Now can someone confirm that the solenoid on the Vac-Retard side is open or closed with 12v?

Most assume it is closed with 12v.

It would actually be better if it opens with 12v!

It could work either way.

Yes, that confirms what I have been told. The full throttle switch and the output from the speed relay tell the solenoid to close when above 2800 rpm and full throttle. Also, the inner diaphram IS NOT blown. It will hold neither boost nor vacuum. It has a bleed orifice in it. Pressure or vacuum must be applied continuously in order for it to work. Without this, closing the solenoid would just trap pressure in there, keeping the diaphram under pressure.

I just tested mine and it would not hold a vacuum with or w/o 12v.:confused:

Dose it raise idle when you pull the vac-ret side (facing the dist) and plug it?

If not, the Vac-retard it not being enabled for some reason. Leak in the Pot or the solenoid failing in the closed position.


SS, why would there be an orifice? There has been some info that might support such a point.

I can see the vac ret stooping of idle. I am a bit concerned if we can not get full boost retard before 2800rpm. Especially with full sport exhaust and or quick spool turbo as they can be well into boost by then.

Guess we are still connecting the dots until we can confirm they can or can not hold pressure putting a vac or pressure on one side.

Sorry, you meant the solenoid.

If so, I would suspect it is down. And if that is the case it sounds like it failed in the open position.

Guys have been using these to block the signal to the WUR to delay boost so it should block pressure.

It would be a long shot if they only helled pressure in one direction but it is possible.

JFairman,

Thought you might like this post from 4/08 I came across.

Except you call it the Vaccum-Advance instead of Vac-Ret.

Here is a good point of referance from DonE. We all know he has an extrem motor.

Per Wiki Answers:

"The easiest way I know to initially test the Vacuum Advance that is connected to a distributer is to simply detach the vacuum line from where the line leads to and suck air thru the line that should still be attached to the Vacuum Advance. If it holds suction, it should still be in good shape, if not, it's bad. "

Thus, the standard Vaccum pot is suposed to hold a vaccum.

Keith, I bought my 930 a little over 3 years ago and when I made that post I was obviously confused about what was going on with the vacuum lines, thermal valve, and the vacuum solenoid.
I don't remember what that thread that was and I'm not going to go looking for it.

I never worked on a 930 other than changing the oil before I had my own so I've learned what I know about them in the last few years from my own experience, this forum, and a couple guys I know in town here that work on them for a living.

Most of my working on cars experience is with some of the Porsche race cars at Gunnar Porsche when I worked there, and on BMW street cars at a street car repair shop I used to work at and my own BMW's and 912's over the years.

I have learned more about 930's since then and I guess could go back and correct and reword what I said there if you want.. and I'm not sure why you're quoting it because you know I am not describing or theorizing it that way these days.
It appears you just want to make me look wrong and embarress me or something, etc.

Originally Posted by DonE
At idle, my timing is 8 degrees, then climbs quickly to 36 degrees around 2500rpm, dropping to 18 degrees at 6500rpm (1 bar). I use a 2D table, so my timing is set by MP and RPM. My timing curve gives me 502 lb ft torque, but more importantly to me, it gives my 8.0:1 CR motor a nice kick at low throttle/rpm.

That is somewhat where I am at, at least with regards to the 8 degrees BTDC at idle, and ending with 18 degrees on boost (calculated based on assumed 8 degree boost retard from the dizzy). I know for sure that I'm getting 34 degrees at no-load 4000 rpm. Unfortunately all I can tell are the starting, middle, and ending points. I have no idea of the "curve"...how fast the timing advances along with the rpm. Need a dyno or a scope or some such thing hooked up to map it out but haven't a clue how to do that. Maybe something as simple as standing behind the engine with a timing light and increasing the rpm's by 100 increments, while taking note of the timing advance....and plot out an off-boost curve in that fashion.

Of course I'm not running with 8:1 compression, nor am I'm getting 502 lbs. of torque either.

JF,

I would not change it. It seems 100% spot on to me or at least what everything seems to be pointing at!

