EGR - What's good for it and what's bad.

[Gdcobra]

I've seen this mentioned in several threads as being a problematic device.  I'm looking for a bit more information on how the setup functions in the hope that I can work out what I can do to limit the possibility of problems.  I have used the search function but unfortunately I've found that most threads specific to the EGR seem to very quickly degenerate into arguments about the necessity (or not) to disable the device and then the legality (of not) of doing so.  At this point I'm not interested in disabling and hence not interested in the legal situation.

 

My understanding is that this is a valve which sits in a pipe which allows exhaust fumes to be drawn into the inlet charge.  One thing I'd like to know where in the exhaust system the fumes are harvested (I'm assuming post DPF) and where these are piped into the inlet.  I've heard that the system can have negative effects on the intercooler so thought the fumes must be introduced upstream of this but have been told that it is more typical to enter the inlet tract after the intercooler,  as close to the inlet valve as possible (and this is what I've seen on other vehicles I've had). 

 

What problems does the system cause?  From what I've read (and what seems logical) introducing exhaust fumes into the inlet can cause problems with clogging due to the content of the exhaust charge, but what specific problems do these cause and what component are impacted.  I'm assuming general build up of 'crud' between the EGR valve and the inlet valve but what is involved and is there any impact on components upstream in the inlet charge?

 

What can be done to limit problems?  I don't commute and my mileage is made up of a small number of long trips, mainly motorway.  I believe this will be good for the EGR and DPF systems.  I also use quality fuel in the hope that this will limit the nasties in the exhaust fumes.  However I'm more concerned about the current state of the system and if there is anything I can do to reverse any negative effects of previous usage.  The car has 60k miles on the clock and looking through the service history and previous MOTs this appears to have been put together as a regular 6k/year mileage.  Obviously quite low and presumably made up of more shorter trips.  Is there anything simple/cheap I could do to asses the current state of the system and any action I can take if it is not in an ideal state?

 

As always, thanks in advance for any input.

[chimaera]

The EGR takes exhaust gases directly from the exhaust manifold on our cars and directs them to the intake manifold. The crankcase vapours are also returned to the intake manifold. One problem this causes is mixing of oil vapour with soot particles to clog up the intake and less often the EGR valve.

 

Most soot will come from high loads on the engine, particularly if it's cold. If you're on the motorway for long periods this will be good for the car.

 

If you're worried about the current condition of the engine, a few Italian tuneups won't do any harm.

[Gdcobra]

3 hours ago, chimaera said:

The EGR takes exhaust gases directly from the exhaust manifold on our cars and directs them to the intake manifold. The crankcase vapours are also returned to the intake manifold. One problem this causes is mixing of oil vapour with soot particles to clog up the intake and less often the EGR valve.

 

Most soot will come from high loads on the engine, particularly if it's cold. If you're on the motorway for long periods this will be good for the car.

 

If you're worried about the current condition of the engine, a few Italian tuneups won't do any harm.

Hi Chimaera, thanks for that.

Interesting that the system appears to take the exhaust gas from the dirtiest possible place (but what do I know?).  Can you say where in the inlet tract the gas is fed in?

The main reason I'm interested in this is that I've had a number of errors thrown up indicating an engine problem and, although they only appear for an instant, I did notice last time that the glow plug light came on at the same time.  One of the threads I read indicated that this could be a symptom of EGR issues.  Do you know if there are any other symptoms I may notice if I had a problem in this area?  Other than these occasional messages the car seems to run fine.

 

By an Italian tune up I guess  you mean drive it like you stole it?  I wonder if this is really helpful on a Diesel, as when you look a a Diesel which doesn't have DPF and so on this is where the exhaust smoke seems at its worst.  Also, while I've used this technique previously, particularly on 2 strokes to clean the exhaust, I don't see how that can help clean up the inlet area.  Is there anything I can blast into the airbox whch may clean the system?

