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EDIS: Spark plug gap.
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Lizard

Joined: 03 Nov 2002
Posts: 9364
Location: Abbotsford BC. Canada

Posted: Sat Nov 26, 2011 12:33 pm Post subject:

Horizonblue, Forget about all plugs except for copper plugs. All the platinum, iridium, multipoint etc plugs will gain life at the cost of a better spark. _________________ 3 928s,

Joined: 25 Mar 2007
Posts: 2637
Location: Australia

Posted: Sat Nov 26, 2011 1:59 pm Post subject:

Horizonblue wrote:

Mr Bitey wrote:

Quote:

Why are the two plugs per coil not parallel connected in the circuit?

Making a spark requires high voltage. when a circuit is in series the voltage remains the same across both plugs. when a circuit is in parallel the voltage is divided.

It could be done in parallel but coil pack would need to generate twice the voltage.

Thanks mate

Sorry, that is incorrect.

Actually, in a series circuit the current is equal with the voltage being divided across the load. With a parallel load the voltage remains constant and current is proportionally shared.

http://en.wikipedia.org/wiki/Series_and_parallel_circuits

Horizonblue wrote:

Why are the two plugs per coil not parallel connected in the circuit?

Although the current is divided proportionally, effectively HV electricity across a spark gap always takes the path of least resistance. Only the plug with the smallest gap will discharge a spark. In open air there may however be a small weak spark from the plug with greater gap, but under combustion pressure will either not fire at all or misfire severely. This is also why multiple (2, 3 or 4 electrode) prong plugs are just an ineffective gimmick. Same principle as lightening only hitting the highest earthed point around, shortest conductive path available.

Correction time disclaimer:
This thread is another of those glaring examples of the misconceptions and simply plain WRONG information that is often posted on the internet by those with little or no education in the subject and then frequently repeated until many readers end up believing in complete BS.
Please appreciate that my post(s) are intended to promote factual information only and are not intended to be a personal attack on any other posters. However, before any posters who may disagree with my corrections resort to executing personal retaliations, I sincerely ask them to conduct sufficient research to determine if any reply is indeed necessary.
_________________
World`s quickest 924 2L slushbox

Allan @ DTA wrote:

I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards

Joined: 25 Mar 2007
Posts: 2637
Location: Australia

Posted: Sat Nov 26, 2011 2:24 pm Post subject:

Min wrote:

Horizonblue wrote:

This is very interesting, I never knew that the sparks plugs were series connected on the EDIS system, causing one spark plug per coil pack to wear out faster than the other.

Not sure why you think one spark plug will wear out faster than the other, but it doesn't happen like that. When the coil fires, both spark plugs fire, the wasted spark fires reverse polarity. Next cycle the opposite spark plug does the same thing. Wear will be even.

Min

No Min, As previously stated but apparently a difficult concept to grasp, ONE plug connected to a dual post coil WILL ALWAYS FIRE REVERSE POLARITY. It makes no difference which stroke it is, in fact it is impossible for this system to distinguish between firing or overlap strokes.

Depending on the direction of winding of the respective primary and secondary coil windings, one end will ALWAYS generate a positive voltage while the other end WILL ALWAYS generate a negative voltage, in respective to the earth (ground) 0V line. Perhaps research on Ford sites as to which particular coil post is which if you are genuinely interested. A basic principle of electromagnetism comes into play here. Haven`t sufficient time or patience to google all the references here, but PLEASE DO.

http://en.wikipedia.org/wiki/Induction_coil
http://en.wikipedia.org/wiki/Magnetic_field
http://en.wikipedia.org/wiki/Transformer

RC wrote:

Whatever stroke is irrelevant, it is the coil design. One of the two plugs will ALWAYS fire in reverse polarity.

What this means is that half of the plugs, that`s 2 plugs on a 4 cylinder, 4 plugs on a V8, will always have a weaker spark. Not just the "wasted" one but the firing spark. Also half of the plugs will wear considerably more at a quicker rate than the rest.

Correction time disclaimer:
This thread is another of those glaring examples of the misconceptions and simply plain WRONG information that is often posted on the internet by those with little or no education in the subject and then frequently repeated until many readers end up believing in complete BS.
Please appreciate that my post(s) are intended to promote factual information only and are not intended to be a personal attack on any other posters. However, before any posters who may disagree with my corrections resort to executing personal retaliations, I sincerely ask them to conduct sufficient research to determine if any reply is indeed necessary.
_________________
World`s quickest 924 2L slushbox

Allan @ DTA wrote:

I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards

Joined: 25 Mar 2007
Posts: 2637
Location: Australia

Posted: Sat Nov 26, 2011 2:53 pm Post subject:

Raceboy wrote:

Min wrote:

Exactly, and due to the nature of wasted spark and combustion gases, only about 10% goes "wasted", thus the wear is slower than for example when firing COP's in wasted spark mode.

Exactly NO again.
See the previous post.

Due to the coil design, with a single floating secondary winding, one coil post will ALWAYS be negative while the other is ALWAYS positive.

One of the plugs, per twin post coil, will wear either ground or centre electrodes at a much faster rate than the opposing plug, ALL the time. Swapping over the paired plug leads, half way through the estimated plug life cycle is another poor, cheaparse and Ford way to extend maintenance, but really the whole system is a far from an ideal design and why even the inventors moved forward technologically.

