Pressure Questions...Air Recirculation Valve
01-05-2006, 04:11 PM
#1
Pro
Thread Starter
Pressure Questions...Air Recirculation Valve
First Wastegate aka bypass valve:
What is the proper opening pressure for a stock 1987 system, Clark's Garage states that the factory manual says ~8psi while observed is closer to ~4.5psi.
When testing mine I can hear it opening at 4.5psi, when i release pressure I can hear the valve snap closed.
I performed the engine running test hand on bypass pipe and all was cool, or so to speak...
When performing the driving boost test in third gear boost seems to peak at the proper amount as displayed by the dash boost gauge (stock).
Question is, isn't 4.5 psi a little low if it's supposed to be developing ~12psi at maximum? and would this 4.5 not 8.? effect spoolup?
Blowoff valve aka Air Recirculation Valve:
Should a vacuum of about 8psi or greater hold the valve open indefinitely? Valve type is of Bailey Motorsport and uses an o-ring design. The valve was bought in used working condition. I disassembled the valve and cleaned the cylinder and piston, used new 15w motor oil and now it holds vacuum better. It held vacuum best when I applied generous amounts of oil to the piston/cylinderwall interface, however after a half minute or so I could hear it sucking air past the o-ring. Is this normal operation or is it in need of an o-ring refresh?
TIA
Jason
What is the proper opening pressure for a stock 1987 system, Clark's Garage states that the factory manual says ~8psi while observed is closer to ~4.5psi.
When testing mine I can hear it opening at 4.5psi, when i release pressure I can hear the valve snap closed.
I performed the engine running test hand on bypass pipe and all was cool, or so to speak...
When performing the driving boost test in third gear boost seems to peak at the proper amount as displayed by the dash boost gauge (stock).
Question is, isn't 4.5 psi a little low if it's supposed to be developing ~12psi at maximum? and would this 4.5 not 8.? effect spoolup?
Blowoff valve aka Air Recirculation Valve:
Should a vacuum of about 8psi or greater hold the valve open indefinitely? Valve type is of Bailey Motorsport and uses an o-ring design. The valve was bought in used working condition. I disassembled the valve and cleaned the cylinder and piston, used new 15w motor oil and now it holds vacuum better. It held vacuum best when I applied generous amounts of oil to the piston/cylinderwall interface, however after a half minute or so I could hear it sucking air past the o-ring. Is this normal operation or is it in need of an o-ring refresh?
TIA
Jason
Last edited by 951North; 01-09-2006 at 07:26 PM.
01-05-2006, 05:01 PM
#2
Three Wheelin'
Pretty normal results for the factory wastegate. The factory unit bleeds boost, starting at 4.5 psi. You should still see .8 bar under full boost, on the factory gauge.
Sorry!
01-06-2006, 12:39 AM
#5
Pro
Thread Starter
Originally Posted by special tool
The wastegate is not "aka bypass valve" 
BTW the reason I put the silly "Porsche Speak" in the question was to aid those performing searches in the future if any usefull information should arise from this thread...
Jason.
01-06-2006, 10:42 AM
#7
Rennlist Member
The manuals also use interesting terminology like anticlockwise ( = counterclockwise).
And I recall the Cycling valve is referred to as the air timed valve.
And I recall the Cycling valve is referred to as the air timed valve.
