924Board.org

[macBdog]

Is it mechanically ok to run the vent from the recirculation valve to atmosphere via a hose (and yes I will plug up the hole in the intake manifold that it will usually run to)? I put my water pump and timing belt on before the little metal line from the recirc valve to the intake manifold
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1979 931 with a 350 chev
1973 911E with EFI

[Paul]

If you're referring to the line from the intake manifold to the bypass valve on the turbo, no it must be connected to protect your turbo and to reduce lag.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[macBdog]

Yes referring to the recirculation fitting on the side of the turbo. So the pressure comes down the line from the intake manifold, pushes on the cylinder which opens and relaseses the extra charge into the intake through the compressor housing?

I though it was the other way around, pressure built up from the turbo housing is released into the manifold, bypassing the turbo...
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1979 931 with a 350 chev
1973 911E with EFI

[flosho]

Hmm both of those ideas are a little different then what I thought.. The recirc valve is built right into the turbos on these cars, so when we let off the throttle, the TB shuts, and there is still air being forced back into the charge tube, and the fuel dizzy measures the air and adds fuel, so if you vent it to the air, between the dizzy and throttle body, you will run rich because the air is gone, but the fuel has been supplied. If you blocked the recirc valve off on the turbo and plumbed in a BOV on the tube running from turbo to dizzy you could probably get away with venting to the atmosphere. It will still protect the turbine from the surge of air back and will make noise if you want it to.
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[This Space For Rent]

[Paul]

The pipe from the intake manifold supplies manifold pressure to the backside of a piston in the intake housing of the turbo. When the throttle is closed, vacuum from the intake manifold is provided to the back of the piston which pulls it down in it's bore thus opening a path between the intake and compressed air sides of the turbine. This allows the turbine to keep spinning instead of being slowed down by compressed air with no place to go.

CIS depends on no leaks, so a BOV is not a good solution. Also the BOV would need to be installed on the intake plenum that runs from the turbo to the TB.
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[macBdog]

Ok this is all interesting... the recirc valve fitting on my new turbo was on the wrong side so I took it apart and moved it around to match my original turbo. In this configuration, the line from intake manifold connects to the spring side of the assembly, is this what you mean by "back of the piston" (would make sense).

For my understanding, the vacuum from the intake manifold sucks the piston in against the spring and opens up the port in the turbo?

The next question, can I take the source of vacuum for this mechanism from anywhere that has vacuum such as the ports on the TB?
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1979 931 with a 350 chev
1973 911E with EFI

[Paul]

Yes, the piston must be on the side away from the block. I didn't notice that when I installed a rebuilt one, what a PITA. My first post on this board was a request for help on why I was only getting 4 PSI of boost even with the wastegate control line disconnected.

You could use another source of vacuum, but why bother, hook it up the way the Dr intended. All it will cost is your time and a new water pump gasket.

[macBdog]

Good advice. What was Ferry a doctor of?
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1979 931 with a 350 chev
1973 911E with EFI

[Smoothie]

Long answer, but - http://www22.porsche.com/usa/accessoriesandservices/classic/classic-world/world-tradition/tradition-ferryporsche/

His father also got an honorary Doctorate from the same institute, but also sat in on some college classes without being registered as a student during his younger years - something that wasn't too unusual across Europe in the old days. http://en.wikipedia.org/wiki/Ferdinand_Porsche

It's probably safe to assume that their honorary degrees would have been in the area of mechanical engineering.

edit - Still no mention of a formal college level education, apparently, after high school he worked at Bosch, then was tutored -

[macBdog]

Interesting.

Handy fact number #45242: If you grind off the small bracket on the recirc tube, you can install it without removing the water pump!


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1979 931 with a 350 chev
1973 911E with EFI

[Smoothie]

"Dr. Ing. h.c." translated by Google language tools comes back as "Dr. Engineer h.c.". Still don't know what the "h.c." means, but as far as I can tell, "Dr. Ing. h.c." isn't specific to mechanical engineering. It's apparently the prefix used for any Dr. of engineering, be it mechanical, computer or any single discipline within engineering.

Actually, on further ponderin'.. The Bosch Automotive Handbook (3rd ed.), amoung its' ≈154 authors, shows quite a few "Dr.-Ing."'s along with a bunch of "Dipl.-Ing."'s, "Dr.rer.nat."'s and "Ing.(grad.)"'s (none with the suffix "h.c."), so the "h.c." might be an indicator meaning something like "honorary certificate".
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox