[Bulti]

Hi folks! I want to check/adjust the ignition timing because my rotordisk shifted a bit by mistake during maintenance and my car seems to be short of torque (under about 3500 rpm).

Has anyone any clue where I can find the right procedure for doing this?

This saturday I will have a strobo -and hopefully- a Bosch DME tool at my disposal.

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[kwikt]

I didn't think the ignition is adjustable. I know the cams are though.

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[Cloud9...68]

Funny, I just had someone ask me the same question yesterday. I think kwikt is right - I don't thing the ignition timing is adjustable - it's controlled by the ECU.

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[Bulti]

[quote name='kwikt' timestamp='1375965467' post='146792']I didn't think the ignition is adjustable. I know the cams are though.[/quote]



My mistake, it is the cam timing I'm talking about. My fellow members of the TACB tell me the same thing, but... The disk behind the rotor with 3 adjustable screws must somehow be put in it's excact right position, and I quote Mr. Clark (CAM-04): " I can't emphasis enough how accurate you need to be in scribing these marks, especially on the cam and housing, since the diameter of the cam is much less than the pulley and hence even a 0.5mm misalignment is about 2 degrees of cam rotation."



I put in 3 temporary screws and dit not make any scribings, the screw-method is even mentioned in the Porsche-manual... But sadly enough this wasn't enough to hold everything in place so my cam timing needs to be reset to the factory-settings...



By the way, is there a way to change the title of this topic? Much easier for people in the future when they want to find some info about cam timing instead of ignition timing?

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[Dubai944]

The method Clarks refers to is a way of marking and locking the cam sprocket location before any disassembly so you can put it back in the same position later and avoid having to retime the camshafts the proper way.



As you didn't lock it and mark it you now have to redo your cam timing. Use the factory manual or look on the web.There is a thread in the DIY section on this forum called "Setting the Camshaft Timing" which should point you in the right direction. You will need a couple of dial gauges as a minimum.



How accurately you find <acronym title='top dead center'>TDC</acronym> determines the accuracy of your timing. The piston is stationary for several degrees of crank rotation at the top of it's travel but the book method works ok to get you close enough. If you want to be dead accurate you will also need a degree wheel to find exact <acronym title='top dead center'>TDC</acronym>.

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[tamathumper]

My apologies for not remembering who originally developed this nice translation of the workshop manual into English. It was in Word document format and I spent some time reformatting it quite a bit and getting the images in-line with the document, then converting it to PDF and loading it into Evernote. In so doing I lost track of who was kind enough to share it with me in the first place! Reading and editing the document helped me understand the workshop manual's way of saying things, such as why there are two different dial gauges involved in setting the timing, and even how to mount them magnetically to an otherwise non-magnetic motor. I still need to look into this degree wheel thing...



http://www.evernote.com/shard/s20/sh/314...0743e4c3c7

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[tamathumper]

Has anyone successfully made the camshaft "feeler gauge" on page 15-9 of the workshop manual? If I could get a true 1:1 copy of the page I could machine them out of aluminum easily enough.

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[Cloud9...68]

[quote name='Dubai944' timestamp='1376037513' post='146860']



How accurately you find <acronym title='top dead center'>TDC</acronym> determines the accuracy of your timing. The piston is stationary for several degrees of crank rotation at the top of it's travel but the book method works ok to get you close enough. If you want to be dead accurate you will also need a degree wheel to find exact <acronym title='top dead center'>TDC</acronym>.

[/quote]

This pertains more to my cooling system woes, but I just want to point out that I timed my cams with the engine out of the car, so I was able to use a degree wheel to set <acronym title='top dead center'>TDC</acronym> (before I had put the head on), I believe using the method that you had described. I then made a pointer which I attached to one of the metal belt shield's bolts, and painted a mark on the pulley that corresponded to <acronym title='top dead center'>TDC</acronym>. So I had the advantage of being dead sure that I had <acronym title='top dead center'>TDC</acronym> absolutely perfectly located, which increases my confidence that my cam timing is at least about as close as it's humanly possible to get it using the WSM method.

