Hi, to get into the underscaled MAF stuff, I did some runs with only underscaled MAF on F-Box without changing anything else but undercaled MAF + adjust fueling like mentioned by prj in another posting. Just to learn from it step by step.

After a short log, I recognized the expected result on rl_w.

With stock MAF curve rl pretty quick hits 191,7 on VCDS so you get to the last column in KFZW.

With underscaled MAF rl stays much longer on lower values and does not hit 191,7 anymore. Maybe with more boost it will.

So the timing table runs totally off, because the real amount of air in cylinders is higher than the calculated load signal. So this will result in to much timing for the real load points if do not change the entire timing table. (remember stock file only MAF scale)

I wonder nobody ever mentioned the effects from downscaling MAF on ingintion maps - or am I missing something?

Are there more side effects?


 

I know but if I modify the ecu with more boost and scale the MAF to a range of 0 - 191,7 the real rl will be f.e. 0-250.

So at rescaled rl 140 the real rl will be f.e. 191,7

So if I leave the KFZW/2 stock (only for example) I will get to much timing on mid range load areas.

Top rpm Timing at 140 load:
19,500
19,500
22,500
24,750
23,250

Top rpm Timing at 200 load:
6,000
8,250
10,500
11,250
9,750

So I get 23,250 deg at real load 200 instead of 9,750 cause ecu thinks it is only 140

I can see this behavior on VCDS because the ecu starts pulling timing via knock control with rescaled maf

Now I'm confused...

this is clear..  the MAF is not maxed out, its just underscaled. Like to prevent to hit max rl_w. 

The question is not if it is right or wrong to do this, its only about understanding the relations.

the only question is - if somebody is underscaling his maf, does he only scale KFLF at the same time as mentioned:

http://nefariousmotorsports.com/forum/index.php?topic=2747.0 and on S4WIKI

because I see, it will harm correct timing by reading the wrong columns in KFZW/2 etc.

so there is a lot more to do - right?  cheers 

So, is the only way to be able to break the 191 rl_w limit and have a fully scaled MAF by doing the 5120 hack?  This is assuming that the car is hitting the limit, of course.

What are we talking in terms of the rs4 limits? I hear a lot of talk about a 16bit load axis in the m-box, but haven't seen it implemented.

Just curious.

rl_w is NOT limited to 181

It was my understanding that KFZW/2 had axes limited to 191. So you could not tune ignition timing with loads >191, and it would just use the value found in the last column of the table. Only ways to circumvent this is to use RS4 flash, or change the axes to 16bit.