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Audi A4 TDi 170 BRD 2006 - Lazy boost, black smoke - Fixed #

Posted by Craig Shiraz on November 19, 2012, 4:27 pm

Year of Manufacture *: 2006
Engine Size and Code *: 2000 BRD
( Optional ) ECU Type: Siemens PPD
( Optional ) Scanner Used: VCDS
( Optional) Fault Codes: None

Hi guys

Vehicle in with complaint of black smoke and very sluggish below 2500rpm, then takes off like a rocket.

-We have manually checked operation of VNT actuator with MityVAC, moves clean and free.
-Checked actual position of VNT (block 43) reported in VCDS whilst MityVAC'd and showing 10%-90% or so.
-Checked and cycled EGR via VCDS and saw approx 80mg/s difference on MAF
-Cycled N75 and monitored movement of VNT rod, showed full travel on/off as VCDS cycled test, change of 50mg/str at 1400RPM, so no obvious issues with N75 control or vacuum circuit but VCDS states this needs to be at least 80mg/str ( and normally see upto 150mg/str without noticable issues )
-smoke tested with no noticable leaks.

During road test the vehicle smokes heavily and is very sluggish below 2500rpm, then literally takes off like a rocket.

I have quickly made a chart showing the problem since it is easier to read. Please note this vehicle is remapped, so values will differ from a stock engine. Take a look at the charge pressure control duty cycle against the actual position, and corresponding specified vs actual boost pressure.

During some searching, alot of people are mentioning altering the dead stop of the VNT actuator arm, apparntly its a common complaint which causes the vanes to 'shut' resulting in high back pressure until higher RPM when the backpressure overcomes the vanes and forces them open.
I havent had to do this before so hoping there is something else i can check first, or someone on here can verify this change?

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Piotr Sokolowski <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1848' width='330' height='300' border=0 style='border:none;'> on November 19, 2012, 8:08 pm, in reply to "Audi A4 TDI170 - lazy boost, black smoke"

when did happen? You are saying car is remapped. Maybe after car remap? For me sluggish under 2.5 k is egr not closing properly leaving .5 mm gap . Try put orginal file into it and blank egr . That would wliminate few things

Link: http://www.pandpauto.co.uk

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 19, 2012, 9:36 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"

Hi Piotr

Vehicle remapped with ourselves a few months ago, no issues until this weekend.

I can blank EGR and try in the morning.

BTW, sluggish is more like 'struggles to accelerate and smokes heavily'

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Mark Carter <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1428' width='330' height='300' border=0 style='border:none;'> on November 19, 2012, 10:12 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"

Your AMM readings and your boost do not tally.

Mark

Modern cars, Its all wizardry and witchcraft

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 20, 2012, 8:24 am, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Craig Shiraz

Are you looking at the wrong blue line Mark?

MAF increases in line with boost...

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by James Eardley <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3143' width='330' height='300' border=0 style='border:none;'> on November 20, 2012, 11:10 am, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"

Hi Craig

Just a thought is the throttle flap working correctly.

So,
I can see the accel pedal being pressed, the blue line that rises shortly after, is this the specified boost?

I may have made the same mistake as Mark when I looked at it last night, it is a bit clearer on my phone.

If I am reading the graph correctly, it seems you have got a serious air flow problem at low rpm?

What does the MAF actual look like against MAF desired?

Have you got a scope?

Can you scope,
Accel pedal position
MAF
Boost

Cool graph btw, what was this done with? VCDS?

Cheers
James

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Mark Carter <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1428' width='330' height='300' border=0 style='border:none;'> on November 20, 2012, 11:27 am, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Mark Carter

If your scaling is correct then your AMM reading (bottom line)is low with regard to your boost figures (next line up)

If I am reading your graph incorrectly feel free to correct me.

Mark

Modern cars, Its all wizardry and witchcraft

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 20, 2012, 12:00 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Craig Shiraz

Installed EGR blanking plate and problem gone, currently removing EGR for inspection and cleaning.

My sincere apologies, yes the scaling is wrong regarding the maf on the graph, 2000rpm we were actually seeing 430-450mg, and theres me thinking i was helping creating a graph

.

Thanks to all for input.

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 20, 2012, 12:03 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Craig Shiraz

Actually no, the scaling is correct on the graph...

Can i ask what airflow you would expect to see at 2000rpm and 0.3bar boost?

Understandably the EGR at fault would cause the airflow to be lower, im just trying to understand how you identified this from just looking at airflow against map?

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 20, 2012, 12:06 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Craig Shiraz

Hi James-

Graph was done in excel from VCDS log, the VCDS graphing function is not very good.

I will post another for comparison once the EGR is refitted, and close this fault as FIXED.