Whoever you were quoting seemed like they knew there stuff.

K

Mark,

From what I believe so far, stock boost-retard is about 10 deg. Plus, what you have from the MSD. 8 seems low but is a safer number to use.

Using the MSD boost retard in series with the stock system seems like an improvement to me.

Stock retard seems to be all in by about 5 lbs of boost. Fuel enrichment at about the same time. Running rich and retarded might be leaving something on the table in the spool range. Might not be any or just a little.

I would love to try killing the stock retard and use the MSD's thinking it might be more progressive. However, as noted early in the thread, we are limited to 15 deg of retard with one of the MSD's so if -17 were an ideal on boost setting, the most cruse timing we could get is -32. An improvement over stock, but maybe not as much as we could use if managed correctly. Still, cruse timming dose not seem to have much impact on performancer, only MPG.


It seems clear that the best way to get the most our of a system no matter what the configuration, is to understand how it works and tune it on a dyno.

We all use different combonations of parts and each motor will respond differently.

Add to that the need to leave a fair amount of safety margin in as our motor do not have compensating features like adjusting fuel and timing for hotter or colder conditions.

I just went out diddled with my vacuum lines and checked both fittings on the distributor vacuum pot with a mighy vac tool.

My distributor was replaced with a new one around 30,000 miles ago according to the receipts I got with my car from the previous owner.
The number on the distributor is 0237302045.

I just connected a mighty vac vacuum pump to each fitting on the vacuum pot on the distributor individually and both of them held a vacuum with no leakdown, so they do hold a vacuum and there can't be a bleed orifice in mine.

Then I started it from cold and checked for voltage to the vacuum retard solenoid and there was no voltage and no vacuum making it through the vacuum solenoid to the blue vacuum retard line at the distributor. Idle was around 1100rpm.

After 2 or 3 minutes the idle abruptly dropped about 300 rpms like it always does after a cold start and if I pulled the blue vacuum retard line off the distributor pot the idle went right back up around 300 rpms.

Now it gets weird... I pulled the electrical plug off the vacuum solenoid and the idle stayed the same with both lines on the distributor and when I checked for voltage at the plug I only got .5 volt.
I really thought it would be 12volts and if I pulled the plug off I thought the solenoid would close back up and idle would raise back up but it didn't.

The electrical contacts are old and kind of dirty so maybe thats why I didn't get 12 volts but now I'm wondering if this vacuum retard solenoid opens and closes with a pulse of voltage instead of continuos voltage and then just stays in that position with no more voltage going to it.

Confusing, so I guess I'll spray some contact cleaner on the plug connection and check it again.
Hopefully my psycho neighbor won't call the cops from me idleing my car in the driveway again...

Here's a pic of my distributor and the vacuum retard solenoid as I have it mounted these days. The polished turnbuckle to the left of the distributor helps to hold down my intercooler.
http://forums.pelicanparts.com/uploa...1254432091.jpg

http://forums.pelicanparts.com/uploa...1254432144.jpg

[QUOTE=911st;4930028]
I would love to try killing the stock retard and use the MSD's thinking it might be more progressive. However, as noted early in the thread, we are limited to 15 deg of retard with one of the MSD's so if -17 were an ideal on boost setting, the most cruse timing we could get is -32. An improvement over stock, but maybe not as much as we could use if managed correctly. Still, cruse timming dose not seem to have much impact on performancer, only MPG.
QUOTE]

You can get as much on-cruise (off boost) timing as you can physically dial in by rotating the dizzy. You shouldn't be limited to 32 degrees advance. If a person were to dial in say 10 degrees advance at idle, and the distributor adds another 8 degrees via mechanical advance, and if your dizzy is curved correctly you should end up with 36 degrees at 4000 rpm...other thereabouts (when stock, mine used to give me 26 degrees at 4000, set at 0 degrees @ idle). The MSD can take off as much as 15 degrees in response to boost, so theoretically in this example you would end up with a boost timing of 21 degrees...maybe a little much to be safe, but who knows?

I know this all sounds like a broken record....

Excellent!

Very clean motor!!!

