DPF regen - hot turbo

[patrickhorton]

170TDi - Noticed that DPF auto regen seems to continue even when the car is idling if the regen cycle is not complete. If you lift the bonnet during a regen the amount of heat around the turbo is tremendous.

I reckon it must be bad news for the turbo if you switch-off mid regen cycle. Everyone always goes on about cooling the turbo after a fast run - this is impossible with the regen on.


Yesterday I could tell a regen was underway when I got home. Left the car idling for 10min and regen continued - still loads of heat. Plugged in VCDS to confirm and took the car out again till it finished (20min and 15miles later). Turbo outlet temp 800degC for whole time then dropped back to normal when finished.
It seems crazy to switch off and cut the turbo's oil supply when it is 800C. It's also pretty crazy to go driving around til a regen finishes...

Can anyone explain that it's ok to just switch off?:confused:

[Adman]

I have the same engine. How do know when the regen is underway?

I just try and take it easy when i know i will be switching the car off

Ad

[randall977]

Ditto - do you need a VCDS? I've never noticed any excessive temperatures under the bonnet...

[patrickhorton]

I have the same engine. How do know when the regen is underway?

I just try and take it easy when i know i will be switching the car off

Ad

I notice a slight roaring noise with the window down as I gently accelerate in low gear through 1200-1500revs. Most of my journeys are 12miles/30min. As the regen only starts with a warm engine and then takes 20min or so, it almost always will still be doing it at the end of my journey. When I switch off and get out of the car everything sounds hot - exhaust tinking as it cools. Also the tail pipe may be very hot to touch; noticeably hotter than after a normal run. Drive characteristics are also a bit different slightly less willing overtaking and slightly less smooth light load acceleration.

Using VCDS, measurement blocks 75 show turbo outlet and DPF outlet temperatures and a % figure for how blocked DPF is. During regen, the turbo outlet is held very steady at 800degC. If the revs are low, or the engine is slowing (accelerator backed off & so no fuel input) the temperature drops sharply - presumably regen is paused. With no regen (normal running) turbo outlet temp generally varies between 300 and 600 depending on load. The % blocked figure falls slowly to around 10% during the regen.

Patrick

[patrickhorton]

Proved that DPF is definitely end of life. This is shown by a value for ash content of the filter read from VCDS/VAGCOM.

With nothing to loose, I've taken a look inside the DPF and done a few modifications:D...

Watch this space if anyone wants to know if my cunning plan has a happy ending.... Now where did I put those lucky socks?

P.S.
Thread started in VCDS section for advice of setting values in ECU for new DPF.

[a8 tech]

lol

[patrickhorton]

The method in my madness was to open up the DPF and grind the end off the matrix to open up the clean outlet channels. The ash in the incoming channels was clearly visible after this - like red fine red sand and impossible to flush out. The idea is that by leaving the matrix in place, the back pressure and temperature differentials of the DPF show look similar to a new one and fool the ECU. The last thing is that the matrix should still function like a cat to burn off hydrocarbons - I don't really want a smelly exhaust. Soot will no longer be filtered but some will stick to the dpf walls which should burn off on the short, timed regen which should happen every few hundred miles.

Done about 70 miles with modified DPF and waiting for the warning lights to appear...
From VCDS I can see:

Soot loading has fallen to zero.
Differential pressure was 28mBar at idle now 7mBar. On the road anything from 50 to 600mBar, now 20 to 60mBar.
Done some logs before and after but not turned into graphs yet.

No regens yet. Should be a scheduled one every 300 or 400km. That could be interesting as it tries to get soot level down which is already 0.

I think the soot figure is low/off the scale as the stored ash value for the old filter is very high. The new filter should still soot up a little and should give the regen cycle some scope for a reduction in measured soot. But it is expecting to see a lot more back pressure all the time due to calculated ash. If I can reset the ash value to zero (new DPF) maybe all will be well.

Disappointingly, economy is not really much better. Getting 39 on 12mile run to work but this figure was a real struggle before.
Power delivery is a bit smoother but doesn't seem much quicker. Difference is i can give the car some stick now without provoking a regen. Before I got a regen started almost every time I put my foot down - which then made it run like dog.

Other things - I'm not seeing any smoke out the back and exhaust smells pretty clean. I now know the engine's not smoking badly so if worst comes to worst can always fit new DPF without clogging it - that was one of my worries.

If I get a bit more confidence ll is well I'l post a few photos and VCDS graphs.

