[LNF] PCV, Blow-Through MAF, and Valve Cover Breathers

[Mayor West]

My main concern is further understanding the LNF PCV system, how I've changed it by going to a different turbo set up, and if it's OK or not.

• I do not have the DF air to water intercooler nor any of the DF-supplied intake piping or sensor brackets (MAF/MAP/Vacuum Port)
• I do not have a catch can
• My PCV is intact within the intake manifold
  • I assume it's working
  • I haven't popped a dipstick (yet)
• I don't have vacuum lines going from the VC to the intake piping
• I'm essentially running the stock tune with GMStage 1 Map changes in place
  • I am wanting to make sure all my ducks are in a row before I attempt to fine tune the MAF scale for blow-through

Photo credit to the world wide web, my engine isn't that dirty.

Referring to the top pictures #1 and #2 ports, my current set-up is:

• #1 is plugged per ZZP's recommendation
• #2 has a breather on it because I don't have any vacuum lines from the intake piping into the crank case

Would this cause the PCV to suck in unmetered air from the breather port?, causing issues with my MAF readings and fuel trims?

My kit doesn't run poorly, but I do have a slight bit of normal-driving KR (<= 3*) but I am working with a blow-through MAF now so there's some expected issues with the scaling that I have yet to fully address.

Adam's mailing me the DF MAP Plate (that has the vacuum line on it as well) so that I can put it on my own piping because I didn't realize the LNF required the 2nd map (LSJ-T guys were my main source of info for this)

Once that MAP plate is installed should I take off the breather and attach a vacuum line to the MAP plate, or should I keep the breather on and use the #1 port for the vacuum line, or should I leave the MAP plate port plugged?

Thanks for any thoughts!

 

[OptimizePrime]

Check this pic out to see the flow - this is with the maf pre-turbo but is easy enough to see how stock operates

Stock routing with the catch-can introduced for Port #2 only. Port #1 is now taking in metered fresh air (as opposed to just putting a filter on the barb or drawing from Port #2). All hoses are 3/8" fuel hose which is closest to stock (this matters)

#1 If you cap it, should be fine. On the turbo side, the 'filter' in the picture above is actually an external PCV, you're missing this PCV now but obviously wouldn't suck in unmetered air because the port is capped.

#2 Just thinking through how this is setup, stock is under a constant source of vacuum - pulling air from your VC via the turbo. With just a breather, it's no longer under vacuum but it'll vent if your VC is under pressure. Slight difference in how it operates, but the net result isn't all that different. I think you're good with a breather here (catch-can not necessary). I've seen a lot of other builds do this, and will be putting an open filter on mine as well with the new winter mods. If you notice the filter get soaked, that's when it's a problem.

I suspect your knock is from not having the second map/vac line installed correctly and when you throttle tip-in you're either dumping a lot of gas or starving her. If you get the DF stuff installed correctly you gotta dial in your trims next before messing with timing or AFR's to get rid of the knock - if you go straight to timing/afr to get rid of the knock you'll be all outta wack and have to start over anyway.

Boost leak test her to rule that out.