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Mike924
Joined: 12 Aug 2004
Posts: 2601
Location: IoW UK
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 Posted: Tue May 06, 2008 5:43 pm Post subject: PCV line - makes a difference! |
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Over the last couple of weeks, the idle on my car has been getting slower and decidedly more lumpy. I tweaked it up a bit, but that didn't really help. I was going to ask you guys about it, but when I had a look around this weekend, I noticed that the PCV line had come off.
So I put it back on (obviously leaving some skin from my knuckles behind...  ) and what a difference! 
Car starts better, pulls better, revs better, idles better, even shuts off more cleanly...
...and then the exhaust pipe fell off!  (But that's another story...)
Moral of the story: don't underestimate the effect of air leaks on these cars... 
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd
'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org |
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blackhat
Joined: 23 Apr 2008
Posts: 66
Location: Junction City, Kansas
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| Posted: Tue May 06, 2008 11:16 pm Post subject: |
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Ahh ha! The PCV does make a difference! LoL I've been trying to track that answer down for a minute now. Since the PO put a screwy carb system in (single Weber on the intake manifold), he left the PCV hose wide open at the elbow on the crank. I ran up to O'Reilly's and grabed a hose and a small cone filter and threw that on.
So where'd ya hook that PCV line up to? Is it ported vacuum, manifold vacuum, atmosphere? If it's ported vac, was it before or after the air filter?
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My First Porsche
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1978 Porsche 924 N/A |
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Ozzie
Joined: 12 Mar 2005
Posts: 4448
Location: Townsville, Qld. Australia
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| Posted: Tue May 06, 2008 11:30 pm Post subject: |
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On a stock system its between the throttle body and the air filter.
It can be found either before or after the CIS.
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance |
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blackhat
Joined: 23 Apr 2008
Posts: 66
Location: Junction City, Kansas
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| Posted: Tue May 06, 2008 11:44 pm Post subject: |
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| Ozzie wrote: | On a stock system its between the throttle body and the air filter.
It can be found either before or after the CIS. |
Cool! Now I'm getting some where. I should be able to T off of the ported vac line going to my dizzy then. Do we need a PCV valve in there too?
One of the other threads I was in mentioned using a PCV valve to protect the crank against WOT.
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My First Porsche
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1978 Porsche 924 N/A |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Wed May 07, 2008 1:01 am Post subject: |
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| blackhat wrote: | | Cool! Now I'm getting some where. |
That happens when you keep asking the same question over and over again until you get an answer you like.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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blackhat
Joined: 23 Apr 2008
Posts: 66
Location: Junction City, Kansas
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| Posted: Wed May 07, 2008 7:47 am Post subject: |
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| Rasta Monsta wrote: | | blackhat wrote: | | Cool! Now I'm getting some where. |
That happens when you keep asking the same question over and over again until you get an answer you like. |
I apologize.
I'm still kind of curious on weither or not to have a pcv valve in there since it seams that the orignal setup didn't have one and it had ported vacuum.
_________________
My First Porsche
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1978 Porsche 924 N/A |
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Ozzie
Joined: 12 Mar 2005
Posts: 4448
Location: Townsville, Qld. Australia
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| Posted: Wed May 07, 2008 2:59 pm Post subject: |
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There is no PCV on the original system.
Even though the hose is 19mm it has an orifice in it. Basically a plug with a 5mm hole.
My setup is like this
I have changed it a little by fitting it to the air box now.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance |
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Mike924
Joined: 12 Aug 2004
Posts: 2601
Location: IoW UK
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| Posted: Wed May 07, 2008 5:06 pm Post subject: |
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| blackhat wrote: | | Ahh ha! The PCV does make a difference! |
It does on the CIS system because it injects un-metered air into the intake making the mixture lean. This won't happen on a carb set-up because the fuel is introduced at the same point the air is metered.
_________________
1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd
'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org |
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