Overboost but not overboost

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sierrafery said:
You can rarely observe those readings in instrument mode, save an inputs fueling log with MAF connected then we'll see if that's the case or not but the fact that the vehicle behaves well with MAF unplugged is enough evidence for me that the problem is with the air flow ...unless you want to spend big money for a genuine MAF to see how it goes then or just to end up the same
Click to expand...

I can get the MAF eliminated from the equation quite simply but would not want to just take the easy route to mask a problem. I know the limiters in EU3 maps use the AAT which Nanocom does not see.
 
The AAT is used only for smoke limiters it can't cause your symptom and if it was that unplugging the MAF would have had no effect, as long as the problem goes away by unplugging the MAF the problem is on that path
 
This is taken from a well-known source. It shows the turbo overspeed limiter.
turbo overspeed.JPG

I will try and run some data logs (if the Nanocom doesn't have a fit before I hit save!) and see what airflow readings I am getting.
 
Yes, i forgot about that, though if you take that formula apart as in the complete article you'll see that the AAT has effect in the air flow ratio calculation ... though you might have a point and be the first i see who has an issue with the AAT with that symptom, take a log and if the MAF reading never drops to 0 while the symptom occurs then eventually unpin the AAT wire(green/blue) from the sensor's plug and see then... would be a revelation
 
sierrafery said:
Yes, i forgot about that, though if you take that formula apart as in the complete article you'll see that the AAT has effect in the air flow ratio calculation ... though you might have a point and be the first i see who has an issue with the AAT with that symptom, take a log and if the MAF reading never drops to 0 while the symptom occurs then eventually unpin the AAT wire(green/blue) from the sensor's plug and see then... would be a revelation
Click to expand...

I am clutching at straws a bit to be honest but a faulty AAP sensor which incorporates the AAT can't be ruled out - I have never changed it. I'll try and catch it in a log at some point and go from there.
 
You gave me some food for thought with that AAT thing which is a good point even if very uncommon... i'm watching now with interest the outcome but the brute logic is that if the symptom is caused by turbo overspeed protection due to wrong AAT input it should occur with unplugged MAF too as the default for MAF open circuit should not disable the overspeed protection as the fuelling goes to a kind of Eu2 calculation and there is overspeed protection in that ecuation too without AAT involvment .... though the reality might contradict that logic, fortunately the 4 pin AAP/T sensors are affordable compared to the 3 pin AAPs
 
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sierrafery said:
You gave me some food for thought with that AAT thing which is a good point even if very uncommon... i'm watching now with interest the outcome but the brute logic is that if the symptom is caused by turbo overspeed protection due to wrong AAT input it should occur with unplugged MAF too as the default for MAF open circuit should not disable the overspeed protection as the fuelling goes to a kind of Eu2 calculation and there is overspeed protection in that ecuation too without AAT involvment .... though the reality might contradict that logic, fortunately the 4 pin AAP/T sensors are affordable compared to the 3 pin AAPs
Click to expand...

I would also expect some sort of recognition in the ECU fault codes that the overspeed protection had occurred but then it does not go into full limp mode which you don't always get a logged fault for
 
If it was with MAF connected then i'm affraid it can be a bad contact somewhere or intermittent boost leak and that's a nightmare to troubleshoot :(
 
Little update, sort of... The ITG air filter I took out looked a bit grubby so I put a cheapo paper air filter in and plugged the MAF back in. Fine for a day but then yesterday started playing up again so I unplugged the MAF again and no problem since. Given it has had two new VDO MAF's I reckon it's probably the wiring. I do have a spare engine sensor loom but for now I will just keep the thing unplugged.
 
You really need to save a log from a drive with MAF connected to catch the symptom on file cos if the air flow drops to 0 from above 600 under load then i doubt that the problem is with the wiring... or at least let nanocom connected and watch the air flow live on instrument mode when the symptom occurs... though that AAT thing is still something to be ruled out if the MAF reading is normal cos once the MAF is unplugged the default is a kind'a Eu2 fuelling which neglects the AAT input
 
sierrafery said:
You really need to save a log from a drive with MAF connected to catch the symptom on file cos if the air flow drops to 0 from above 600 under load then i doubt that the problem is with the wiring... or at least let nanocom connected and watch the air flow live on instrument mode when the symptom occurs... though that AAT thing is still something to be ruled out if the MAF reading is normal cos once the MAF is unplugged the default is a kind'a Eu2 fuelling which neglects the AAT input
Click to expand...
I have a log from yesterday and I noted the times it did it, but it was captured using the app on my Android head unit and it records the raw values so I will have to convert them all. https://github.com/hairyone/TD5Tester
 
Little update....

I was thinking along the lines of pedal problems as I have just once had a driver demand fault logged. I was sat with the Nanocom playing with the pedal and bingo, "Problems detected with driver demand (logged)". The readings I have got are:

Acc Way 1 0.759v (3.9v when pressed)
Acc Way 2 4.301v (1.256v when pressed)
Acc Way 3 4.682v (1.202v when pressed)
Acc Supply 5.020v (5.026v when pressed)

There are slight variations in the above, but looks like it could be the pedal ?

Taken from a previous @sierrafery post I believe good readings should be:
ACCEL. WAY 1 - about 0.3V with the pedal released, about 4.7V with pedal to the maximum position
ACCEL. WAY 2 - about 4.7V with the pedal released, about 0.3V with pedal to the maximum position
ACCEL. WAY 3 – this track must have values very near to the second track.(only 15P-16P engines)
ACCEL. SUPPLY – this value must stay between 4.9 a 5.1
* an up to +0.5V for WAY 1 and -0.5V for WAY 2 are accepted
 
Final update: I replaced the throttle pedal and no more issues.

Faults relating to the throttle pedal itself were very scarce however I thought it was worth a try and seems to have done the trick. I guess there was a corroded area on the potentiometer although i have not yet dissected it.
 
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