Hey all, thanks Fflores for steering me in here.
A NA car may not need to do the drill mod, but it does not hurt. The RX systems have integrated flow controlling checkvalves so there is no worry about to much flow, but any other with just fittings there would be.
With the added blowby from FI the tiny fixed orfice holes are not large enough to allow the crankcase to be evacuated at the rate it needs to and excess pressure can build up. Drilling is a simple way to fix this.
With the OEM configuration any excess pressure will back flow through the fresh air tube to the main airbridge....and it takes oil mist back with it. Using an open breather will allow more air in not metered by the MAF and then your fuel trims will go nuts.
The PCM looks at data from the MAF, the MAP, and the upstream O2's to determine how much fuel to add or take away. If this data is not withing the parameters the PCM expects to see it trys adding and subtracting fuel and you see the fuel trims going nuts thus the flow controlling breather is calibrated to only allow in the amount of fresh air the PCM can adapt to.
Now on to the crankcase evac.
If evacuating from the valley cover, the entire driverside bank remains stagnant and the combustion byproducts are not evacuated or "flushed". Evacuating from the rear of the drivers side valve cover the filtered fresh air enters the passenger side valve cover, either through the OEM line that attaches to the inner front of the passenger side cover, or the breather kit if used, past the valvetrain on the passenger bank, down the pushrod valley, through the center of the crankcase pulling and flushing the harmfull combustion byproducts through with it up the drivers side push rod valley and past the valvetrain out the rear of the drivers side valve cover.
On a top mount PD blower, there is no intake manifold pressurized like a turbo or centri blower so the evac system is slightly easier. Simply (and do the drill mod on ALL FI applications or oil leaks may occur) install the oil separating catchcan between the vacuum barb on the blower snout and the valve cover vent, but a turbo or centri application you will want to evac at both boost and non boost operation.
The intake manifold provides the evac at idle and non boost, but as soon as the primary valve senses positive pressure it closes, and the secondary valve opens using the inlet side of the head unit for suction/evacuation and the reverse after out of boost so no matter what the operation your engine is under it is always being evacuated.
Have to get back to work so ask any questions in detail and I'll be back to answer them.
Originally Posted by RichsGreyGT
