coils

widebodyhachi · Post by **widebodyhachi** » Mon Dec 31, 2007 9:49 pm

do the coils have to be EDIS based, I want to upgrade the cols but theres not much choice if have to base it on EDIS system

MartinM · Post by **MartinM** » Tue Jan 01, 2008 5:17 pm

They don't have to be - I've seen Peugeot wasted spark coil packs being used very successfully. Strictly speaking you would need to make sure an alternative had similar electrical characteristics (inductance and primary resistance being the two main parameters)

What leads you to think that "upgrading" (whatever that means) the coilpacks will make any difference?

widebodyhachi · Post by **widebodyhachi** » Tue Jan 01, 2008 8:07 pm

the more "energy" I can put out of the coil and less resistance in the leads is going to help a cleaner mor efficient burn

Post by **brentp** » Tue Jan 01, 2008 8:24 pm

Accel makes an somewhat upgraded coil compatible with the EDIS system:
http://store.summitracing.com/partdetai ... toview=sku

However, you may save some money by first seeing how well the OEM ford coil packs work with your engine. You will be impressed with how hot the spark is going away from your distributor setup. I'm currently running up to 20 lbs of boost in a turbocharged AW11, and never detected an ignition misfire.
http://www.autosportlabs.org/viewtopic.php?t=1168

Regards,

widebodyhachi · Post by **widebodyhachi** » Tue Jan 01, 2008 8:33 pm

youre right I probely will be, I cant find any infomation on factory specs and getting hold of FORD EDIS stuff i NZ aint easy, im going to be paying big bugs like MSD replacement Huyndi twin coils kinda price so why get standard stuff anyway,

im not trying to be a bastard but you have boost to help ill be running rough cams 12.5:1 with 98 octance the better burn I can get the happier ill be thats all

Post by **brentp** » Tue Jan 01, 2008 8:38 pm

To circle back to your original question, yes- it's been found that many different coil packs are indeed compatible with the EDIS module. If you can measure about .5 - .7 ohms on the primary and about 13K ohms on the secondary, you should be golden.

Another topic on the subject:
http://www.autosportlabs.org/viewtopic. ... light=ohms

MartinM · Post by **MartinM** » Tue Jan 01, 2008 9:03 pm

The main factors that affect "coil performance" (which is a pretty undefined term - but let's take it as the amount of energy in the spark) are the inductance and primary resistance - I don't know what the inductance of a Ford OEM spec coilpack is and the Accel coilpack doesn't state one - and ACCEL just quoting coil primary resistance and a fixed output voltage might get you bragging rights at the local inn/pub but don't stand up to any great electronic scrutiny. I'm pretty sceptical about the ACCEL coils (but, of course, I've never even seen one, let alone used one or measured one in action), but I do like the yellow towers

http://www.bgsoflex.com/igncoil.html uses standard electronic theory to calculate various output values depending on the main electrical parameters of the coil...it's worth spending a few moments at...

Interestingly, the secondary resistance doesn't seem to play a part in the equations....

Post by **brentp** » Tue Jan 01, 2008 9:13 pm

It has been a while, but I measured about 0.1 fewer ohms on the primaries of the accel coil compared to an a few sampled OEM units. I performed no other testing than that.

widebodyhachi · Post by **widebodyhachi** » Tue Jan 01, 2008 11:07 pm

one of the biggest give aways of coils is resistance vs impedance, ie coils have iductance, capacitors have resitance any mix of these should be refered to as impedance as the Power table no longer is relavent, secondry power or apparnt power is not relevent in a coil as it wont have it it has a frequency to deliver its amperage witch isnt in tme with the volatge, so resistance in the leads yes is relivent resistance in the coil isnt, I mean who cares how low the resistance is in the coil whentheres noting going throuh it for want of a better phrase, had I not studied electrotechnology I might not no any better and it wouldt be a problem for me

MartinM · Post by **MartinM** » Wed Jan 02, 2008 12:50 pm

Well I'm not sure what point you're trying to make as I find it rather difficult to decode what you've written

But here's a few more simple thoughts...

