930 Vacuum Regulator Replacement

[philipguziec]

So my 89 930 wasn't coming up to full boost, And my shop tracked it down to a leaky vacuum regulator. It sounds like the job of this thing is to release over pressure in front of the throttle plate when there's vacuum in the intake manifold and the Turbo is spooled up. I would just replace it but Porsche is asking 800 bucks for what looks to be a $10 part. It also appears to be a part that's common to other Porsches of the era and probably to many other vehicles. Is anyone else familiar with this part or have a substitute or rebuild process?

[gsxrken]

Got a picture? Sounds like you’re describing the shuttle valve’s function. There are some seals that are easy enough to renew.

[philipguziec]

The small line attaches Downstream of the throttle body and one of the big lines attaches to the outlet of the intercooler and vents to atmosphere

[Speedy Squirrel]

Your picture is of the pricey “Golden Saucer”, but the function you describe is the compressor bypass valve that GSXRKEN is showing. If that little teflon bumper seal is worn, it leaks. Makes a noticeable tapping sound when you hop off the throttle from full boost if it is worn. Seal is relatively cheap.

[philipguziec]

It's the golden saucer. My shop was addressing another issue and noticed it was slow coming up on Boost and didn't get the full Boost. They plugged the line from the golden saucer and it gets the whole boost but of course Chatters on deceleration. The pricing on this little diaphragm valve is absurd so I was just looking for alternatives. There has to be another vacuum actuated valve used in other applications that could serve the same purpose. This seems like it might be suitable. If not has anybody else found a reasonable replacement off of a Volkswagen or Chevy or something? Given the diameter of the saucer it's clearly a valve that's designed to open with relatively low vacuum relative to atmospheric.https://www.pelicanparts.com/More_Info/99311033751.htm?pn=993-110-337-51-M93&gad_source=1

[SLNT930]

Here's a question on the decel valve:

What's the specification difference between 930-110-173-02 (Porsche 930) and 930-110-190-00 (78-83 911 and 78-82 928)? Other than the $500 price difference, of course. Both have 930 part numbers...

[philipguziec]

Originally Posted by SLNT930

Here's a question on the decel valve:

What's the specification difference between 930-110-173-02 (Porsche 930) and 930-110-190-00 (78-83 911 and 78-82 928)? Other than the $500 price difference, of course. Both have 930 part numbers...

Great question. My bet is direction of flow or the vacuum threshold when it opens. What are the two ends connected to in the non Turbo application?

[SLNT930]

The 928 PET lists 930-10-173-02 as "from from year 1980 on" and 930-110-190-00 "up to year 1979." It looks like all ports connect to the throttle body just like the 930. Vac line connects to a barometric pressure sensor of some sort since no boost.

https://rennlist.com/forums/928-forum/1200111-where-does-the-deceleration-valve-vacuum-line-connect.html#post16719753

[RarlyL8]

That is not the function of the decel valve, you may have multiple issues.
The sole function is to hang the throttle during off throttle events such as when shifting gears or coming to a stop. Engine deceleration is slowed allowing the turbo to stay on boost between quick shifts or for the engine to not dip too low in the RPMs and possibly stalling when coming to a stop. You can eliminate this valve (I have) if not running a light weight flywheel and simulate it's function with your right foot. Result is more popping on decel and the quicker RPM drop as previously stated.
I would replace the seals in the BOV first and plug the vacuum line to the decel valve and see where you are. If this fixes the boost issue you have time to find a used decel valve or just delete it. Part number for the BOV seals is 930.110.149.00

[SLNT930]

Brian couldn't a leaking diaphragm in the decel valve contribute to these issues - and also a high idle speed?

[gorskined]

while we are on the subject does any one know what level of vacuum the golden sauces should open at?
i was playing around with my saucer and a 964 bov contemplating running the bov in place of the saucer to try and alleviate some of my popping that drives me nuts . I noticed my Bov opened at less of a vacuum that the saucer. possibly my saucer is old also

[SLNT930]

Originally Posted by gorskined

while we are on the subject does any one know what level of vacuum the golden sauces should open at?
i was playing around with my saucer and a 964 bov contemplating running the bov in place of the saucer to try and alleviate some of my popping that drives me nuts . I noticed my Bov opened at less of a vacuum that the saucer. possibly my saucer is old also

I think the SC pancake opens at 17 in/hg or about 8.3 psi. Can't find the specs for the 930 or 928 ones, which I presume are different.

