Options for spark ignition for twin plug heads

[Harry Lillo]

I have two twin sparkplug per cylinder heads, one OHV and a flathead. i have been playing around with some different ignition systems to fire these. I am familiar with the modern twin ignition systems and actually have a 4 cylinder Du Coil set up that I could use. I am looking for something unique and different.
One attempt was to use a high tension DU4 magneto and try to rob some induced current from the spark plug wire by wrapping fine wire around it and running it to the second plug. Apparently Evinrude did this in the 30's with some of their high performance engines.
I could get a secondary spark but I saw it as too weak to be useful.
Another option would be to convert Model T coils to fire twin plugs through internal rewiring.
Where I have finally landed is a true separate twin ignition system.
I have had very good luck with Bosch DU4 high tension magnetos. I plan to make one of those my primary ignition source with manual spark advance through the generator location. My secondary system would be an E Timer. It has its own spark advance system so should run independently. I did look at running two DU4 magnetos but would have to synchronize the manual timing.
Has any one run a system like this or variation with two independent ignition systems?
Harry Lillo

[walber]

Sounds like an interesting experiment. Would also be nice to compare running either by itself as well as combined.

[Bill Dizer]

In dual plug aircraft engines from the thirties and forties, the two mags are timed a couple of degrees apart, so that the flame propagation doesn't start at the same time from two sources, and meet in the middle, which can cause spark knock detonation or pinging as it is sometimes called. Keeping the advance curves the same might be a good idea, even at the low compression of a "T". The early airplane engines are pretty low compression too, at just over six. Most aircraft mags are no advance, fixed timing.

[big2bird]

What is your goal?

Redundancy? Meh

HP? Pretty negligible. Possibly more harm than good. (Performance wise).

Any system should be identical and triggered by a single source.
(With two types of systems, your timing will be a chaotic).

Using modern stuff okay or just old tech?

A 1919 car or later with a distributor is hard to beat. A pre 1919 car with a DU4 is best. IMHO.

[Kevin Pharis]

Could always start scrounging for a twin ignition Pierce Arrow distributor...? They run on any standard DU4 type magneto mounting bracket.

There are 2 variations... 2 single ignition heads, or 1 dual ignition head

[Les Schubert]

Harry
Well you have seen my solution, a Nissan cap and rotor on a Bosch plate distributor firing a Onan dual plug coil. Fires both plugs at the same time every time.
I am now making a copy of the distributor drive that I put on the 21 car 40 years ago and might make a dual plug version of it. The nice thing is it has automatic dual advance (vacuum and centrifugal)
All the best and be safe

[big2bird]

Have you done a side by side comparison?

Sounds like a good solution.

[Rajo23]

Bosch made a Two spark magneto.

Or, better yet, use a Bosch Two Spark Dual magneto.
With this, you can have two spark plugs per cylinder and have the option of
starting with either magneto or battery!

[RajoRacer]

Yes, the Bosch ZR4 dual is the ticket BUT rare & pricey ! When I built up my BB RAJO racer, I searched for quite some time for one but at $1600.00 near 30 years ago, it wasn't in the budget !

[big2bird]

Yes, the Bosch ZR4 dual is the ticket BUT rare & pricey ! When I built up my BB RAJO racer, I searched for quite some time for one but at $1600.00 near 30 years ago, it wasn't in the budget !

Honestly, you probably would not recover enough hp for the added weight and agrivation.
The general aviation guys tell me they notice a tad more hp, but those engines are a tad more sophisticated.
All auto makers gave up on this long ago. Too much effort for negligible gain.
If you want the "cool" factor, it has to be done correctly.

[Kevin Pharis]

Here’s a pic of the Pierce arrow dizzy that I reworked a while ago. The original plan was to redesign the internals to incorporate the centrifugal advance mechanism from a VW 009... turns out that fixed timing was OK for the application, and the 009 centrifugals ran the other direction anyway...!