Although the plug under no appreciable combustion pressure, at the exhaust stroke or valve overlap stage, referred to as the "wasted spark" will require less energy, the available spark voltage is proportionally divided according to the respective series resistance in the circuit. I do not know off hand what the averaged ratios may be but IMHO the "wasted spark" consumes more than the 10% estimated here. Perhaps someone here may like to read up and post some referenced figures for us.

http://en.wikipedia.org/wiki/Wasted_spark
http://www.richieburnett.co.uk/static.html

Correction time disclaimer:
This thread is another of those glaring examples of the misconceptions and simply plain WRONG information that is often posted on the internet by those with little or no education in the subject and then frequently repeated until many readers end up believing in complete BS.
Please appreciate that my post(s) are intended to promote factual information only and are not intended to be a personal attack on any other posters. However, before any posters who may disagree with my corrections resort to executing personal retaliations, I sincerely ask them to conduct sufficient research to determine if any reply is indeed necessary.
_________________
World`s quickest 924 2L slushbox

Allan @ DTA wrote:

I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards

Joined: 25 Mar 2007
Posts: 2637
Location: Australia

Posted: Sat Nov 26, 2011 3:01 pm Post subject:

Horizonblue wrote:

Min wrote:

Horizonblue wrote:

Ford has been using two different spark plugs on the same engine, I don't know for how long, but why did they do that then?

Read the link you posted? it says quite clearly it was to save money.

Min

I saw that. What I wanted you to notice, was that Ford (also) used different spark plugs, because those with reversed polarity wears different than those with normal polarity.

This writing gave me the impression that half of the plugs wear out faster than the other. Off course, if you use plugs with platinium coated tip and electrode or whatever is "topdollar" these days, and change them regulary, there will probably never be any issues.

Horizonblue, sounds like you actually have a pretty good understanding of the basic physics principles involved and I`m sure that now some misinformation has been corrected that certain points appear much clearer and logical.

_________________
World`s quickest 924 2L slushbox

Allan @ DTA wrote:

I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards

Horizonblue

Joined: 13 Oct 2011
Posts: 307
Location: Sorring city, Denmark, Europe

Posted: Sun Nov 27, 2011 2:37 am Post subject:

RC wrote:

Horizonblue wrote:

Min wrote:

Horizonblue wrote:

Ford has been using two different spark plugs on the same engine, I don't know for how long, but why did they do that then?

Read the link you posted? it says quite clearly it was to save money.

Min

RC, thanks a lot for all this helpfull information, it was very informativ.

This winter I'm replacing the engine in my 924 with a newer 2.0 and at the same time ditching the old injection/ignition in favour of Megasquirt. The old engine has a slight knocking when cold, and I found a 1984 engine which appears to be in good shape.

I was recommended to use the EDIS system for ignition, a friend of mine only had good things to say about it. He is a Ford guy, so off course he's not bragging about the down side

The EDIS off course works fine in many cars, so it's not that I'm claiming it's a complete faulty system.

But I have discovered that a VW Golf 3 1.8 distributor fits perfectly into the housing on the 924 cylinderhead. Only the gear has to be switched. This distributor is made for electronic engine managment, so I'm going this way, saving installation time and using some standard VW components.
_________________
Euro 924, 1976

"If you can't fix it, don't break it"

/P.G. Andersen

Min

Joined: 04 Nov 2002
Posts: 2368
Location: Vernon, British Columbia, Canada

Posted: Sun Nov 27, 2011 5:01 am Post subject:

RC wrote:

Due to the coil design, with a single floating secondary winding, one coil post will ALWAYS be negative while the other is ALWAYS positive.

Fair enough, I was wrong. I thought the EDIS module switched it, however after thinking about it (before you posted this) I realized that was not possible.

RC wrote:

One of the plugs, per twin post coil, will wear either ground or centre electrodes at a much faster rate than the opposing plug, ALL the time.

I have two daily driven megasquirted EDIS vehicles at the moment, I can say without any hesitation that the wear you speak of is close to negligible. I have put well over 300,000 KM on my 924 with EDIS. I never noticed any sort of abnormal wear patterns on spark plugs. I use copper plugs and change them somewhat irregularly. I closely inspect the electrodes on all plugs I remove. I will certainly pay closer attention in future to relative wear on the spark plugs. I believe I have a used set in the shop I can mic even.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

Min

Joined: 04 Nov 2002
Posts: 2368
Location: Vernon, British Columbia, Canada

Posted: Sun Nov 27, 2011 5:05 am Post subject:

RC wrote:

This thread is another of those glaring examples of the misconceptions and simply plain WRONG information

I think I will point out at this point, that sometimes RC, you are also wrong. You also spread misinformation. You are part of the problem the moment you make a post on the internet.

The only way to avoid this is to simply not post anything.

Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting.

flosho

Joined: 01 Jul 2004
Posts: 3160
Location: Eau Claire, Wisconsin

Posted: Tue Nov 29, 2011 2:26 am Post subject:

Personally I think this 'downside' to EDIS is blown way out of proportion. Ford used EDIS on probably 100 different models and if spark plugs would really show/experience such significant wear difference this would be much more well known. I've owned 2 or 3 different ford vehicles with EDIS and never ONCE been recommended or put in two different plugs. It appears from my experience that it simply isn't an issue, until someone can show first hand experience that there is an adverse affect of EDIS. If you're not a fan of using EDIS, fine, but to disregard it because of this "issue" is nonsense, imo. _________________ [This Space For Rent]

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