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

[willtel]

Originally Posted by 964 T #304

How dificult would it be to use a Megasquirt ecu to program the timming with and still run the cis injection. Those are pertty reasonable, but don't know about the reliability for use on our cars.

I'm wondering the same thing, it does appear to be possible, http://dinsen.net/murena/efi/megasquirtignition

This thread is getting confusing.

Even if we route all the vacuum stuff correctly who is to say that our distributor internals are any better than the one copterdude took apart? It seems that most of us are depending on old technology that may or may not be working as designed to control one of the most important aspects of our engines.

Dreaming of a crank triggered individual coil dual-plug ignition system...

[drmatera]

that there is engine porn

after reading this thread I am so glad i'm going with crank trigger coil pack ignition control.

[willtel]

Some more stand alone ignition info using a Ford EDIS-6 coil pack. This guy appears to have it working on a carbed car.

EDIS6 Running on Flickr - Photo Sharing!

[Speedy Squirrel]

It would be easy. The distributor is compatible with the fm hei ignition module. That is what I use. Megasquirt and others have directions for controlling hei. Plus, you can still use your cd ignition.

[WERK I]

Originally Posted by drmatera

that there is engine porn

after reading this thread I am so glad i'm going with crank trigger coil pack ignition control.

+1

The only benefit I could see if there were people who wanted to keep their engines ABSOLUTELY concours. All these measures used back in their day for emissions and boost compensation were pretty crude by today's standards.

[John at J&S]

+1.

I'm a stranger in a strange land and had to hold my tongue, but I've been thinking that for a while.

All those that want to keep it stock on the other side of the room. Conspirators, mutineers, etc, on this side.

[356-930]

Originally Posted by Speedy Squirrel

'Without it, timing at idle needs to be 10/12 degrees advance so engine can get to 28/29 deg above 3000 rpm, no load to get power out of the fuel/engine.'
the above statement is completely false. There is no vacuum to the solenoid side at 3000 rpm and no load, as the port is above the throttle. You get the same timing at the 4000 rpm check speed whether you have the hose connected or not. Anybody can verify this for themselves.

No, the above statement is 100% correct.
With no vac retard to start with (as when no vac pot is used) and initial timing is left at 0 BTDC,no load timing at 3000 rpm and higher, will be 18 degrees, not the desire timing of 28 degrees.
No vacuum retard, no advance due to loss of vacuum. (10 vac +18 mechanical =28 total.)

[Speedy Squirrel]

Originally Posted by 356-930

No, the above statement is 100% correct.
With no vac retard to start with (as when no vac pot is used) and initial timing is left at 0 BTDC,no load timing at 3000 rpm and higher, will be 18 degrees, not the desire timing of 28 degrees.
No vacuum retard, no advance due to loss of vacuum. (10 vac +18 mechanical =28 total.)

Now you are double wrong. Two wrongs make a ... bigger wrong. All solenoid equipped cars should have the timing set with the hoses off, to 26 BTDC at 4000 RPM:

[mark houghton]

Actually, I think you're both saying the same thing. Per the engine sticker, with the vacuum lines removed to check timing, it should be at 26BTDC @4000 rpm. And even if you didn't remove the lines, you would still end up with 26 at 4000, because no vacuum retard will be available at anything beyond idle (provided you're not on boost).

When you time these engines, it's all done at 4000 rpms, and the idle will then fall within factory 0-2 degrees BTDC if the mechanical advance and vacuum retard are both functioning properly. 0 degrees at idle with the lines connected becomes 10 degrees advance if you were to unplug the lines.

With everything hooked up, as soon as you step on the gas and the vacuum retard goes away, you're almost instantly at 10 advance. Add another 16 to 18 degrees of mechanical advance as the rpms rise and WHALLA....you got your 26 at 4000. That's my understanding and experience anyway, as hard as it is to explain in writing.

And if this still doesn't ring true, then I'm going with the latest MSD 6AL2 6530 and set my own timing curve. Post number 249 and we're all still confused. Having fun yet???

PS: My vacuum solenoids are not there....don't need them.

[willtel]

Originally Posted by mark houghton

And if this still doesn't ring true, then I'm going with the latest MSD 6AL2 6530 and set my own timing curve. Post number 249 and we're all still confused. Having fun yet???

That little unit looks interesting. You be the guinea pig and let us know how it goes.

Originally Posted by mark houghton

PS: My vacuum solenoids are not there....don't need them.

Me too. It was a good feeling getting rid of those things, this engine is pretty good looking when you start getting it cleaned up.

[356-930]

Speedy:
You write, “”Now you are double wrong. Two wrongs make a ... bigger wrong. All solenoid equipped cars should have the timing set with the hoses off, to 26 BTDC at 4000 RPM:”

My statements were not provided to advise where or how to set timing nor did they suggest this is how proper timing is achieved. They were in response to a question about what the vacuum side of the distributor’s vac/boost pot assembly did. They report accurately the effect of vacuum on the distributor’s vacuum diaphragm side of the distributor’s advance/retard module and what one has to do to compensate for the lack of vacuum at idle (add about 10 degrees at idle).

I’m glad you chose to put me in my place. I’ve enjoyed sharing what I learned as a 930 pepper tree mechanic, but no more.

Respectfully,
Chris Toy

[911st]

Originally Posted by mark houghton

...with the vacuum lines removed to check timing, it should be at 26BTDC @4000 rpm. And even if you didn't remove the lines, you would still end up with 26 at 4000, because no vacuum retard will be available at anything beyond idle (provided you're not on boost).

When you time these engines, it's all done at 4000 rpms, and the idle will then fall within factory 0-2 degrees BTDC if the mechanical advance and vacuum retard are both functioning properly. 0 degrees at idle with the lines connected becomes 10 degrees advance if you were to unplug the lines.

