Plastic case coils

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Model T Ford Forum: Forum 2016: Plastic case coils
Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Osterman on Tuesday, March 22, 2016 - 08:38 pm:

Is the capacitor in the modern plastic cased coils the same as those used when rebuilding the wood case type? I know those with show cars wouldn't be using these .. but for the driver car I'm curious if people have a preference as far as performance between the wood and plastic variety.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Trent Boggess on Tuesday, March 22, 2016 - 09:40 pm:

Yes, you can replace the capacitor in plastic coils with the same one used when rebuilding wood ones.

However, my experience with plastic coils has been that they do not produce as good a spark on HCCT as wood KW coils. It is really hard to do better than a properly rebuilt genuine Ford or KW wood coil.

Your results may vary...

Respectfully submitted,

Trent Boggess


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker, Ramona, CA on Wednesday, March 23, 2016 - 12:41 am:

I wonder why the spark is inferior?
Any theories??


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Wednesday, March 23, 2016 - 12:53 am:

Inferior or not, I have a stock 27 touring running 4 plastic coils and she will still do 50mph if I ask her nicely!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Wednesday, March 23, 2016 - 10:50 am:

Older post on placing new capacitor in a plastic case coil.

http://www.mtfca.com/discus/messages/179374/218010.html?1308225894


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Housego (United Kingdom) on Wednesday, March 23, 2016 - 12:12 pm:

I have refurbished a number of plastic coils successfully but found the setting up of these always seems a little more critical in adjustment compared to wood ones. Also when pouring tar gently support the sides, I use a vice to clamp them, that way it stops the sides deforming with the heat.

John


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Carnegie Spokane, WA on Wednesday, March 23, 2016 - 12:22 pm:

When I was studying coils, the particular set of plastic coils that I had were quite inefficient.

If you are interested, you can read about my testing methodology and results here:

http://antiqueautoranch.com/montana500/12no2/Volume%2012%20%20no%202web.pdf


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Osterman on Wednesday, March 23, 2016 - 10:21 pm:

Hmmm ... actually my question was do these plastic cased coils have the same capacitor that are sold for rebuilding. Not that I wanted to rebuild one.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Carnegie Spokane, WA on Wednesday, March 23, 2016 - 11:01 pm:

Mark, here is your question:

"Is the capacitor in the modern plastic cased coils the same as those used when rebuilding the wood case type?"

I took that to mean:

"Is the capacitor in the modern plastic coils interchangeable with the new capacitor that is currently being sold to replace the one in original wooden coils"

In which case Trent answered your question.

You then asked:

"I'm curious if people have a preference as far as performance between the wood and plastic variety."

In this case Trent and John and I all posted our opinions on plastic coils.

So, what more would you like to know?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bill Harper - Keene, NH on Wednesday, March 23, 2016 - 11:44 pm:

I take Mark's capacitor question to mean is the value of the cap in the plastic coils of the same value as the ones sold as a replacement, that is 47 micro farads at 400 volts?

Does anyone know what the value of the cap in the plastic coils is?


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Housego (United Kingdom) on Thursday, March 24, 2016 - 06:06 am:

Mark, I have always used the .47uf 400v capacitor, the same used in the wood coils, with high dV/dT rating. We get ours from Fun Projects part number 5007CAP-HiD. I do believe the original capacitor value in plastic coils may have varied from the replacement value of.47uf but I have fitted about 30 of these to plastic case coils over the last few years with no issues at all. As I said previously the plastic coils are a little more critical on adjustment I find. Hope that helps.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Thursday, March 24, 2016 - 10:27 am:

The real problem with those black plastic coils is that one company evidently makes those cases and several different companies make the coils that fill the cases.

The coils are made in several different voltages for different uses.

Some are only made to work on DC and do not do well with the extra Mag voltage.

Some are filled with tar, but most appear to only have a cardboard piece to position the internal components.

The weight is quite different and the heavier ones are closer to a Model T wood coil in contents and performance.

Some actually appear to work well.

