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fwood
Joined: 26 Apr 2010
Posts: 40
Location: Yadkinville,NC
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 Posted: Mon Oct 10, 2016 9:05 am Post subject: Fuel flow |
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I have downloaded a Model 81 Service Information manual by Porsche. It states that the NA and turbo use the same external fuel pump supplying 750 cc's in 30 seconds. The Factory Service Manual calls for a fuel delivery rate of 1050 cc's in the same time. Which is correct?
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Frank Wood
82 931 |
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fwood
Joined: 26 Apr 2010
Posts: 40
Location: Yadkinville,NC
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| Posted: Wed Oct 12, 2016 10:09 am Post subject: |
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Or better stated why does the PET only list one fuel pump for both turbo and na or am I just chasing a shadow
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Frank Wood
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11723
Location: PacNW
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| Posted: Thu Oct 13, 2016 3:28 am Post subject: |
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As for the volume number, I've understood the higher one to be correct for 931.
As for the PET, it appears both turbo and NA have been superceded to a 911 part number. I'm guessing that wouldn't be the case if you were looking at a catalogue from the era in which the cars were produced.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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ideola
Joined: 01 Oct 2004
Posts: 15548
Location: Spring Lake MI
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| Posted: Thu Oct 13, 2016 4:35 am Post subject: |
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The Model 81 Service Information booklet I have indicates the 911 part number, which matches what is in the version of PET that I have. I agree with Rasta, I think the higher volume number cited in FSM is more likely to be correct.
These work well: http://garage.ideola.com/prod-TuneUpKits.html#Fuel
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erstwhile owner of just about every 924 variant ever made |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11723
Location: PacNW
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| Posted: Thu Oct 13, 2016 8:49 am Post subject: |
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+1 on the Walbro. I started with Pierburg, but it was unable to keep up with cam, increased boost, etc. The Walbro handled it fine.
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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RC
Joined: 25 Mar 2007
Posts: 2636
Location: Australia
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| Posted: Thu Oct 13, 2016 11:17 pm Post subject: |
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| Rasta Monsta wrote: | | +1 on the Walbro. I started with Pierburg, but it was unable to keep up with cam, increased boost, etc. The Walbro handled it fine. |
+2 on the Walbro.
Same story, started with stock, then Pierburg but insufficient flow at high boost/RPM. Now happy running Walbro external GSL392 255LPH (>4LPM).
Personally would use the FSM flow figures as a bare minimum since it is merely free flow. Have found that old/ worn stock Bosch metal roller pumps are still capable of 750mL->1L per 30 seconds open flow but unable to supply sufficient fuel at 3-4bar EFI pressure, let alone the 5-7bar required for CIS.
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World`s quickest 924 2L slushbox
| Allan @ DTA wrote: | | I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards |
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