MAF question (correct or not correct)

[Airliner]

I¨'m looking at group 003 on engine module on my 2001 Audi A4 1.9TDi PD. It says "Engine speed", "MAF specified", "MAF actual" and "EGR duty cycle".

When the engine is idling, the MAF specified is indicating 250 and MAF actual is aorund 250 (230 to 255 or something). BUT, when the engine has been idling for 3-5 min. the MAF actual is increasing to about 450, but the MAF specified is still showing 250. If I push the throttle and release it again the MAF actual goes back to around 250. But after 3-5 min it increases again to around 450.


Is this correct or not ?

 

[jaydhall]

I believe you are seeing the EGR affect the MAF reading.

The only way to really test a MAF is to do a run while loging 3 and MAP measuring block. It is on either this site or Ross-tech site.

 

[Airliner]

Ok.

Yep, I have seen the "MAF test" where you give full throttle from 1500-2000 rpm to 3500 rpm and log MAF vs rpm.

But I have a little problem: I have used Excel alot, BUT never to make a grahp from some numbers. So if anyone could post a little step by step list on how to make a grahp in excel after I have logged the nubmers, that would be great.

 

[Uwe]

You could just use VAG-Scope to play back the log..

-Uwe-

 

[Cheshire Cat]

I belive that the EGR valve is switched every two minutes on idling hence the variation in fresh air flow, you will see this on a vag scope especially if you block off the egr line and let it idle the signal will go to each extreme and give a square graph line

 

[jaydhall]

Open the log file in excel. Mark what you would like to graph. (Select the numbers.) Use the chart wizard to graph them. Quite easy.

 

[Airliner]

Hmmm, the problem is:

1. Every numbers is in the same column (in this format ,0.31,903,250.0,235.2,53.4,,,,,,,,,,)

2. I cant figure out what chart to use when i want RPM to be one axis, and MAF to be the other axis. I can only figure out how to let RPM be one line, and MAF to be another line on the chart.

 

[Uwe]

If you're using a non-english version of Excel, use CSVConv.exe first.

If you want to plot something as a function of RPM, use an "XY (Scatter)" type graph.

-Uwe-

 

[Airliner]

Thanx. I have a english version of excel, but when I run CSVConv.exe the file formatted perfectly.

I even managed to make a chart with RPM on one (bottom) axis and MAF actual on the other (vertical) axis !

 

[Uwe]

Non english version of Windows? It's possible even an english version of Excel will assume it should accomodate whatever the Windows defaults are.

-Uwe-

 

[Airliner]

I have a norwegian version of windows since the shop didn't have the english version left when I bought the computer.

 

[Uwe]

Well, I don't speak Norwegian. The difficulties usually happen in langauges which use commas instead of periods as decimal seperators. If Excel thinks you have that, then it will not handle the standard "Comma Seperated Values" file format correctly, and that's why we have the CSVConvert utility..

-Uwe-