Most seem to have a .1 or .15 yfd capacitor, which is 20 % of the Model T specification.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Thursday, March 24, 2016 - 10:29 am:

The real problem with those black plastic coils is that one company evidently makes those cases and several different companies make the coils that fill the cases.

The coils are made in several different voltages for different uses.

some are only made to work on DC and do not do well with the extra Mag voltage.

Most seem to have a .1 or .15 yfd capacitor, which is 20 % of the Model T specification.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Osterman on Thursday, March 24, 2016 - 04:02 pm:

Thanks ... that's the information which I was seeking.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Thursday, March 24, 2016 - 04:13 pm:

Think you mean uf (or microfarad) there instead of yfd.

Regards,
Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jared Buckert on Saturday, March 26, 2016 - 10:47 am:

I've been told that the plastic box coils are junk. That being said, I have one or two laying around.

I run wood box coils rebuilt by the Coil Doctor, and they are fantastic. When I bought the car it had a mixed bag of wood and plastic coils. I have one spare rebuilt wood coil in the toolbox just in case, and if I'm going to be away from home for awhile I throw a plastic one in there too. It works OK enough if I have an ignition emergency and can't get home otherwise.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Monday, March 28, 2016 - 11:42 pm:

I have eight of the plastic KW® coils being built by Bob Branson of Branson Enterprises who owns the KW® trademark.
There WERE some inferior plastic coils a few years ago but they weren't his.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tom Carnegie Spokane, WA on Tuesday, March 29, 2016 - 12:34 am:

I think Craig makes a good point. Just because the coils I tested were less efficient than some doesn't mean that all plastic coils are the same. Also, I wouldn't characterize them as junk. Even a coil of lesser quality would likely run your T just fine. Especially in a system where everything else was up to snuff.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Kossor - Kenilworth, NJ on Tuesday, March 29, 2016 - 07:55 am:

Here is another data point. The few black plastic coils I've tested had significantly lower inductance (fewer turns of wire) compared with original wood Ford or KW coils. That means it ramps to fire much faster for the same average RMS current reading on a current based coil tester like the HCCT. That guarantees ignition timing variation between cylinders if black plastic and wood coils are set up on a current based tester like the HCCT and run in the same car. This may explain why black plastic coils get a bad reputation. It also means the a higher peak firing current (~7A versus ~6A for wood coils) for a given voltage which may make the black plastic coils more difficult to hand crank.

Again, these are just observations form measurements I made on a couple black plastic coils I measured. I don't know if that is the norm or exception. Would have to measure a lot more to establish that.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Kossor - Kenilworth, NJ on Tuesday, March 29, 2016 - 10:20 am:

Looks like my data on black plastic coils is consistent with Tom's data; Average inductance was 2.78mH versus Ford spec of 3.3uH. That's ~16% lower which means firing current will be ~16% higher (6 x 1.16 = 6.96A) and ramp time to fire will also be ~16% faster which equates to ~5 degrees advance at the top end (~2300RPM) with respect to Nominal Ford or KW coils, slightly more variation if those coils are on the high side of typical inductance which would further limit top end engine performance.

This is a good example of the limitations using coil current as an approximation of coil ramp time to fire and benefit using the ramp time to fire (aka dwell time to fire) method of coil point adjustment where the time to fire is actually measured. All coils are adjusted for the same ramp time to fire regardless of coil inductance or point arcing that can skew the coil current and lead to maladjustment.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Tuesday, March 29, 2016 - 06:02 pm:

Mike, those coils may have been designed or manufactured to operate with 6, 12 or 24 volts for different uses.

There may be other coil voltages.

When some were new, they came with a round yellow sticker that had the voltage number on it, but it soon came off.

One new coil I bought had a 12 on that sticker.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gene Carrothers Huntington Beach on Tuesday, March 29, 2016 - 06:37 pm:

Mike you "forgot" to mention how these coils would perform if adjusted on an ecct?

SORRy guys, I just had to put in a plug.... I was very quite during the last recent go around.. AND Thanks again for your help on mine.


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