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What am I looking for on the post you mention?

I am talking about the intake side, not the exhaust. Bleeding exhaust off through the wast gate is how we maintain our boost at the level we want. If your wast gate is to small or restricted you would go into an overboost condition. This can be a problem with the Turbos with an oversized compressor wheel and an aftermarket header system that has a poorly designed WG system.

Some race cars do have provision to bleed off boost on the intake side under throttle as a safety feature or as a guarantee that they do not exceed a mandated boost level by the race org. No production Porsche Turbo dose this.

EFI motors are different from CIS. They can shut off there fuel based on values programed into the map depending on throttle valve angle, intake vacuum, and rpm. Thus, when the throtle is closed at any rpm, fuel flow is stoped.

With EFI they can use blow off valves on overrun to atmosphere. However, Porsche still chooses to vent this pressure back into the intake even on its EFI turbos like the 993 & 996.

CIS is always flowing fuel in a steady stream. (Continuous Injection System) The amount is determined by the among of air flowing over the metering plate and pushing it open. If you bleed off any intake air after the fuel metering sensor and before the intake valve, the motor can not figure this our and will be sending to much fuel.

Like wise, if you develop an intake leak after the metering system and before the turbo where extra air is sucked in, the motor will be getting to much air and will go lean.

If the leak is developd in the intake after the throttle plate the motor will be lean pre-boost as air is sucked in under vacuum, and will go rich on boost as air escapes.

I do not know how you can find one but there is a factory digram of the C2T's plumbing. It better indicates how CIS is plumbed and works.

A digram from a 930 should have the same basic thing. The CBV is just different.

When I had my Turbo set up I got instant .2-3 bar boost off idle and .5 bar off cruse upon acceleration. Also boost stayed at full boost between sport shifts. It did not have to build back up.

The goal for a responsive 930 is in the eliminating all restriction possable after the turbo in the exaust. Keeping the turbo spinning. Getting the metering plate out of the way fast. And getting the best timming and A/F values you can.
Old 12-08-2008, 06:27 PM
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Quote:
Originally Posted by 911st View Post
snip
Want to make more power, open up the intake ports to 36mm. It will be easier for the air to get into the motor and will not hurt you low end at all.

snip
Well OK then!!!


A 1 3/8" holesaw plus finish-sanding took them to 35.5mm. My intake ports were bored out to 38 in anticipation of a Carrera manifold and EFI. But I have to get it broken in and running good on CIS for smog inspection.
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X-1, AFM744, Jon, '92 C2 Turbo
JE 8:1 pistons, 964 cams, 38mm intakes ported/polished/twinplugged, ARP hardware, B&B headers/exhaust, 355whp. Full-blown GT35R 3.2 intake EFI pending...
Where my misspent time and money is currently going.

Last edited by AFM744; 12-09-2008 at 08:32 AM..
Old 12-09-2008, 08:20 AM
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Cool!
Old 12-09-2008, 08:51 AM
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Quote:
Originally Posted by AFM744 View Post
Well OK then!!!


A 1 3/8" holesaw plus finish-sanding took them to 35.5mm. My intake ports were bored out to 38 in anticipation of a Carrera manifold and EFI. But I have to get it broken in and running good on CIS for smog inspection.

are there any parts that i can modify for better power if I leave the heads untouched on the engine, i thinking mabye the stock inlet manifold?

here is how my engien looks right now



anyone have i tip of a good book i can buy that describing engien rebuild,
i going to change the cams for 964 but i have never done that work on a porsche engien
Old 12-12-2008, 01:47 AM
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Many like to have the intake manifold Extrude Honed. I think it is about $500.

This can equalize air flows to each cylinder and increase flow capacity.