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by James Eardley <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3143' width='330' height='300' border=0 style='border:none;'> on November 20, 2012, 1:04 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
James Eardley

Hi Craig

'I will post another for comparison once the EGR is refitted, and close this fault as FIXED. '

That would be great

Cheers
James

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Mark Carter <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1428' width='330' height='300' border=0 style='border:none;'> on November 20, 2012, 3:48 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"

>>> im just trying to understand how you identified this from just looking at airflow against map? <<<

Fix your EGR fault (which caused your figures not to tally) and re-graph the same parameters. Study them and if it does not become clear I will assist.

Mark

Modern cars, Its all wizardry and witchcraft

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 20, 2012, 9:45 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Craig Shiraz

Will do, thanks Mark.

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 21, 2012, 3:23 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Craig Shiraz

Hi guys

We stripped the EGR and complete manifold assembly including ASV, found EGR sealing ring had dislodged itself causing EGR not to seat, cleaned all parts and refitted, problem solved.

However, Mark if you could go through what you were able to identify from just the airflow against boost pressure, and the theory behind it, im sure it will prove very useful.
I can see that there was clearly an aiflow issue below 2500rpm, but i dont understand your comment regarding MAF and Boost dont tally. Much appriciated

Below is graphed data after cleaning.

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 21, 2012, 3:31 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Craig Shiraz

Do we still have a problem with boost response?

Official figures for peak torque suggest around 1800rpm, we are around 2100rpm on this remapped vehicle.

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Tony Attwood <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3025' width='330' height='300' border=0 style='border:none;'> on November 21, 2012, 6:56 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"

Hi Craig,

>>Vehicle remapped with ourselves a few months ago<<

Did you graph this vehicle when you remapped. If so, out of interest, could you post the graph relating to Specified & actual boost at the time?

Seeing peak torque has moved up around 300 rpm I imagine you now have an output of around 220??

Cheers, Tony

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 21, 2012, 7:34 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Craig Shiraz

Hi Tony

Im not saying peak torque has shifted up by 300rpm since the remap, just a comment against factory claims, this will obviously depend on loading of the engine. I believe there was a software revision since the release of the 170ps, that limited torque low down due to issues with the DMF and clutch, every 170 i have driven has a noticable lag, IMO the 140 is a much better vehicle and at Stage 1 levels makes very simular power to a stage 1 170 model with much better response.

Stock 170ps cars in good shape on our dyno run around 167-172bhp and 250-255ftlbs, Stage 1 cars run around 185-190bhp and 290-295ftlbs. Thats not just with our supplier, we run a large variety of vehicles on club days which are tuned by other companies claiming 200+bhp. They dont make much extra power above 3500rpm over stock.

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Mark Carter <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1428' width='330' height='300' border=0 style='border:none;'> on November 21, 2012, 10:20 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Mark Carter

Thats better, the two now tally very well.

How did your study time go?

I notice from your web site(WWW.gotboost.co.uk)that you specialise in performance tuning and rolling road work, do you re-map in house or just upload and then download back to the vehicle?

Mark

Modern cars, Its all wizardry and witchcraft

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 22, 2012, 8:02 am, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"

Hi Mark

I’m sorry, I just don’t see what you’re seeing, and i'm very keen to learn as I believe this would be very beneficial.

I understand the effect of an EGR not sealing correctly at full load, the resultant effect on the VNT vanes and the displacement of clean airflow, I just cannot see what you have identified purely from the boost against maf without knowing compressor flow charts and some in depth research into flow characteristics of the turbo in question, you seem to have been able to just look at the first graph and instantly notice an irregularity in the shape of/ relationship between the actual boost and maf....

Comparing the shape of the before and after, boost and maf, they are pretty comparable, the difference being around a 3:1 delta before and a 1.9:1 delta after ((boost mbar / (maf g/str)), how could you have known what to expect without flow knowledge of the compressor in question?

I don’t want you to give me the answer, if you are prepared to help please just give me a nudge in the right direction and I will study further.

I own/run GotBoost Performance, it started as a hobby around 7 years ago mainly working with Honda aftermarket ECUs, I got pretty popular and decided the next step to be a dyno purchase, again working mainly with aftermarket ECUs on older ( simpler ) vehicles. The business has grown to a point over the years, where we now primarily take care of a range of race vehicle for clients, providing a full service from build/repair and maintenance to trackside support. Due to the current economic climate, and customer demand, we are seeing more and more OEM vehicles, we quite often get vehicles other people have given up on, I like these as it often provides an opportunity for me to develop a new skill/though process.
I still run GotBoost around my main occupation; it will always be a 'hobby' even if it is run as a business, hence my willingness to learn. I've always said that if/when I start not to enjoy it, I will pack it in! Whilst I openly admit that diagnostics is not our strongest point, we do offer honest, impartial advice and offer what we believe to be a much higher level of service compared to most others locally. There are many benefits to running a business like this without having financial commitments, added to the fact I run it simply because I want to, allows me to spend as much time as I choose with vehicles I decide to take on

Customers really appreciate our approach, and most of our return business is through word of mouth recommendations.
I am not at a level where OEM ECU modification is going to be possible in house, equipment or knowledge, although I am learning. OEM ECU tuning is a completely different ball game to aftermarket. We currently operate with a number of file developers that we have found to be reliable and provide a good quality product. You would be surprised how many 'tuners' claim to be developing their own work, when in fact they are mostly supplied through a few select people.