Patrick

[a8 tech]

Check the injector fuel quantity and the valve timing as well because if the belt has been replaced and not aligned 100% on the camshafts this alters the critical timing and fueling.The engine will run the same but the valve timing angle required for dpf regen will not allow the dpf to reach the correct heat range.

[patrickhorton]

Not sure how to know if injection quantity is ok. Plenty of VCDS blocks to show quantity but don't know if right or wrong. Cam belt done 60k ago (12months) - can't imagine the effects of mistiming would take this many miles to show themselves. Presumably valve timing is a mechanical check? Don't mind doing this.

Car running lovely today averaged 44mpg of four mixed 12mile runs. This is what I was hoping for. Perhaps it's just the nice spring weather??

Regarding temperatures for regen - 800degC was always held rock solid during regen. Presumably this is the heat range referred to.

Another point of interest... a reason for sorting the DPF was rising oil level. Drained half a pint about 500miles ago and it returned to the same high level so took out a bit more last weekend and now it's holding steady. Theory is this was due to overfrequent DPF regen. Will keep an eye on it and will give it an oil change once DPF business is settled.

Patrick

[a8 tech]

Ok the timing should be fine but if the oil level increases on the dip stick then this is a sure sign the tandem pump is leaking causing fuel and oil to mix which either returns oil to the fuel tank or fuel into the sump

[patrickhorton]

Brill - failed injector, DPF finished, maybe tandem pump too... All I need is for my BRD engine to have chain oil pump?? It better be a gear drive. How many more common and expensive faults has the 2.0TDi got?

Rant over. Sorry about that. Cheers for the advice anyway.

So if I check diesel return to tank is clean the tandem pump could still be leaking? Sounds like it would be more difficult to check if it leaks to the sump other than what you say about oil level. For now I'll keep checking the level.

Patrick

[a8 tech]

Why do think I drive the 8 valve 1.9 tdi.
If the oil level increases then its leaking but if you inspect the fuel lines or filter there will always be soot content which darkens the fuel and only by emptying the filter can you assess if excess oil is present.

[patrickhorton]

Is the pump about £300 and is it easy to fit? Do you recommend genuine VAG part or other?

Can't see why soot gets in fuel lines. Does it blow between the injector and the head into the fuel return passages?

[a8 tech]

Can't see why soot gets in fuel lines. Does it blow between the injector and the head into the fuel return passages?


Spot on.

[patrickhorton]

That's interesting as I reckon it also leaks the other way. When the car's just done a regen, the next cold start usually does a kind of missing for about the first three seconds. After it's had a couple of runs, it doesn't do it. This has happened since I changed the injector. I think the replacement one isn't seated quite perfect (like you warned a while ago). When there' s a bit of soot in the head it blocks the leak but the high temp of regen burns it all off and allows it to leak again. It doesn't seem to do it with modified DPF as there have been no regens.

Better call it a day now or I'll bore you all stupid with my ramblings.

Patrick

[a8 tech]

Patrick, out of interest what is your occupation?

[vwcabriolet1971]

800deg C is red hot !
How many unattended cars are going to catch fire ?

[a8 tech]

The temperature will only rise to 800 deg C in regen mode but if you force the ecu value to show a invalid content then the dpf could melt.

[patrickhorton]

Patrick, out of interest what is your occupation?
See my page.

[patrickhorton]

300km regen done today. Is this the last big milestone for the modified DPF?

On way to work this morning I noticed a DPF regen (mileage about 190miles since refitting DPF). Nothing like as rough as they used to be though. Smooth through 1600revs which used to be really twitchy. From what I could tell it went on for about the last 10minutes of 12 mile journey. Couldn't be sure it was completed and so half expected it to do it again tonight.... but it didn't.

VCDS now shows 35km since last successful regen and rising. So I guess this was the 300km regen that I have read about (see attached pdf for "mileage controlled regen"). The standard software calls one every 300km if no other need to regen occurs. My local dealer didn't know this function existed.

So, am I out of the woods? Quite happy to have a short regen a couple of times every tankfull to keep everything clean. If it lasts a thousand miles, I'll recommend this fix to anyone faced with a £1500 DPF bill. There will be many people out there in this boat as the miles start to clock up on these TDi 170's. How many 120k+ milers are there out there?

The choices are:
1. New DPF £1000 + labour
2. DPF off remap + new straight through/hollowed out standard downpipe £1500/£500.
3. Modify the DPF matrix. Labour only + £105 ash mass ECU reset at dealers.

