Ultimate 930 Distributor, advance, retard, timing, Turbo lag, MSD, mod, thread.

[cole930]

AGAIN GUYS, THE 930 ROW DOES HAVE RETARD !!!!!!!!!





Cole

[cole930]

AGAIN GUYS 930 ROW TIMING 29 DEGREES @4000 RPM






"These are from the Porsche Factory Turbo Maunal"


Cole

[JFairman]

This is offtopic but i noticed you have a synapse blow off valve listed in your list of modifications.
I thought those vent to atmosphere so I was wondering how you have that hooked up with CIS?

[cole930]

Fairman,

First I waned to tell you how much I appreciate your contributions to the forum.
Always good solid information with no BS. Please keep it up.

There is so much crap on here about the Synapse BOV I didn't even bother replying to the threads. It is by far the best, fastest acting, best quality, and most versetile BOV available. It can be plumbed to recirculate (which we want) or vent to atmosphere. It's adjustable for pressure, boost pressure holds it shut (no leak or creep), has increditably fast transition time, AND NO, IT DOES NOT QUACK !!!!! The downside is it is rather large but has enough mounting versetility that it's size becomes a non issue.
I've relocated my CIS to the right rear of the engine compartment (ala 934) to where the AC used to set. So the BOV is mounted on the 14" intake pipe between the CIS and the Turbo intake. This eliminated about 4' of intake plumbing and
a couple 90 Degee bends and also added a lot of space in the engine compartment to provide more cooling. It also eliminates about 700 cu. in. of tubing you have to refill before you get boost back. It's like removing the old pancake recirculation assy. 3 times.
I have been putting the "Old Sled" back together after painting so my engine is out or I would post pics. I'm actually dinking around with seeing if you can make it dual purpose and use it as the BOV and the wastegate at the same time.
I'm planning on being operational by Spring. I live in Indiana so I don't take the old girl out during the winter anyway. The interior is in and I'm finishing up wiring in the engine compartment now. (posted some pics of the MSD install on page 2). When I designed the house I put a small Porsche garage next to the rec. room in the basement so it's a heated and air conditioned Porsche bed room. Very easy access and my office in in the basement also so when my head is ready to explode from work I can just walk out and dink around on the car to chill out.

Cole

[911st]

Brian big thanks and good info!

We are just trying to figure this stuff out and I have a bunch of questions.

What is the factory procedure for timming a single Pot European distribuitor?
Vac line conected or not, at 4000rpm? What is the spec at 4000rpm and idle if you have it.

Can you confirm what timming should look like under boost. In the -16 range or in the -25 range?

I like this set up much better as if there is a failure at the can (pot) it would fail in the direction of safety (on boost timming).

[911st]

Cole,

I talked about that some in the "Advanced CIS tunning thread". http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/461279-advanced-cis-turbo-tuning-discussion-thread-ultimate.html

The concept of how it works if valid. About 7 years ago I flipped an aftermarket adjustable BOV to my turbo and set it up to do the same thing. It would allow air to pass and spin up the turbo during idle and cruse. Then with acceleration it would snap shut for instant boost. I would get .2 to .3 instant boost off idle and .5 bar instant boost off cruse.

They are using the same concept with the Synapse BOV. It keeps the turbo spinning in reserve and the valve closed with loss of intake manifold vacuum.

I am a big believer that turbo response can be greatly reduced using the Synapse BOV concept, a conversion to a 'vac-sensing" WUR like the 3.0Turbos run (or via a D-WUR) that lowers control pressure to reduce restriction created by the metering plate, and a much more ideal timing off idle. I was able to combine the modified BOV concept in my C2 with my custom programmable WUR and I had great throttle response compared to even an EFI turbo.

I have been drooping that piece of information here for the last year or so but no one seems to grasp or use it. With the S-BOV maybe they will.

I am fascinated by what you are doing and would love to see pics on your relocation modifications but probably not under ignition or it might get lost here.

[cole930]

Keith,

I'm the one that posted the 930 Graphs. Here is the one for the Advance Curve





Cole

[Speedy Squirrel]

"AGAIN GUYS, THE 930 ROW DOES HAVE RETARD !!!!!!!!!"

Do the Euro cars have the clockwise distributor or the counter-clockwise distributor? I think they either have the clockwise distributor, or the vacuum port for the distributor diaphram must be on the back side of the can. The manual shows no vacuum advance for Euro cars, only retard. That would be possible if one of the two scenarios above is correct.

