Changing 930 dump-gaskets, pictures galore

[beepbeep]

Picture(s) tell more than thousand words, so here is picture-guide to changing dump-valve gaskets on your 930...

Those gaskets dry out over years and get ingested into the engine, dissapearing almost completly. Result is tell-tale "clonk-clonk" sound when you step on the throttle, bad idle, slow boost buildup etc. They are cheap and can be changed in two hours by any home-mechanic like me and you.

When you start unbolting things, make sure you put all bolts, screws and washers into named plastic bags. Also, make a "assemble-checklist" when disassembling. There are plenty of things to forget when putting all back together.


Here we go:

1. Undo two bolts holding your airbox to CIS air-plate and a nut hold it underneath (don't drop third airbox nut and washers), make sure you don't drop your wrench behind the engine. Also, detach two oil-breath hoses and one small hose underneath the airbox. Carefully, lift out the airbox:


2. Disconnect all hoses going to the intercooler. There is one thick going to warm-up regulator (fallos thing), and one thinner hose going to the wastgate. Take out bolts holding the IC:


3. Take out the IC, clean it up:


4. Start unbolting intermediate-throttle body (thing between throttle-body and intercooler that contains dump-valve, electric pressure-transducer and overboost safety switch), make sure you document every bolt, hose and cable you undo:



5. Take out intermediate-throttle body, check it out:


6. Open dump-valve on hose-connection side first (Warning! It's spring-loaded!), note piston direction (some of them have a notch on one side) and reinstall accordingly:


7. Check out dump-valve internals, clean them up and place new gaskets where old used to be (chances are, you won't find any left):

[RJ Gilliam]

Thanks for the effort and all the pictures!

Hope I wont have to use them..

[beepbeep]

While there, check your oil pressure switch behind the engine. It's plastic body often cracks, leaking oil over clutch hose and make tell-tale dual oil drips underneath the tranny. Replace it while you are there if it's leaking (cost's peanuts and saves from frustration):

8. Clean everything and install parts in reverse order.

Major sources of frustration and loosing time:

- Big rubber hose between CIS and intermediate throttle-body is stiff,short and hard do put back. This is the fastest way: install and tighten intermediate TB with all hoses first, put loose clamps in the middle of the big rubber hose, then slide it over TB first (do not tighten yet!). After that, slider it over CIS-body with front side first, then use screwdriver from inside to pry the rest of it in place.(it'll take lot's of finger-strength and swearing).

- Short length of hose going from vakuum-device on TB into plenum chamber as hard to put in place. It's clamps are hard to tighten. Start by tightening the clamp on TB-side first. Then (while holding second loose clamp in the middle of the hose), put it in the place. With TB in place, use one hand behind it to tighten it's clamp. You'll need screwdriver of right length and nimble fingers. Make sure you do it right beacuse it's a source of bad idle and other things evil. My clamps were loose, probably beacuse last shop working on my car it didn't bother wasting time on it, being such a PITA-job.


Don't forget to connect two electrical wires going to overboost switch and pressure-transducer. Do not mess them up or you'll probably fry your boost gauge.

That's about it. Easily done in your garage...3 hours tops including swearing on two things mentioned...

Price: 20$ for gaskets.

Getting really personal with your engine: priceless!

[John Rogers]

I did this a long time ago on our 930 and it is a pain. I finally installed a "long neck" type of intercooler that eliminated the valve assy completely which makes throttle response much better and boost comes on full at 2200 RPM or so. There was an article I read that said the valve can be blocked closed, which does the same thing but I never tried that? An item you did not mention is replacing all the o-rings for the boost piping and intercooler since they get flat over time and can leak. Great photos.

[beepbeep]

Blocking valve closed is a bad thing beacuse it effectivly renders dump-valve useless.

Valve is there to prevent pressure buildup and impeller cavitation when you shut your throttle at full boost. If it doesn't happend, turbo will keep on spinning by force of inertion and try to pump air into pressurized intercooler, blowing gaskets and producing impeller surges.

