Oil Cap Removed While Engine Running / Idling - PRESSURE!

[GTGallop]

I had a half quart laying around and figured I'd add it to the engine tonight.
Engine was still running and I twisted off the cap (not hard at all) and when the threads were in the off position, pressure nearly popped it out of my hand because I wasn't expecting pressure. I held my hand over the fill hole ti see how much "air" was coming out and in no time it had covered my hand with oil. There was no way I'd be able to pour the oil in with that much air and oil coming out, so I capped it real quick, shut the engine off, uncapped and filled. Then ran it for a few minutes. No big deal.

But what the hell is up with the pressurized crank case? Is that for water crossing? Is that normal on turbo'd engines? Unique to the EcoBoost? No car or truck I ever had generated enough pressure to be detectable if you held your hand over the fill hole and I think the Nissan 5.6L actually had a little suction.

#oil #oilcap #oilpressure #crankcase #pressure #air #oilfill

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[Racket]

found this:
hope it helps?

https://www.knowyourparts.com/techn...essure-managment-in-turbocharged-applictions/

Interesting article, and more validation for a catch can ? I understand UPR was testing then withdrew their valve cover vent, although other vendors sell them. I don't know how I feel about crankcase 'respiration' so I'll wait for a solution that makes sense. Curious how our stock trucks resolve pressure changes now.