I would at least match port it to your intake ports and injector blocks.
Old 12-12-2008, 07:49 AM
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Quote:
Originally Posted by spjuvern View Post
are there any parts that i can modify for better power if I leave the heads untouched on the engine, i thinking mabye the stock inlet manifold?
The airflow bottleneck on our engine is the 32mm intakes. This is a contiguous size from the intake manifold to the intake valve bowls. You can hog out your intake ports (in the head) as big as you want (Ted Robinson showed me some 935 heads with 43mm), but you have to pull the heads to do that. You can open up the intake manifold and injector stacks (like I've pictured above) but there's no sense in it if your intake ports are still 32mm.
The stock injector blocks are 40.5mm OD, and they're phenolic fiberglass. 35.5mm bore-out leaves me 2.5mm walls to withstand boost and vacuum, that's as big as I'll take these (and I still half-expect them to fail).
The 993TT had the same 43mm intake ports as the 935, and used these successfully because of Motronic sequential electronic injection. 935 used CIS and huge intakes because it didn't have to pass smog, didn't have to make torque below 4,000rpm, and ran on liquid crack.
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X-1, AFM744, Jon, '92 C2 Turbo
JE 8:1 pistons, 964 cams, 38mm intakes ported/polished/twinplugged, ARP hardware, B&B headers/exhaust, 355whp. Full-blown GT35R 3.2 intake EFI pending...
Where my misspent time and money is currently going.

Last edited by AFM744; 12-12-2008 at 08:47 AM..
Old 12-12-2008, 08:23 AM
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Quote:
Originally Posted by spjuvern View Post

anyone have i tip of a good book i can buy that describing engien rebuild,
i going to change the cams for 964 but i have never done that work on a porsche engien
http://www.pelicanparts.com/catalog/ShopCart/BOOK/POR_BOOK_bkptec_pg3.htm

Our gracious host's book. I have greasy fingerprints on every single page of mine now. It's not perfect or complete, but damn close.
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X-1, AFM744, Jon, '92 C2 Turbo
JE 8:1 pistons, 964 cams, 38mm intakes ported/polished/twinplugged, ARP hardware, B&B headers/exhaust, 355whp. Full-blown GT35R 3.2 intake EFI pending...
Where my misspent time and money is currently going.
Old 12-12-2008, 08:44 AM
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the intake manifold nuts was a bit lose, i think i have had some leak there



i allso have some oil leak in the rear middel of engien

i have not found someting that for sure caused the oil leak,
anyone else have had the same leak?
i have cleaned the area around the sensors there was a lot of oil before too.

Old 12-16-2008, 10:42 AM
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Quote:
Originally Posted by AFM744 View Post
http://www.pelicanparts.com/catalog/ShopCart/BOOK/POR_BOOK_bkptec_pg3.htm

Our gracious host's book. I have greasy fingerprints on every single page of mine now. It's not perfect or complete, but damn close.
that seams to be the book for me

do you what the differents are in this books

http://www.bokus.com/b/9780760310878.html

that one i found here in sweden

it did not look the same but same name
Old 12-16-2008, 10:46 AM
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That oil pressure sending unit is notorious fir leaking. Replace with a new aluminum washer.

Quote:
the intake manifold nuts was a bit lose, i think i have had some leak there

i allso have some oil leak in the rear middel of engine

i have not found someting that for sure caused the oil leak,
anyone else have had the same leak?
i have cleaned the area around the sensors there was a lot of oil before too.
Old 12-16-2008, 11:26 AM
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I might add a couple of pictures of the car
to introduce my

965 -91 ROW




Old 12-16-2008, 12:37 PM
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Cool pics!!
Especially the flame shooting last one
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Old 12-21-2008, 06:57 AM
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Here is my engine bracket after the reinforce.




