I am in communication with a pro in VA Beach, Peter Florance who does professional work with Mega Squirt. I have asked him if he could help me get the distributor installed, and timed, and then put the MS II ECU in the system and get it started for me, all for a fair fee of course. He came highly recommended by Matt Cramer, so I have great confidence in him.

He wrote back and said fine, he would be happy to help me, and then brought up a subject that I have never read in any of my reading on any of the EFI systems: Distributor Phasing. Here is his reply, and his wording.

"My only concern is the distributor. I'm worried that it might not be
phased the way we want. Can the phasing be changed if we need to or is it
welded?"

I then wrote back asking him to explain further what distributor phasing meant, and this was his reply:

"Basically there's a mechanical relationship that must be established. At the
center of your advance curve during # 1 compression stroke, the rotor must
be phased so it points directly at #1 post so the rotor will be lined up for
the entire advance range.

But also, the HEI should fire at 10 degrees in bypass mode, so the reluctors
should line up at the correct time as well.

You should be able to check that on the bench; right after rotor passes #1
(~ 25 degrees), the reluctor poles should line up (about 7 degrees more
measured at the distributor which is 14 degrees crank) which will fire the
HEI in bypass at the right time.

If you can rotate the "points plate" independently from the rotor, you
should be able to satisfy both conditions."

I must say, it was satisfying to have someone bring up something I have not heard before, as I was not able to find a fix within the ideas I have been processing before. I am hoping this will explain why an engine that was timed correctly and ran fine with fuel only ECU control would not fire when the ECU was put in the system.

Anyway, this opens up a question I have been pondering for awhile but have not had the occasion to bring it up. Since the rotor is under the cap contact for a fairly long arc if you count on the width of the rotor tip, and the width of the cap contact, this cannot actually set the timing. This will pass a spark over a long arc of rotation. It seems the spark timing must must be the points, or reluctor, or what have you passing its pick up. But as the base plate rotates and thus changes the relationship of the pick up to the cap contacts, can it actually pass out of range of the spark over the rotor cap gap?

And, to add to this complication, is the firing of the ecu signal and the coil instantaneous for all intents and purposes? Peter talked as if there was a 10 degree lag in the firing of the HEI module. Did I get that right?

What are you thoughts on this? What is your knowledge of how the electronics in an ecu controlled timing system effect that actual timing of the spark in relation to the engine crank? What do you think he meant by that first sentence: "At the center of your advance curve"? I read that to mean that if you have 50 degrees total advance you will want your rotor to be centered under the cap pickup at 25 when the engine is at TDC. Agreed? It sounds as if he wants the pick up vane on the VE to be next to the pickup at 7 degrees after that. But, that seems backwards to me. Maybe I am reading that wrong, or just don't understand what he has said there. Wouldn't that retard the timing instead of providing the ignition advance we want? I think bypass must mean when the reluctor vane is bypassing the pickup.

I am certainly not questioning his knowledge here. I am eager to learn from him, and hope he get get me out of this black hole I have been in with MS II. I just thought it might be helpful, and interesting to share this with the group. There are some geniuses out there who will likely shed a little light on this for me. Maybe just my writing it down will shed a little light on it for me. The mechanical relationship between the firing point or pickup, that of the cap and rotor is going to require a little grey matter concentration. And I assume all this counting of degrees is with the distributor rotating as if the engine were running. That may sound like a dumb statement, but failure to get this right has caused more than one car to not start.

Sam

_________________

Sam, I think you have hit on something. I read an article quite a while back on distributor phasing. I had no idea it existed at the time and it was an eye opener.

Based on articles I have read, phasing in mechanical timing systems, such as centrifugal advance/vacuum advance distributors, is a matter of eking out the last bit of economy and good running. However, in an electronically timed system, such as you (we) are introducing, phasing is a huge issue because the timing is varying a lot, without the corresponding movement of the reluctor/rotor relationship keeping the phasing constant.

It is quite possible that the phasing in your distributor is such that it can run fine with mechanical/vacuum advance, and not run at all with electronic advance. MSD has a tech article on phasing here: MSD Tech Article that explains it pretty well, and they specifically mention boost retard systems (same idea as our electronic timing) that can take the distributor so far out of phase that it causes problems.

It sounds to me that your consultant in VA knows exactly what he is talking about.

_________________
It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!

Yes, I suppose that could be the problem. I had trouble with this once back in the early 90s when I tried to retrofit an ACCEL optical pickup and ign box to my '68 Dart. Never did get it to work right, and I'm sure that was the problem.

