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Join Date: Jun 1999
Location: Vernon, CT
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tobster1911 - You've got it backwards. The cam gear is the one with the clearance in the keyway. The 3-fingered "spider" for lack of a better name for it, is the one that has a tight fit with the woodruff key. When the central bolt is loose, the cam gear can rotate in relation to the cam lobes a degree or two in both directions. The central bolt locks it down. The distributor rotor attachment bolts go through the elongated slots in the cam gear, and thread into the "spider" This way, regardless of where the gear is adjusted relative to the cam, the rotor stays in a constant position relative to the camshaft, not the gear.

This timing adjustment has nothing to do with ignition timing, it adjusts the timing of the valve opening and closing with the piston stroke. The ignition timing is fixed relative to the camshaft, based on the hall sensor pickup, which is the "dish" clamped between the cam gear and the spider.
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'92 968
'01 VW Jetta TDi
Old 08-12-2004, 01:32 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #41 (permalink)
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Quote:
Originally posted by mike944
The ignition timing is fixed relative to the camshaft, based on the hall sensor pickup, which is the "dish" clamped between the cam gear and the spider. [/B]
Well, not quite...

The ignition timing is still controlled by the DME and is either advanced or retarded by the DME as conditions (i.e. throttle position, rpm, airflow sensor position, etc.) dictate. The rotor is certainly fixed relative to the camshaft, through the three lobed fixture, but the ignition timing is variable and is controlled by the DME.

If you put some timing marks on the flywheel and used a timing light to see changes, you would definitely see the ignition timing move.

I've never quite understood what the hall sensor pickup was supposed to do, but it might actually be letting the DME know exactly which cylinder it is firing (whether 1 or 4, or 2 or 3, since it may want to not fire into a cylinder at the top of the exhaust/intake stroke)

gb
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www.944ecology.com
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Last edited by 944 Ecology; 08-12-2004 at 02:04 PM..
Old 08-12-2004, 02:01 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #42 (permalink)
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Quote:
Originally posted by 944 Ecology
but it might actually be letting the DME know exactly which cylinder it is firing (whether 1 or 4, or 2 or 3,
that's my understanding, and with the 2 knock sensors can retard ignition accordingly when required
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Early '85 944
Old 08-13-2004, 05:40 PM
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vott does ziss do?
 
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oh really? how did he die?
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Old 08-15-2004, 12:59 AM
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vott does ziss do?
 
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gruesome, simply gruesome. the poor bastard
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Old 08-15-2004, 09:31 AM
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Hey. I know this is a very old thread but I'm trying to install my cams and I have done it all according to the manuals and I just have one question, should i not be able to turn the camshaft sprocket by hand?
Old 06-15-2011, 11:00 PM
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944S cam timing

MY old hands are too wimpy to just grab a cam and turn it, installed and all. I can take a 27mm open end wrench and easily turn the cam a bit. Remember, when all is warm and fully oily, and running 2000 rpm, friction drops on all those lobes and plain bearings. At nearly zero RPM, there is a lot of extra friction. Remember cams ran in plain bearings for the first hundred years. Roller cam bearings in blocks just got to megabuck NASCAR teams a few years ago.

I like the factory valve lifter/ crank timing method. I ran into a new snag today on my 1987. I left the dial indicator in place when I rotated the engine a bit. the cam lobe pinched the tip of the dial indicator, and dislodged the steel ball which was supposed to be permanently on the unscrewable tip. I found the ball, and retrieved it with long needle-nosed pliers. I set the crank a few inches before the under car mark hits its notch. I set the dial indicator before the lobe hits the lifter. I used a 27mm open end to help the intake cam in a tiny bit of back and forth. If you do not, you can hit stuff, as the intake cam will drop back quite a bit.

The factory says 1.4mm pus/minus 0.1, which is .055 plus minus 0.004. When the crank is perfect, I nudged the cams with the 27mm until the dial indicator said about 0.055". This is with the cam belt under proper tension, and with the cam hardware a bit loose. I was out by about 0.012 on the lifter the first time, then about 0.002 too much lift, which is where I left it. Remember if you have your dial indicator shaft at a 15 degree angle, you will read a bit less opening than is really there. (cosine 15 degrees, you do the math...) If you make a zigzag extension for your dial shaft, you can keep everything parallel to the valve stem. I was too lazy, and I like a bit of trig every once in a while.

Don't ever bump start your car on the road. The cam belt, even when newish and properly tensioned, cannot take the torque needed to start the cams from zero RPM and take them to 1000+ cam rpm in a split second.

Best of luck,

David
917guy@gmail.com

Last edited by 917guy; 06-20-2011 at 12:03 PM..
Old 06-20-2011, 11:58 AM
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