Ok I am trying to follow this thread with the little knowledge I have of the 930 timing and appreciate all the input from the gurus here and also 911st for starting the thread!! :)

I have tried to research it a bit further and I can assume Euro models should have the one hose vacuum pot on the distributer and the two hose pots were for the California cars (for smog reasons idk)?

So in other words my Euro/ROW car which has a two hose pot and no solenoids is incorrect.

I am finding it hard to track down a one hose pot as a replacement. Is it a matter of just replacing the pot (I presume the actual distributor is the same??) or could I prehaps plug the boost line at both the distributor and throttle body and leave the vaccum retard line connected to get the same effect as a one hose pot? :confused:

Helmsy - You have to go by the part number on the outside of the distributor. What is it? The difference in part numbers on the 930's comes down to:

Direction of rotation
Rev limit
Centrifugal advance curve
Vacuum timing control (Pot)

Generally, you can make one distirbutor into another, as long as they rotate the same direction, by readjusting centrifugal advance, changing the Pot, and using a different rotor. You need to find the specs of the distributor that you want. One place to start is here: Bosch Automotive Tradition

Sir Speedy Squirrel!

So fricken beautiful!

So, it looks like there is a stop we can modify for more retard! Maybe not much. I believe when Brent 930 sent his dist to Andial to be recurvedhe thought they modified the pot to.

The drawing dose not show a resting position stop. If it did not have one, we could also see Vac-Advance???

----

In your opinion, should there be full boost present in both sides, would this thing still retard!

Forces pushing for retard: pressure on the outside of the retard diaphragm plus pressure against the "donut" or seal diaphragm. <----, <-------------------

Forces pushing against retard on full boost: return spring, pressure on back side of the retard diaphragm. -->, ------------------>

If the force on the seal is more than the return spring tension the pot should still retard with boost pressure being equalized on each side of the pot. If not, the operation of the solenoid is essential to retard on boost.

This comes down to if the pressure against the seal donut is greater than the force of the return spring.

So, so cool!!!http://forums.pelicanparts.com/support/smileys/clap.gifhttp://forums.pelicanparts.com/suppo...s/beerchug.gifhttp://forums.pelicanparts.com/suppo...s/boldblue.gifhttp://forums.pelicanparts.com/suppo...ys/drummer.gif

Putting some math to it. :confused:

Assume,

Diaphragm is 2" in diameter or 3.14 sq in.

Seal diaphragm is 1" in diameter or .8 sq in.

Boost is 12 psi.

Thus, on each side of the diaphragm under full boost would be about 37.7 lbs of pressure which would zero each other out.

The seal diaphragm would have about 9.6 lbs pushing against the spring toward retard.

If as one test done saw full retard with 5 psi of pressure to only the outside chamber. If so, this puts the spring tension at about 5psi/3.14 sq in or 1.6 lb.

Thus, if that is the case and the small diaphragm is pushing at 9.6 lbs against 1.6of the spring, we should see retard with equal boost pressure to each side.

Further, we would not see full boost retard with only 5 psi of boost, retard would be much more linear which is what we want.

Am I totally off base here in concept or dose this make sense to anyone else?

K

Solenoid, dose it close again after warm up or on boost?

Mike has done some great drawings that will help others understand how the ignition system works.

We need to come to one last conclusion. Dose the Solenoid close again at anytime after idle warm up?

Or, because of the construction of the pot, it still can retard with full boost to each side?

We need this before he can finalize the cruse and on boost drawings.

Yeah, I know that. But, I was more concerned about having too much advance beyond stock when the boost starts to build....thus I set it up to drop 1.5 degrees for each 1.0 psi, affectively removing all 8 degrees of additional advance by the time .3 bar was reached. Then the MSD will drop another 7 degrees beyond that, leaving me with only about 9 degrees advance at full boost.

Following your recommendation, I would still have 5 1/2 degrees more advance than "stock" by the time I hit .3 bar. Maybe I'm worrying about that being a risk for nothing, since I believe all the distributor boost retard is in by then....but still it would be more advance than stock intended.

The question is, should ALL the extra advance be taken out shortly after boost begins to build, or is it ok to leave some in and only make sure it's all gone by full boost?

Help guys!

We need to conclude, dose the dizzy retard with boost to both sides or dose the solinoid on the Vac-Ret side close?

Per Eric's findings he seen neather advance with boost to both sides or his solinoid closing.

The only thing I could think that might be creating the conflict is if the AAR is what is creating the cold idle but the soliniod is not working. Or, the solinoid is working on cold start they the TPS or speed govener is not tirgering the on boost solinoid closing needed.

