Oil breather check valve? (1987 auto)
04-30-2016, 02:52 PM
#16
Rennlist Member
Rgds
Fred
04-30-2016, 03:03 PM
#17
Nordschleife Master
I don't think that valve is a US-style PCV in the sense that the the flow rate would be inversely related to the pressure differential. It's my understanding that the US style PCV valve gives a small orifice with high manifold vacuum and a large orifice with low manifold vacuum. That 928 safety valve seems to be just a regular one-way valve with a cracking pressure of about 90 millibars.
Not having that "de-icer" or safety valve in the S4 models is, in my opinion, a bad idea.
...which brings the question why did they do away with it in GTS? That hose breathes openly from the filler neck into the MAF elbow in the GTS without any check valve. Seems like they had a lot of fate in the higher port in the filler neck resulting in a lot less oil mist in the crankcase gas. I think that the higher pickup location is good, I use it, but is it really that much better? ;-) Reading dead people's minds is difficult.
Not having that "de-icer" or safety valve in the S4 models is, in my opinion, a bad idea.
...which brings the question why did they do away with it in GTS? That hose breathes openly from the filler neck into the MAF elbow in the GTS without any check valve. Seems like they had a lot of fate in the higher port in the filler neck resulting in a lot less oil mist in the crankcase gas. I think that the higher pickup location is good, I use it, but is it really that much better? ;-) Reading dead people's minds is difficult.
04-30-2016, 04:04 PM
#18
Former Sponsor
Pretty obvious that the "first line" engineers were not involved in the 928 program by the time of the GTS models.
04-30-2016, 04:09 PM
#19
Former Sponsor
I don't think that valve is a US-style PCV in the sense that the the flow rate would be inversely related to the pressure differential. It's my understanding that the US style PCV valve gives a small orifice with high manifold vacuum and a large orifice with low manifold vacuum. That 928 safety valve seems to be just a regular one-way valve with a cracking pressure of about 90 millibars.
Not having that "de-icer" or safety valve in the S4 models is, in my opinion, a bad idea.
...which brings the question why did they do away with it in GTS? That hose breathes openly from the filler neck into the MAF elbow in the GTS without any check valve. Seems like they had a lot of fate in the higher port in the filler neck resulting in a lot less oil mist in the crankcase gas. I think that the higher pickup location is good, I use it, but is it really that much better? ;-) Reading dead people's minds is difficult.
Not having that "de-icer" or safety valve in the S4 models is, in my opinion, a bad idea.
...which brings the question why did they do away with it in GTS? That hose breathes openly from the filler neck into the MAF elbow in the GTS without any check valve. Seems like they had a lot of fate in the higher port in the filler neck resulting in a lot less oil mist in the crankcase gas. I think that the higher pickup location is good, I use it, but is it really that much better? ;-) Reading dead people's minds is difficult.
04-30-2016, 04:17 PM
#20
Rennlist Member
How that check valve in the S4 filler neck body can help anything breath is beyond me given how small it is.
Rgds
Fred
04-30-2016, 04:19 PM
#21
Nordschleife Master
Yes, I agree that there are a lot of curious design decisions in the GTS. It's as if they threw all they got into the initial '87 S4 design and then when the sales tapered down faster than expected and the company fell on hard times, they didn't have the budget to do the GTS engine design properly.
Last edited by ptuomov; 04-30-2016 at 11:06 PM.
05-10-2016, 02:04 PM
#22
Rennlist Member
Has anybody sourced a suitable replacement for the NLA check valve?