prossi

well from what i understand he had issues with the AIT sensor i have bypassed the stock AIT and tuned the MAF readings by using restrictors which he didnt without actually "tuning" the metered air on the maf meter it WILL send incorrect signals to the DME causing it to richen up the fuel i think he was unsuccessful because he really didnt seem to understand how a MAF works...as of now the car runs great idles a tad rougher but not bad. Power seems stronger and more linear and the AFR's at higher RPMs are richer which is good for me running 17.5psi... but like i said i wont really know until its on the dyno.. so i hope you all hang in there because if it works ill post a complete white up with dyno graphs.....if it doesent work i have an old K star piggie back from one of my benzes worked great on that........BTW why would i need to recirculate the BOV? and how would it be metered if its just going back into the J tube post maf or stock afm? my understanding porsche and other companies just recirculate to keep the swoosh noise from happening? i have always vented the BOV on all my turbo cars to atmosphere.
There really is no down side to it but if you know something different please let me know i always like learning new things

Rogue_Ant

prossi,
Once the air passes the AFM/MAF, then the air has been metered by the DME. If the BOV is vented to atmosphere then that metered air never enters the engine. This causes a momentary rich condition, as the DME thinks that air is entering the engine, and provides fueling as such.
Usually this isn't a problem, but the proper way would be to re-route the BOV to the intake - post AFM/MAF.

You have a PM.


-Rogue

prossi

really? i guess im not really understanding this concept since im so used to stand alone systems, if you dont mind can you please elaborate on this concept?

Andy1212

Its no different on standalones. Ok, so since the BOV is after the MAF, the ECU is fueling the amount of air the MAF sees. But if you release some of this air (metered air) the engine will supply too much fuel for the amount of actual air, because it was released from the intake via the BOV. The purpose of a BOV is to release the air in the intake before it backs up when the throttle body is snapped shut. So when you vent the BOV into the intake maniflold, the throttle body is bing bypassed, and the metered air is kept.

xsboost90

i had a BIG HKS bov on my car after my rebuild and it made the thing run suuuuper rich. Put a Forge recirc valve on and its fine.

prossi

well thanks for expaining ive always seen custom turbo builds with the BOV vented to atmosphere including my other car and i have no issues like this with it, . guess this is another thing ill have to test on the dyno....man im going to be on that thing for a long time

alxdgr8

Yeah, MAP sensors aren't a problem when dumping to atmosphere. You can have a BOV with a MAF car so long as you run a blow-thru setup (MAF goes between compressor and throttle body with BOV before the MAF)

Andy1212

Well atmosphere venting really isnt to bad. You'll just be running very rich while the BOV is venting. But its really not hard to just tie it into the intake after the throttle body.

V2Rocket

problem solved lol

Rogue_Ant

Fixed it for you...


-Rogue

Andy1212

How would the air get past the shut throttle body then?

Rogue_Ant

You don't want it to... at least not yet. The BOV simply diverts the air to circulate in the intake piping pre-throttlebody 2 pre-turbo. The BOV is there to allow the turbo to 'freewheel' when the throttle-plate closes.


-Rogue

Andy1212

Yes i understand that, but if the metered air is never getting past the throttle plate, then wont the mixture be just as rich as if it were just vented out of the intake? The targeted mixture cant be acquired if the air isnt getting into the engine.

Rogue_Ant

The air will get into the engine, it is just delayed for the short time that the TB is closed. And going slightly rich during drop-throttle is normal.


-Rogue

black944 turbo

It also helps to keep the turbo spooled up between shifts. You will significant gains on responce recircing.