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Carrera RSR · Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK

Cool feature of our WG's is that the top port can be used to become dual port and then run an air regulator to balance the boost on both sides of the diaphragm giving you your desired boost level. But you need a low spring threshold to dial up and down. Assuming you have a 1.0bar spring, you can only go up and down from 1.0bar, never lower.
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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chuck21401 · Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD

chuck21401 · Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD

I decided to test the boost control line for leaks. Figured I could slather the rubber parts of the line with soapy water, then blow some air through with the air compressor. Started at the wastegate first. Soaked up everything and hit record on my phone...no problem. Did the same thing on the top side...bingo...we have bubbles. I enlisted my son to do the filming.

23 second video: https://youtu.be/CKPAPK28EQ0

That’s enough to cause a problem I’m guessing...
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

Carrera RSR · Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK

What psi did you put in the line? Potentially yes, boost bleeding from the line could reduce the wastegate opening and could cause higher boost. Ultimately this is how a boost T controller like those from Turbosmart work. Depends how much boost is lost at the WG end
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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Fasteddie313 · Joined: 29 Sep 2013 Posts: 2596 Location: MI

Maybe..

You could probably grind off those ferrules and replace that hose with a normal piece of fuel injection grade gas line and worm style hoseclamps..
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80 Turbo - Slightly Modified

chuck21401 · Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD

Not sure if I believe my own theory. So I would like to test it by creating a new boost control line. Anyone know of sources for the fittings needed?

Boost control line port on charge tube -->
Male Metric adapter (what size?) to female NPT 1/4 --> Hose barb --->
1.5 ft (or so) 1/4" automotive fuel hose -->
banjo fitting with hose barb (what sized? source?)

Is the banjo bolt that connects the control line to the WG removable without removing other components? I"m thinking maybe a 17mm swivel socket?

Fasteddie313 · Joined: 29 Sep 2013 Posts: 2596 Location: MI

I don't recall their being a check valve in there but it's not too hard to pull the banjo bolt off the bottom and then you could blow air through it both ways..

Actually, I doubt their is a check valve of any sort in there but clogging is possible..

Your bend down there looks strange actually.. I don't remember mine having any hose on the bottom side.. I think it was straight hardline to the WG and only a hose at the top..

Possibly that kink in your hard line down there just before it meets the hose is your problem..

Has anyone else seen the bottom of the WG line look like that?

Trying to find a pic of a WG line..

I think I get that banjo bolt with an open end wrench, on it a bit crooked..
Those bolts don't take much torque.. Just until they hit bottom and a little bump from there is what I do..
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80 Turbo - Slightly Modified

poor-sche · Joined: 06 Jan 2017 Posts: 80 Location: Los Angeles, CA

There's one for sale on German eBay that is a hard line...

https://i.ebayimg.com/00/s/NzY4WDEwMjQ=/z/MGkAAOSwe6ZaU31w/$_72.JPG

And there used to be one available from this site with a hose on both ends...

https://www.rosepassion.com/media/photo/31852/web93112313503.jpg?w=300&h=300&e=0

The version of the parts catalog I have shows the one with a hose on both ends.
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1980 - 931

chuck21401 · Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD

This page has a picture of the control line.

https://www.rosepassion.com/en/cat/porsche-924-1979-924-turbo-coupe-manual-gearbox-5-speed/M348/turbo/turbo-pipe-and-hose/B794/turbocharging/I963/control-line/P31852

(poor-sche beat me to it...I couldn't figure out how to link directly to the picture)

There is a bend, but not quite as extreme as in my picture. I'll take another look to see if that is really a kink.

Part number is 931-123-135-03. One of the parts catalogs notes the following:
Supersession(s): 931-123-135-01; 931-123-135-02; 93112313502; 93112313501
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1981 Porsche 931 w/S1 engine & g31 transmission. Water-cooled intercooler

Fasteddie313 · Joined: 29 Sep 2013 Posts: 2596 Location: MI

Cedric · Joined: 27 Aug 2004 Posts: 2614 Location: Sweden

The little extra hose at the WG side might be a later modification by porsche. If you ever removed and installed the WG you know exactly why they did that, it can be really tricky to get that bajo on if everything doesnt line up perfectly.

But in general, this might be the most over speced WG control line pipe/hose in the history of automobile. If you want to do a new one just buy a banjo an silicone hose. But you have to be careful with the exhaust manifold, dont route it closely. To be completely sure I put a heat resistant sleve/sock (whatever its called) when i did a new line to the top of the WG to control boost.
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1980 924 Turbo
www.instagram.com/garagecedric/

Carrera RSR · Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK

I have two versions of the WG line. One has a flexihose on the WG end and one doesn't.

Personally I used the flexi version for the bottom WG port. Having the hard line ensures its routed without anything being melted by heat or chaffed/cut on sharp items. The small flexi at the bottom will also help install and avoid the line snapping. You don't want this line failing...... At the top of the hard line I cut off the flexi to boost tube section and used silicone hose on top of the engine. I kept the adapters into the boost tube and kept a small tail of hose and used a barbed joiner and hose clamps to link into the silicone hose.

For the top port I used the hard line. Again only using silicone hose once at the top of the engine to avoid rubbing and chaffing at the back of engine.

But agree with Cedric, it can all be done more simply as long as nothing melts or gets trapped/cut/damaged.
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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chuck21401 · Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD

Carrera RSR · Joined: 08 Jan 2010 Posts: 2309 Location: Somerset, UK

Go to your local hydraulic hose company. They can make anything you want and should have fitting options. Or just make your own out of copper brake lines, silicone hose, barbed fittings etc. Not hard to do.

PS don't even consider a boost tee like the photo. They don't work well with our large volume WGs'
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252

chuck21401 · Joined: 20 Feb 2005 Posts: 532 Location: Annapolis, MD