 

When I'm not on the motorway I like to "make progress" so it does rev' reasonably during acceleration, and as it's DSG it makes its own decisions about gear changes although I could use S mode a bit more.  On the motorway I go with the flow which means either about 80 in the outer lane or 60 in the next one in (I'll let you guess which I prefer) or stationary/stop-start in the roadwork sections which no trip is without these days (I'm so glad they are taking the time to 'improve' our motorways).

 

 

[TLV]

Ideally the EGR takes unburnt gasses from the exhaust and routes them back to the inlet to increase efficiency (unburnt fuel) and decrease pollutants (byproducts of incomplete combustion) by burning said gasses in the engine again. The main purpose is still reducing harmful emissions and the increased fuel efficiency is minimal if there at all, might even require extra fuel to burn the pollutants over. It would be an engineering challenge to build a decent system for returning gasses from after the catalytic converter to the inlet and would also reduce its effectiveness, thus nullifying that consideration since the catalytic converter burns the same gasses once. If you route exhaust gasses back in to the engine and then through the catalytic, ideally you get the advantage of burning the same gasses twice.

Edited 26 April, 2017 by TLV

[Gdcobra]

1 minute ago, TLV said:

Ideally the EGR takes unburnt gasses from the exhaust and routes them back to the inlet to increase efficiency (unburnt fuel) and decrease pollutants (byproducts of incomplete combustion) by burning said gasses in the engine again. The main purpose is still reducing harmful emissions and the increased fuel efficiency is minimal if there at all. It would be an engineering challenge to build a decent system for returning gasses from after the catalytic converter to the inlet and would also reduce its effectiveness, thus nullifying that consideration since the catalytic converter burns the same gasses and once. If you route exhaust gasses back in to the engine and then through the catalytic, ideally you get the advantage of burning the gasses twice.

From the point of view of ensuring all fuel is burned this makes sense but I was under the impression that the need for EGR on a Diesel engine was to decrease the temperature and hence reduce Nox, Personally if it was only about greater fuel efficiency I'd live without it, I don't really care if my car does 50MPG or 51MPG.

Anyway, I need to remind myself I asked the questions so I could better understand the system and how to work 'with' it rather than try to redesign and 'fix' it!

 

[chimaera]

1 hour ago, Gdcobra said:

Hi Chimaera, thanks for that.

Interesting that the system appears to take the exhaust gas from the dirtiest possible place (but what do I know?).  Can you say where in the inlet tract the gas is fed in?

The main reason I'm interested in this is that I've had a number of errors thrown up indicating an engine problem and, although they only appear for an instant, I did notice last time that the glow plug light came on at the same time.  One of the threads I read indicated that this could be a symptom of EGR issues.  Do you know if there are any other symptoms I may notice if I had a problem in this area?  Other than these occasional messages the car seems to run fine.

 

By an Italian tune up I guess  you mean drive it like you stole it?  I wonder if this is really helpful on a Diesel, as when you look a a Diesel which doesn't have DPF and so on this is where the exhaust smoke seems at its worst.  Also, while I've used this technique previously, particularly on 2 strokes to clean the exhaust, I don't see how that can help clean up the inlet area.  Is there anything I can blast into the airbox whch may clean the system?

 

When I'm not on the motorway I like to "make progress" so it does rev' reasonably during acceleration, and as it's DSG it makes its own decisions about gear changes although I could use S mode a bit more.  On the motorway I go with the flow which means either about 80 in the outer lane or 60 in the next one in (I'll let you guess which I prefer) or stationary/stop-start in the roadwork sections which no trip is without these days (I'm so glad they are taking the time to 'improve' our motorways).

 

 

 

I'm not quite sure about the logic of taking the exhaust from the manifold, but it has been the standard practice for a long time. I would imagine a lot of engineers have considered the problem in that time so there's something going for it. I suspect some of it has to do with gas pressure being highest at the manifold.

 

On the intake side, it's fed into the intake plenum - there's an assembly bolted onto the manifold that includes the EGR pipe and the shutdown valve.

