
I suspect the owners' experiences with the Audi TDi are much better than some of the Ford Diesel owner experiences. I haven't had problems with my DPF, but I make extra efforts to avoid conditions that might cause operational issues (like interrupted regen, shutting down during high EGT's, etc).
After reading the TDi forum, I might want to consider an aftermarket monitoring device like another Scan Gauge II (I have 2) or a Banks IQ if I find I need to track the regen cycles or DPF & EGT temps.
Thanks again,
Vincent
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08-26-2014, 09:45 PM
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I've noticed at least 6-8 times over a 24,000km. This is the fan staying on. It is not to say that it didn't happen more often - like on a long road trip. I noticed zero indication when I was driving and regen was on.
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