Arnoud

While currently busy with my Intake Refresh project, I noticed that on MY1994 part 928 107 603 00 - which is the hose from the throttle body housing to the oil filler & evap vent valve - has a plastic T-junction in it which is held together with two (2) "ear" hose clamps as from the factory (see underneath photo for what I mean). On the earlier cars this appears to not be present?

Two questions:
1. As the plastic T-junction part seem to be just that (no restrictor nor one-way valves inside): is the function that of a test port?
2. Is there somewhere in the WSM where this change is mentioned? I checked all the technical bulletins, and I could not find anything in there at least...

Hope the collective here can answer this, as I'm curious why this was done.

SteveG

Arnoud: I don't think the hose you picture is original; I don't think there is a test port at that location. In the '95 Porsche parts PDF, Katalog, that part number does not show a junction. My '93 hose does not have a "T".

Rob Edwards

I've never seen any literature that points to there being a test point or 'T' in that hose, nor have I seen it on any other '94. If you could find another GTS with it, that would be interesting.

Arnoud

Thanks for your reply Steve, and the fact that your MY1993 does not have it. I think it is standard on MY1994+MY1995, so let me bring more proof as per my underneath further reply.

Thank you for your reply, Rob.
Proof #1: On the spare engine which Herman K. sold and put for sale pictures (well: pictures as part of several PDF files) here on Rennlist:


Proof #2: as per following youtube video screenshot

P.S. One possible theory on my behalf: my engine has been replaced by the factory when in possession of the first owner, which can be seen from the engine plate additional stamp of: "AT" = German for AusTausch. Most likely this was done for too much oil usage. So: could it be that on all MY1994+1995 "AT" engines, Hans & Frans had to put this in so it could be measured somehow (before returning the car with new engine back to the owner)?

Rob Edwards

Duh, I have seen Herman's motor in person, should have remembered! That 'crate' motor is from a '94 5-speed, but it's not new, nor is/was it an exchange motor, there's no AT on the stamp pad. So I'm not sure that the T'd filler neck hose is unique to the exchange motor program.

Arnoud

Thanks Rob, for your immediate follow up and confirmation and additional info: much appreciated. But remains then a mystery for the moment, for what reason this was put in by the factory.

At the moment I am not sure if I want to replicate this as part of my Intake Refresh renewing, and cut a perfectly good brand new hose in half for an unknown function that most likely I will never use...

SeanR

Strosek Ultra

Arnoud, I have the T-junction on my blue Strosek car (1987 S4 manual). Not on any of the other cars.
Åke

Arnoud

Thanks for your confirmation, Sean, and what you also think it's functionality might be.

That is very interesting, Åke, that such an earlier car has it too - thanks for sharing that fact.

worf928

GregBBRD

Fairly common on late model engines. Complete mystery regarding function.

I've never considered that they might be only on factory rebuilt engines.

I'll pay more attention to model year and engine number.

I, also, replace with the one piece hose, if that hose needs to be replaced.

Arnoud

Thanks Dave, for your observations confirmation as well. If only we could speak to Hans und Franz: so many questions we all would like them to ask and answer over the years!

Thanks Greg, for providing your insight as to what you do when replacing it (same as Sean, so I will follow suit and do the same on my ongoing intake refresh). And with Hans und Franz long gone, I guess we will never know for sure why they did that for - so this mystery remains...

GregBBRD

Since that hose is a combination of intake manifold vacuum and crankcase pressure (with a restrictor), I'm guessing that data gathered over a long period of testing new engines would give Porsche an indication of how well each engine performs.

.....An engine with poor cylinder sealing would have a different vacuum/pressure reading on that hose than an engine with perfect cylinder sealing, right?

Arnoud

Yes (nice short answer, Finnish style like. Although I think this was more of a rhetorical type of question to begin with ).