Do you have an oem plenum or an IPD plenum? IPD uses a different hose with a check valve in it, yellow valve in the pic.
Oem has a built in check valve in the plenum, so I've been told.

 

?!? i have an ipd plenum! and have not had to use any other "check valve". in either event, the plenum isn't my issue. its just a hose to the pass side of the plenum.

that might be a 74mm and different to accommodate the larger ( and necessary ) TB? and mine is a 68mm. 68mm ipd utilizes all the same oem connecting bits.
also, the oem plenum has no built in check valve, but WOULD make a great hash pipe. in a pinch

 

There must be a check valve on all Ipd plenums as like the yellow one. The old ones were black or white. U don't have it then you blowing boost into your oil
Passage - not good.

 

Here's the 68mm, it has the check valve.

 

Can you get a camera in the area you're talking about and show us a pic?

 

possibly, but its a three step process. a lotta hassle from phone to laptop to post etc.

i mistook what you called a check valve and what is shown on that series of pics for the infamous #16 "check valve" which is part of the throttle intake. i don't recall any of those extra bits with my ipd. so again, mine does not have ( or require ) that piece your pics show..

 

i dont recall either of those parts coming with the ipd although i do have a small bag of a couple of small pieces that when i did get the ipd came in a small plastic bag. but they dont resemble those. in fact i'll look for them now...but my tech who has probably installed a 100 of them in varying sizes has it installed properly, and i don't really know where this is going.

i dont have any intake ( beyond a COLLAPSED hose! ) or throttle or plenum issues, but if you guys would like to talk me into having one? lol fine.

i have a collapsed hose to the passenger side ( right ) of the plenum. it is probably a result of my having been recently blasting around and testing this "sprint booster" thing and a lot of successive wot at 1.3, and i believe under wot recently i collapsed an old hose. nothing more, nothing less.

now, while i stood there a couple years ago while my old plastic plenum was removed and the ipd 68 was installed, i cannot say with 100% certainty that a part was NOT used that came with the plenum though that is not my recollection at all, but i can tell you that i have never had any issue with it, so i'm not sure what you're suggesting may or may not be missing.

but what would that have to do with a visibly collapsed hose?!

i just found the plastic bag from ipd and inside it is that small 1.5 inch black hose and three black hose clamps. i cant recall with any certainty if that
"yellow" piece at the end is/was installed when mine went in. its too long ago. what i DO know, is that i do have the bag with the blk hose and 3 hose clamps still in it.

how could i NOT have that piece installed and the car still run fine for these cpl years since it went in? thats odd. but again, NOT my current issue...though this begs the question..

what is a symptom of "blowing oil into my oil passage"? and how can the car run properly and yet still be doing that??

 

Ok, so your current issue is your boost has gone from 1.3bar to 0.8bar. I don't think the oil tank vent hose collapsing would cause that. Have you done a leak test?

 

not yet but was my first request. when i got to my buddies who has the tester, he had a chevy short bed truck frame blocking access to the compressor. etc.

but..

he took one look at the engine compartment after we tugged on the y pipe/ic's etc and any other reachable other hoses etc, it was then we ( he ) saw the hose i have been discussing as fully collapsed into itself, and i know for certain it was not like that prior to my wot's constantly. he is of the immediate opinion that that is what is inhibiting boost. i have no reason to doubt him as the only thing he cant repair on the car is the inside of the transmission. he;'s extremely knowledgeable, does this 9-5 daily, and i trust his judgement. I'm not saying he couldn't be wrong!? but it would be a first.

but now I'm more interested in knowing how my ipd plenum is "seemingly"?!? operating properly when i have at the very least! that small black rubber hose and three Unused clamps in a small ziplock bag from ipd!

that is more of a mystery. obviously, my hope is he can get to his compressor and we can properly boost leak test. either way, I've ordered the hose he told me is toast. i'll try to snap a pic tomorrow. but cars is covered, etc etc. but i suppose it'd help anyone else to identify the hose that's collapsed. still my money is literally and figuratively on the collapsed hose as being the source of reduced boost.

 

I don't think anyone is saying that a missing check valve would be causing this issue but rather pointing out that you may be pressurizing your oil tank with boost through the breather that normally sucks oil fumes and seals with a check valve under boost. Would it cause problems? Maybe, but the car would likely still run okay seat of the pants. The tanks seem a little flimsy from the little I've seen of them and the oil pump might not be happy with 20psi of pressure shoving on it. Certainly Porsche put a check valve there for a reason, an inspection camera could probably easily allow you to find out what's up if you have access to one...

 

inspection camera? i'm barely capable of taking a pic with a cell phone. in either event, all of this requires that i disassemble the majority of my intake anyway, and armed with the peculiar reality that i DO have a section of 1.5 inch hose from IPD that is sitting in a bag and NOT connected ( as near as i can tell ) to my IPD plenum, i'll be certain to ask relevant questions as well as inspect for myself how my plenum is installed and whether the nipple connectors have any lines connected to them.. and i'll ask specifics so i'm able to better to answer for myself what sounds like reasonable queries from folks here.

but that still isn't the cause of my collapsed hose. i'll get to the bottom of all this soon enough. appreciate everyone's input.

i wonder can anyone explain how the car would perform without ANY IPD check valve? it cant be an optional piece, can it? anyway.. it'll all be opened up hopefully by the weekend as I'm waiting for the porsche west coast hub to deliver a hose. until then, i ( and my tech for that matter ) are speculating. but a collapsed hose is just that. barely one step better than "split" lol.

 

It's possible your tech who installed the IPD reused the old tubing by cutting it in 1/2 and installing the check valve in it. That would leave you with the small length of hose that comes with it as extra.

 

well jeanmarc, i sure hope you're right!? !!..

and i cannot honestly say (?) the only memorable moments ( 1/2 hour! of extra wrangling ) i remember from my plenum install, was that we had to wrangle the sh*t out of the plenum to get it past some restraint piece in there and had to even rubber mallet/hammer at it even with the mm's lowered to the max since its really a tight fit as you know.. but you guys really got me wondering why i have 3 clamps and a bit of rubber hose! but your suggestion makes sense. all i know is it went in flawlessly and runs like bandit, when normal and the ipd even the 68 was a vast mid level torque increase that i can certainly feel. any gain up top is questionable... but i digress..

the car has not had ONE issue re leaks and i have boost tested a few times before. when i just was there re-bleeding my spoiler! i obviously wanted to test it but he had, as i said, access to the compressor limited by some half of a chevy half ton pickup in his driveway lol

 

It must have been the sprint boosters fault, haha.
Hope you get everything sorted out soon so you can get back to carving those mountain roads. My car is put away for the winter so no fun for me for several months

 

well, in a way it was! I was pushing the car pretty hard testing all three modes of that gizmo and that's what finally caused it to go south. but ya know, hoses get old, and it was obviously due! i'll do a BL test too though. I'm not as dumb as I type.


thx for the kind words. sorry about your cars winter "respite" lol