924Board.org

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

OK, in order for me to swap on the Weber carb kit I purchased ( http://www.924board.org/viewtopic.php?t=22244 ), I need to have my distributor modified to work on centrifugal advance only, as there is no appropriate vacuum advance source available from the carbs.

I have a 1977 distributor lying around from my old parts car. If I get this 1977 distributor modified for mechanical advance only, could I use it on my 1980 ignition system?

Why not just send of your 1980 distributor for modification you ask? Well, I'd like to avoid downtime, so I'd rather just send off the distributor I already have sitting on a shelf as opposed to the one that is running my car...
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1987 951 - M193 Version for Japan

Min · Posted: Mon May 28, 2007 3:39 pm Post subject:

Or you could just take this opportunity to install edis

Min
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Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Always one change at a time. First I need to get the carbs running with an ignition system I already know works, then I can change something else. I don't want to make too many changes at once, there was a member here who did that and could never get his car running correctly despite throwing $$$$ at it, now who was that....

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1987 951 - M193 Version for Japan

augidog · Joined: 03 Mar 2003 Posts: 1360 Location: New Jersey

If you put the distributor in and plug both vacuum holes it will run on strickly mechanical advance. If you set your timing to 0, if will give you a max advance of 36 degrees. It is a 30 degree distributor with (2) 3 degree centrifugal weights in it. I never owned an 80. I don't know if the ignition box plug in the side of the distrib is the same.
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1978 924 95 mile daily driver.
Audi TB/POR174M/High Flow Cat/2.25" exhaust
I knew that positive thinking thing wouldn't work.

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

No, the it won't work.

The early and later distributors use different signal pickup designs and are not interchangable between designs.

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

If they are both reluctor types, ie- have a coil of copper wire and a 4 point star pickup, with a 2 pin plug then the electronics will at least be compatible.
If they are interchangable the vacume advance is easily just disconnected. The vac advance plate should remain stationary with only the centrifical advance operating.
Under acceleration when manifold vacuum is low the vac ad has no effect anyway. It is primarily there to improve economy and emmissions at constant throttle and on decell.
USA versions also give vac retard for emission control and this too can be disconnected and plugged.

Roger

Smoothie · Posted: Wed May 30, 2007 1:00 am Post subject:

That would be my guess - that anything pre-'81 would be compatible. They were all inductive pickup (TCI-I)(except of course for the points and condenser distributor) up to and including 1980. Then changed to hall effect (TCI-H) pickup in '81. Gohim, are you saying there's non-compatibility among different years of inductive pickup distributors?
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Hmmm, some interesting points guys. The plugs on the side of the 77 and 80 distributor are definitely the same.

I'm wondering if, based on what RC wrote, I should just keep the 1980 distributor as is, and just block the advance and retard vacuum connections, forcing the distributor to operated on mechanical advance only?
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1987 951 - M193 Version for Japan

RC · Joined: 25 Mar 2007 Posts: 2637 Location: Australia

This is an 80 n/a variable reluctor pickup.
If both yours look like these are interchangable electronically, however the mechanical as well vacuum advance curves are different, but not much.
There is sufficient detail in the haynes p131 to calculate your settings running no vacuum advance or retard.
This distributor is modded with both the mechanical and vacuum advance removed and locked, with all advance controlled by electronics.

Roger

[img]http://au.msnusers.com/_Secure/0SQCYDw0Vbvqo*Q5ALVOQJ5850cRr5WbirbKhtUK4oPBB4ccR18x37Hlw9k!lrSJVryf2q!kpStHqeAkj*w3dLa3WcHJKumcxZd9kD!41zxzRYBHpnloW*A/P?dc=4675619037822905547[/img]

PS cant do this photo, i dont know WTF. its there if you want to look it up.

Smoothie maybe.......please

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Thanks RC, I'll do some reading of my Haynes when I get home...
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1987 951 - M193 Version for Japan

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

The 1980 model year 924 and 931 were unique from other model years. Porsche made several major changes to the car, and as a result of what they learned, changed those new parts the following year (probably to correct weaknesses and improve the design).

Some of these changes include the Audi 5-speed transmission (which was given what Porsche claimed was an "improved/strengthed" transmission housing section the next model year), making the 1980 5-speed interchangable with later years, but containing parts that were only used for one year.

The ignition system, which featured a modified ignition system and a distributor changed with a different pickup coil (specific to 1980 model year), vacuum assembly (same as 1981-1982 models), and a different cd ignition unit (specific to 1980 model year).

I do not know if the distributor housing is the same between early and later 924s, but I do believe that the distributor will physically fit, if you want to take a chance.

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

A few vacuum/mechanical advance curves for the 924...no 1980, but I think this image is from the older Haynes manual, I have the 1976-82 manual at home...

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1987 951 - M193 Version for Japan

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Alright, the factory manual had the curves for the 1980 distributor...

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1987 951 - M193 Version for Japan

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

What is the 'modification' you're thinking of having done to the dist.?

If you don't want vacuum advance, just disconnect the vac. line to the dist.

But, why would you not want vacuum advance? What so magical about the carbs that let you they get away without load sensing?

Surely, if the carbs themselves don't have a vacuum line take-off point, it's a simple matter to add one in elsewhere - a T-piece off the booster hose, for example...
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

'There is no substitute for a little grease under your fingernails.' - Chrenan, 924board.org