Electronic or points...good question?

[Anonymous]

I came across this phase while reading an article in Mustang and Fords (tm).

electronic ignitions advance the timing slower than point ignitions, and they also dial in up to 45 degrees of advance at higher rpm, which is too much for vintage cars that require only 36-38 degrees.

I wanted to get the opinions of others in this forum. From a maintanance stand point, it's easier to swap to an electronic ignition but are we sacrificing power gains at higher rpms when we do this swap?

Anyone?

 

[CobraSix]

For some reason, I don't think they can be talking about electronic ignition swaps. The dizzy(mech and vac), not the points (or pertronix or magnetic pick up), control the amount of advance. dizzy position also sets total advance, not the points or electronic ignition.

I really think they are refering to modern, electronic distributor box type ignitions, where a computer controls the timing and uses a crank sensor and not a physical connection to the engine to figure where the engine is on it's cycle. On modern cars, it is my understanding that they do more to the timing to get it to pass emissions better and still have good power and economy. by making the timing advance slower initially, you maintain economy and emissions. By giving it more total advance, you are giving it more top power. This is also part of the reason a lot of newer cars require higher octane gas (along with higher CRs).

Simple test. time your car with points, plot out a timing curve from initial to total. Now do the same with pertronix or DS2. I'm pretty sure you'll find they are the same (well, DS2 may be different due to slightly different settings from one dizzy to the other, but you get the point). one the same dizzy with points or pertronix (best head to head since you can use the same vac and mech advance) you'll see the timing curve should be the same and total advance should be the same.

Slade

 

[cdherman]

Slade said it well.

Interesting thing occured to me in thinking this over -- some folks advocate using an external box, such as MSD makes, that allows for customized advance curves. These typically are attached to a Duraspark Dizzy. But the dizzy has its own advance built in.

Does one, or should one disable the mechanical advance in the DSII distributor when using a programable external box? Otherwise, you would get advance from the distributor and the box both. I could seen leaving the vacuum advance alone, as it provides advance in different settings that the external box cannot detect.

Just thinking.....

 

[CobraSix]

herman...

yeah, you have to lock the advance to use the programmable function. You disconnect the vacuum, and lock the mechanical advance. You then have to set the dizzy to the max amount of advance you want and the external programmable computer retards the timing from there based on RPM. MSD makes a good system for it. I've played with the software, very nice and easy. I bit overkill for our engines though, but very nice for engines maybe looking at forced air (some of the programmable ones have a boost referenced retard curve too). It is is nice from a consistancy stand point since you should never have to worry about the vacuum diapghram or mech springs wearing out.

For some reason though, I just can't bring myself to get rid of my vacuum advance for the car.

Slade

 

[Anonymous]

I think what the quote is referring to is the fact that emissions controlled cars are contolled more with distributor vacuum advance in the 70's & 80's. In order to lower NOX emissions, they retarded the timing and used ported vacuum sources. They also ran less initial timing. The effect was a hotter engine that burned cleaner. Compared to the distributors of the 60's, the newer distributors had less centrifugal advance and more vacuum advance. The engine of the 60's typically ran more initial advance, so when you put on an emissions distributor, there was too much advance because so much of it came from the vacuum advance which was typically hooked up to full manifold vacuum instead of ported vacuum. The electronic emissions distributor can be used but will likely need to be recurved to yield acceptable performance.

 

[addo]

I'd agree with that. Two weeks ago fitted a recurved electronic dizzy to an International 345; the points unit was past unwell, and about to die! Total advance came out as 38° approx (if you can trust a Snap-On timing light ).

 

[Anonymous]

I don't know where the quote came from, so it's hard to decipher what it means, but...the DuraSpark simply replaces the points with an electronic pickup (except for the Yellow-grommet version), so the advancing depends on the mechanical/vacuum aspects of the distributor in use. The same applies for the Pertronix kits I've seen.

Ford's Yellow-grommet Duraspark adds one extra feature: a vacuum sensor to monitor engine activity. This sensor comes in 2 versions: one is used for manifold vacuum detection and the other for port-vacuum detection. They are basically switches. In both units, the Yellow-grommet unit adds 4-6 degrees of spark advance under high-vacuum conditions. This is done to improve engine efficiency at high altitude (manifold vacuum) or reduce knock (port vacuum model, a reverse-acting switch).

 

[80broncoman]

the reason for the big difference in the amount to advace both centrifcal and vacume is that most all electronic dizzys came out when all the cars were using 8:1 compression and emission controls.
I belive crane cams sells a excellent conversion called a XR3000. It uses a infared light in stead of a visable light like a unalite.
one thing that I true about points they start to wear just as soon as the dizzy is turned at all, and then it is all downhill.
Jim

 

[addo]

I've been told that a dizzy (mech or electronic) typically loses quality after 60K miles. The mechanical advance gets sticky (grease is old), and the pivot pins the weights swivel on can get chafed or worn and the return springs lose tension. You can get a dizzy that sticks with no advance, or more typically, advances too soon and doesn't retard quickly enough.

The Pertonix, and all its ilk - Optospark, Lumenition etc, do nothing to change this. This is one aspect of their marketing that grates with me; they sell it as an "upgrade" without clearly advising it may not be all or even what you need most for the ignition.

No matter what upgrade you choose, make sure it's accurately "graphed". Just my grumble for the day.

Adam.