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Dutch924-racer
Joined: 23 Jul 2007
Posts: 1081
Location: The Netherlands
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 Posted: Tue May 22, 2012 5:56 pm Post subject: Working on custom manufold for 931 |
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I am working on a custom manifold to suit the 951 intercooler.
What thickness flange do I need, i saw in a nother topic they use 10mm flange (see picture below).
[img]
http://i224.photobucket.com/albums/dd298/min113/924TurboIntakeFlange.jpg[/img]
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937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller |
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Rasta Monsta
Joined: 12 Jul 2006
Posts: 11733
Location: PacNW
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| Posted: Wed May 23, 2012 1:02 am Post subject: Re: Working on custom manufold for 931 |
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| Dutch924-racer wrote: | I am working on a custom manifold to suit the 951 intercooler.
What thickness flange do I need, i saw in a nother topic they use 10mm flange (see picture below).
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Toofah King Bad
- WeiBe (1987 924S 2.5t) - 931 S3
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WEASEL149
Joined: 19 Aug 2005
Posts: 595
Location: UK, Sheffield
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| Posted: Wed May 23, 2012 5:59 am Post subject: |
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I also made mine from 10mm aluminium:-
These are the velocity stacks I'm using:-
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1979 UK 932 |
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Joes924Racer
Joined: 03 Nov 2002
Posts: 11964
Location: Oregon, Denver Colorado native!
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| Posted: Thu May 24, 2012 12:56 am Post subject: |
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Your going to have quite a horn section.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo. |
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WEASEL149
Joined: 19 Aug 2005
Posts: 595
Location: UK, Sheffield
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| Posted: Sun Jul 01, 2012 2:45 am Post subject: |
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| Joes924Racer wrote: | | Your going to have quite a horn section. |
Yeah, I'm hoping the music will be nice and powerful 
Hey Dutch924-racer, what are the rest of your plans for a custom manifold?
What type of plenum are you going for?
I was set for a single plenum with a central side entrance but now I'm going for a WRC/Audi style dual plenum with a diffusor.
The main plenum will end up approximately 2.8L volume - I think as long as your main plenum is 2L+ you'll be ok.
The pre-plenum will be tapered and run the full length of the main one front to rear.
With my straight runners, the main plenum will be around 400mm long.
My new throttle is 65mm, so the diffusor area will need to exceed the area of the throttle plate, although I'm still not sure what size slot to cut for the diffusor.
The idea is to slow the air down as it enters the main plenum and so equalising the pressure within from front to rear. This hopefully ensures equal air distribution.
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1979 UK 932 |
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leadfoot
Joined: 11 Dec 2002
Posts: 2222
Location: gOLD cOAST Australia
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| Posted: Sun Jul 01, 2012 9:33 am Post subject: |
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read this post...
this one has pics from the original thread discussing diffuser design and pics and links to the audi cars they came off.
http://www.924board.org/viewtopic.php?t=15967&highlight=manifold
this is the first and second manifolds I made with diffuser/bellmouths,
the first with diffuser only, second incorporating belmouths,
both manifolds were tight in the area of clearance to the brake booster and the second had a larger diameter and shorter main plenum. Also note with the clearance to port centres I adjusted my belmouths.
The hardest part is getting your welder into the gaps required and if your penetration is to much you'll need to allow yourself access to cleaning up the runners.
Stu
http://www.924board.org/viewtopic.php?t=20576&postdays=0&postorder=asc&highlight=manifold&start=0
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress... |
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Raceboy
Joined: 01 Mar 2004
Posts: 2327
Location: Estonia, Europe
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| Posted: Mon Jul 02, 2012 4:31 pm Post subject: |
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Here's how I did the intake on my 931:
And this is how it looks from the inside (the gap is radiused in the finished manifold, not sharp):
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold 
'84 924, turbocharged, sold.
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WEASEL149
Joined: 19 Aug 2005
Posts: 595
Location: UK, Sheffield
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| Posted: Tue Jul 03, 2012 8:20 am Post subject: |
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| leadfoot wrote: | read this post...
this one has pics from the original thread discussing diffuser design and pics and links to the audi cars they came off.
http://www.924board.org/viewtopic.php?t=15967&highlight=manifold
this is the first and second manifolds I made with diffuser/bellmouths,
the first with diffuser only, second incorporating belmouths,
both manifolds were tight in the area of clearance to the brake booster and the second had a larger diameter and shorter main plenum. Also note with the clearance to port centres I adjusted my belmouths.
The hardest part is getting your welder into the gaps required and if your penetration is to much you'll need to allow yourself access to cleaning up the runners.
Stu
http://www.924board.org/viewtopic.php?t=20576&postdays=0&postorder=asc&highlight=manifold&start=0 |
Thanks for the links, I'd forgotten all about those. I must say that was nice work on both manifolds.
Did you notice any difference between the two?
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1979 UK 932 |
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WEASEL149
Joined: 19 Aug 2005
Posts: 595
Location: UK, Sheffield
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| Posted: Tue Jul 03, 2012 8:27 am Post subject: |
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| Raceboy wrote: | And this is how it looks from the inside (the gap is radiused in the finished manifold, not sharp):
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Thanks. Apart from making sure the diffusor is greater in area than the throttle, is there anything else that determines the size of the gap?
I mean, if the gap is too big the diffusor idea obviously won't work but how small in width can you go before that also becomes detrimental?
Should the tapered plenum reduce 25% per cylinder?
I suppose with you running ITB's you get the best of both worlds maybe with great air distribution.
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1979 UK 932 |
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Raceboy
Joined: 01 Mar 2004
Posts: 2327
Location: Estonia, Europe
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| Posted: Tue Jul 03, 2012 2:30 pm Post subject: |
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Gap was 20 mm wide and only the diffuser is tapered.
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
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leadfoot
Joined: 11 Dec 2002
Posts: 2222
Location: gOLD cOAST Australia
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| Posted: Tue Jul 03, 2012 4:38 pm Post subject: |
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well... one car was supercharged with efi, the other is turbo CIS and now twincharged but untested so far, I only drove it for about a week before starting the new project.
I spoke to the guy I sold the SC car to the other day, still going strong after 5 years with no issues if that helps... the one benifit is a cleaner engine bay and less piping...
all in all with the amount of mods we stick on these cars it's a bit hard to tell sometimes, i checked the plugs for the first 6 months on a regular basis to see if any were running hot or fowling, same injector opening times across cylinders and heat ranges is generally a good thing.
I never did flow either of them...
Stu
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress... |
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