Does anyone here know if the early two cylinder Fords used one coil to fire both spark plugs at once, resulting in a wasted spark on one cylinder, or did they use two coils, one for each spark plug? I'm referring to original equipment only, and not later replacement coil(s). I'm trying to restore an original non-Ford single coil unit for a two cylinder engine, and I'm trying to determine if the coil I have will do the job reliably. Thanks in advance!
2 cylinders, 2 coils.
I really don't believe the one coil, wasted spark idea will work. Electricity, taking the path of least resistance, would probably dictate that the cylinder not under compression, (in other words, the wrong one), would fire its plug, while the other cylinder's plug would not fire at all due to the increased electrical resistance caused by the more dense, compressed atmosphere. That's with all other things being equal, like plug gap, etc.
I may be mistaken, but I believe that the wasted spark systems wire the simultaneously fired plugs in series, so the spark energy has to cross both gaps.
Well, that's an interesting thought Mark, but I'm not sure it's possible, since each plug is independently grounded, which to my thinking, creates a parallel circuit no matter how the plug wires are routed.
I don't know for certain whether there was one or two coils for the 8hp 1903 Model A. But I have seen what appears to be relatively unmolested examples that have one coil with two spark plug leads.
The 10hp A's and C's, as well as the 12hp Model F's all had two coils originally. Both coils did, however, fire at the same time, wasting a spark.
One of the coils failed on my 10hp Model A while on tour, and I attempted to run the car with both spark plug wires connected to the one lead for the one functioning coil. It was a no go. I suspect that Jerry's explanation above is the reason it was a no go.
I have proven to my own satisfaction that connecting two spark plugs to the same output terminal on a single coil will not work.
However, I have seen many single coils, including those on the unmolested 8hp Model A's, that have two leads for two spark plugs. It appears that if the single coil was designed and manufactured to fire two cylinders, it will indeed do so even if one is not under compression.
Darren: In your post above you state: "I'm trying to restore an original non-Ford single coil unit for a two cylinder engine....." Query: Does the single coil in your hands have one spark plug terminal or two? The answer to that question may well determine the answer to your question.
I'll post photos later as I'm just home at lunch from work. Thanks for all the info guys! My coil unit has four terminals on one coil. The two front posts are marked "P" for primary, and the rear ones are both marked "S" for secondary. The size of the coil assembly is literally twice as big as the primary and secondary units in a model T coil.I'm quite certain this coil unit was with my car since new.The two secondary posts should each go to a spark plug.
If you did have one coil firing on 2 cyls. the one "doing nothing" would be on exhaust. Used on some moderns. Actually causes a cleaner burn in some cases.
Yes, as mentioned above, one coil, with "wasted" spark on the other cylinder. This 1904 "Automotor" magazine article explains the system:
I meant to add, the article above reviews the 1904 10 hp Ford Model A. If anyone is interested, below is the two part, nine page link to the article:
(Message edited by Rob on November 18, 2015)
For some reason the post above wouldn't make the Dropbox link "hot." Re copying it seems to get the job done......
"The two front posts are marked "P" for primary, and the rear ones are both marked "S" for secondary."
Wouldn't this suggest that the timer terminals go one each to each of the primary terminals? Meaning only one secondary/spark plug fires at a time?
"The size of the coil assembly is literally twice as big as the primary and secondary units in a model T coil"
Might this suggest that "both" coils, (i.e. #1 & #2), are simply wound around the same core and therefore use only one set of points? (I'm assuming there's only 1 set of points)
I don't know the original set up for the Model F. But, there are a lot of early two-cylinder cars running around using Harley ignition coils precisely because they are dual fire. For many decades, all Harley v-twins used a dual-fire, waste spark ignition system.
I've updated my Maxwell to this system and I'm happy with the results. Using a single set of breaker points with a dual fire coil gives perfect 180 ignition timing.
The coil box is wood, not connected to the engine block electrically. The current passes from one wire to one plug, to the block, from the block to the other plug, and from the other plug back to the coil box. There likely being no other electricals on the car, the block serves only as a "wire" connecting the plugs in series.
We're too used to thinking of the frame, block etc. being one side of the electrical circuit!
Here are some photos of two cylinder coils that are being used on 1903 Fords. They might or might not be right, but they are in the file I have on that car.
Once again, thank you everyone for your help and assistance!
Here is a photo of the primary and secondary windings:
To answer Jerry's question: Yes, there are only one set of points. The leads for the secondary windings go to each of the terminal lugs marked with the letter "S" for each one. The photos show the original coil from many years ago on my car. There are no other holes in the firewall, and the car's body is all original so it is very likely it's been on the car since new.
