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Discussion Starter · #1 ·
<v:shapetype coordsize="21600,21600" o:spt="75" o:preferrelative="t" path="[email protected]@[email protected]@[email protected]@[email protected]@5xe" filled="f" stroked="f" id="_x0000_t75"> </v:shapetype>

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Discussion Starter · #3 ·
To be honest I'm not sure. I've had opinions both ways. Tuner says could I log another boost run and he will know more. It's running perfect with good mpg and power so I'm not worried, just interested :)
 

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The 'specified' red line is for a 100bhp A4, yes?

Yours is not a 100bhp A4, it's been modified.

Here's my wrong (possibly) and misguided (probably) take on it...

The turbo comes in earlier due to the map, so the car sucks in more air earlier - initial spike in blue line. When the blue line goes below the red line, that's the revs approaching the limit of diesel combustion but the car is still requesting more air as it's at full throttle.
 

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I would do the same test but also log Air pressure requested vs actual including duty cycle.

To me, the dip around 2200 rpm indicates you either eased off or the MAF is becoming faulty. It should follow the turbo spike very closely. When its in the higher revs I would expect the actual air flow to be higher if it has been chipped.

If your car was a standard setup I would say just monitor it but for you I would expect the airflow to be around 1000-1100 up until the higher revs.
If your getting the performance you require and your happy, save £60.

If the dip is an MAF problem around 2200rpm you'll first notice the car hesitating before fuel economy is affected.

Andrew
 

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Discussion Starter · #7 ·
I agree. It should be higher across the range and the tank is going 55mpg per refill and performance isn't affected so far. But it will need changed. In the words of philosopher Davemkas moderaterous- " if it ain't broke....
 

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Check that your air filter is clean and aslong as it remains unrestricted airflow it should be fine. Once it's around 550 instead of 850 requested then you will start limiting the diesel quantity.

People with huge turbos sometimes tune the maf sensors to fool it I to thinking it's not getting 2x more air than required (which the car can also trip out with).

Really, the only concern is the dip where it should be pulling the highest amount of boost.
 

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Stevee - how did you produce the data from VCDS - what blocks are they? I'd like to have a go at making the graph and posting it here as it seems like there are a couple of really clever people here and I'd love to have mine interpreted too!
 

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Discussion Starter · #10 ·
Benjie - I logged block 3. And boost is block 8.

Then VCDS put the results on a excel chart, then i converted it to graph.

Aham uk - I was talking to my tuner about the results and he said its low all the way accross the graph. It spikes earlier because the pd100 turbo isnt that big and the boost comes on down low, and isnt that good higher up the rev range. Saying that, it shouldnt trail off like that.

Brand new air filter on it too. [Y]

The Maf hasnt been changed for along time so i will probably do it on the next service and i will log it again afterwards to see what the results are.
 

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Below is a log of a 115bhp which has a tuning unit on it.
You can see the steady airflow above the requested and they all drop off like a stone at high revs.
As the diesel engine is designed to have unrestricted air flow, the MAF is just an indicator to the engine which can contol boost pressure and injection amounts.



The turbo pressure log shows the boost pressure is the same shape as the airflow readings. Aslong as they are within 100 later in the graph I'm happy.



When your recording the torque aswell, you can make a close guess at the bhp and torque. Note that this is vague when a proper map is carried out

 

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Hi guys, hope you can help with my MAF results... aham_uk - I think your comments are relevent to me as I think it is hesitating a bit.

It looks like I have a MAF on it's way out... any other observations guys?

3rd gear - from 20mph, full throttle, no letting off etc.



4th gear, from about 25mph, full throttle again, until I had to lift off for safety reasons. The dip at the start was from the previous gear, clutch in.



Any thoughts, observations?
 

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I would disconnect and reconnect the maf sensor a few time to make a good connection but It looks like the maf is breaking down when full boost is being applied. Because it's still within limits it won't trip out your car but it will not be smooth.
As you have lots to play with I would be inclinded to rotate the maf slightly to see if it improves things (so the flow is not passing over the maf sensor too much). This would not be a long term fix but as you can log it you should get another 6 months use.
To make it much more smooth I would make sure it's not an electrical then try a replacement.
 

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Ooh, didn't mention the car is remapped!

Thanks for the reply aham_uk, I am working on the car all this week on various stuff, so will try the things you said and take readings again... see what happens! I will also keep regular readings to see what's going on, thanks!

Out of interest, you don't know what measuring blocks I can use (and then number crunch) to find out rough torque/bhp values do you?
 

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Your car will have a torque figure, its different between nearly every car so just keep going up channels (past some with error codes) until you find it.

Do exactly the same driving as the maf (full beans) and plot the figures against RPM.

In excel you will have to make columns
RPM
Torque (NM)
Torque (Lb/ft) (=Torque NM x 0.738)
BHP ((Torque Lb/ft x RPM) / 5252)
 

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I'll try that aham, thanks - forgot to reply, sorry!

Hmmm... slightly lower mpg, slightly poor performance and more black smoke than a power station under max acceleration - that'll be the MAF nearing death then!
 
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