 

The glow plug light doubles up as a general check engine warning light, so it will light up for any engine malfunction. Without connecting an appropriate diagnostic tool up to the vehicle it's not really possible to comment on possible causes.

 

Yes, Italian tuneup = drive it hard for a little bit. The best option is floor it in third on the on-ramp of the motorway. If the motorway is quiet, you can slow back down and repeat the flooring it in third bit a few times.

 

What it does is increase gas pressure and gas flow through the engine which knocks any deposits loose. The higher temperatures also help burn stuff off. EGR will stop during high load so it won't have as much of an impact there but it will help with general engine health. There are some cleaning products which claim to work by being sprayed into the intake while the engine runs. I don't know if they're any good. Like many additives/cleaners, it's very difficult to find independent test data.

 

 

4 minutes ago, TLV said:

Ideally the EGR takes unburnt gasses from the exhaust and routes them back to the inlet to increase efficiency (unburnt fuel) and decrease pollutants (byproducts of incomplete combustion) by burning said gasses in the engine again. The main purpose is still reducing harmful emissions and the increased fuel efficiency is minimal if there at all. It would be an engineering challenge to build a decent system for returning gasses from after the catalytic converter to the inlet and would also reduce its effectiveness, thus nullifying that consideration since the catalytic converter burns the same gasses and once. If you route exhaust gasses back in to the engine and then through the catalytic, ideally you get the advantage of burning the gasses twice.

 

Sorry, it has nothing to do with recycling unburned or partly burned fuel. The function of EGR is to reduce the concentration of oxygen in the intake air which reduces the amount of fuel that can be burned during that stroke, reducing combustion temperatures and therefore reducing NOx.

 

Any additional combustion of the combustion products in the recirculated exhaust is incidental rather than a design goal.

[Gdcobra]

2 minutes ago, chimaera said:

Yes, Italian tuneup = drive it hard for a little bit. The best option is floor it in third on the on-ramp of the motorway. If the motorway is quiet, you can slow back down and repeat the flooring it in third bit a few times.

 

What it does is increase gas pressure and gas flow through the engine which knocks any deposits loose. The higher temperatures also help burn stuff off. EGR will stop during high load so it won't have as much of an impact there but it will help with general engine health. There are some cleaning products which claim to work by being sprayed into the intake while the engine runs. I don't know if they're any good. Like many additives/cleaners, it's very difficult to find independent test data.

 

Well I tend to drive more or less like that anyway so no change required there!

[silver1011]

The bulk of the failures of the EGR on the MkII Superb aren't related to the build up of deposits.

 

There is / was a design fault which allows water ingress onto the electronic controller from the inbuilt cooling system.

 

Also mentions of loose pins and some with clogging...

 

 

[lichfielddriver]

EGR craps up...

 

 

 

Then the VGT craps up

 

 

and the DPF craps up

 

 

 

 

 

Rip em all out defeat the lot, save yourself £2000 and more in heartache

 

 

 

 

 

 

[Sjk68]

Hi all

Just bought a superb estate 1.6tdi had it for a day and the glow plug light came on and it went into limp 

mode (not happy) Had the car plugged in and it showed the fault as Egr valve sensor circuit B. Rang the garage took it in and they have changed it. But had to wait for part, but the car is running OK now. But as you all know they are not cheap to have done, I was quoted £800+ for oe part and £735 for best of the rest this included  fitting and vat

[lichfielddriver]

1 hour ago, Sjk68 said:

Hi all

Just bought a superb estate 1.6tdi had it for a day and the glow plug light came on and it went into limp 

mode (not happy) Had the car plugged in and it showed the fault as Egr valve sensor circuit B. Rang the garage took it in and they have changed it. But had to wait for part, but the car is running OK now. But as you all know they are not cheap to have done, I was quoted £800+ for oe part and £735 for best of the rest this included  fitting and vat

 

 

at a dealership?

