Hello Raisbeck, don't often disagree with you about anything. But, Mike is correct in as much as we are all talking about the effect of soot on the economy of the engine. But I can see why you may have thought otherwise. As you are most likely aware, the DPF forms a central part of why economy seems to be so affected on 1.6cr engines after regening and it regens more I've found if the engine is driven in higher gears at lower revs. I've realised this after studying owners with this engine, and my own bench testing on our new diesel engine development, on which we are running a NOX cat too. Driving at lower revs, light throttle etc soots the engine internals, which then gets passed onto the DPF. Incidentally, the DPF unit is a combined Cataylist & DPF in one. All diesel engines are required by law to have a catalyst, just as petrol cars are, to reduce the Carbon Monoxide and convert it to Carbon Dioxide and water, but you know all that. What I and my colleagues have discovered is that soot builds up remarkably quickly in the DPF when on light throttle for very long periods of mixed driving. Back pressure can increase alarmingly quickly on some engines and drastically affects fuel economy. Although, I agree with your statement that the DPF itself is a completely non issue for mostly everyone. They don't normally give and trouble at all and seem to last the life of the car or truck when you look back over history, no matter what type of DPF it is (paper disposable ones excepted). So people shouldn't be worried by the AA report, just be aware of it.

Hello again,

Interesting post. If you talk about back pressure increasing alarmingly, presumably this is when the DPF starts getting sooted up? If this drastically affects fuel consumption, it seems to be doing th exact reverse on my car. The car gets the best economy when the DPF is beginning to soot up. Immediately after a regen, MPG is poorest and it gradually gets better till the next regen. Isn't this the reverse of what you're suggesting? Any idea why it occurs this way. It seems rather counter intuitive to me and I would expect the engine to perform best immediately after a regen.

Yes Mike. As the DPF soots up it restricts the exhaust gas flow. This increases the pressure in the exhaust between the exhaust manifold, and DPF. This can, if very bad, affect the way the engine runs by interfering/altering the way the engine breathes and some other functions. In reality, the manufacturers will have allowed for the engine to run smoothly with some sooting up of the DPF so most of the time economy should not be affected too much, but there is some effect. The engine is running at it's best and most effiecient usually after a regen, but this may not show up on your trip computer for a while so you are not always getting the true picture relying on the computer.

OK, October to March my normal commute to work is 5 miles each way in a semi rural area with a max speed limit of 30mph all but one 1/4 mile stretch of 40mph. I then do lots of sub 20 mile round trips to the shops and taking the kids where they need to go.

From the end of March to October I then add 155 mile round trips about twice a month across country on fast B roads (50) and dual carriageways (70).

I average around 12500 miles a year of probably the worse type of driving for a DPF.

I have had a GL2 with a DPF and only had the funny smell twice, and no other regen problems - other things kept breaking.

I am now driving the 1.6 105 and so far no problems with regens. I did get a bit of a smell when it was new.

I have only got just over 3000 miles on the clock at the moment and have just come into miles on time. On my way to work I am getting between 44 and 50mpg depending on temperature and traffic, on a run fully loaded I get around 58mpg.

Around town I drive like a granny and then when I get to a stretch of dual carriageway I tend to blast the car in 3rd and 4th, Did the same with the GL2. On the motorway/dual carriageway I cruise at around 70 in 5th.

Both cars have been run in in the same way- ops I did not bother just drove them.

Raisbeck's has a GL1 with a PD engine and the time span between regen's is set differently to the CR engine. My understanding is that the PD engines produce more soot and regen more often than the CR.

Yes Mike. As the DPF soots up it restricts the exhaust gas flow. This increases the pressure in the exhaust between the exhaust manifold, and DPF. This can, if very bad, affect the way the engine runs by interfering/altering the way the engine breathes and some other functions. In reality, the manufacturers will have allowed for the engine to run smoothly with some sooting up of the DPF so most of the time economy should not be affected too much, but there is some effect. The engine is running at it's best and most effiecient usually after a regen, but this may not show up on your trip computer for a while so you are not always getting the true picture relying on the computer.

Hello,

The interesting thing here is that whilst I'm relying on trip computer as thats the only thing available at that level of granularity. However, I'm talking about readings from the individual trip, not over mutliple trips. So, this should be for the one trip. The other thing is this isn't just for a period of time (as say the computer averages over 50 or 100 miles), but over the whole team. The majority of the change occurs in the first 100 miles after the regen, but it does still get slightly better all the way to the next regen. The manual says the computer averages over 50 miles, so even if it is averaging over 50 miles, this doesn't explain the changes. For some bizarre reason, my car (and a couple of others listed in this thread) seem to get better the more soot there is in the DPF. Can you think of a reason, as I'm stumped?