[cole930]

Speedy,

I've attached a pic. of the single pot Euro distributor and it is counter clockwise driven. To the right of the picture there is also an explanation of the US/CA dual pot distributor advance / retard operation.

My distributor is exactly like the one pictured. The single pot port on my euro distributor moves the contacts plate counter clockwise in advance of the rotor when vacuum is applied. Also note in the earlier post there is a graph of 78 Euro 930 centrifugal advance curve. Which is the same distributor.



Cole

[Speedy Squirrel]

I think the third possibility is just mis-communication. When they say vacuum retard, they mean retard from the vacuum mechanism. I say this because there is no way to get both vacuum advance and vacuum retard from the same port, on the distributor diaphram, as long as the source is also the same at the throttle body. You can get retard from boost pressure on the same port though, which is what I think they are really saying. The note says:

"The charge air pressure is used for full throttle retard ignition control, to avoid coming into the range of excessive advance ignition at full throttle with the ignition timing which is 5 degrees earlier than the USA version."

I think this statement refers to the Euro cars, which would confirm that the vacuum retard is really from boost.

With regard to ignition controllers with timing adjustment, keep in mind that they are adding or subtracting to the centrifugal advance that will still be in the distributor when the vacuum lines are removed, and that intake manifold temperature has a BIG effect on detonation limit, so stay conservative until you can drive your vehicle on a hot day to make sure that you are safe.

[RarlyL8]

Dave,
I have that exact same shop manual and distributor. The explaination is misleading which leads to confusion. The pot does not work both ways, if the pot performs an action under vacuum it cannot perform the same action under boost using only one input line. When on throttle, vacuum switches to boost which cancels out any function of the pot allowing only mechanical advance. This can be verified by applying vaccum then pressure to the pot.
There is also a schematic of the mirriad of hoses and switching devices for smog that manipulate the vacuum/boost signal. Posting pages from the manual is forbidden on this forum so a hand written schematic should be used.

[911st]

It looks like there are a lot of varations on the 930 distribuitor theem.

75-76. right turning, Vac-advance only.

3.3's all being left turning.

3.3's with just vac-advance --OR -- 3.3's with vac-retard & boost retard.

Calif. may have its own dist or just be advanced 5 deg.

There may be different levels of mechanical advance depending on the distribuitor.

The direction of rotation meens nothing to us exceept that we can not put a 3.0T in a 3.3t without changing the gear on the crank.

Thus:

1) There is a single-conection-pot that has Vacuum-Advance.

2) There is a double-conection-pot that has Vacuum-Retard & Boost Retard.

----

The single conection pot (1) would have to work somthing like this:

It would start at idle at somthing like 0 deg.

The pot would be hooked up to a "ported-vacuum" port that is a hole just outside the throtle butterfly so it sees no vaccum at idle.

With acceleration mechanical advance would take it up to about -18 deg.

At cruse or part throtle, the manifold port would then be just past and inside the butterfly so it will see vaccum. This vacuum would creat the vac-advance function and pull timming up to about -29 deg if above 3000rpm.

On boost the vacuum would go away and the vaccum-advance will stop' bringing us back to about -19 for on boost operation.

This is a safer system in that if there is a failure of the pot's conection or a rupture of the diphram it will fail so boost will not exceed a safe level of timming boost (apx -19).


-----

The double pot (2) distribuitor would have to work somthing like this:

At idle the low pressure port on the distribuitor is seeing vacuum and is pulling back timming about 9 deg in total.

Thus, at idle we should see about 0 deg of timming. With acceleration such vaccum quickly goes away as noted above and timing is no longer in retard an timming jumps to about -9deg. (loss of vac-ret advances timing)

Mechanical-advance then advances timming further to about -26 deg (USA non-CA) for cruse above 3000rpm.

With acceleration boost is then supplyed to the high-pressure side of the pot. At the same time that little solonid that is conected to the low-pressure side closes so the pot only sees the boost signel and we get boost-retard. With this timing drops back to about -16 on boost.

What I do not like about this set up is if there is a failure in the plumbing to the boost retard side we will not see needed boost retard and put the motor at risk.

Furher, if the solinoid that is plumped to the low pressure side fails when it is suposed to close on boost, the can could see boost on both sides of the diphram. This should then cancel each other out and we would not get needed boost-retard and again put the motor at risk and not even know it.

--------

What dose not add up is the mechanical-advance curve shown above. It is way to short for any of the above.

I can see a way such a short mechanical-advance (about 6 total degrees) might work.

Using a single-pot / vac-advance dist, at cruse and pulling vacuum we might see about -26 deg of timming.