 

VAG are reported to have 8000 EGR valves on backorder

 

TPS valves are £300 something

[lichfielddriver]

BTW, always use the right oil, change oil and air filters often and consider if branded diesel is the best for your pride and joy, oh, and do over 15,000 miles ayear with some motorway running

[Gdcobra]

On 01/05/2017 at 11:56, lichfielddriver said:

BTW, always use the right oil, change oil and air filters often and consider if branded diesel is the best for your pride and joy, oh, and do over 15,000 miles ayear with some motorway running

Those pictures in the earlier post of frightening but without knowing more about the car the parts came of it's difficult to tell too much.  Is this a typical story or were there other factors contributing to what I hope is an extreme case?  I'm thinking of :

        Type of driving (short trips)

        Fuel quality

        Engine oil type and quality

       Other issues with engine (possibly leading to more oil in lnlet).

But there are probably other factors.

Although my mileage will only be about 10,000 it will be composed of mainly long, motorway trips (100+miles) and very few, if any which don't get the engine fully warm (I don't like starting any engine unless it will be fully up to temp' before it stops again)  I also won't skimp on maintenance, I never do anyway, always use best quality oil and filters and change more often than recommended.  I've been using higher quality branded fuel and (possibly my imagination) the car does seem to feel a lot smoother since I've got a few hundred miles on the clock with this in.

 

[andy-fisher]

I think that picture of a clogged up EGR is the extreme.  I took a photo of mine after 179,000 miles and it's nothing like that.  I changed it anyway and the fault is still there so may consider having it mapped out if I cant find another solution.

 

My EGR thread

 

[lichfielddriver]

2 hours ago, andy-fisher said:

I think that picture of a clogged up EGR is the extreme.  I took a photo of mine after 179,000 miles and it's nothing like that.  I changed it anyway and the fault is still there so may consider having it mapped out if I cant find another solution.

 

My EGR thread

 

 

 

ok............google "clogged EGR valve" and "images"

[lichfielddriver]

https://www.google.co.uk/search?q=clogged+egr+valve&client=firefox-b&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjX1MDe1tTTAhWsLsAKHX3cBtwQ_AUICygC&biw=1216&bih=600

[andy-fisher]

44 minutes ago, lichfielddriver said:

 

 

ok............google "clogged EGR valve" and "images"

That search will always show a clogged valve though as you would expect, it's unlikely to show images of EGRs that are sparkly and new.  I would also expect there would be few people posting images of an EGR valve that is functioning as it should as they would have no reason to take it out to photograph it.  I'm not saying it doesn't happen and it's not a problem but from my experience those pictures show the extreme.  Mine is a picture of the valve out of my car that had covered 179,000 miles on removal and has never been cleaned or removed before.  The only reason I removed it was due to an 'EGR insufficient flow' fault and expected to see a valve like the picture you posted as that's all you find when searching for an answer.  I had purchased a new valve before i removed the old one as can't be without the car for long so wanted all the spares I would possibly need ready.  I would have happily left the old one on and carried on with my search for the cause of the fault but as I had a new one I put it on anyway.

 

The car has been serviced according to the variable service intervals since new which worked out at once a year due to mileage covered.  Always used 507 spec oil in line with that type of service regime and has been driven quite gently in the pursuit of MPG which is (according to many forums) the way to ensure it gets blocked.

 

If you search Google images for 'clogged air filter' you get photos of very dirty air filters which mine has never looked close to being like.

 

https://www.google.co.uk/search?q=cats+in+cars&source=lnms&tbm=isch&sa=X&ved=0ahUKEwibu97f4tTTAhWKB8AKHVlADYMQ_AUICigB&biw=1600&bih=775&safe=active&ssui=on#safe=active&tbm=isch&q=clogged+air+filter

[peterposh]

Running the motor at operating temperature for long periods is good, short commutes are bad

[psycholist]

On 5/3/2017 at 19:55, Gdcobra said:

Although my mileage will only be about 10,000 it will be composed of mainly long, motorway trips (100+miles) and very few, if any which don't get the engine fully warm (I don't like starting any engine unless it will be fully up to temp' before it stops again)  I also won't skimp on maintenance, I never do anyway, always use best quality oil and filters and change more often than recommended.  I've been using higher quality branded fuel and (possibly my imagination) the car does seem to feel a lot smoother since I've got a few hundred miles on the clock with this in.