Hi Mike

Sent you a couple of PM's in response to your post to me. Appears you have not seen them yet.

Not really Mike. More backpressure than normal (some back pressure is required to maintain all of the freshly injected diesel charge at TDC valve overlap) normally leads to less mpg in a car like the 1.6cr and after a regen the mpg should return to normal instantly, but that won't show up on the trip right away.

My mpg certainly didn't return to normal after a regen. It was much lower (I started the average as soon as I got on the motorway). I struggled to average 50mpg at 70mph for about 100 miles.

Hello Raisbeck, don't often disagree with you about anything. But, Mike is correct in as much as we are all talking about the effect of soot on the economy of the engine. But I can see why you may have thought otherwise. As you are most likely aware, the DPF forms a central part of why economy seems to be so affected on 1.6cr engines after regening and it regens more I've found if the engine is driven in higher gears at lower revs. I've realised this after studying owners with this engine, and my own bench testing on our new diesel engine development, on which we are running a NOX cat too. Driving at lower revs, light throttle etc soots the engine internals, which then gets passed onto the DPF. Incidentally, the DPF unit is a combined Cataylist & DPF in one. All diesel engines are required by law to have a catalyst, just as petrol cars are, to reduce the Carbon Monoxide and convert it to Carbon Dioxide and water, but you know all that. What I and my colleagues have discovered is that soot builds up remarkably quickly in the DPF when on light throttle for very long periods of mixed driving. Back pressure can increase alarmingly quickly on some engines and drastically affects fuel economy. Although, I agree with your statement that the DPF itself is a completely non issue for mostly everyone. They don't normally give and trouble at all and seem to last the life of the car or truck when you look back over history, no matter what type of DPF it is (paper disposable ones excepted). So people shouldn't be worried by the AA report, just be aware of it.

Cant be agreeing all the time, where is the fun in that !!

I completely agree that pootling about is going to gum up your innards. A good run , even an Italian tune-up is always a good thing for a diesel. My point which I failed to put across was that thinking anything you do in how you drive will assist in keeping your DPF clear is a waste of time. Its an intelligent monitored system and your just a passenger to it. Passive regen on an active regen designed DPF is minimal.

My regen frequencies are completely normal. I chatted with other GL1 drivers and my dealer, its all as it should be. Either my DPF is smaller with less capacity or because the PD isnt as efficient at regen as a CR engine they opted for a little and often approach to regens. I dont agree that a PD produces more smoke. PD injection pressure is much higher than a CR and I would go so far as to say in GL1 guise its more efficient than a CR as well.

Interesting about CR economy being worse after its cleared the DPF. Wild guess but maybe the car can use dpf diferential pressure to ofset economy display. Otherwise most owners may have heart failure at the fuel used during regen. After regen with clear dpf the car reverts to unadjusted economy reading, the balance is just not perfect between actual and offset.

My economy is unchanged no matter whats going on with the DPF. If anything it improves just prior to regen when the egr valve shuts.

My dealer gets lots of reports from customers about poorer economy from the CR. Also many people with VAG CR engines across the ranges report issues with economy from this engine. Seems smoothness and driveability have a cost. My PD is a noisy, vibrating rattly little tractor of a thing but I wouldnt swap it for the VAG CR.

As for cleaning additives, that BG stuff will be going in my car in the future , of all the snake oils out there its the only one that gets repeated good feedback.

Edited 24 April, 201214 yr by raisbeck

Not really Mike. More backpressure than normal (some back pressure is required to maintain all of the freshly injected diesel charge at TDC valve overlap) normally leads to less mpg in a car like the 1.6cr and after a regen the mpg should return to normal instantly, but that won't show up on the trip right away.

You sure about that ? If it was a 2 stroke racer needing back pressure to maintain fuel charge in the cyclinder then yes, but on a 4 stroke diesel I cant see back pressure at valve overlap having such a significant effect. If anything back pressure will incur pumping losses robbing horsepower.

Edit: Besides valve overlap occurs on the exhaust stroke close to TDC. No fuel enters with the intake air and fuel is only injected close to TDC on the compression stroke. I dont buy that as explaining the loss of economy after regen

Edited 24 April, 201214 yr by raisbeck

You sure about that ? If it was a 2 stroke racer needing back pressure to maintain fuel charge in the cyclinder then yes, but on a 4 stroke diesel I cant see back pressure at valve overlap having such a significant effect. If anything back pressure will incur pumping losses robbing horsepower.