With acceleration vacuum would go away and timming might pull back to somthig like -16 if the rpm is above 3000.

Then at idle before mechanical advance timming would run at about -10.

That would actually be a very good set-up for off throtle response and a set up I think I would prefer over any we have discussed for a weights and springs turbo set up.

I am just trying to figure this out and appricate any correction.

----
(Speedy Squirrel, thank you very much for helping me understand the different vac-boost signels available at the throtle body. Very important to understanding how our systems work.)

[Speedy Squirrel]

Keep in mind that the graphs are for distributor timing. Both rpm and adv/ret are double for crank timing.

[911st]

I understand that rpm is doubled to reach crank rpm and that would give us full advance by just past 3000rpm.

I do not understand how advance would double???

For most I am expecting about 18 deg of total mechanical advance.

I also understand the this is the total amount of mechanical-advance, not the net advance curve.

It is interesting that total mechanical advance tappers with increase in RPM after full mechanical advance. I would like to know how they are doing this.

Again, thanks.

[cole930]

Keith,

In response to your reply on the Synapse Bov. Your description of flipping the BOV on your C2 Turbo is exactly what made me decide to buy the Synapse. It's
porting and adjust ability allows me to easily try different configurations. So someone was paying attention but I was not to that stage yet.Now the brakes are upgraded, doors and fenders on, 993 mirrors and door handles done, new headliner installed, glass in, RS carpet and door panels installed, Wevo shifter and coupling in, MSD, Boost Retard, LM1, Greedy EBC, AFR Display permanently in
place, Sparco's sitting in the office with side mounts,sliders,and extinguisher on,
just finished molding up some custom rockers and they are sent out with the bumpers and that outrageous old school tail for paint. I have to terminate all the
new wiring in the engine compartment and the body is done. It's going up stairs to the big garage to cover up for the winter and the engine and trans are coming into the Porsche garage for a good cleanup.

Brian,

Sorry about posting from the manuals. As I understood it manual pages could be posted as technical reference data to illustrate and or validate technical subject matter being discussed in a thread. But advertising for sale or offering them for duplication was strictly forbidden. If I misunderstood I sincerely apologize.
Thanks for the explanation. I looked at it and understood that vacumme would be present when just off idle and as soon as pressure went positive the contact plate would return to it's original position. But it certainly could have been explained better in the text.
I think most of us find timing for forced induction a different animal and thought I would post later and see if we can get back to some of the basics to better understand what is needed.

Cole

[911st]

OK, euro boost retard is as I concluded and as Brian stated from his test of putting vac and pressure to a euro dist.

Looking at the first graph bellow, the euro retard is not "boost retard".

It is "vacuum-retard". To the tune of about 11 deg's.

Again, at cruse Vaccum-Advance is in control of timing. With acceleration and loss of vacuum, advance is reduced and in effect retarding timing for on boost operation.

Mistry solved. Cool

Originally Posted by cole930

AGAIN GUYS, THE 930 ROW DOES HAVE RETARD !!!!!!!!!





Cole

[RarlyL8]

Dave,
Others have been scolded by the moderaters concerning posting copywrite protected schematics, thought I would give you a heads-up.
The 930 distributors really are all over the place. It is best to just lock them down and apply your own timing curve if looking to optimize.

[911st]

Originally Posted by RarlyL8

Dave,
...The 930 distributors really are all over the place. It is best to just lock them down and apply your own timing curve if looking to optimize.

Brian,

Can you expand on this?

How are you locking them down?

How do we "apply our own timing curve"?

Also, what do you think is a safe level of timing on boost might be for most?

Thank you.

[cole930]

Brian,

I do appreciate the heads up. It's a shame because they are such a help to everyone.

On the timing, your advice is probably the best idea I've heard so far. I know you've done some dinkin around with springs and weights and I be interested in
what you think a ideal curve should look like. I know I would be looking at as much initial advance as I could get without bogging and then start retarding at the onset of boost and be at 26-28 up top. I'm talking sc cams, good intercooler,
exhaust, safe afr,s and race gas. Is that even reasonable. I've got a call into a buddy that can get my distributor on a machine for me so I can see what it's at now as far as setup is concerned. What are your thoughts.

Cole

[TimT]

Have wondered about which "copyrighted" material is ok... since Pelican has links to many schematics

Pelican Parts - Porsche 911 Parts Listings & Diagrams

So If I scan then post something from my shop manuals.. its not ok... yet Pelican can...

What a bunch of Boolsheet