 

Sounds like you're doing the ideal driving for your engine. For my car for the last few years it gets driven 100 km almost every time the engine is started and it'll pass 210,000 km (130,000+ miles) on Friday, the next time I expect to drive it. The only engine issue was a pressure sensor in the DPF giving a plausible but incorrect reading that made the car think the DPF was clogged and regen a lot for a couple of weeks while I worked out what was going on (It was an intermittent fault, combined with only driving every few days, so it took time to be sure something was up) and got it sorted.

 

I use whatever fuel is cheapest (From reputable stations - if the car won't run reliably on standard diesel it's not fit for purpose.) and leave the car on long service intervals but tend to check it immediately if I suspect anything is wrong with it. I'm curious as to what uprated oil you are using - anything that meets the VAG oil spec for this engine is already very high end to begin with.

[Gdcobra]

2 hours ago, psycholist said:

Sounds like you're doing the ideal driving for your engine. For my car for the last few years it gets driven 100 km almost every time the engine is started and it'll pass 210,000 km (130,000+ miles) on Friday, the next time I expect to drive it. The only engine issue was a pressure sensor in the DPF giving a plausible but incorrect reading that made the car think the DPF was clogged and regen a lot for a couple of weeks while I worked out what was going on (It was an intermittent fault, combined with only driving every few days, so it took time to be sure something was up) and got it sorted.

 

I use whatever fuel is cheapest (From reputable stations - if the car won't run reliably on standard diesel it's not fit for purpose.) and leave the car on long service intervals but tend to check it immediately if I suspect anything is wrong with it. I'm curious as to what uprated oil you are using - anything that meets the VAG oil spec for this engine is already very high end to begin with.

From the responses here I think I'm good with the mileage I will be doing, I was more bothered about he current state of the system as it seems that, although the car appears to be well looked after, the annual mileage has been quite low (circa 7000 miles/year).  I was wondering if there was any way I could check the current status (maybe and endoscope in a convenient orifice - Oo-er!) or anything I could do to reverse any possible build-up of crud.

I don't go crazy on oil changes, but stick to the minimum recommendation and maybe err on the side of caution with that.  Likewise I don't use expensive aftermarket parts, quite happy to use VW quailty, but don't use cheap aftermarket stuff either.

 

One thing the got me a bit worried was the smell of the exhaust, when I got the car it had the aroma I'd associate with an old Diesel engine (E.G. Old Comma van) not what I'm more familiar with the recent Diesel cars I've had, equipped with modern emissions equipment which had me wondering if there was something amiss, however after putting some miles on it this seems to have changed.

 

I'm interested to know how you knew you had a problem causing frequent regens, I've done about 2,000 miles in the car now and have no idea if it has ever done a regen.  I really wish there was some kind of indicator to alert you to when this was happening.

[chimaera]

4 minutes ago, Gdcobra said:

From the responses here I think I'm good with the mileage I will be doing, I was more bothered about he current state of the system as it seems that, although the car appears to be well looked after, the annual mileage has been quite low (circa 7000 miles/year).  I was wondering if there was any way I could check the current status (maybe and endoscope in a convenient orifice - Oo-er!) or anything I could do to reverse any possible build-up of crud.

I don't go crazy on oil changes, but stick to the minimum recommendation and maybe err on the side of caution with that.  Likewise I don't use expensive aftermarket parts, quite happy to use VW quailty, but don't use cheap aftermarket stuff either.

 

One thing the got me a bit worried was the smell of the exhaust, when I got the car it had the aroma I'd associate with an old Diesel engine (E.G. Old Comma van) not what I'm more familiar with the recent Diesel cars I've had, equipped with modern emissions equipment which had me wondering if there was something amiss, however after putting some miles on it this seems to have changed.

