2.5 Boost logs? Graph? Help?

[S4_dan]

Think I did some boost logs today. I did measuring blocks 003,004 and 011. Here are the result in 4rd gear:



I think I have fluffed up the Duty Cycle on the graph though. It was pretty much a flat Yellow line along the very bottom until I added it as a secondary axis? as per this guide: [Mk4 Golf] Vnt Tdi Turbo: How To Adjust Actuator & Cure Boost Problems - D.I.Y Guides and How to Instructions - uk-mkivs



Have I cocked it up or is my car doolally?!

Have I logged the right measuring blocks?

 

[quattrodave]

Just to confirm, I take it the orange line is requested boost, grey actual boost and yellow N75 duty cycle ?

 

[desertstorm]

Looking at those readings the MAF actual looks low to me.Especially at lower rpm at 1370 rpm it's only reading 183mg/str which is low.
Have you tried changing out the MAF with another one.
The smoke map will limit fuel according to the MAF output so low MAF outputs will result in poor acceleration until the ECU is seeing sufficient air flow to put a meaningful amount of fuel in.
Try disconnecting the MAF and see how it runs.
Have you got or has the car had a performance K and N air filter as the oil off these can get on the MAF.
They sometimes recover with some cleaning from alcohol or a non aggressive cleaner. Brake cleaner iisn't non aggressive .

Karl.

 

[S4_dan]

I actually bought the car with the maf disconnected. The seller said he had it diagnosed as a bad maf and as he was selling it he didn't want to spend over another £100 pound on it. So I bought a good known working one and fitted it. Made no or little improvement. I will give.it a thorough clean with some electrical contact cleaner I have then try two runs. One with and one without. I still have the original maf which again I could clear. I suppose and try that one.

No aftermarket filter is being used and the p.o. never mentioned anything. He was in his late 50 ' s. But that didn't stop him fitting aftermarket hids and reverse parking aid and retrofitting cruise control either.

 

[S4_dan]

Just to confirm, I take it the orange line is requested boost, grey actual boost and yellow N75 duty cycle ?

I believe so. But I may have somehow cocked up the duty cycle line when adding it to the graph as it is really bizarre.

 

[S4_dan]

Another MAF log from earlier:


Looks like maf a little low. I've dug my original MAF out and the contact cleaner. Will give it a good clean, fit it and run some more logs tomorrow. Then do a run with maf unplugged too for comparison.

 

[S4_dan]

Another boost log:



The requested pressure is less than actual up until about 1800rpm. Is that normal?

What's with my duty cycle?!

 

[quattrodave]

Looks to me like the n75 is requesting boost because actual is way behind requested, as the boost lines come together the n75 duty drops. Are you sure there's no boost leaks (which are more noticable at low revs) ?

 

[desertstorm]

Sort the MAF and you will sort your problem. Fuelling is being limited by the smoke map, no fuel is no heat is no boost.
Are you sure the MAF you bought is good and the correct part ?.
The only other place air can come from is through the EGR system. If the EGR valve is stuck open then you are recycling EGR gas.

Karl.

 

[adamss24]

As Karl said, boost requested and actual is fairly close but you're triggering a smoke limiter hence the low power response. Maf is indeed low, you should see a big improvement with a new, genuine MAF...check wiring too...

 

[S4_dan]

As Karl said, boost requested and actual is fairly close but you're triggering a smoke limiter hence the low power response. Maf is indeed low, you should see a big improvement with a new, genuine MAF...check wiring too...

Cheers Chris, will look at sourcing a new maf. Only ever bought genuine mafs for audi's in the past. My A6 used to eat the plastic bodied mafs!

 

[S4_dan]

More logs today. First log is with cleaned MAF:


And graph:


Now logs with the MAF disconnected:


And graph:


So with the maf disconnect the N75 curve is lower. So it is pointing to the maf even though the cleaned maf has made some improvement over the 2nd hand one I fitted.

BUT....With any MAF connected there still feels like no torque below 2k and a pause in acceleration after gearchanges.

With the MAF unplugged it feels the same, maybe slightly better but no pauses after gear change.....

New MAF then?!