Old 01-15-2009, 10:47 AM
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Very nice work. I swear I'm going to take some welding classes...
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X-1, AFM744, Jon, '92 C2 Turbo
JE 8:1 pistons, 964 cams, 38mm intakes ported/polished/twinplugged, ARP hardware, B&B headers/exhaust, 355whp. Full-blown GT35R 3.2 intake EFI pending...
Where my misspent time and money is currently going.
Old 01-15-2009, 11:44 AM
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how do i loosen this bolt,

do i need a Porsche tool or have you guys come up with some other idea?

i want to hold the sprockets still and turn the bolt

Old 01-17-2009, 12:14 PM
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It takes a Porsche tool. Mine is available for local loan-out... but it doesn't look like you're local. Search the Engine Build forum for Cam Tool, you'll need the late style.
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X-1, AFM744, Jon, '92 C2 Turbo
JE 8:1 pistons, 964 cams, 38mm intakes ported/polished/twinplugged, ARP hardware, B&B headers/exhaust, 355whp. Full-blown GT35R 3.2 intake EFI pending...
Where my misspent time and money is currently going.

Last edited by AFM744; 01-17-2009 at 01:10 PM..
Old 01-17-2009, 01:07 PM
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I will borrow the tool this weekend.

are ther some other special tools neaded for my cam change operation?
or could i do this with my ordinary work shop tools, i thinking of the cams axial play and timing

is it someting special about the porsche dial gauge and the holder or could i do this with my ordinary dial gauge and magnetic stand

Last edited by spjuvern; 01-21-2009 at 06:28 AM..
Old 01-21-2009, 05:52 AM
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To set or re-set the cam timing these tools were helpful to me and sold by our sponsor:
Dial indicator holder the "Z-block":
PEL-TOL-P207

Metric dial indicator (If you don't already have one):
PEL-TOL-MDG1

Mark
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Old 01-21-2009, 06:24 AM
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Yes. Because you're changing to a different camshaft grind and/or manufacturer, you will need a tool to measure the offset of the cam sprockets. There is one tool for this that makes it a lot easier and it's from Stomski. It's expensive....surprised?! You can do it with a machined straight edge, but it's annoying for the first timer.

The other tools you might consider are;
spark plug adapter to pressurize the cylinder so you can remove valve springs with a valve spring compressor tool. I'm assuming you are changing springs, retainers and locks for the new cam, yes?

Valve timing you'll need a dial indicator and a Z-block which allows the dial indicator to mount on cam tower with little hassle. Personally, I like to use two dial indicators/z-blocks (one on each bank) for repeatability and sanity.

You'll need a device on each side to keep tension on the cam chains while the cams are being timed. I like the old mechanical adjusters for this, again, expensive. Some use big c-clamp vise grips on the oil-fed tensioners. Others have fab'd their own mechanical adjusters for timing the chains. Once you get the cam covers off, you'll see what has to be done and what route to take.

Other things I can thing of are;
Soft aluminum rod so you can softly tap out the rocker arm shafts from their bores without scoring the cam tower surfaces.
Allen socket and extension to allow you facilitate the removal of rocker arm allen bolts and caps.

Enjoy.
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'85 930 Factory Special Wishes Flachbau
Werk I Zuffenhausen 3.3l/330BHP Engine with Sonderwunsch Cams, FabSpeed Headers, Kokeln IC, Twin Plugged Electromotive Crankfire, Tial Wastegate(0.8 Bar), K27 Hybrid Turbo, Ruf Twin-tip Muffler, Fikse FM-5's 8&10x17, 8:41 R&P
Old 01-21-2009, 06:25 AM
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Adding to Dave's above suggestions, you'll need to re-set the valve spring stack heights for some cams. Some sources say 34.5mm on both valves, some say just the intake side. (Stock stack height is 33.5mm)
Also, IMHO disregard what the cam sprocket alignment was. Mine came out of the never-before-opened engine all wrong.
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X-1, AFM744, Jon, '92 C2 Turbo
JE 8:1 pistons, 964 cams, 38mm intakes ported/polished/twinplugged, ARP hardware, B&B headers/exhaust, 355whp. Full-blown GT35R 3.2 intake EFI pending...
Where my misspent time and money is currently going.

Last edited by AFM744; 01-21-2009 at 08:42 AM..
Old 01-21-2009, 08:40 AM
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