Distributor

[fredmeister]

Originally Posted by Speedy Squirrel

Fredmeister, I agree with your idea, and Porsche930, it is another way to go. Even with the same pressure on the front and the back of the diaphram, there is a retard effect under boost, due to the way the springs inside the capsule bias the two pressures.

so there is a spring inside the can that biases the movement of the diaphragm when the same vacuum or boost is applied across both ports on the dizzy by teeing the line as i suggested. That is what i found from experimenting on my own unit and is why i did it. i just did not know what the internal guts of the dizzy can looked like to account for this.
To be sure if it works, I suggest that 930 porsche install a tee in the line like I suggested and apply a vacuum and then a boost pressure to the unit while it is idling to see if this works on his dizzy. You can see the effects of vacuum and then boost with a timing light and measure the advance and retard in degrees for each scenario as well to get a feel for what static ignition timing to set it to at idle and still meet the 4000rpm requirement.

[fredmeister]

I want to add that the fact that porsche having used many variants of distributor and throttle body as indicated makes this a difficult job for someone to sort out. Something like a distributor set up becomes a job like sending a man to the moon....I sense alot of frustration among members on this forum.
I found that investing in some experimentation with a vacuum pump and boost pump and a timing light will go along way in at least isolating what your particular dizzy does. Then it just becomes a matter of setting the idle timing so that you don't have too much advance under boost yet still enuff initial timing advance so that the car moves out of its own way from a stop light.

[930 porsche]

Fredmeister it seems like this vacum thing about the connections between the distributor to the TB is a mess. I need your expertise to guide me into finishing this project this week-end once and for all. This is definitely a frustrating subject for all of us members but we as a group should be able to come up with a solution and agreement. From the diagrams and from all of the inputs that I have gathered until now from all of you, it seems like it should be hooked up this way:

A to BOV
B to WUR
C to Port1
D Plugged
E to Port2

[jwasbury]

930 Porsche

As others have stated, there are many different distributors out there depending on which year car. Add to that the possibility that you do not have the original distributor in your car and then you have a recipe for mass confusion. I can tell you that I have read every freaking distributor thread on this forum, as well as the factory service manuals and was confused as HELL by how the thing is supposed to work. I would recommend that you purchase a mity vac and test for yourself what happens to the timing when you apply vacuum, or pressure to each of the ports on the distributor.

I hate to add another voice to the confusion, but it appears that you have a 1978 49-state US model. Assuming you still have the factory distributor it should be the same as mine or as Fredmeister's. I found this thread to be particularly enlightening:

http://forums.pelicanparts.com/showthread.php?t=400685

Check out in particular the posts by 356-930 as he is using a US 1979 engine so should be the same as your '78.

I can tell you with absolute certainty that my distributor has no vacuum advance, (only vacuum retard) and does have boost retard, and behaves exactly as described by 356-930 in the post I mention above. I know this because I have tested it myself.

In my case, port 1 (on the outside of the can) is plumbed to the TB and sees manifold vacuum. I would also note that there is a thermo-time switch between the distributor and the TB. The thermo-time switch blocks the vacuum signal to the distributor for 15-20 seconds at start up, effectively advancing the timing and increasing the idle speed for a few moments. With vacuum, the timing is retarded considerably (~20 degrees). When manifold vacuum drops upon opening the throttle, the retard goes away effectively advancing the timing. Applying pressure into this port has no effect. Port 2 (on the inside of the vac can) is plumbed to the boost recirculation housing. Once upon a time, it was hooked into some gizmo's related to the air injection system (long gone on my car and most others probably). Pulling a vacuum on this line has no effect on timing, while applying pressure will retard the timing.

Only a shade-tree mechanic here, but this is what I have observed with my own eyes very recently.

[fredmeister]

Originally Posted by 930 porsche

Fredmeister it seems like this vacum thing about the connections between the distributor to the TB is a mess. I need your expertise to guide me into finishing this project this week-end once and for all. This is definitely a frustrating subject for all of us members but we as a group should be able to come up with a solution and agreement. From the diagrams and from all of the inputs that I have gathered until now from all of you, it seems like it should be hooked up this way:

A to BOV
B to WUR
C to Port1
D Plugged
E to Port2

Nope, i said either C or E to both Port1 and Port2. As long as C or E is a port that connects below the throttle plate so that it sees engine vacuum under idle and small throttle openings. Basically split the hose that comes off either C or E and run it to both Port 1 and 2.
Without seeing the exact throttle body you have it is hard for me to make a clear 100% recommendation.
You know if it did not involve completely disassembling my intercooler to see my throttle body connections I would take pictures and notes of my set up as on my 79 930 turbo for you. i just cannot see it well enuff right now with all this gear in the way.
Maybe others will chime in to confirm. Check out jacob's post above it explains what i am saying.

[930 porsche]

We are almost there. The 2 dilemas are:

Does C go to Port1 and D needs to be plugged?
Does E go to Port2?

Jim Fairman you said:
C to Port1 and D plugged.
E to Port2.

Speedy you said:
C and D plugged.
E to Port1 and let Port2 to atmosphere.

Those answers sound logical except one. Jim Faiman mentioned earlier about E(vac retard) to Port1(vac advance) that they sould not be connected together since they do totally diferrent functions. I need your reasons of which one to pick from the other. Thank you.

[930 porsche]

Fredmeister, the picture of my TB in on this thread. Take a look at it.

[930 porsche]

Speedy, I need your final touch and input of Jim Fairman and yours. Which combo should I finish with.

[Speedy Squirrel]

THE FOLLOWING INFORMATION IS FOR '76 to '79 USA CARS ONLY!

Vacuum Connections
There is confusion due to the existence of the two different throttle bodies. There was one type of throttle body used from '76 to '79 USA cars, and a different type used from '86 to '89 USA cars. THE CONNECTIONS ARE NOT THE SAME BETWEEN THE TWO. They do not even have the same number of ports.

I did some searching in the forum, and someone has in fact posted the correct hose routing diagram for ALL '76 to '79 USA cars. The only difference between the California cars and other USA cars is that California cars have EGR and the timing cut-off valve. First, study the picture in billjam's post in this thread:

http://forums.pelicanparts.com/showthread.php?t=437913&highlight=boost+retard

This is exactly the arrangement that Porsche_930 has on his car. He has no EGR so the ports that we have labeled C and D should be capped. Ports A and B go to the vacuum control valve and warm-up regulator, respectively. Port E goes to Port 1 on the distributor, after passing through the thermo switch (Porsche_930 says he does not have it).

If you have thrown away the timing cut-off valve (labeled as item 9 in the diagram), the most conservative thing to do is leave Port 2 open. This will produce the most retarded timing under full load. If you want to mess around a little, you can tee Port2 into PortE as Fredmeister has done. This gives you more timing under full load, but maybe too much!

I will cover the function of item 9, which I would advise everyone with these years of 930 to keep, in another post.

[930 porsche]

Speedy I looked at Biljam diagram on my thread on page 1 and shows Port 1 to C, and Port 2 to E. The other one from Biljam shows also show Port 2 to E but Port 1 to nothing. Question for you isn't Port 2 the Vac Retard and E also the Vac Retard? If they are the same, aren't they suppose to connect to each other instead of Port 1 being Vac Advance hooked up to E Vac Retard? Explain why do you think Port 1 should be hooked up with E?

[930 porsche]

Speedy I got it. thank you very much for your dedication and patience.Also thanks to all the members which helped me educating myself about this complex vacum maze.