Edit: Besides valve overlap occurs on the exhaust stroke close to TDC. No fuel enters with the intake air and fuel is only injected close to TDC on the compression stroke. I dont buy that as explaining the loss of economy after regen

You make a very good point Raisbeck. But, yep, quite sure. But sorry if I confused you, I didn't make my point properly, hardly ever do!! . All engines these days need back pressure to function correctly, petrol or diesel, two stroke or four stroke. If like the CR engine it's direct injection rather than Ricardo Comet, the back pressure simply holds in the freshly inducted air and/or any pre-charge added just at the end of the exhaust stroke and at TDC prior to the induction stroke when both valves are open, and before the next charge at other various points in the cycle. The main purpose of valve overlap is to allow the new incoming air or charge to 'scavenge' (push out) the last of the exhaust gas from the combustion chamber. That's the only way to get it fully clean. It works in two strokes and four strokes, but relies on the back pressure to stop too much of the new charge exiting via the exhaust port. Too much back pressure means scanvenging doesn't take place properly so you get less smooth running and less efficiency. So a partially sooted up DPF won't help mpg's or performance. I think I'm right in saying the 1.6cr injects upto 5 times per cycle and 6 when regening. But haven't read the book on that one. That's the beauty of mulitpump cr engines, lots of chances to inject and mix ready for a complete burn. And it's a shame the PD engine couldn't be modified to carry on. It's a dirty engine compared to the technically more advanced cr although it's more efficient fuel economy ways as you indicate.

Edited 25 April, 201214 yr by Estate Man

.....

For everyone's benefit concerning your last above post, your car was just doing a default regen I'm sure. These are included in the common rail engines to make certain you get the best life from the DPF and the fuel economy stays at a good level. As you have found out, this causes a temporary lowering of the average economy for a few minutes as the computer takes account of the extra fuel used to regen.

I never realised that they did 'default' DPF regens. I can live with that, but I don't understand how the fuel consumption was so bad for 100 miles after it!

......

My mpg certainly didn't return to normal after a regen. It was much lower (I started the average as soon as I got on the motorway). I struggled to average 50mpg at 70mph for about 100 miles.

xrevuk,

As I've posted numerous times like you I get at least a 12% mpg drop for 100 or more miles after a regen, and my normal regen interval is about 300 miles.

Indeed a couple of times over the coldest part of winter I didn't see the mpg jump up at all between regens, which were at slightly more frequent intervals. The cold temperatures, winter diesel etc lowered the overall mpg significantly but I would still have expected to see my 'normal' pattern of a relative increase when monitoring the single journey mpg.

EstateMan,

Like 'xrevuk' I can understand ' a temporary lowering of the average economy for a few minutes ' after a regen but not for so long/far after.

Pretty sure it's a software thing Delta. It can't really be anything else that I'm aware of.

Pretty sure it's a software thing Delta. It can't really be anything else that I'm aware of.

I saw a post you made in another thread, about a sticky EGR valve, is this possible?

Yes, any egr can stick if driven around too slowly without excercising the engine a bit. But your symptoms don't really suggest that, and mostly you get a light on the dash come on if the emmissions go through the roof such as if the valve sticks closed, or even fully open.

Another thought for debate ......

For those of us who for whatever reason experience significantly higher fuel consumption for 100+ miles after a regen could we get a MOT emmissions test fail if the test was during this higher consumption period because the engine is running less efficiently?

I also ran vpower diesel in the same engine, until I sold both my fabias for a golf lol

Traitor ;-) lolz

Another thought for debate ......

For those of us who for whatever reason experience significantly higher fuel consumption for 100+ miles after a regen could we get a MOT emmissions test fail if the test was during this higher consumption period because the engine is running less efficiently?

No! The MOT test is just a smoke test for diesels. Your DPF prohibits virtually all smoke.

No! The MOT test is just a smoke test for diesels. Your DPF prohibits virtually all smoke.

In jest:

Would a shot of AdBlue help?

Only jealous of these problems: after having my car for 5 weeks it is again in the garage having failed to start!

Edited 25 April, 201214 yr by punyXpress

Puny, that's tough! Sorry to hear you have a problem. At least it's all covered and you'll get her back ready to roll. Let us all know if you can what they find wrong. It might be useful for us all to know. Ta!