Mopar Action, the greatest periodical journal on the earth, has covered this topic more than once.

Lou

_________________
Home of Slant6-powered fun machines since 1988

Thanks for the link George. I read it several times. I still do not understand why Peter would want the VR vane to be in bypass mode 7 degrees after the rotor tip passes center of the cap contact. If I understand him right this is would be set up so the distrbutor was timed at half your anticipated advance curve,or typically 25 degrees or so.

There is the issue of the polarity of the VR pickup as well. There is a sign wave emitted from the pick up, one side is fairly rapidly changing and straight on a scope, and the other is more gradual. When you reverse the polarity of the VR pickup the straight edge reverses. If it is on the rising edge one way, it will be on the falling edge the other. This is why reversing this polarity can sometimes make your Mopar electronic ignition work better. It will run when timing is triggered by the less precise edge, but not as well.

This must effect timing as well. Which would also affect distributor phasing. It would make a difference whether it is to pick up the signal from the rising or falling edge, which is a choice in the tuning programs. I was never was clear about the the writers of the MegaManual wanted you to do regarding this phenomenon. It seemed as if the ECU reversed this and I was never sure if you were supposed to specify what the VR was producing, or what the ECU was producing after it processed the signal.

The bottom line is I am happy someone is going to help me deal with this who knows what he is doing. He says he has a Dodge Dart there now which is tuning the cold start settings on.

Any more thoughts out there on this?

Sam

_________________

Now you see why the OEMs went to distributorless systems

As far as the waveform from the VR circuit, you are right about the polarity. Back in my circle track days, I was running a Chevy HEI that was gutted out down to its reluctor and pickup. I ran that to a Mallory Hyfire box similar to a MSD. It ran like poop until I reversed the polarity of the wires, which made an instant vast improvement. I have encountered that since then with my Ramcharger, where I was running the MSD box off the VR in the distributor, and incidentally driving the MS-I off the tach output of the MSD. Once again, I got it wrong the first time and had to reverse the VR pickup wires.

_________________
It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!

Basically what distributor phasing is just locking in the timing so rotor is fixed to the distributor's shaft so both rotor and trigger are in specified relationship then weld both together. This is in order so megasquirt have sufficient range that trigger signal is there to trigger for a computer-controlled to fire around different range of timing YET spark can jump across the rotor tip without missing the rotor's tip and the cable contact.

EDIS is very simple set up, read up on EDIS FAQ. 6 cylinder fire every 120 degrees. Missing teeth do count during installing the 36-1 teeth wheel and the VR sensor relationship. With the engine rotation, missing plus 5 teeth (60 degrees) AFTER the missing is the teeth where sensor SHOULD be exactly be on.

http://www.megamanual.com/ms2/EDIS.htm

Cheers, Wizard

It does seem as if a pick up wheel with a wasted spark coil pack would eliminate all this phasing concern. And you could run as wide an advance curve as you want with no fall off or concern about cross firing.

I still wonder why you phase the reluctor pick up after the rotor and cap match each other. I think I will write Peter again and ask him to clarify that.

It is interesting that I have not seen a word of this in the MEgaManual. NOw that I have said that, someone is bound to post a link.

Sam

_________________

I fought a distributor phasing problem back in the 90's on a big block Mopar. I had altered the timing curve, and used an adjustable vac advance can. For whatever reason, apparently, all the mechanical tolerances for me were stacked in the same direction, and I had issues with misfiring with light or no load.

My eventual solution for PROVING and then fixing the problem? I found a clear aftermarket distributor cap. I then used the timing light to look through the side of the distributor cap to see where the rotor was when the plug fired.

That was good enough for me to discover that was, indeed, the source of my misfiring and then some simple mechanical tweaking was all that was required to get things back under control.

While I was working on this, I stumbled onto yet another relatively simplistic mechanism, where a distributor cap had been cut open using a dremel/die grinder, leaving a window to see the rotor pass the plug wire contact / electrode, and using a timing light to ascertain the precise position at moment of fire during various rpm scenarios.

I made the mistake of keeping the clear cap, which fell apart under the underhood thermal assult provided by the 440 under the hood of a Chrysler Town and Country.

However, windowing the side of a regular distributor cap and using a timing light to "freeze" the position of the rotor at the moment of fire is actually more effective.

If you are trying to set up a distributor for a car that doesn't run yet, you could use the same cut away side, or maybe cut a hole in the top, to see how the pick up vanes relate to the rotor cap relationship. I wish I had an extra used cap now. I think I threw them all out. That's how you know you are going to need something. Just throw it away.