(Still planning to get my ash mass reset done as it keeps the VCDS readings sensible - soot values are off the bottom of the scale at the mo. I am told it is not possible with VCDS/VAGCOM as the adaption channels are not known)

I'll be happy to pass on more detail to anyone who wants to give this a go.

Thanks for listening folks!

Patrick

[a8 tech]

http://wiki.ross-tech.com/wiki/index.php/Diesel_Particle_Filter_Emergency_Regeneration

[patrickhorton]

Since this thread's reared its head after a some time,here's an update on the modified DPF....

5000 miles in and things seem to be running as they should. Until last week a regen occurred every 200miles regular as clockwork. The only time it misses is on a long motorway journey when it appears to do a different kind of regen (stage 1?). Ash mass viewed on VCDS has carried on climbing slowly as it is calculated from mileage (85 in March, 88 last week). Soot loading sits at a constant minus 27% as the ECU expects there to be more backpressure than there is due to calculated ash. Driving during regen has been predictably notchy at 1600rpm but not a big issue. All other times its pretty normal.

Last week went to Audi Stafford for service and MOT. The guys there reset the ash mass to zero free of charge and loaded latest software 9973 (software info from A8tech, thank you). Three cheers Stafford Audi for good service.

Car drives quite different on new software but that's another story. Waited to see what the 200mile regen felt like with new software but it now seems to have been delayed . VCDS shows 394km since last regen (246miles). Either this is due to ash mass value or software. Watching with interest to see what happens.

Biggest snag has been the regular regen which is far too frequent for my liking. Perhaps the new interval will be more acceptable.

Before the DPF mod I reported oil level rising to scary levels. After the mod the oil level falls about 1/2 litre every 2-3000 miles (pretty normal). This was obviously really bad news before. The engine must have been burning oil same rate as now but was being slowly diluted with diesel during excessive regens. Various service schedules I've seen list a check of DPF ash at higher mileages so that DPF can be replaced when at end of life. If owners are going to independents as their cars get older this will probably be missed.

So if anyone fancies giving it a go, this method of DPF-off works for 5000miles.

Patrick

[mini-mad-matt]

Hi Patrick,
Can I just thank you for sharing your excellent knowledge of this subject.
I have a few questions, not related to the modified DPF, but just to the standard regen cycle.
I've owned my car now for a month and as you know from other threads, I've had a few niggly problems with it. (Fuel filter seems to have fixed it)
I've done 2300 miles in it which apart from me thinking it had low power, have been totally smooth.
How often will the DPF normally do a regen?
The reason I ask is that I've never felt anything out of the ordinary until today. I have driven from Manchester to N.Ireland, and was about 30 miles from Stranraer and stuck behind a couple of trucks doing 40. I was in 3rd and noticed that the car was really jerky, almost like a petrol engine missing. Even my wife in the passenger seat could feel it. Thinking it might have been the regen, I drove it to keep the revs as close to 2500rpm as I could. It lasted about 15 minutes and then normal service was resumed, and I arrived at Stranraer. I opened the bonnet to see if I could feel the extreme heat, but I couldn't really tell. The rest of our journey in Ireland was perfect. When it did it, there were no other symptoms other than the missing effect. Not sure about power being down as I was scared to open it up whilst it was doing it.
Would it be likely that this was just a scheduled regen?
Thanks in advance,
Matt

[patrickhorton]

Sounds like it to me. The give-away is the fact that after a certain time the car just switched back to normal behaviour.
Unless you opened the bonnet during or straight after a regen, the heat level would be normal. An easy way to confirm a regen is that the tail pipes become almost too hot to touch after about 5 mins of regen, even the shiny trim bits get hot. Normally the tailpipes only get slightly warm.
Scheduled regen used to be every 200miles on mine but Audi have reset something in the software for me and now it is extended (to what, I don't know).
Cheers Patrick

[theskyfox]

Sounds really good. This is a great thread. I've been quoted £700 for a DPF delete + remap. Don't intend doing it unless I really have to or the DPF fails though.

-Andrew

[a8 tech]

Sounds like it to me. The give-away is the fact that after a certain time the car just switched back to normal behaviour.
Unless you opened the bonnet during or straight after a regen, the heat level would be normal. An easy way to confirm a regen is that the tail pipes become almost too hot to touch after about 5 mins of regen, even the shiny trim bits get hot. Normally the tailpipes only get slightly warm.
Scheduled regen used to be every 200miles on mine but Audi have reset something in the software for me and now it is extended (to what, I don't know).
Cheers Patrick


The update allows the better management of dpf regens with the criterion changed so more passive regens occur instead of the previous software version which required more frequent driver regens and in some cases only emergency regens.

