IQ open loop / closed loop

struikie

struikie

Veteran Member
Joined
Oct 19, 2007
Location
Netherlands
TDI
BMW 335d E91
like my previous car (Audi A4 B5 with longitudinal AHU),
my current car (Audi B7 with longitudinal BLB) is stuttering/ shuddering/ juddering in all gear on constant speed between 1500 and 2100 rpm...

correct me if I am wrong...
the ecu compensates IQ below 1500 rpm for a smooth running/ smooth idle...
this is closed loop right?
above 1500rpm the ecu is not compensating... open loop?

it seems to me the gain of the IQ PID controller is too high, causing it to be unstable..

is there any way to adjust this P-action/ gain ??

JW
 
dieseleux

dieseleux

Théoricien -TDIClub Contributor
Joined
Nov 14, 2006
Location
Pas assez loin pour vider ma tank!
TDI
Jetta TDI 02
On my AHU i reduce shuddering by ajusting voltage map of the pump just right, no extra volt.
PID section of the pump take on old 110hp chip (i think AFN if i remember) are also good effect on shudder.
PID are very difficule to modify because is not only few number... is many table map for all possibility (idle, cruissing, accel, full trottle, over run, etc...)



Dieseleux
 
struikie

struikie

Veteran Member
Joined
Oct 19, 2007
Location
Netherlands
TDI
BMW 335d E91
dieseleux said:
On my AHU i reduce shuddering by ajusting voltage map of the pump just right, no extra volt.
PID section of the pump take on old 110hp chip (i think AFN if i remember) are also good effect on shudder.
PID are very difficule to modify because is not only few number... is many table map for all possibility (idle, cruissing, accel, full trottle, over run, etc...)

Dieseleux
Click to expand...
I was hoping you would respond ;)
judder is only present on constant speed/ light throttle...
can you give me some info on the locations in the software of a PD engine?
perhaps in a PM ?

JW
 
Last edited:
C

chapelhill

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Location
Scotland
TDI
03 Ibiza pd13- 2260vk Turbo etc.., Merc E280cdi
What do you think is causing the shuddering?
The pID for boost?
Check logs for duration and soi for the places you have the shudder.

Do you have single mass flywheel?
Have you removed the egr?
Do you have a custom tune?

Does it do it when it is cold?

Not sure how much the ecu does smooth running adjustment it may not be a PID algorithm, but if you have standard injectors and cam it is unlikely to be the cause of the problem.

On my PD130 Ibiza with single mass flywheel and standard injectors I had a slow speed judder 1500-1800rpm. Changing injectors that had better balance helped improve it. Reducing soi by a couple of degrees removed remaining judder, not sure if it resolved the issue or softened the combustion and reduced efficiency.
 
struikie

struikie

Veteran Member
Joined
Oct 19, 2007
Location
Netherlands
TDI
BMW 335d E91
stock injectors
custom turbo_johan tune
brand new DMF
removed egr and egr cooler

I have logged the SOI and Johan couldn't find anything wrong...
it really feels like an oscillation...

running 60kmh in 4th at 1800rpm really judders...
shifting to 5th at 1400rpm and still at 60kmh... very smooth...

judder is speed and gear independent...

JW
 
struikie

struikie

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Location
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BMW 335d E91
there are many longitudinal PD engines that suffer from this...
Johan has cleaned the injectors a few weeks back, but he didn't mention any faults on the cam...
belt tensioner is a point to be checked...

rev sensor or road speed sensor??

JW
 
C

chapelhill

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03 Ibiza pd13- 2260vk Turbo etc.., Merc E280cdi
2100 rpm is quite high for any smoothness issue especially with the duel mass flywheel.

One failure mode is that the injector seal the metal one between the injector and the head is not sealing properly allowing some air to blow by getting into the fuel system which is where it goes on a PD system. Most likely cause would be insufficient pressure from the injector hold down bolt. Most of the cycle even with loose injector hold down there is sufficient pressure applied by the injector being pushed down by the cam/rocker assembly but at light cruise soi is later so force is less.

Has this only occurrred sice the injectors were out, has it been getting progtessively worse. If it is getting progressively worse that would suggest a loose injector hold down bolt.
 
struikie

struikie

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Location
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BMW 335d E91
I wrote 2100 but at 2000 rpm the judder is gone...

the injectors have been cleaned and refitted with new rings...
it also juddered before this AND it was completely stock...

JW
 
struikie

struikie

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Location
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BMW 335d E91
there is another BLB equipped A4 on audiforum.nl that has the same issue...
that one also shakes standing still, keeping the revs around 1600rpm...
so no influence of the speedsensor on the gearbox...

JW
 
J

jstruijk

Member
Joined
Mar 30, 2012
Location
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2005 Audi A4 2.0 BLB
struikie said:
there is another BLB equipped A4 on audiforum.nl that has the same issue...
that one also shakes standing still, keeping the revs around 1600rpm...
so no influence of the speedsensor on the gearbox...

JW
Click to expand...
That "another BLB" would be me ;) I have the exact same issue as described by Struikie and to me it feels like the ECU (fuel) is acting very nervous in the mentioned rev range.
 
JFettig

JFettig

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Yes, but I'm not sure what measuring block it would be for your motor. For me its measuring block 4, but that is an AHH engine. Run a log on injected quantity and injection timing and post it up. On my motor I have reduced it quite a bit and it went from really feeling like I was lugging the motor to not so bad at low RPM.

Jon
 
dieseleux

dieseleux

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Location
Pas assez loin pour vider ma tank!
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Jetta TDI 02
The problem is like a engine mount move, do a feedback on ecu torq/rpm evaluation, affect PID loop.
People test more rigid engine mount?
I know is ecu PID trouble...



Dieseleux
 
struikie

struikie

Veteran Member
Joined
Oct 19, 2007
Location
Netherlands
TDI
BMW 335d E91
chapelhill said:
What is the duration that goes with the timing approx 6 degrees?
Click to expand...
in my log I see that 6.6° is 12.4 mg/str

dieseleux said:
The problem is like a engine mount move, do a feedback on ecu torq/rpm evaluation, affect PID loop.
People test more rigid engine mount?
I know is ecu PID trouble...

Dieseleux
Click to expand...
it does have an engine mount with a connector on it...
this is used for smooth idle control as far as I know...

what channel is the feedback from the engine mount?

JW
 
J

jstruijk

Member
Joined
Mar 30, 2012
Location
Netherlands
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2005 Audi A4 2.0 BLB
Do you know if we have 1 or 2 mounts with connectors and if i can unplug these from above? Can't check right now, my wife has the car atm...
 
struikie

struikie

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Joined
Oct 19, 2007
Location
Netherlands
TDI
BMW 335d E91
jstruijk said:
Do you know if we have 1 or 2 mounts with connectors and if i can unplug these from above? Can't check right now, my wife has the car atm...
Click to expand...
as far as I know it only has one on the drivers side...
pull off the engine cover and you can reach right down..

I tested with the mount disconnected...
no difference at all...

JW
 
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