Sam

_________________

I had a bunch of trouble with this for the First few months when I switched to MS-II from the carb and Electronic ignition.


I had to use the Trigger offest function in megatune a bunch and then also I had to play around with the distributor "advance" (like you were setting timing) to get everything to line up.


I burnt through a few caps and rotors before I was able to solve the problem. - The arc was jumping at an angle that caused the plastic -like rotor and cap material to burn up.

Through a lot of fiddling and experimenting I did get this to work - It helped that I way driving the car everyday too.


Greg

_________________
http://www.youtube.com/hyperpack

Was the angle off from the side? The spark was jumping from some fairly advanced or retarded position? When you say you fiddled with it as if you were setting the timing, were you simply rotating the distributor this way and that? What was your strategy there?

I always wonder how you could shift the timing 40 degrees and not move the relationship between the rotor and cap contact. Hopefully Peter will help me get this all figured out.

Sam

_________________

What we are talking about phasing, well. More like sufficient amount of rotor's tip vs. distributor electrode at any overlap when ignition is fired *regardless* of where advance/retard had occurred. If there is any distance (no overlap; that there distrance between both item that there will be longer arc to jump that gap) between rotor's tip and the electrode when ignition is initiated, then there will be no phasing and eating at corners of both happens and problems, missing, no starts etc.

Clear as mud?

Cheers, Wizard

I finally wrapped my mind around the logic of what Peter told me, but I don't understand one of the properties of the MS II ECU. When you are setting up the distributor, you are told to time it with a light at 10 BTDC. Then you are to indicate in the ignition page what your initial timing is. From there, you can advance you timing as much as you wish through the timing map.

How is it possible for the ECU to advance the timing? How can it predict when the reluctor will pass the pick up before it actually does so? It seems like it would be a simpler logic for the ECU to retard the timing. It could simply withhold the signal to the ignition module for a specified number of ms. The only thing I can figure is that it uses the previous reluctor vane for the next cylinder. Does anybody know about this?

Be that as it may, here is the logic of Peter's phasing instructions.


First here is the goal: At start up and idle, the spark will be happening about 20 degrees after the rotor is centered and at full 50 advance about 20 degrees before. But it should be centered when the engine is humming along at 25 degrees advanced.

If you assume the engine is going to spend most of it's life with spark timed around 25 degrees, then you want the rotor centered under the cap contact at that timing. To accomplish this we must put the reluctor in bypass after that, since the ECU advances the timing only. You want the reluctor in bypass mode after the rotor contact is aligned because when the ECU advances the timing from this location, it will bring the spark in at a more advanced spot on the cap.

How much to retard the reluctor timing is the question. Since the initial timing will be around 10 BTDC, then you want the reluctor in bypass mode about 14-15 degrees retarded at initial timing (again assuming 25 advanced in most operating conditions). Since the distributor moves half as fast as the crank, this would be 7 degrees at the distributor. Hence his statement to set it up so the reluctor is in bypass mode 7 degrees retarded from the centered position of the cap rotor alignment.

There you go. Anybody understand how the ECU can advance timing? I suppose it is as simple as setting the timing from the previous reluctor vane. I guess the ECU does not care which is which, since they are equally spaced. But, that could throw the timing of by a whopping 60 degrees, which would explain why my car would not start. ARGH! It might have started if I had twisted the distributor a bit this way or that.

Obviously this is not as simple as the Megamanual makes it sound. If you want to really make somebody feel stupid, answer their questions about this with the recommendation to simply read the manual. Right now I only feel about half as dumb as I did a month ago. Not smart yet, but not sooo dumb.

Sam

_________________

I guess it must use the previous vane. I thought MS used a high number like 50 deg and then retarded timing, but my memory is murky since I don't have it running on a car yet.

Keep in mind that 60 deg of dist rotation is 120 deg of crank rotation, and timing specs are listed in crank rotation. So, 40 deg of (crank) advance is only 20 deg of dist advance, so that rotor/cap can handle that.

Whenever I start an engine, I just assume I might have goofed on timing, and I just turn the dist around until it fires up, if it doesn't fire right away.

Lou

_________________
Home of Slant6-powered fun machines since 1988

Trust me, the ECU take care of ignition timing with a locked out distributor. Look at the 2.2L/2.5L do this already.

The megasquirt instructions will step you through the set up of distributor (it has to be fixed, no advance or vacuum nothing, just locked by welded or something similar on the mechanism so distributor is one piece with correct phasing of rotor and the trigger unit/sensor relationship.

Also the megasquirt forum helps you with your questions there.

Cheers, Wizard