 

I'm interested to know how you knew you had a problem causing frequent regens, I've done about 2,000 miles in the car now and have no idea if it has ever done a regen.  I really wish there was some kind of indicator to alert you to when this was happening.

 

The only telltale from within the car that it's doing a regen is that it will idle around 950 rpm instead of 750 rpm if stationary, or 825 if moving. If you're outside the car you'll feel the heat from the engine area and all the fans will be running. I agree it would be useful to have a dash light indicating regen in progress - I suspect quite a few engines suffer problems from being consistently interrupted during regen and it might help stave this off.

 

Some installed OBDII readers either as a phone app connecting to a bluetooth reader or using something like Scangauge: you can monitor engine operating parameters live and keep an eye out for regen activity. Exhaust gas temperature increases a lot during regen.

 

Most cars will see a regen every 500+ km depending on how the vehicle is driven. If it's happening much more than that you have a problem. On psycholist's car we ran a scan with VCDS to confirm the issue.

[Gdcobra]

7 minutes ago, chimaera said:

 

The only telltale from within the car that it's doing a regen is that it will idle around 950 rpm instead of 750 rpm if stationary, or 825 if moving. If you're outside the car you'll feel the heat from the engine area and all the fans will be running. I agree it would be useful to have a dash light indicating regen in progress - I suspect quite a few engines suffer problems from being consistently interrupted during regen and it might help stave this off.

 

Some installed OBDII readers either as a phone app connecting to a bluetooth reader or using something like Scangauge: you can monitor engine operating parameters live and keep an eye out for regen activity. Exhaust gas temperature increases a lot during regen.

 

Most cars will see a regen every 500+ km depending on how the vehicle is driven. If it's happening much more than that you have a problem. On psycholist's car we ran a scan with VCDS to confirm the issue.

I've noticed the smell on previous cars, first time I thought there was a serious problem, smelled like I'd burned out the brakes or clutch (but it didn't have a clutch), the problem now thought is that most of the time I'm on the motorway and as the car is DSG I don't notice idle speed.  I also think that interrupting the cycle is not a good idea and may cause issues but due to my mileage probably won't affect me, I'm thinking more about the issue psycholist mentioned where the car was performing regens too frequently, I don't know how I'd know if that was happening.

[psycholist]

It will also suggest lower gears than usual while running a regen and sometimes the engine note will change slightly. I haven't noticed a regen in at least the last year since most of my driving is around 80 km/h with very little start/stop use (It's nice to use a car for what it's good at  ). The hilarious thing was that while that sensor was failing, a couple of times it gave genuinely impossible readings and the glow plug light would come on and all the nasty regen symptoms would go away because the system was ignoring the sensor completely and the engine ran perfectly.

 

If you're looking at the idle speed, while my car is moving, even while coasting, the revs are held around 950 rpm, so the only time you can check whether there's a regen running via the idle speed is while at a complete stop.

Edited 10 May, 2017 by psycholist

[TLV]

I coast as much as I can. Got a manual and when doing long coasting, the car will not let the RPM's drop lower than 900, it will just accelerate on its own to prevent stalling. Lugging the car is no fun. When I take the car out of gear, it will keep idling at 900 RPM until the car has come to a stop, then it'll drop the idle to 750 RPM.

[TheRobinK]

4 minutes ago, psycholist said:

I haven't noticed a regen in at least the last year since most of my driving is around 80 km/h with very little start/stop use

 

Same here on my 1.6CR. The only time I've noticed a regen was just after getting the car and abusing it in snails pace/stop start Dublin traffic for a week.

After a 1 year and 9 months of having it at home in Clare, I've never noticed one again. I forget I have start/stop until I'm in a city and in a traffic jam....

 

I'm not saying they aren't happening - but I'd guess that every time I've got close to provoking one a trip comes up with a couple of hours on the motorway so the regen wouldn't be apparent/would be passive (2000'ish rpm, 130kph, >100C oil temp for 2 hours).