- the coilpack is a mechanical construction - bits of metal and wire in a plastic case - which exhibit the main (and fundamental) electrical characteristics of interest in the primary coil of resistance and inductance. These present an impedance to any applied power, depending on the power frequency and according to standard electrical theory equations.

- the designers can't aim for/have zero primary resistance as that makes the coil a short circuit to 12v applied to it for a "long" period of time ("long" is in the order of around 10 milleseconds) - so it will blow fuses/transistor drivers etc

- the designers aim for an inductance that maximises the ability for the coil to be energised whilst also acting as a step up transformer to provide the high voltages needed to create a spark

- the EDIS system pretty much replicates a Kettering ignition system in that it just switches the coil -ve between ground and open circuit once per ignition event. It doesn't do anything clever with regard to multiple spark discharge etc (although there is some evidence that it might do MSD below 1800rpm, but the MJLJ does not exploit that, even if it does).

So to "upgrade the coil", all you can do is choose another that has different primary resistance and/or inductance - despite what the coil upgrade marketing men might try to convince you with their technobabble spin

Taking the ACCEL coil as an example,
- a Primary Resistance of 0.5 ohms is some advantage compared to the alleged 0.6-0.7 ohms of a standard EDIS coil
- the Maximum Voltage of 42,000 V, Turns Ratio of 85:1 and Secondary Resistance of 11.6K ohms are are pretty irrelevant parameters

And the other most important parameter (inductance) isn't quoted at all.

So we are talking about the upgraded coil having at best 0.2 ohms less primary resistance than a standard coil:

- playing around with http://www.bgsoflex.com/igncoil.html shows that this has very little affect at high rpms (and at low rpms the benefit is not really needed as the spark energy is more than adequate with a standard coil)

- you need to take into account the equivalent resistance of the switching components (transistors of some sort) in the EDIS as they will have an effective resistance when switched 'on' which will reduce the effect of the lower primary resistance (e.g. if the switching transistors are equivalent to say 0.1 ohms then you have 0.6 ohms v.s 0.8 ohms difference between the two circuits which is less of a % improvement)

- you need to make absolutely sure that your wiring around the coil primary (whichever coil you use) is top spec - thick, short and with perfect connections. Introducing a series of joins that give a 0.2 ohm equivalent resistance will wipe out the gains of an "upgraded" coil compared with a well-wired standard system.

So.....I remain unconvinced about any Value For Money aspect of upgrading a coil pack from standard. But I suppose if there's only a small incremental cost of one over the other when you have neither, then at least you get bright yellow towers!

Oliver Sedlacek · Post by **Oliver Sedlacek** » Thu Jan 03, 2008 10:22 am

As Martin says, primary inductance is the most important spec when estimating spark power. The energy stored in the coil is 0.5 * Inductance * Current ^ 2. The EDIS controls the coil primary current, so the inductance is the most important parameter. Note that the current is not a function of resistance, which has only a secondary influence.

aarc240 · Post by **aarc240** » Thu Jan 03, 2008 2:22 pm

The only factors not mentioned above are physical format and connector design.

The first relates to how easy is it to fit and/or mount the selected coil.
The second relates to availability of cables/connectors in the location of operation.

Frankly, for anyone in New Zealand or Australia use of Ford EDIS series 1 coil packs is daft.
Ford doesn't market a production car in either country with those coil packs so there is zero availability of plug leads or connectors.

Sure, one can import the parts and make up a HT lead set but if the vehicle is the daily driver, what happens when a lead fails or is damaged?

For that reason alone I use Chrysler coil packs which have the much more universal tower HT connections.
Even Ford Australia has leads available to fit those as they use those style towers too!

Interesting that the Chrysler/Dodge Grand Caravan 6 cylinder packs appear to provide a hotter spark than the Ford EDIS pack I first used.
Must get around to measuring the inductance to see why.