Looking at the solenoid it would seem that it would need 12v to make it work judging by the size of the coil around it. Look forward to your solving the current issue.

Great to confirm there is no orifice or check valve built into the pot. An orifice did not make sense to me.

Also, dose the valve close when the throttle switch indicated you are no longer at idle? Or at 2800rpm as Speedy Squirrel notes? Just a thought.

Say hi to the neighbors for me.SmileWavy

Interesting that you mentioned that, I pulled the plug on my solenoid after the idle dropped to see what the voltage was. I too was surprised to see .5V. I had the day off today, and have been farting around with this all day. I took it for a drive with a vacuum guage teed into the vac retard (inside) port to see how it behaved. It of course showed vacuum until you accelerate then went to pressure, up to .9 bar? Further, I tried 911st's suggestion to remove and plug the vac retard side, and went for a drive like that. It did have noticeably better throttle response. But did not have the huge kick in the rear on boost. Soo, I am now wondering how long I have been driving around without boost retard protection, and why my motor hasn't blown? Also just for giggles I made a half azzed attempt to measure the boost retard capability of the dizzy by comparing the timing while applying pressure to the port, it seemed like it was capable of retarding around 15 degrees all the way to the stop. I was not able to measure the amount of retard at .8 bar because I ran out of tees to hook the guage to. Again not very scientific, but it did seem that it was able to retard more than 9 degrees that have been talked about.

Now I am starting to wonder if perhaps there may be a pressure differential between the two ports? I measured and saw .9 bar on the vac retard side, so kind of doubt it unless the other side that I did not measure had more pressure some how and was able to move the timing. Otherwise I guess I have been running without boost retard. No wonder my car is soo fast! Guess it is time to do a leakdown!

I don't know, it's too hot to fool around with now.. after 4-5 minutes of running it's too hot to touch things around the distributor so it's cooling off and maybe the creep that lives behind me is too.

When I put around 15" of vacuum into the left side or outer advance pot that the red line goes to the engine speeded up.
When I did the same to the inner or right side retard pot the blue hose goes to, the engine slowed down..
That means the left one is advancing the timing when vacuum hits it and the right side one is retarding the timing when vacuum hits it and my guess is they cancel each other out when boost pressure replaces vacuum in the 2 lines leaving only centrifical advance which may be what boost retard amounts to..... but thats a guess and I don't know.

I don't have a degree wheel so I didn't bother hoking up a timing light to try and guess how many degrees the vacuum pot is changing the ign. timing.

Great work guys. So cool.

Look forward to hearing what you guys figure out about the solenoid issue.

I am hoping it takes voltage to hold it open, not close it.

(Could the .5 v be from some type of leakage back through the bolted connection and or the ground wire? Or could there be enough vibration from the metal plunger inside the coils to generate .5v or something? Electricity is not my area.)

I am wondering how much timing these cars can take on boost? There seems to be a fair number of guys that might be running without full factory boost retard.

I also saw one post that said one expert on a turbo recommend -22 on boost as being ok on a modified 930 on boost. Maybe there is enough safety built into the motor. Maybe that is why the full advance numbers are so Conservative to begin with and why a Calif car can run -29 deg advance with what seems like it might be the same distributor.

I pulled the plug off the solenoid and measured the two female contacts in it directly with a digital voltmeter so the solenoid wasn't affecting the reading.

At the moment I'm guessing that the solenoid just gets just a short pulse of current to open or close it and it stays in whatever position till it gets another pulse.
Thats totally a guess but if thats how it works then thats good because it would use less battery or alternator current while driving the car.... oh yeah, we do actually drive these things sometimes.

The ports the two vac/boost connections are made to are a version of a "ported" connection.

The boost-retard connection is just outside the leading edge of the throttle butterfly so it dose not see boost at idle which is possible (I pulled about .2 bar at idle.) When the throttle is opened this port moves to a point past the butterfly and it sees the intake and sees the same vacuum or boost the motor sees.