Sorry Timothy,I meant to include your name with Jerry's in my above post
I'm pretty sure that coil does not give a wasted spark. I believe it's essentially as I described, two coils in one, using a common core and common points.
Does both the coil box and the timer have two independent terminals to trigger the spark?
Timothy: the timer has two independent terminals which both go to engine/ground.
Jerry, I think I have solved this mystery
Here is the schematic of the coil as I took it apart. The whole thing was encased in rosin, which melted out with an hour with a heat gun. Please excuse my crappy electrical diagram. I have not included the switch for shutting the car off, which goes between the + side of the battery and it's resoective terminal. The drawing in the bottom right corner represents the timer.
Here is the coil "jury rigged" for testing:
The results are, that it makes a very good looking spark with a 9 volt battery. The brass strip represents the engine casting. It makes a REALLY good spark with my 12 volt motorcycle battery that I normally run the car with along with the T coils. I only tried it a couple of times that way.
My worry is, this coil was originally designed to run on 6-8 volts. Four 1.5 volt dry cells wired in the battery box together is shown in the original literature. Would the 12 volt battery eventually ruin this coil? This coil makes a real funny sound when it operates, very much different than a T coil.
The coil was always only used as a static display on the car, but if it would run reliably, I might actually use it. I know the T coils will always get me home, but maybe this system can be made reliable(?) I know why my grandpa never used this coil for long... the capacitor was pooched. I don't know it this was a good idea, but I put two orange drop capacitors wired in parallel. Since there's two spark plugs, I figured this might be a good idea(?) The original capacitor was roughly 3 times as large as an original T example. It literally occupied the whole back of the coil box.
What do you think Jerry, is it set up to actually work this way? I know it "works", but is is supposed to operate this way? I appreciate any and all your input, as well as all the kind help from everyone else!
Here's a photo of the timer assembly taken during the engine restoration a few years ago. The second contact is 180 degrees from the front one, and out of view:
For those who don't know my little "Queen" here's the whole thing. The REAL Queen is riding shotgun
To complete the test, and set up a similar situation as the timer included in the circuit, I added a wire from the brass strip to the negative side of the battery, representing the timer making contact. Results were the same. Good spark on both plugs.
The principle of "wasted" spark has been around for a fair amount of time and is based upon solid engineering principle. The thing you have to remember that I think you are leaving out guys is the idea of COMPRESSION and its pressure that surrounds one plug gap and not the other. A spark gap that is not surrounded by pressure is a very easy gap for the voltage to jump and almost insignificant compared to the "effective gap" of the plug under compression. Lets assume a gap of 1/32 for both plugs and a compression of 4 to 1 then when both plugs fire the effective total gap across both plugs when wired in series is 5/32 because the plug in free air (exhaust stroke pressure is essentially zero at TDC on exhaust stroke) is 1/32 while the 4 to one pressure on the "active" plug is 4 x 1/32 or 1/8" thus all of the spark voltage is used to jump this wider gap and little of the voltage (about 1/5 of it) is lost at the exhaust stroke plug. Get it? the True Fire uses this exact principle and it was just taken from the small V8 motor used in 1997 for sure and perhaps other Ford motors. Splitdorf coils sold during the earliest years for Curved Dash Olds and other cars were made with both ends of the primary and both ends of the secondary brought out so you could ground one of the secondary coil ends and use the thing as a "standard" hit/miss stationary engine coil or wire the ends of the secondary to 2 separate plugs and use the wasted spark method of firing on a 2 cylinder motor. Wiring 2 spark gaps in series results in both gaps being jumped at the same time if there is enough voltage to jump the combined gap. It can be done with gaps at each end of a winding or with gaps in series at one end but placing 2 spark plugs in series at one end is not possible because of the common ground of the plugs but IS possible if you place one plug gap at each end of the secondary wire.
I wish I could explain it well but as I understand it, the Maytag Model 72 twin cylinder with single magneto coil had a spark plug connected at each end of the coil winding's. Both fired, one a waste spark. You had to have both spark plugs in play or ground the wire (or both) if turning the engine over with the plug(s) out.
Thank you John for the highly informative and helpful info! Again, thanks to all for your help and assistance. It's great when we can all help each other here. This has been a wonderful learning experience for me!
Al Bittner's True-Fire as well as many cars manufactured during the eighties and nineties use the waste spark principle. The Ford 4.6l Modular engine was a good example and I believe the True-Fire features one of its two coil packs.
A spark jumping two gaps is nothing new. A second spark has been occurring in the distributor for years and we've all replaced scorched rotors in our lifetimes as a result, I'm sure.
Thanks Tom and you are correct that the coil in the TF and the driver for it is taken from the 4.6L V8 which had 2 of the spark coil modules with one for each bank of 4 cylinders.