If pulling the Vac-Ret / inner conection when warm increases idle, the solonoid is working, but still would not know if the signel from the ECU is getting sent.

Another point. Now that we know what the inside of the Pot looks like it seems like the second seal-diphragm might add force that should let the dist retard with equal boost to each side.

Confused. :confused:

How can we verify this please?

This about the last pice of the puzzel.

Mike and I have been working on some drawings and are posting them for review and approval if we can agree they are correct.

1)Cold start
2)Warm Idle
3)Cruse
4)WOT/On Boost

1) Cold start: shows no timing retard as both connections to the dist are blocked. The Thermo-Valve is blocking any resident boost and Solenoid is blocking intake vacuum. If either signal was to reach the pot, it would retard timing and not let is run a steped up idle. Solenoid bleeds any resident pressure in Pot to atmosphere. Also, AAR is open.

http://forums.pelicanparts.com/uploa...1254788759.jpg


2) Warm Idle: Timing is retarded with combination of small resident boost that might be present from turbo at idle and mostly from intake vacuum.

http://forums.pelicanparts.com/uploa...1254788893.jpg


3) Cruse. Butterfly moves past ported connections. The Boost-Retard side of pot sees vacuum and the Vac-Ret side sees modest resident boost and all retard function is suspended. (If there is any advance function we would see is by reconecting the pot and running up to 4000rpm.)

http://forums.pelicanparts.com/uploa...1254790167.jpg


4) WOT/ On-Boost.
This may need to change. I now believe the dist is constructed so there are two diaphragms. One being the larger Retard diaphragm which can see boost pressure from both sides at WOT. The other being the Seal-Diaphragm that will push toward boost-retard and might be overriding the stalled larger diaphragm for a more progressive on boost-retard.

Thus, we show the no effect from the idle-solenoid. And, on boost we are showing boost to both sides of the pot and --full retard.

This is open for discussion.

http://forums.pelicanparts.com/uploa...1254789265.jpg

Big thanks to Mike/copterdude for the wonderful graphics!!! :D

assuming the solenoid does nothing after 2 min at starup what does the TPS do??

Thanks

Not sure. Maybe kicks it out of Lambda at WOT. Good question.

Sorry to re-direct the current direction this timing thread is going, but personally I'm not concerned about thermoswitches/solenoids/boost vs. vacuum retard, etc....though it's good to understand all the inner workings. You boys just keep it up!

Back to the quetion I posed, re: when is too much advance too much with regards to varying levels of boost, and my MSD method of increasing advance safely. I've come up with a simple method to limit the additional retard that the MSD will add (up to 15 total), giving me some extra control on what the curve looks like. I have installed a small pressure regulator set to 5 psi (about .3 bar) which will stop any additional retard from being introduced after .3 bar via the MSD. So now I can add as much static advance as I want and have the assurance that it will all be gone when I want it gone....and that no additional retard will occur beyond that set point (the thought being that additional retard will hurt performance at full boost).

Just something to consider for people using the MSD boost ignition retard module as I do. I can now keep my full boost advance at factory 16-18 degrees and still control just how deep into boost I want to go before returning the entire system back to stock timing. Call it a poor man's approach to re-curving the ignition.

I did the following test today
I wonder if the solenoid goes back to 12v at boost?
Anyone game for testing? Mine is taken apart again
http://forums.pelicanparts.com/uploa...1254796579.jpg

Cool.

Only see 12v closing the solinoid during the cold start.

Anyone been able to comfirm any activity at the solinoid after cold start?

Some good engineering work Mark. And still no time to install that LM-1/2?

“When is too much advance too much with regards to varying levels of boost. . .”
When timing is sufficient to produce detonation or pre-ignition. The advance timing limit is a function of effective compression and fuel octane. I’ve seen reference to 21 deg BTDC and 15 deg BTDC at full (0.8-bar) boost. Jack Raby of Aircooled Technology noted in an article that lots of timing does not equate to more power under boost.

If one wants to push the limit on timing, one needs a knock sensing/automatic retard system. Perhaps the Safeguard <http://www.jandssafeguard.com/index.html> from J & S Electronics?
Hint-hint: John @ Safeguard – Give a unit to Chris Carroll of Turbokraft for installation test and evaluation on a 930. If Turbokraft finds the unit to work as advertised and advises the 930 community of positive findings, you will have the 930 market sewed.
Disclaimer: I’ve never met John or Chris. Am a satisfied customer of Chris and well aware of his stellar reputation in the 930 community.

