Mr_Meaty

"e-*****"

aen

wait. if we are recirculating the BOV, are we supposed to do it before or after the MAF sensor?

like, where am i drilling the damn hole on the stupid intake

Obike

Put it after the MAF, you don't want metered air to be re-metered.

It should be as follows: Filter ->MAF->PCV hookup->BOV/BPV/DV recirc->compressor

aen

pcv?!

wait. i think i aasked you that before, pcv is the oil thing right?

Obike

Yes, it is how blow-by gasses escape the valve cover.

Shaka_Z

ok obike... let me get this right as to the whole relationship of the components in a recirculating setup:

in normal oeration
air->compressor->MAF->BOV->

when BOV releases
BOV->compressor->MAF->BOV(again)

am I right on this? cuz I would really like to know what the setup looks like. I'm only really familiar with atmospheric release.

Obike

Normal operation: Air->MAF->Compressor->Throttle Body

Throttle Lift (seeing vacuum behind the throttle body) you have simultaneously:
(outside air) Air->MAF->Compressor->DV->Compressor->DV->Compressor->DV
(air already inside intake tract)MAF->Compressor->DV->Compressor->DV->Compressor->DV

You will continuously loop until all air finally makes it's way to the engine past the semi-closed throttle body or you get back on the throttle. Generally in a vent to atmosphere setup you will have the MAF or MAP after the BOV/BPV/DV so that no metered air is dumped out of the system. The primary thing to keep in mind is that you do not want to loose any air that has already been measured and accounted for in the ECU, whether you are dumping to atmosphere or recirculating. It's just in a recirculating setup any energy spent compressing air is not wasted when you get off the throttle.

Almost all manufacturers will recirculate, as it is easier to do so for emissions.

Shaka_Z

ok... the approach you just illustrated is for a setup where the MAF is placed at the intake side of the compressor, like so:

air->MAF->comp->BOV->throttle body

would there be any major drawback to mounting an atmospheric BOV - if available space or other routing requirements prohibited the layout above - like so:

air->comp->BOV->MAF->throttle body

other than some negligible loss of work done by the compressor?

Obike

The MAF can get dirty from the blow-by gasses, requiring cleaning or replacement. Emissions. If you run a pure MAP sensor the only thing you'd have to worry about are emissions and the lost work done by the compressor.

Shaka_Z

ok so finally, the ideal setup would be this:

'xxxxxxxxxxxxxxxxxxxxx ____Bypass Loop___'
'xxxxxxxxxxxxxxxxxxxxx |_________________|'
air->MAF->Compressor->Charge Tubing->BOV->Throttle Body

is there anything Im missing? any particular length or size of tubing for the loop back?

Obike

The spacing didn't show up, but the bypass loop goes through the compressor, charge tubing, and BOV. No length or size, but the shorter the better (for response)... the only diameter you need to worry about is 1" I.D. as that is how almost all of them are.

Shaka_Z

ah, so the BOV should be in close proximity to the compressor, regardless of the actual amount of charge tubing running from the compressor to the throttle body.

Obike

Generally speaking the shorter length of the piping, the less the pressure drop is going to be. Of course you will always have to make compromises for pressure drop and piping diameter, but pressure drop is the number one thing you'd like to eliminate.

Mr_Meaty

Well, my BOV is not recirculating, and I'm not haveing any issues. Also, my blow by on my valve cover is not connected to my intake pipe, so I dont' have any excess blow by going into my intake. Even on the stock setup, it's after the MAF sensor, so it would not dirty that sensor.

Obike

1) The MAF getting dirty from blow-by only applies if you place the MAF after the compressor and will see boost.

2) You'll notice a huge improvement in drivability by going to a recirculating setup, you can tune around dumping to atmosphere (especially if you have a MAP sensor).

Mr_Meaty

yup...to much hassle for me...I'll stick with what I got.

aen

im having loads of problems without the recirc, had it for a bit but it came off and now i lost hte fitting so i have to make one lol.

Mr_Meaty

When did you have a recirc? And if you lost the fitting, don't you have a hole in your intake pipe now?

aen

nope.

SePaTc

obike, not trying to flame, but i've seeen a lot of your posts in this thread that aren't totally accurate. so i'm just going to step in this time.

1) the MAF can get fouled up if its placed after the PCV hose, ie. between the PCV hose and the throttle body.

it can even get fouled up if its too close to either an oiled filter medium or the PCV hose, even if upflow of the actual bung.

2) no one with a tc is going to have a map sensor, so thats a pretty useless statement.

obviously, measuring air pressure inside the manifold is more accurate than metering in the intake tract because its closer to the actual combustion chambers.... but thats neither here nor there.

the point is, recirculating your BOV is the best and most efficient design. And no, it would have no effect if you hook up your recirculated hose BEFORE the MAF and add that air to pre-metered air. It is effectively boosting the intake charge before it even reaches the compressor, which is helpful to have the air measured so as not to totally confuse your ecu.