With everything hooked up, as soon as you step on the gas and the vacuum retard goes away, you're almost instantly at 10 advance. Add another 16 to 18 degrees of mechanical advance as the rpms rise and WHALLA....you got your 26 at 4000. That's my understanding and experience anyway, as hard as it is to explain in writing...

+1

Having the both the vac lines hooked up, or any combination of one or none should make for very close to the same timing at 4000rpm.

With none hooked up there is no retard.

With just the vac-retard or inner connection hooked up, because of it's ported connection it will see low level boost instead of vac and it will push the pot against its stop and there should be no retard.

With just the boost-retard or outer connection hooked up, because of it's ported connection it will see vac instead of boost and also push the pot against its stop and there should be no retard.




Chris & Speedy you have both been very,very helpfull to me and I hope other's to better understand how these systems work. We all love these cars!

[911st]

Modification Proposal:

It seems there is a stop on the vac/boost retard pot that can be modified and that will increase to total retard amount (Vac & boost).

If we can increase total retard from stock at about 9 deg to say about 14 deg we should end up affecting timing as follows:

Stock timing is apx:
+0 at idle
-9 just off idle (w loss of vac retard)
-17 on boost
-26 at cruse.

Modified with more retard:
+0 at idle
-14 off idle*
-17 on boost
-32 at curse*

This would increase off idle pull and increase freeway efficiency while at the same time keeping the stock on boost timing.

The keys being to increase the amount of retard and then just set timing at idle and to factory spec instead of setting it at 4000rpm.

I would still then check at 4k with lines to pot removed to see that total advance has increased as expected.

Further improvements could be possible by 1) re-curving or changing the amount of mechanical advance and or by 2) testing for timing ideals on a dyno.

However this mod a very simple, low cost, and a low risk mod that most could do to increase off idle acceleration and freeway efficiency.

[ertech]

Just replaced my pod since the vacuum side was not holding vacuum .I had to readjust the idle since it was to low after the replacement .it took the distributor apart and it was all gummed up the advance plate .now it is nice and free .did not see much difference with the new pod .I might be slow at understanding but what dors the vacuum side of the pod do off idle ?? From what I read it does nothing but lower idle when conected at idle?
Thanks

[911st]

The inner part of the pot is vac-retard. It gets vac at idle only and retards timing about 9 deg. Off idle the vac-ret goes away at timing advances the apx. 9 deg which increases efficiency /torque. With it retarding at idle it helps emissions some.

The inner also balances out the boost side on boost. If the inner or vac-ret side is not functioning it may be that one would get full boost retard with 5 lbs of boost. With a proper balance between both sides of the pot I believe this brings in the boost retard in a more liner manner.

At least that is what I believe at this point.

Would be interesting to tee vacuum to both sides of the pot to confirm it will retard timing with boost. At idle doing this should slow idle with about 10 lbs of pressure/boost. This would confirm that the solenoid's function is cold start.

[mooney265]

Changed my Vac Retard Pot and here are the results:

1. Popping on decel has been 70% eliminated... I believe this is a result of my timing being 9-deg retarted at decel. Am I correct? Advanced = More popping on decel???

I can absolutely say it's the only thing I've changed and I saw IMMEDIATE results on the popping.

2. Now, at idle, I see 8-deg advanced and at 4K rpm I see 28-deg mechanical advance. The car runs great!!

3. Idle rpm's down about 200...

[JFairman]

"From what I read it does nothing but lower idle when conected at idle?"

Vacuum retard is for emissions and it isn't only lowering emissions at idle, it retards timing and lowers nitrogen dioxide emissions every time you let your foot off the gas or every time you decelerate or take your foot off the gas to shift gears and this is a large amount of accumulative engine run time that it is lowering tailpipe emissions.

and the little solenoid is for removing vacuum retard to allow more advance when the engines cold to raise the idle speed, along with the aux TB bypass air slide valve.

[Speedy Squirrel]

I have my brand new vacuum module now, and I have done some more tests:

1. The red stuff that came out of my old pot was not rust. It is the disintegrated covering of the inner diaphram, which was leaking on my old one (would not hold vacuum). My car is a 1988 so I bet there are a lot of similar failures out there (sounds like mooney265 had a failed one too).

2. The new one holds vacuum on both sides. With equal vacuum on both sides the outer connection can still advance timing. The internal springs must balance out the vacuum from the inner connection. Note that this condition should not be possible on the car since the location of the vacuum ports is designed to prevent vacuum to both ports at the same time, even with no solenoid.

3. With equal pressure on both sides nothing happens. It neither advances or retards. I am still looking for someone with a stock car to see if the solenoid switches on again at full throttle above about 3000 RPM to cut off the boost pressure to the inner connection, allowing the outer connection to retard timing under boost.

[911st]

Speedy Squirrel!

So cool. A new working Pot!


Just to confirm. What you are saying is probably not what I would expect.


I would expect the following:

With about 5 pounds of pressure to the outer connection of the pot for the linkage to extend.

With vacuum to the inside connection of the pot for the linkage to extend.

With about 10 psi of pressure to both sides of the pot for the linkage to extend.

With Vacuum to both sides I would expect it would to not move or maybe, pull in just a little against its stop.



Speedy Squirl, if you can confirm it would be greatly appreciated.

[John at J&S]

I just received this unsolicited user report:

J&S Vampire Knock Control - Lightning Forum | LightningRodder.com

Even if you were to replace all your distributor parts and have Andial set everything to factory specs, your tune would be a compromise.

To protect themselves and their customers, factory tunes have to be a compromise, leaving as much as 20% power on the table, especially when timing is set with a distributor.

Go searching for that power without a knock controller and you are liable to get bit. Individual cylinder knock control WILL give you power safely.