You also raise an interesting question. Isn't the decel valve just a diverter valve? And if so, can't we simply replace it with an adjustable recirculating BOV (diverter valve)?

[mark houghton]

If you've confirmed the decel valve is malfunctioning, then just delete it as Brian has mentioned...and deal with it with your throttle foot to keep the rpms from dipping to fast. Then search for a replacement.
Me, being the Macgiver person I am, I would take it apart (only after you're 100% sure it's toast) and see if the diaphram is torn (most likely is), then repair or replace with suitable material. Sounds simple, probably would take some ingenuity. Maybe pull a vacuum on the port with a mightyvac to see if it holds.

[Speedy Squirrel]

You can determine if the diaphram is leaking by seeing if it holds vacuum using a Mityvac.

Here is a crossection. It is designed to open faster than it closes to get the right amount of air into the intake. They mess around with the springs to adjust that. Since the amount of air is proportional to engine displacement different size engines would get different springs and would have different part numbers.

Originally Posted by mark houghton

If you've confirmed the decel valve is malfunctioning, then just delete it as Brian has mentioned...and deal with it with your throttle foot to keep the rpms from dipping to fast. Then search for a replacement.
Me, being the Macgiver person I am, I would take it apart (only after you're 100% sure it's toast) and see if the diaphram is torn (most likely is), then repair or replace with suitable material. Sounds simple, probably would take some ingenuity. Maybe pull a vacuum on the port with a mightyvac to see if it holds.

[mark houghton]

Originally Posted by Speedy Squirrel

You can determine if the diaphram is leaking by seeing if it holds vacuum using a Mityvac.

Here is a crossection. It is designed to open faster than it closes to get the right amount of air into the intake. They mess around with the springs to adjust that. Since the amount of air is proportional to engine displacement different size engines would get different springs and would have different part numbers.

Thus the $800 price tag. Such a simple thing but engineered to death. Hey, if it holds vacuum, then squirt it full of the miracle WD40. Could just be gummed up inside.

[SLNT930]

Again, it looks just like a recirculating BOV. A $200 adjustable BOV would be a great replacement for an $800 non-servicable unit from Porsche.

[gorskined]

Originally Posted by SLNT930

Again, it looks just like a recirculating BOV. A $200 adjustable BOV would be a great replacement for an $800 non-servicable unit from Porsche.

adjustable bov looks to be a great option.I just ordered a cheap adjustable Chinese one, if it solves my popping issue i will replace with a greedy . this will allow me to can play with the settings to see if i can mitigate some of my deceleration popping.
if nothing changes i will just put my saucer back in ....

[aschen]

decel valve is 800$ these days, yikes. This used to be pretty routinely available used and take off, maybe all of the original ones leak by now.

It looks like a valve that opens on vacuum. Looks pressure and piston area balanced so more force is on the top chamber and it stays closed under positive pressure.

Good call on the BOV it seems like the exact same thing really.

[Mocker]

I don't get why you guys don't convert to the 964-style diverter valve mod that's been around for years. Get rid of all that crap--that's what Porsche did!

[SLNT930]

Originally Posted by Mocker

I don't get why you guys don't convert to the 964-style diverter valve mod that's been around for years. Get rid of all that crap--that's what Porsche did!

This thread is about the decel valve, which the 964 also has and is unrelated to the 964 and later style diverter valve.

Plenty of people have deleted the decel valve. Some people still want it's function. The 964 style diverter valve (Bosch 710) is normally open at idle. An adjustable unit, like the Turbosmart Kompact, can be had with 20mm ports (which should fit the 19mm hoses on the decel valve) and can be fitted with a heavier spring (rated for -14InHg to -24InHg vacuum). Furthermore, the spring pressure Kompact can be fine tuned to be closed at idle and open only when the vacuum spikes when the throttle is released. Then you get a $180 serviceable fix (including the spring) to replace a non-serviceable $800 unit from Porsche.