SHO DIS ignition

[Dinosauro]

Am I correct, that as the DIS is firing cylinders in pairs (2 & 6, 3 & 4, 1 & 5). that high-tension plug wires could be swapped between the same paired cylinders without adverse effect ? Just wondering.

Dinosauro

 

[Phoenix]

If your DIS is faulty , you will never have only one misfire. Its at least 2 at a time. And yes it will be paired , no randoms.

 

[Rockledge]

Am I correct, that as the DIS is firing cylinders in pairs (2 & 6, 3 & 4, 1 & 5). that high-tension plug wires could be swapped between the same paired cylinders without adverse effect ? Just wondering.

Dinosauro

Interesting question. I think you might run into issues with polarity. See: Ford DIS/EDIS "Waste Spark" Ignition Systems

 

[Dinosauro]

DIS & EDIS ignition systems

Dear Rockledge -

Thanks for the link to this very (!) interesting site !! Still leaves the question unanswered, as it seems that the secondary-circuit signal from the coil(s) would, if leads were reversed, flow quickly through the cylinder w/o compression pressure, (without signal-strength dissipation (?)), on to the cylinder with pressure. Would it arrive with sufficient juice to fire the plug ? I guess someone brave will have to try it to see what happens.

In the meantime, the DIS/EDIS article explains a lot about how our SHO ignition systems work ! Thanks so much for forwarding it on to me ! Should be mandatory reading for all SHO owners !

BTW, I suppose that EDIS stands for Electronic Distributorless, etc. ?

Thanks again !


:thankyou:

 

[luigisho]

BTW, I suppose that EDIS stands for Electronic Distributorless, etc. ?

http://www.dainst.com/info/edis/edis.html

 

[Dinosauro]

Ford DIS/EDIS "Waste-Spark" Ignition Systems

Every time I read this article, I learn something new (or something I glossed over the first time around) !

New (to me) is the fact that when sending a fire-signal to a given cylinder in the SHO, the PCM (EEC) will scan both cylinders in a pair, and send the signal to the cylinder with the most electrical resistance (caused by high compression pressures, I.e. on the compression stroke). Thus, getting us back to my original question: "What would happen if secondary wires were switched between cylinders in a pair ?

It would seem, given the above, that even if the wires were switched, the computer would still send the signal to the correct cylinder.

Another question arises from the statement in the article "Half the spark plugs actually see a different polarity than the others do."

I would think that this would only be the case when a cylinder was the trailing cylinder in the pair, completing the circuit back to the DIS system, and that the computer would only send positive (polarity) signals out. And that each cylinder would sequentially be the "firing" cylinder, and later in the firing order, the trailing or exhausting cylinder, carrying a negative signal back to the computer.

Right, or Wrong ?

Again, thanks to Rockledge for starying all this with the DIS/EDIS article !

Dino

 

[Dinosauro]

Thanks also to LuigiSHO for sending the tech sheet on Ford EDIS systems !

Dino :thankyou:

 

[Rockledge]

Hi Dino,

I think you are giving the PCM too much credit here. In the Ford DIS system, all the PCM does is help the DIS know when to fire a certain coil. The PCM does not determine which cylinder gets the "good" spark and which gets the "waste" spark. That is done by physics, in relation to which stroke a particular cylinder is on. As noted in the article:

In a nutshell, the amount of pressure in a cylinder - and the associated electrical resistance that it creates - determines which spark plug (compression stroke) gets the majority of the coil's voltage, and conversely, which plug (exhaust stroke) gets the "waste" voltage.

As for polarity, I'm not well-schooled enough about electricity/electronics to state one way or another whether it matters with regard to your original question. I myself have occasionally wondered what would happen if someone were to swap plug wires in the manner that you suggested in a Ford "waste spark" system.