I wouldn't advise it. The MAF is very sensitive and putting it behind a pressurizing turbo prolly wouldn't be good for sensor longevity. Not to mention the heat that the turbo makes might throw off readings by a longshot, since the MAF uses a heated wire to determine air flow.
When I first put in my K&N panel filter it screwed up my MAF so I can attest to the sensitivity of the sensor. If anything I would be looking to rid myself of the MAF, not move it. But short of SAEM that's just not possible I guess.
-Matt
'92 SS 5mt. All go and no show. Sold :(
'94 Audi UrS4 Modded (new project)
'96 Outback 5mt.
'07 Legacy 2.5i SE
[quote="Redlined"]
Oh... and I hope the fucker get bunked with Gunter, arrested for raping Gorillas.[/quote]
Would the car act normally? Would there be any ill effects?
What got me thinking about this? I saw this picture, and it almost looks like the BOV is in front of the MAF. Am I crazy?
If you did mount a BOV in front of the MAF (which would be post turb), would you still run rich at the shift?
I think it might be because it's 3:30am, and I've been working on my car all day long, that I'm cracking up
I think you might be getting confused here (or maybe I am).
Airbox>MAF>BOV return>turbo>BOV out.
The reason why the BOV return is post MAF is so that the MAF doesn't read the same air twice. If you vented the BOV back in front of the MAF still run RICH, as the ecu will think more air is being ingested than is actually going into the engine.
*trying to suppress BAC5.2's fascination with the BOV sound in exchange for performance again*
Jason, right, I know how the stock system is setup. I was just curious as to what would happen if the MAF was post turbo. I have no plans on doing it, lol. But if it was, you could run atmospheric without running rich (you would have to actually I suppose). I have a fascination with the BOV sound, but I have no plans of actually giving up performance for it.
This is the picture I saw. It almost looks like the BOV is pre-MAF, yes? If you follow the piping from the left, you can actually see that it IS pre-maf. You've got cone, turbo inlet, outlet through the IC, then up, BOV, then MAF, then throttle body. With no stand alone engine management (or fuel controller) it would seem that he could run Atmopsheric without any richness problems. Is that true?
mTk wrote:IF the maf is post-turbo you would want the bov before the maf, you would also want it venting to atmosphere.
MK
I'm not sure if this is a good idea either.
You're suggesting this setup, correct? DIAGRAMS OWN!
Airbox>turbo>BOV (atmo)>MAF>throttle body
Doesn't this mean that the MAF will get some REALLY screwy readings when the throttle's closed, because the air will get shunted back PAST the MAF again to relieve the pressure?
Phil, I don't see a MAF. You could be talkin about that plate-looking thingy just behind the BOV, but I don't think that's a MAF sensor. I could be wrong, tho.
BAC5.2 wrote:That thought also crossed my mind, that the car is now MAP based.
Which is what started this whole thing at 3:30 in the morning this morning. Damn that picture, lol.
I aslo thought of what you said about the air going BACK through the MAF. I have no idea WHAT would happen there.
Insomnia owns Phil! LOL!
In regards to the air going back through the MAF, condering the turbo would still be pressurizing the intake tract before it, coupled with the air being diverted back through the BOV, I'm sure you'd make sort work of the MAF sensor.
I think I've heard of some DSM guys moving their MAF sensors to after the turbo compressor. I don't remember the reasoning or anything though... But their sensors are Karmann-type, not hot-wire.
Like these other guys have said, our hot-wire sensors might not be able to handle the heat from the compressor (if only because it would put transducer signals outside the acceptable range), and the small amount of blowby oil would likely contaminate the sensor quickly.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
Any amount of blowby will ruin a hot-wire sensor's ability to work correctly. A catch can might let you get away with using it for one lap or something, but I don't think it'd be a practicable solution for a car driven on the street.
I think the biggest reason people want to move the MAF sensor closer to the throttle body is to improve throttle response.
On our cars with the stock configuration, the ECU really is just guessing how much air is coming into the intake ports. It measures the air coming in through the air filter and measures the throttle position, and computes derivatives and whatnot, and estimates how much air is actually entering the engine itself. I believe this computation is actually folded into the power enrichment/enleanment functionality, which all ECUs (even speed density ones) have anyway, but it's more important with mass flow.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
There are some advantages to mass-air systems over speed density: they adapt better to changes in volumetric efficiency (witness Jason Grahn running an EJ25 with his stock EJ22 ECU), the fuel calculations are more accurate (witness good performance on our engines even running without oxygen sensors), they are easier to tune (particularly to handle things like altitude compensation), et cetera.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
Are you sure that the thing that you're calling a MAF in that picture isn't a MAP? What is that a picture of anyways, a turbo Eclispe or old Evo or something?
-Matt
'92 SS 5mt. All go and no show. Sold :(
'94 Audi UrS4 Modded (new project)
'96 Outback 5mt.
'07 Legacy 2.5i SE
[quote="Redlined"]
Oh... and I hope the fucker get bunked with Gunter, arrested for raping Gorillas.[/quote]
vrg3 wrote:There are some advantages to mass-air systems over speed density: they adapt better to changes in volumetric efficiency (witness Jason Grahn running an EJ25 with his stock EJ22 ECU), the fuel calculations are more accurate (witness good performance on our engines even running without oxygen sensors), they are easier to tune (particularly to handle things like altitude compensation), et cetera.
But short of SAEM that's just not possible I guess.
My bad, I guess that makes sense. 
Well, do Mistu's use a MAF setup?