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[tamathumper]

Yes, that's one of the posts I read in the past that made me concerned about finding <acronym title='top dead center'>TDC</acronym> - the "piston is stationary for several degrees of crank rotation" thing.

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[Cloud9...68]

Agreed - this made me nervous about the WSM method, but I've also read that getting <acronym title='top dead center'>TDC</acronym> absolutely correct actually isn't that critical, but I have some trouble swallowing this. I had the luxury of having my engine out of the car, which made setting <acronym title='top dead center'>TDC</acronym> very accurately an easy task.

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[tamathumper]

Everything I read says a couple of degrees of cam rotation is a critical thing, and hence I have to believe a couple of degrees of crank rotation is equally critical?

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[Cloud9...68]

You would think...

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[Bulti]

A fellow member of my local club told me that even setting the cam timing from one side of the disk to the complete opposite side should only make a few hp's of difference? My car seems to be lacking more than -let's say- 10 hp.

Could it be a problem with my O2- or Hall sensor?

So many parts, so little knowledge...



Tomorrow a friend will stop by who has a Bosch Hammer which he uses for his 993. Is this thing usefull for reading my car's error messages?

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[Cloud9...68]

Have you done a blink test yet? If not, this should be the first item on your list. It doesn't provide any quantitative information, but will tell you if you have a bad sensor of some kind. Best of all, it's free.

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[tamathumper]

Bulti, there are many things it could be to cause a drop in horsepower. Is your air filter clean? Are your spark plugs in good condition? Are your plug wires, distributor and rotor in good condition? Are you maintaining about 20 inches of vacuum at idle? Is your <acronym title='mass air flow'>MAF</acronym> putting out the correct voltage? Is your timing set correctly? Is the exhaust plugged by broken/dislodged baffles?



There is a good section of the workshop manual you can go through along with the Bosch Hammer for troubleshooting things like low power, stumbles, rough idle, etc., and you can read the values from things like the <acronym title='mass air flow'>MAF</acronym> using the Bosch Hammer (a version of which I believe is referenced in that section) - it is in section 24/28 at the end of Volume 1. The Hammer should read your error codes too, if you have any.



On the issue of timing, does anyone have the original, unscaled version of the shop-made cam reference tool? If I can get two measurements off the original, I could make them, although an original or 1:1 scaled photocopy would be awesome. The inner faces of each camshaft appear to be vertical and parallel on the gauge, so a measurement of the space between the faces of A and E, and as a backup the total width and then total height of the rectangle would be enough to go on.

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[Cloud9...68]

Somebody needs to explain to me what this tool actually does. The marks on the cams should be sufficient to tell you that you've got everything oriented correctly, and then you still have to go through the timing procedure to set the overlap, so I don't understand the purpose of this tool. Thanks.

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[tamathumper]

Based on the instructions on page 15-9, my assumption is those profiles should fit exactly over the cam lobes for cylinder 1 when timed correctly and with the lower chain section tensioned. If there's any daylight on the curved faces, then your timing is off... Seems like a lot simpler way to verify timing, even if only roughly, without breaking out the dial gauges.

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[Bulti]

Mr. Tamathumper, my spark plug wires were fine before my maintenance and so was my exhaust. My K&N airfilter is close to new and I just installed a brandnew rotor and distributor cap. My sparkplugs show a brownish deposit on them so they should be fine too? I will measure my <acronym title='mass air flow'>MAF</acronym>-sensor's voltage.



My apologies for my ignorance, but That vacuum-thing I do not understand... How can something like that be measured?



PS: can't a local Porsche-dealer send you a fax of the page from the original you need? The scale would be as good as it gets.

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[tamathumper]

You can measure vacuum with an inexpensive vacuum gauge - your friend with the Bosch Hammer should definitely be able to help you there.



Faxes are notoriously "fit to margin" and usually very low resolution, so no I can't trust them, and unfortunately Porsche dealers don't want to share anything, not even the distance between two straight lines.

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[DaveN]

My mechanic of some 30 years still does my car cams with that silly paper gauge. He just prints it from the PDF and cuts it out. That leads me to believe the PDF isn't that far out in scaling.

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