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Discussion Starter · #1 ·
I was scratching around in the engine recently and notice something I think is rather strange regarding the plastic piping attached to the intake manifold, inlet tube and intercooler cold pipe.
Let me see if I can explain it in a way people can understand. I have attached some images and you can always go and look at you ST to work out what is going on.
Let me start with the plastic pipe that connects just in front of the MAF sensor. If you follow this line down it connects to the intercooler cold pipe. So when ever the turbo produces boost, boost pressure is allowed to bleed or purge straight back to the inlet tube. The line has an ID of 8mm and the 2 fittings an ID of 5mm. I would be interest to know what the flow rate would be at 20psi or better still the purpose of bleeding boost pressure off like this.
Teeing into this pipe is what looks like a disc shape one way valve. I pressure and vacuum tested this line and the valve or what ever it is remained closed. From this disc valve the line then tees into another plastic line with one end running to the intake manifold through a check valve just above the throttle body. The check valve allows vacuum into the line only. The other end of this line then runs to an electrical switch and forms part of the fuel tank evaporation system, I think. This part of the system does not concern me it’s the constant bleed off, of boost pressure that I find unusual .Anyone got any ideas on the purpose of this boost bleed/purge line.


 

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This is the recirculation system which dumps the excess boost back into the intake. Does the same thing as plumb back blow off valve.
 

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Discussion Starter · #3 ·
This is the recirculation system which dumps the excess boost back into the intake. Does the same thing as plumb back blow off valve.
Its not a recirculation system, the pipe is constantly open. It bleed boost off at all times.
 

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Maybe it's there to bleed boost off at idle? With such high compression and such a small responsive turbo it's producing boost at idle. This would help spool but wouldn't be good if the turbo was stalled due to no where for the boost to go. Being such a small line once driving the boost wouldn't be bled off as maybe once vaccum pressure is positive or( boosted air) the purge line somehow stops bleeding boost the way it is set up. Could be a possibility?
 

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I wish I'd saved the link - But I came across some info about how the EcoBoost engines work. The bleed valves are there to prevent pre-ignition. Apparently the engine is able to control throttle by using the wastegate on the turbo, and at some point switches over to that. Its there to prevent unsafe pressures which would cause it to run lean.
 

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Man, there really is no messing with this stock turbo is there?
 
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I was scratching around in the engine recently and notice something I think is rather strange regarding the plastic piping attached to the intake manifold, inlet tube and intercooler cold pipe.
Let me see if I can explain it in a way people can understand. I have attached some images and you can always go and look at you ST to work out what is going on.
Let me start with the plastic pipe that connects just in front of the MAF sensor. If you follow this line down it connects to the intercooler cold pipe. So when ever the turbo produces boost, boost pressure is allowed to bleed or purge straight back to the inlet tube. The line has an ID of 8mm and the 2 fittings an ID of 5mm. I would be interest to know what the flow rate would be at 20psi or better still the purpose of bleeding boost pressure off like this.
Teeing into this pipe is what looks like a disc shape one way valve. I pressure and vacuum tested this line and the valve or what ever it is remained closed. From this disc valve the line then tees into another plastic line with one end running to the intake manifold through a check valve just above the throttle body. The check valve allows vacuum into the line only. The other end of this line then runs to an electrical switch and forms part of the fuel tank evaporation system, I think. This part of the system does not concern me it’s the constant bleed off, of boost pressure that I find unusual .Anyone got any ideas on the purpose of this boost bleed/purge line.
The "disc shape one way valve" mentioned in article is a one direction valve that allows air flow to go from the flat side to the T at the other end. Tested it . Why is it there ? I can only guess it is for either specific testing bij the control module (there is indeed quite a lot going on , or for some specific conditions.
 
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