I have found recently a few failed driver dpf regens caused by incorrect valve timing on the exhaust cam after independents changed the cambelt so ash content reaching emergency regen and no means to regen as per usual method

Check mvb 4 zone 4 must be around 2.5 at idle, if its out then the exhaust temp will not be reached for regeneration

[patrickhorton]

...... independents changed the cambelt so ash content reaching emergency regen .....

Glad to see this pulling in some useful warnings for folks. You would never think changing a cambelt would kill the DPF.
Likewise you won't get useful software updates without going to the dealer.....

Patrick

I am sure A8 knows a darn sight better than me but for the record, "ash content" can only build up over tens of thousands of miles. Soot content can fill the DPF in less than 50 miles.

[a8 tech]

Another problem which prevents regen by the driver is the clutch switch.

The switch shows no fault code however if you have cruise control then it prevents the operation but without cruise the problem goes undetected.

mvb 5 or 6 shows the switch positions and the clutch switch should change from 0 to 1 pressed unpressed.

The engine ecu needs to see the switch status to and rpm plus dpf pressure sensor readings and dpf filter upstream and downstream temp to allow the burning process and check the loading of the volume of ash left in the filter.

There are lots of little things which prevent dpf regen and there are a few awkward problems I have dealt with

The valve timing is now fairly common after a cambelt change, the engine will run fine so its overlooked by the driver and tech but mvb 4 zone 4 tells the true story.

[patrickhorton]

Got the first scheduled regen today after installing latest software 9973. Occurred at 273miles. [Remember that effectively I have no DPF so this is not due to soot build-up; it is purely done by the ECU as a timed precautionary measure.] So there has been a change from old to new software.

Since the mileages are not round numbers (miles or km) maybe the trigger is amount of fuel burned since last regen, not distance driven. This is recorded also in the same meas block on VCDS. I'll check this figure over the next few regens.

Driving is much smoother during regen now to the point that I doubt drivers would notice it happening. The twitchyness at 1600 rpm has gone. It is only really detectable by small changes in profile to the engine's "characteristic" torque curve.

Another thing I plan to check is the temperatures during regen - incase it is less severe now (lower temp).

Patrick

[patrickhorton]

Since the mileages are not round numbers (miles or km) maybe the trigger is amount of fuel burned since last regen, not distance driven. This is recorded also in the same meas block on VCDS. I'll check this figure over the next few regens.

Another thing I plan to check is the temperatures during regen - incase it is less severe now (lower temp).

Patrick

Second regen at 273ish miles. This time put VCDS on. End of regen was at exactly 460km (287miles). I guess it must be mileage related then.
Exhaust temp is still exactly held at 800degC during regen.

So, software 9973 gives another 70miles between regens and a much smoother drive during regen. Nothing else noticed.

Patrick

[Zaz]

Was on a motorway run the other day and the DPF regen light came up on the dash. This was probably the second or third time in less than 6 months. So I slowed down, shifted into 5th and set cruise so that the revs were at 2k. Time passed and the light was still on. After some time the coil light started flashing, the emission control system light came on and the car went into pathetic mode...(that would otheriwse be known as limp mode). I continued my journey to where I was going and came back 80 miles home later in the evening....in wimp mode.

Car went to Audi yesterday who diagnosed it to be the DPF pressure sensor. Duly fitted today they also ran a forced regen and software update. Pressure sensor cost £45+vat but the labour was £293+vat for over 2 hours.......total bill £393.....

I so love my car................been looking at BMW 330/335 diesels lately...I think I'll step up the campaign.

[theskyfox]

To be fair, I think itd be a bit wrong to blame the car for it. The DPF is only on the car because of the EU emissions laws....all Diesel cars are fitted with DPFs now. Thats a lot of money you spent there getting it fixed...for what its worth, for about £200 more than that you could have had the DPF totally removed by an independent specialist if you really hate them that much...and you don't fail your MOT by doing it.

[Zaz]

I guess so....oh well. Collected the car yesterday, it's running well now and drives different too which is probably a result of the software update (?). Will see how it goes in the coming weeks and also see what will go wrong next......... :-(