I used 2 009 dizzy electronic pickups triggered off the same magnet ring, and the pickups could be loaded into 1 of 3 locations to allow simultaneous firing, +3 degrees, or -3 degrees.

[big2bird]

Kevin,
That looks good and thought out well. My concern would be operation with a caveman charging system.
If you use an alternator, 12 volts, and is regulated, it should work well.
What does that weigh?

[Kevin Pharis]

There are 6 volt options out there too...

https://www.steinertractor.com/EIGN16?c ... gKwVvD_BwE

The Pierce Arrow dizzy is an aluminum base housing, and fits on any one of your favorite accessory mag drives too!

I’ve always felt that one of the coolest accessory combinations was a dizzy conversion in a mag drive!

[kmatt2]

Back in the early 1980s I ran a Bosch ZR4 mag mounted on a Matco cross drive on my BB Rajo. It ran really well at 80 MPH +. There was only one person back then on the west coast who could rewine that mag and he was busy most of the time working on P51 Mustang mags for the Reno air races. It was a lot of bling for a lot of $$$$.
As I remember there is a early 1940s Nash twin fire 8 cy distributor that can be reworked. It fits the Bosch front plate, had dual points and uses two coils. There were some speedsters running the Nash back in the late 1970s. It is kind of like the 1980 Datsun distributor but looks a little more late 1920s early 1930s .

[big2bird]

So has anyone done an A-B test on a dyno?
( Dual propagation vs single)?

[Harry Lillo]

Thank you for your thoughts on this guys.
I have had two ZR4's offered to me but the cost was approaching the value of my engine.
It appears that not too many have ran two independent ignition systems.
It would create some interesting eye candy for those who like go fast engines.
I doubt there will be a significant or even noticeable increase in performance.
Tucked away somewhere I have a cross drive that has both a mount for a magneto and a mounted distributor.
It appears to be Fordson but could be modified for a Model T. I will try to dig it out when out winter storm front moves on.
A simpler question may be "How are some of you firing your twin plug heads? "
Harry

[big2bird]

I would be willing to say that back in the day, it was redundancy.
NASCAR uses back up ignition boxes because of a high failure rate.
Dont forget marketing. After market hype was born the day after the automobile.
Your plate has a back up magneto in case the battery or generator quits.
Its a hobby. Whatever you like, but dual propagation is not worthy of the effort.

[Les Schubert]

Jeffery
As a small airplane pilot, in the “run up” prior to takeoff you switch the engine from running on both magnetos to running on each separately and you watch for a small drop in rpm (maybe up to 10%). EVERY light aircraft I’ve been in behaves similarly. That big fan on the front draws full horsepower and the engine produces less on just one magneto (either one). Certainly these engines combustion chambers are designed to take advantage of dual ignition working all the time.
Now how many T combustion chambers are designed to utilize the advantage is open for debate!

[big2bird]

Post an airplane head chamber for giggles. Lets dive in deeper, as this discussion is 100 years old.

[Charlie B in N.J.]

By all means enjoy yourself in your experiment but I have to agree with Les and Big2bird. The results as far as performance will be minimal maybe even unnoticeable however visually it would be interesting. Good Luck!

[Gary_in_MN]

This setup is a little more involved. I used Bosch dist. mounted on 1920's Dodge 90 degree dist housing. The rear dist has the trigger to fire a coil pack from a Buick V6.
Gary in MN

[Shane Lach]

More info on that engine and transmission Gary? I'd love to see more photos as well.

[Gary_in_MN]

1927 T block, A crank, A rods. Himico cast oil pan and starter housing . Billet flywheel, V8 pressure plate, aluminium adapter to mate the V8 transmission to the Himico. Gary

DSC01279 (300x169).jpg (74.23 KiB) Viewed 4772 times

[Les Schubert]

Nice looking engine Gary. Thank you for the pictures!!

[Michael Peternell]

Very cool Mr Anderson. What is the new build?