Mark, since you/I purchased our trick MSD stuff, MSD has introduced a better, less expensive device, the programmable 6AL-2 @ $410 list. See specs @ MSD Digital Programmable 6AL-2 - 6530
This system, like yours, is a poor man’s approach to distributor re-curving provided you don’t have to pay someone else to install and adjust. (But that’s true for any introduction of MSD’s ignitions to the 930).
And, if doing the MSD dance, don’t forget to “fix” the rotor and change the spark plug wires!

Jake Raby uses a SafeGuard on his dyno:

Don't miss the last two posts in this thread:
Shoptalkforums.com :: View topic - JS Safeguard- Knock retard system

http://forums.pelicanparts.com/1404393-post34.html

As of 8/31/09 he planned to use it on a new project:
TheSamba.com :: View topic - The Build: 223HP Type 4 & 915 Tranny into a '68 Double C

Mark,

I had some thoughts early in this thread on using the MSD in place of the factory Boost-Retard. You are running yours in searies with the stock retard. Running it as a stand alone might be a little less complicated.

Testing on a dyno is the only way to find the ideal timing on boost.

However, if you read earlyer in thread it could be in a range from -15 with higher boost, poor intrecooler in a hot climite. -20 might be possable with a stock compression, stock boost, and very effecent intercooler where better fuel is available.

However, if you disabled the boost retard functin at the dist and used your MSD instead and if -17 on boost is your goal, set you timing at 4000rpm per factory spec at -17 plus the 15 your MSD will make or -31 for cruse.

Where is might be possable to run up to -40 on curse with agressive pull back with acceleration it mosty just improves gas mileage, not performance.

Now you can set your MSD to fully advance by .8 bar or about .8 deg of retard per pound of boost so you are fully retarted by .8bar. You can adjust your strategy depending on your fine tunning.

If you set your timing at -31, and the mechanical advance is good for 18 deg, your timing at idle should come in at about -13 at idle. (You may have to reindex you dist.)

That is prety agressive. If the car balks you could keep the Vac-Ret function. This would pull timing back to about -3 and instantly jump it to about -13 with loss of vac. Or, you might step up your idle to 1000rpm. This way when you start from a start you will pretty much be at 1500rpm. By then we cand take a lot of timing.

------

Your boost clamp on the MSD line is interesting.

I do not know what the ideal retard curve should look like. One retard curve I have seen of unknown origin for a 930 was as follows.

boost - timing (4000rpm)
.0--- -28
.2--- -26.7
.4--- -23.5
.6--- -20
.8--- -17.7
1.--- -16.5
1.2- -15

The best.

More boost retard for more boost by modifying the pot limit.

I talked to the shop I use. He told me back in the day he used to modify the stop that limits the amount of retard the Pot contributes so be would get more timing retard on 930's he set up to run more boost.

This is a better idea than just pulling back the factory spec. It would however also retard timing further at idle. However, once acceleration begins, timing will jump back to stock.

I would look into this as a way to advance total timing at idle and cruse and keep on boost timing in place. If we can get another 2 deg we could set timing at -28 instead of -26 for better curse economy and get another 2 deg of timing just off idle for better throttle response.

Timing Advance Warning!

We do not have any capacity to pull timing back with increases in the air temp entering our motor.

Most EFI motors pull timing back with heat. I believe the pull back on an EFI motor can be as much as 5 deg or more.

Thus, if one sets up there motor under fair conditions and takes there car out 100 deg day without building in a safe margin, the car may go boom! :eek:

A recording of "inaudible knock", played into one of my controllers:

Picasa Web Albums - John - J&S Vampire I...

The bargraph voltage represents the amount of retard that cylinder will experience the next time it fires.

The unit on my bench is trying its best to retard timing of the engine on the tape:)

That's the piece I was looking for, but keep in mind that those boost levels happen considerably below 4000 rpm, so I'm not sure why you referenced that in particular...unless it's just being "normalized" to a 4000 rpm base.

I indicated in blue what my current theoretical curve looks like using the MSD progressive retard. This weekend I'll install the pressure regulator I mentioned earlier to limit the amount of pressure the MSD sees to no more than .4 bar and let the normal distributor boost retard finish the job from there to achieve 16 BTDC@.8 bar boost. At that point all my added 8 degrees of advance will be gone, the MSD will no longer continue to retard, I will have more advance in the mid-range boost levels, and I'll retain the proper advance on full boost. Like I said - it's a poor man's boost curve to be sure!

That's probably as good as can be done with the technology, other than completely disabling all normal distributor retard functions and let the MSD do it all in response to boost.