I just wanted to point out that the wasted spark coil can work just as well with magneto as with battery since the source of the power doesn't matter since both plugs are firing at the exact same instant and thus the timing and power sourcing the system really has nothing to do with it.
Splitdorf made an "Oldsmobile Formula" coil for the CDO that only had one spark plug connection but the coil itself was the same box and winding as their standard coil. The only difference was that Splitdorf got rid of one of the secondary connections on the OUTSIDE of the box and ran it internally to the ground connection that the primary was also wired to. Manufacturers liked to force customers to use their own genuine car replacement parts and this simple change made the CDO coil seem to be unique and then as now customers were warned NOT to buy a part not sold by the car maker. Splitdorf also participated in the charade by making it appear to other car makers that they too needed a "totally different" coil for their unique application. Splitdorf catalog parades a lot of different coil and points setups that essentially were almost the same inside the coil itself. Makes for job source security Even later I am astounded at all the different types and values of capacitors that were on the market during the distributor era when probably one or 2 values and/or mounting types could have covered the entire automotive market.
Is it a good or bad idea to use two capacitors? I have no idea what the value of the original one would have been. It it's a good idea, should it be wired in series or parallel?
Bumping in hopes John Regan or anyone who can answer my capacitor question
Capacitors in parallel increases capacitance, capacitors in series reduces capacitance. Dave in Bellingham, WA
There is no reason that you would need 2 capacitors because of having 2 spark plugs because you still have just one spark event. Thus the capacitor needs are not related directly to number of spark plugs in any way. Capacitor does 2 things. One of those is to help the coil produce a high voltage output from the secondary winding but another very important thing it does is reduce the sparking at the points so that the points last a decent amount of time. The coils we are talking about here are all similar to the T coil by having a low resistance low inductance primary winding and a high resistance high inductance secondary winding. Actual values for these I could measure rather easily but could not begin to guess at by looking at the coil but it really doesn't matter. Capacitor value is not super critical but capacitor "type" is very critical. Modern capacitors purchased somewhere with the purchaser mainly being interested in price and size will almost guarantee the purchase of a wrong type of capacitor. The new hi dv/dt capacitors that we all sell now are pretty rugged and would work the best and also be easier to get into the box. While running your test spark - look at the points and watch the arcing then remove one of the 2 capacitors you have and see if you see any noticeable increase in the amount of point sparking. If nothing seems different then you don't need the second one in parallel You could try then 2 of them series (which cuts the capacitor value in half) and if that also produces no noticeable change then a capacitor of half the value you are using would probably work OK too but frankly you are not running a high RPM motor here so the only real downside of a larger than necessary cap would be perhaps some lack of high RPM performance and I don't think that is an issue. For long life I would hope that you could use ONE of the typical T coil capacitors since they would outlast the coil if you use the new ones and they work OK. You also can use the older version commonly called an "orange drop" type but be careful since the term "orange drop" does NOT guarantee you will get the right type of capacitor since the company that makes those also sells the wrong type in that same exact physical package and also calls it out as part of their "orange drop" line of capacitors. If the orange drop part you are using seems to work for a short time and then is no longer working then it is likely you have the wrong type. If you send me the numbers off the side of the part (not the .47uF and 400V markings) which tell the type then I can look it up for you.
With regard to 6V versus 12V operation of the Coils they tend to get pretty warm when you simply power one up on a DC 12V source and let the coil sit and "BUZZ" but they generally do not get hot when you actually run them with a motor because the duty cycle is much smaller when running with a motor that calls for timer connection for a mere fraction of the engine rotation rather than the permanent connection the you make when BUZZING the coil on DC power. Since the firing of a buzz coil occurs when a particular current is reached, it really doesn't make too much difference whether you use 6 or 12 to fire it except that it will fire sooner on 12V since the higher voltage makes the coil primary current build up faster but it isn't critical in a low RPM motor. 6V is safer since a common issue is to have a short in the timer wiring and this can result in the coil then buzzing continous for a few minutes while you stop and get the problem located. With 12V this can in fact result in a melted coil or one that pukes out the tar or sealing wax inside of it depending on how much current the coil is set up with.
Hope this helps.
Thanks so much David & John!!
I have two different styles purchased recently from the vendors. The "orange drop" ones have the following info on them:
This is the other one:
Bumping for John Regan
Once again thank you all for your help, ideas,opinions and wisdom!! I have finished restoring the coil and it is back on the car doing it's job as it should. It works with gusto and the car runs perfectly. Merry Christmas everyone!
I should also add that it was set up and calibrated successfully using John Regan's "Strobo-Spark"
Congratulations on your success. With people like John giving advice I suspected a good outcome. Enjoy,