What do you see at idle?  I always see 3.5-5.5 it seems...  this is the same with bone stock cars.  Regardless of MAF housing diameter or placement.  every car i log here at 6000ft reads this at idle.

As I have been testing various MAF setups on my single car in both draw through and blow through I have been seeing a lot of weird things.

First and foremost, how is it possible that with the same map values I could have a 73mm housing read the same as a 88mm (1.47 times more area)?

I recently switched back to blow through again as i never really got into fine tuning it.  A 73mm is reading LOWER post turbo than a 88mm was pre turbo, same car, same conditions, same boost levels.  At 15 psi and4000rpm it was reading 120gs (4.63 G/S @ idle).  The 88mm reads 160 pre-turbo at the same point (4.63 G/S @ idle).  Stock MLHFM and a KFKHFM of all 1s to remove further variables.  How is it the same at idle yet lower at high flow, yet a smaller housing?  I get that the air is now compressed and heated, but it is still the same volume of air.

Every shred of info i have read about blow through says that the readings will be skewed HIGHER.  This is the opposite of what is happening to my car. 

Next observation is that if I scale the MAF voltage table (MLHFM) at all, even 1%+ it will read 9-17 G/S and be creating 40-50% engine load at idle with AFRs in the 10s.

Today i am going to try two things, first a maf scale that progresses from 0.01% to 15% positive of the stock map across the 512 points and then also a standard upscale of the map with KFKHFM changes to just low loads and idle.

I know very few people are doing anything blow through on the cars, but if I am not somehow screwing things up, this could open up a lot of options.  Imagine a stock housing that you can run more air through than a 90mm and still have resolution.

thoughts?  anyone know the answers to these events already?

thats what I was thinking to.  like the 4.5ish G/S i see is just locked in as an assumption because the air flow is so low?

btw, this is all the same regardless of hitachi or bosch so far in my testing.

I still keep going back to the bosch sensor though.  that is what I am currently on, stock 73mm housing with stretched 3" hoses within my 3" charge piping.

I was under the impression that a blow through setup would read lower?  Not quite up to speed on these setups though.

Either way I can't wait to change over to the HPX sensor

Best its ever ran!  Pardon the haggard ass looking piping, I have yet to decide my final configuration as you can tell by all this testing.  Once everything is done the intake will be a one piece CF tube and the charge will all be thin wall tig-ed stainless like my first section there.

post turbo, post BOV, pre inter-cooler.  It seems to have head room to over 800CHP.  I exploded a stock housing (my original stock one from 2000) at 35psi on e85

fyi, twin turbo guys can run two tdi maf housings with a stock sensor and put a 2.25 ohm resistor in their clips, shared wiring like on a touareg and like that you can be blow through for testing/running bovs, dual intake, whatever...

with all that said, I am obviously still figuring out some of the nuances of this.  blow through MAFs on other platforms obviously do different things.  all their info has to just be taken as info, not facts regarding our ECUs and even sensors themselves so please approach this with caution.  When I first put it to blow through it was going lean at boost onset until I cleaned up other areas of my tune.

i've compered 2 different diameter maf housings one from bosch 70mm maf (1.8t 180ps) and the other from 80mm bosch maf (1.8t 225ps). It seams that the scaling is not linear. In lower voltages the bigger housing reads less than the smaler about 8% and in higher it keeps readind more and more increasing up to +25%. I have attached some pictures. The first one is the % difference between the 2 and the second the 2 different callibrations. These are oem values taken from original files. Also i think there is an offset MLOFS (200kg/h) in the damos that i have.

hey - so have you tried the stock/stock pull-through as-in basically bone stock?

You should also check KFMLDMN and FWMLHFMMN.