The Vac-retard connection sits just inside the other end of the butterfly. At idle it sees vacuum. Once the throttle is advanced it moves outside the butterfly and sees the same pressure that one would see at the inter-cooler exit tank.

Thus, past idle, there will be no vacuum on the Vac-retard side and at cruse it will actually see boost.

At cruse the boost-retard side will see significant vacuum. With WOT when the intake manifold shifts to positive pressure it will see it.

Idle: vac on inside port, boost on outside port.

Cruse: Boost on inside port, vac on outside port.

WOT: Boost on both ports. --- This is why we need the solinoid to close. If we see boost on both sides, there will be no boost retard as proven above with the teeing to both sides of the pot and adding pressure.

----

With the single port Euro it only has Vaccum-Advance. It is hooked up to a port that sees no vaccum at idle (we do not need advance there) and on curse it will se vaccum. With acceleration the vaccum goes away and the vac-advance is pulled back to a safe level for running on boost.

----

I am very interested if there is more than 10 deg of retard past .8 bar. I was expecting a stop as 365-930 found he got full retard with 5 lbs of pressure.

On the first higher flow fuel head were I cam up with using a MSD rpm switch to delay enrichment, Brent used one of those solenoids that was left over to pinch off the signel to the WUR so he would not go pig rich.

Thus, I am not expecting it to be pulse on /off valve. I will try to check if it was the air pump or Vac-retard solenoid that was used and if it was open or closed with current. I do not know if there is difference between those two valves or not. Again, I am an idea guy.

I checked mine again, and it definitely does not hold pressure or vacuum on the back side diaphram connection using the mityvac. But if I hook it to engine vacuum it does. The engine can more than make up for the vacuum "leak". I would assume the same would be true under boost.

The reason I think a bleed must be required is that, if you close the solenoid under pressure or vacuum, won't it just trap the pressure or vacuum in the hose and diaphram if there is no bleed? What would be the point in that? You would just seal vacuum or pressure in. I think the solenoid must cut off boost to the back side so that retard can occur, so I think there must be a bleed.

As far as those who have taken their solenoid off, if you leave the hose on the back side off, then you get retard sooner than you want it. If you leave the hose on the back side on, and connect directly to the original port on the throttlebody, you get more retard at idle, and no boost retard. I don't think it will knock in all cases, maybe not at all if you can get 94 (r+m/2) octane fuel.

What year is your car? What are the numbers on the distributor? and is your car USA or ROW?
Also which vacuum pot connection are you referring to when you say "back side", the red hose to the left or the blue hose to the right?

My distributor is fairly low mileage, I mentioned the numbers on it in an earlier post. I believe it is in good condition and working correctly.

And both sides of the vacuum pot on my distributor hold vacuum with a new mighty vac hooked up to it directly on one port at a time... no leakage at all.
Maybe yours is a different model or maybe yours has a leak.

I just drove mine a little with the blue vacuum retard line disconnected and it idles about 300rpms higher and does seem a little peppier under 3000rpm. Then I stopped and put the blue vacuum retard line back on, burning my hand on the fan housing in the process and drove some more and it seemed to loose a little pep under 3000rpm.
I was on city streets and never really got into boost.

I'd like to just leave the blue vacuum retard line off and lower the idle speed at the throttle body down to 800rpm where I like it but then I don't know what the timing will be under boost and I don't want to take a chance on breaking piston rings or whatever with detonation.

If we were talking about fluid it would be a real issue. With air, the trapped air will compress. Especially if you add the volume of the supply tube.

It might even be possible the solenoid can be pushed past or closes with vacuum on the back side. Just thinking out loud.

That is preferable to having equal boost on the back side.

Maybe this slows down the retard a little. Remember, 930-356 found that he got full retard of about 10 deg with only 5 lbs of boost.

When Brent 930 sent his distributor to Andial my understanding was they told him to leave the back side / Vac-Ret side unhooked.

We have two reports today that with the Vac-removed we see a little bit snappier acceleration. This might indicate that there is potential on the off idle portion.

We are only removing the Vac-retard part and not really advancing the off idle part.