Collected 21 March. Salesman on introduction to car said interior light was at wrong setting. Drove 1 mile home, brimming tank on way. Spent next morning checking odds & putting clutter in.

23 March wouldn't start. Dealer used battery booster & did about 20 miles with 1 stop.

Week later wouldn't start agai, this time with instrument lights flashing. Taken to dealer for 'proper' charge.

Used couple of times over next 2 weeks on reasonable runs, then weekend 14/15 April for couple of 60 mile brisk runs.

Tuesday 24th, failed to start again & back to dealer. Although no battery fault shown on diagnostics, a new one to be fitted tomorrow. Worrying that no definitive fault yet found but will be glad to get it back and use it.

My 2003 TDi Estate had very few problems, but that was a Mk1!

Apologies for long spiel.

I've been monitoring my fuel over the past couple of days but looks like it may have been off due to a slow puncture. I've lost 7PSI from one tyre in 1 1/2 days, so can't really say I was getting accurate readings.

Don't know how much that would have effected mpg anyway.

Yes, would affect it, again not sure by how much.

Collected 21 March. Salesman on introduction to car said interior light was at wrong setting. Drove 1 mile home, brimming tank on way. Spent next morning checking odds & putting clutter in.

23 March wouldn't start. Dealer used battery booster & did about 20 miles with 1 stop.

Week later wouldn't start agai, this time with instrument lights flashing. Taken to dealer for 'proper' charge.

Used couple of times over next 2 weeks on reasonable runs, then weekend 14/15 April for couple of 60 mile brisk runs.

Tuesday 24th, failed to start again & back to dealer. Although no battery fault shown on diagnostics, a new one to be fitted tomorrow. Worrying that no definitive fault yet found but will be glad to get it back and use it.

My 2003 TDi Estate had very few problems, but that was a Mk1!

Apologies for long spiel.

Interesting start. All car manufacturers and dealerships rely far too much on diagnosis by the onboard computer and use this as an excuse for mechanics who are little more than fitters. Basically, if the computer doesn't say yes, it isn't so. Even though computer management systems can only see a fraction of actual errors. They then dismiss the customer saying everything is OK. I've forwarded on the information I got from Astra1 as evidence that, contrary to their comments, my problem has been reported before. I've yet to get an intelligent response. I did point out that either Skoda technical are incompetent at looking up symptoms, or they know it's happening elsewhere and are simply denying it. I'm getting constant messages from customer services asking if I'm now happy and can they close the call.

To anyone thinking of buying a Skoda, I would say don't. Not because their cars may not be good, or even a majority of them, but because in the event of a problem, Skoda customer services are the most incompetent, uncaring and least customer focused people I have ever dealt with. They deny problems have been reported before when they have. Their sole interest is in closing the call. They offer absolutely no help to the dealership trying to find the problem etc.etc. I certainly won't be buying a Skoda again unless something dramatic changes.

Its not just Skoda that have such problems.

To anyone thinking of buying a Skoda, I would say don't. Not because their cars may not be good, or even a majority of them, but because in the event of a problem, Skoda customer services are the most incompetent, uncaring and least customer focused people I have ever dealt with. They deny problems have been reported before when they have. Their sole interest is in closing the call. They offer absolutely no help to the dealership trying to find the problem etc.etc. I certainly won't be buying a Skoda again unless something dramatic changes.

Just registered on here to say this. I think you're expecting far too much, Mike. As you said in your thread at the start, you're replacing a Euro3 engine with a Euro5. These Euro5 engines are complicated beasts, with so many emission controls to try and satisfy stupid European taxes.

All diesels need a good while to bed in, particuarly VAG diesels. They don't generally start going properly until north of the 50k mark.

Anecdote: One of our pool cars at work is an old Passat B5 with the 130hp 1.9PD engine. I've done long trips in that, filling brim to brin and got well over 65mpg. Not bad for an old junker with 90k on the clock, and a 5 speed box. I've then gone on to do the exact same trip, in basically the same time in a 1.6TDCI Focus (90hp). The Focus with 10k on the clock only got 44mpg. There's progress for you.

Personally, I wouldn't touch a diesel engine car that's less than 10 years old. I had so much trouble with commonrail diesels. Now I drive an old petrol Mondeo, and the engine is sweet as a nut at 72k, and apart from filters and oil and one set of plugs, it's had nothing. It's run perfectly. It gets a consistant MPG all year. True worry free motoring, and it's cheap to run as I only do 6k a year.