Every turbocharged car has a dump valve , except some rally cars but they don't care about longevity of their turbochargers.

[Kurt B]

I don't even have a 930 and I thoroughly enjoyed that post. You trying to set some kinda kick @ss standard for posting picts now? Jesus...Okay, from now on, this is considered a grade A project picturepost!
[I'll do my best to compete!]

[beepbeep]

Thanx Kurt!

It's actually pretty easy to post good pictures to Pelican BBS.

Just do it this way:

- Carry your digital camera with you when working, snap a picture every time you feel for it (it might help you remember how to put things back together later on)
- When done, dump all your pictures into Photoshop or similar software.
- Find out how many percent you need to resize pictures to bring them down to approx. 600 X 400 pixels size.
- Crop those pictures that contain obsolete information
- Resize all pictures by given percentage
- Appply "Adjust Levels" and then "Sharpen" in your image-editing software (Those commands might be called someting else in your software in case you don't use Photoshop).
- Save all pictures in JPG-format, use as high quality setting as possible while keeping file size <100k.
- Write your post off-line, insert "" into your document.
- Go to Pelican, create post, upload pictures using "Attach Multiple Pictures" -button, replace your own "" with according links you get from upload-window...

Voilá!

[rattlsnak]

For those with newer turbos,.. from '91 and up (C2T) does not have this valve.(or any of that big piece in the photos!) Completely redesigned plumbing.

[Doug E]

Great pictures - these should probably be in some technical manual or book.

All that stuff under the decklid makes me appreciate my SC - even though the sacrifice is HP!

[wrx paul]

When's Wayne gonna write that 930 book?? There is far too little info on our turbo's. I never even thought to look at this part so I just want to say thanks!! Now I gotta go order some parts.

[RickM]

Goran, thanks for the great turbo info...as usual.

[kycarguy 935]

Thanks for this really good post. I haven't done this job yet on my car but may do it soon thanks to to your efforts posted here. Thanks.

[wrx paul]

Does Wayne have these parts? I can't find them under the CIS section for an 88.

[john70t]

Excellent write-up Goran. thanks.

[diabolos88]

Originally posted by beepbeep
Blocking valve closed is a bad thing beacuse it effectivly renders dump-valve useless.

Valve is there to prevent pressure buildup and impeller cavitation when you shut your throttle at full boost. If it doesn't happend, turbo will keep on spinning by force of inertion and try to pump air into pressurized intercooler, blowing gaskets and producing impeller surges.

Every turbocharged car has a dump valve , except some rally cars but they don't care about longevity of their turbochargers.

is it possible to switch from the OEM dump valve to the later style 965 external dump valve. I read that the Kokelyn IC removes the entire OEM blow off valve(dump valve) and runs the later style one.
Is it possible to force it permanently closed then install the external valve somewhere coming off the IC?

my 930 is a '88 running an Andial IC.

[beepbeep]

Yes, you can block OEM valve and replace it with any kind of recirculating BOV you like.

They do the same thing, it's just that Porsche made it somewhat unecessarily massive in those early days.

[copterdude]

Great Post! April 2006?
Having problem finding the gaskets mentioned here in Pelican catalog.
Little help
Is there now a better way to handle the clanking issue? My idle when cold is terrible hoping this will fix both problems.
1988 930

Thanks

[gsxrken]

Bumping to the top - can anyone tell me the part number for the recirc gaskets? I have searched PP here and cannot come up with them.

[911st]

Great thread!!!


If I may, I have some questions about how the dump valve might work.

It looks like the piston is spring loaded.

Is the connection to the intake after the throttle body and the piston sucked open by intake vacuum?

Dose the spring pressure seem pretty light or firm?

That is, do we think or know if the piston is held open by idle or cruse vacuum or just with the high vacuum that comes with lifting the throttle at speed?

Thx.

[James Brown]

No vacuum, pressure (it's a turbo)! there is always some + pressure even at idle. When closing the throttle when wide open, pressure spikes and the pop-off valve opens with a "puisssssssshhhhh" sound. Got to love it. I think I need a turbo someday.