JF: Your description makes the most sense to me... My car goes into the shop to have the "vaccuum pot" changed next week [while i'm on vacation]. Hopefully, by then, we can come to some sort of solution as to what [and how] the heck the vaccuum solenoid does and works! Right now, my soleniod is disconnected...

On a side note: It's amazing how something so simple and "assumed" can turn out to be "not so!!"

Mooney,

Please get the take off and cut it open or send it to someone that can so we can see what is inside?

That would be major.

Thx.

This dose not directly relate however, I came across it and it dramatizes how different builds will be able to handle different boost depending on inter-cooler efficiency.

We have the same issue on the ignition side. It will depend on the AFR's being run, inter-cooler efficiency, cam, C/R...

Thus, a "dyno tune" is going to get the most from our motors. Still, we need to build in a safety margin as these motors do not have knock sensing or the ability to adjust ignition or fuel.

will do... I'll get back on this when i return [after the 14th]

One source seems to think the Solenoids are Normally-Closed.

Maybe just try to blow or such through one with the key off.

If this is so, it would see voltage at idle when warm to close it.

We still need to verify this.

My part number is the same as yours 0237302045 and the other number is PGFUD6. I was referring to the blue hose, so maybe mine and copterdude's are broken.

If someone can tell me where to get another one, I'll cut this sucker open right now, unless it costs $500 or something!

Piston, not diaphragm???

Looking at a dual connection pot, I am wondering if they might have a piston in them instead of a diaphragm?

10 deg of range is more than most Vac-Advance pots that use a diaphragm I suspect usually have.

If there is a piston it might be shaped like a cup and thus be directional.

Then with boost from one direction and vacuum from the other, it would better seal when working.

If this is the case and we put pressure on it from the vac side, such pressure might push past the side-seal of the piston. Same thing if vac is put on the boost side.

This might explain some of the differances in findings on some of the tests.

The dual port pot dose not have the seam on the side like a normal Vac-advance pot where the diaphragm might reside. It has a barrel to it and a recess where a spring would set if you wanted it to push inside a piston cup.

Just a thought???

No, I have seen the inside. There are two diaphragms. One is like a disk, and the other is like an annulus, and there are two springs, and two sets of stops. One set limits the minimum and maximum that the red hose side can move, and the other makes it so the blue hose side can only retard, not advance.

I have one. I will have to dig around for it. it had a broken vac retard port so I found another one. Will disect it and report.

I tested voltage at the female also and just turning key on , not starting, read battery voltage for a min or so then 0. I will put it all back together and play more.
This is getting expensive, a vacuum advance, and solenoid. The MSD 6530 is now a clear option. It's fully programmable, incorporates the 6420 and the 8977 into one package. Then I can get rid of it all.

Copterdude.

Great info.

So the solenoid is powered during cold start which means it must be normally-open and closes with power.

A programmable MSD that gets fully mapped ignition is probably a best practices set up! Has the potential to make improvements on many levels. Would be great if it had a temp sensor input. Most modern EFI set up I believe pull back timing with intake air temp.

Copter, are you in need of a vacuum pot? I found my old one, I believe it is functional, if you can figure out how to attach a line to the inner nipple as it is broken off and the PO I guess tried to JB weld it back on. I don't know if it would be of any use to you, but I will send it to you if you need it. I know first-hand that they are expensive. Just a thought before I crack it open in "the name of science".
Eric

According to the little symbol in the workshop manual it is a solenoid valve with three ports and two positions. When the solenoid is unpowered, the vent port to the atmosphere is blocked, and flow can go through the valve from port 1 to port 3 (unpowered = open). When powered, the port labeled "3" goes to port 2 (atmosphere). It does not show latching, so it has to be powered all the time to vent. The vent also explains how the blue hose side of the diaphram is bled down, so that makes sense, and further convinces me that copterdude and I have broken diaphrams on the blue hose side.

Can the ring change the pressure ratio from side to side so the boost side can overwhelm the vacuum side should it see an equal boost signal on both sides?

That is, if we have two pistons pushing against each other. One has twice the surface area and both get the same pressure, the larger piston will dominate.