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Tony Attwood <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3025' width='330' height='300' border=0 style='border:none;'> on November 22, 2012, 2:31 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"

Craig

>>how could you have known what to expect without flow knowledge of the compressor in question?<<
(This is with Mark’s knowledge, so not jumping in his boots)

A bit of background first:
What relation is there to one Mg of air & one CC?

Are, as a rule, diesel engines throttled? ie an intake restriction/butterfly.
(hence James’s Question about throttle flap)

How much air will one downward stroke pull in, regardless of engine speed? (ignoring any valve overlap inertia or ‘ram effect’

Now, using only your last MAF reading & actual boost reading graph, take measurements at several points & work out the common denominator.

As your MAF & actual boost are now ALMOST perfect, you may have to round up or down VERY slightly.

Hope this brings on the light bulb.
EDIT:
The answer will be an equation of your engine configuration.

Cheers, Tony

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 22, 2012, 6:59 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"

Rounded and assuming 1000mbar atmospheric pressure.

Cc of engine - 2000
Cylinders - 4
Maximum cc of air per cylinder at atmospheric pressure and 100%VE - 500cc

500cc per stroke at atmospheric pressure and inlet temperature of 35*c = 575mg

1bar boost pressure = 1150mg/str
1.5bar boost pressure = 1437.5mg/str

Now assuming this is what you guys are referring too (please confirm) I would like to discuss further, want to check we are on the same page first though.

EDIT -
Taking this a step further and adding estimated intake temps (not logged) and estimated VE. Some figures are false, but it will prove the theory if correct

And with the fault condition present -

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Mark Carter <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1428' width='330' height='300' border=0 style='border:none;'> on November 23, 2012, 3:52 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"

Sorry for the delay in replying, it's been a busy week.
Tony's pointed you in the right direction as to how I noted your issue.

You are totally right with your maths and I only use the equation as a quick first look tool, but allowing for temperature change and VE measurements you will find that it works very well.

2000cc 4 cylinder Diesel engine should show about 500 mg/s with no boost and EGR switched off.

Apply boost and use it as a multiplier to your base value.

500 mg/s times 1.5 bar boost = 750mg/s

Rpm does not of the come into the equation because
Of the type of measurement.

If you look at your first post you will see that your air mass is well below 500 mg/s but you are generating good boost.

Now look at your second post and you will find that the air mass matches boost to the letter.

If the figures were the other way around, eg high air mass and low boost you could be looking for an air leak on the boost side. ( I know that it could be caused by many other things as well)

Regards
Mark

Modern cars, Its all wizardry and witchcraft

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 27, 2012, 10:20 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Craig Shiraz

Thanks to everyone for the input, much appriciated.

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Peter Lomas <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT5466' width='330' height='300' border=0 style='border:none;'> on November 28, 2012, 9:33 am, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Peter Lomas

Hi
What an excellent post, indeed a light did come on
Regards Peter

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Hewison <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3409' width='330' height='300' border=0 style='border:none;'> on November 28, 2012, 6:47 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"

ouch!! my head hurts now, i think ill be reading this post through a few times until I get to grips with it!

Craig

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Craig Shiraz <iframe src='https://members.boardhost.com/ukautotalk8/info/user=ukat3492' width='330' height='300' border=0 style='border:none;'> on November 29, 2012, 8:00 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Craig Shiraz

At least im not the only one who needed a refresher!!

I may actually advance this post a little further when i get some spare time, if the other guys are willing to input. I'd like to discuss the required fuel with relationship to MAF ( parts air : parts fuel ) and the effects of SOI in relationship to EGT and AFR. I have the ability to measure and log AFR and EGT ( actual not calculated )and think it would be interesting and useful in diagnostic comparing calculated values against measured values and drawing conclusions to possible fault conditions.... Im a little busy at the moment, but will get around to creating another post.

Re: Audi A4 TDI170 - lazy boost, black smoke

Posted by Mark Carter <iframe src='https://members.boardhost.com/ukautotalk8/info/user=UKAT1428' width='330' height='300' border=0 style='border:none;'> on November 29, 2012, 9:07 pm, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Mark Carter

>>> At least I'm not the only one who needed a refresher!! <<<

We ALL need a refresher on most things every now and again,

Yes more than happy to go deeper at another time.

The AFR of a diesel is a strange non linear beast at the best of times, with AMM's and Lambda's being used for different reasons when referenced to a petrol vehicle.

Mark

Modern cars, Its all wizardry and witchcraft

Audi A4 TDI170 - lazy boost, black smoke - Fixed #

Posted by Craig Shraz on February 2, 2013, 11:13 am, in reply to "Re: Audi A4 TDI170 - lazy boost, black smoke"
Message modified by board administrator February 2, 2013, 1:54 pm

Thanks for the help guys

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