NefMoto

Can I just run a single, small blowthrough MAF and overscale the piss out of it (so that it reads double) to allow me to run blowthrough with my GT2871R's?

Yes or run two tdi mafs and add the resistor to them like the toureg mafs to cut the voltage (signal) in half.  Then you wire them in parallel.  Did this in 2005 and it was awesome.  They read just like an 88mm maf.

Thanks Jared! What's happenin'?

Why not run mafless and add a MAP sensor to the manifold?

I would go Prj's route seems like less of a hassle and I'd look into something similar to what Gonzo is working on. Its a barometric based fuel correction map not sure how he's doing it.

Not to take away from Snow troopers suggestion which is downright genius not sure I've even heard of that being done and I've been around the tuning scene for a while. 

here is some info from this post (i dont suggest clicking, its audiworld and you get bombarded with pop ups and ads) http://forums.audiworld.com/showthread.php?t=1577716

"Get two VW TDI MAFs (part# 0 280 218 063, also cross references to the 2.0 N/A motors) ...

At first I ran them at 60mm (area of 2827.43, basically the same as an 85mm MAF) ... The housings have a step in them for a flow straightener to sit in, the ID of this step is 63.5mm...

... this is very easy to do and if you dont have a lathe the time to pay someone for this should be less than 20 bucks. The reason I opened them up to 63.mm is because the area of two MAFs of this nature is just barely shy of the area of a 90mm MAF (3166.92x2= 6333.84 opposed to 6361.72 for a 90mm). Just perfect for most of us stage3 or 3+ guys. The housing could be opened up a little less for someone with less hardware or with less air flow needs. FYI dual 62 is about equal to an 88mm Maf(3019x2= 6038 opposed to 6082 for a 88mm), and dual 60mm is the same as a 85mm as mentioned before ... Fine tune as neccasary."

Looking back at notes, it worked best as a simulated 85mm setup with the grids in place.  I cannot find the resistor specs but its easy enough to figure out.

I've heard bad things about running draw through MAF's in blow through configuration.

I guess we'll see.

Yeah, mostly from me and Lee I bet. :P Just focus on the numbers.  If you go get tdi mafs they are only good for modifying or running draw through.  You can epoxy different bases in to make whatever you need for blow through.  I have had them work fine up to 35ish psi after that you need metal.


You can source a maf of just about any size and any material these days.  I would love to see a solid dual blow through setup with what we have learned in the last few years.  then, we used them to dial in speed density, throttle cut defender and lemmi tweaked setups.  So ashamed, but cars were still dumb fast.

Well, whatever I do is going to be an undertaking. I intended on a 3.0 build, but given the turbos and lag, I'm leaning now towards a higher rev 2.7 build. Decisions, decisions I guess.

Tup! snowtrooper good info. I'll have to say I'm not fond of the blow through approach because of the potential for failure. The maf would obviously be dealing with pressure, turbulent air(which should be a hell of a time to tackle although I can't say I have experience on blow through) and if your compressor side seal starts to bleed oil into the housing eventually it will make its way onto that heating element.

Anxious to see what route you end up going.
I've been thinking of just running a 2in 1 out FMIC with VMP Sensor on my car

Did I miss something recently?

Is the MAP sensor (if put into the manifold) able to be used as a load input now for fueling calcs for true SD?

You did not miss anything, because I have not posted anything publicly.

Then it is pointless for anybody to do it

1) its a huge amount of work
2) re-invention of wheel

It's not as much work as you think.

Are we talking about SY EGFE?

That's a compile time constant.

I think PRJ and I had the same idea.

It only needs to alter 1 ram and tweak few constant for sensor diagnosis. And relocate the sensor, of course.

If you really understand how motronic works and calculate load, etc, you will figure out quickly what we are talking about.  ;)

Going to be implementing dual maf's as well, though I'm taking the pains to do it in a fashion that can be widely adopted by the general B5 populace.  But sub'd to this thread for more discussion.

Just go look at any vw / Audi application that uses dual mafs.  Look at how they are wired, look at the sensor itself also.  It would be really easy to build a kit for this.  I just never saw a big market for it.

Are you guys talking about the map literally supplying the 0-5v over the maf circuit? If ky thinking is correct we could darn near swap one for one.  Load is load, signal is signal, voltage is voltage.  Or maybe I am way off base.

Dual MAF is extremely easy.
If you look at RS6 code, all it literally does is (voltage 1 + voltage 2)/2.

Copy paste that into your binary and voila you have dual MAF.
Just need to find a free ADC, but with the removal of the rear O2's you get two free ADC's.

Speed-density is a different story.

So you mention TDi's and say that they utilize a resistor and simple wiring with a single maf input to the ECU, and other people mention RS6's and how they do whatever combining of signals that they do within the ECU processor, not via wiring.  So apparently not all Audi/VW applications accomplish this in the same manner? 

Also, MAF transfer functions aren't linear, so how would a simple summing of voltages maintain accuracy (for example, say in the case that different amounts of air are flowing through each maf)?

Also, there is only one KFKHFM in the RS6 file...

There's two inputs, two sets of variables, and B1 and B2 share the tables.

Seems unwise to have the same correction map for each bank.

You said the RS6 has two uhfm's, one MLHFM, and two mshfm's. I assume sometime shortly after that it sums both mshfm's?  Curious, as this goes against prj saying that it 'sums the voltages and divides by two'. Though it makes more sense that they would sum the mass air flow values rather than summing the voltages, especially considering the type of sensors it is using.

Considering that both of the MAF's have essentially symmetrical intake geometry pre-maf, maf mounting, etc, it makes sense that they would share a KFKHFM.  Since KFKHFM is not like a variable 'trim' for the MAF's, and it is calibrated once at the factory, you would expect MAF's that are the same sensor and same geometry to have the same KFKHFM.

I did the legwork on this about a year ago, but don't remember all of the details.

I posted the details that I do remember from the diassembly. I always second guess myself when disagreeing with prj, but I can tell you for a fact that the voltages are not averaged and that seperate variables for each bank goes through the the same linearization, offset, and correction tables.

Correction, one mshfm_w / mshfms_w.

Airflow is calculated seperately for each bank, then summed becoming mshfm_w and mshfms_w.

Yes, this is true indeed, I just looked up the code. Both go through KFKHFM etc…
Not terribly important though - voltages can be just summed and averaged as a quick hack.

That said, this is not difficult to port over properly, as the RS6 file is right there, and it is not hard to implement the routines from RS6.