Magneto coil

[mmdm4]

I'm working on a Funny Car chassis that I am going to put under a resin body and I have some questions about the engine. This kit has a twin magneto set up and I am replacing the kit part with aftermarket magnetos and they come with a coil and wire to run from the coil to the mags. My questions are 1. Where would be a good place to mount the coil? 2. Would a double mag set up use 2 coils (I guess)? 3. Would there be a wire running to the coils and if so from where? This is what happens when you decide to give a try at wiring things!

[John Pol]

there usally on the frame of the car right about under the mag

[Ace-Garageguy]

Older magnetos, at least all the ones I've ever worked on in 1:1 cars, don't use a coil. They generate their hot spark internally and have no need for an external coil.

BUT, here's a good video on wiring a funny / top fuel style setup for a more recent car. It shows the amplifier boxes and coils. Good luck.

[Muncie]

The Mallory super mags used on Funny car and top fuel in the 70's (probably 60's and 80's also) had an external coil for each magneto - Revell may have created the impression that there was no coil because they molded the coil into the engine block on the 70's funny cars... Google, Yahoo and the Mallory website should produce lots of reference for the time period that you are intersted in.

[Ace-Garageguy]

This style Vertex magneto, extremely popular in the '60s is the one I'm most familiar with on cars. This and many aircraft mags have internal coils.

This is the total extent of the wiring, other than the secondary wires out to the spark plugs.

[mmdm4]

Thanks these are asll great responses. I'll have to decide which way to go from here. Thanks for your help.

[southpier]

got to Youtube and search "Ted's Modeling Technique" and then "ignition wiring for a top fuel or funny car engine with pro tech parts"

sorry; website won't allow me to cut & paste the url.

fellow is very informative and articulate!

[Muncie]

Bill,

enjoyed the video, looks like a good resource - and the vertex diagram is perfect for some early dragster projects in the queue -

thanks,Steve

[Force]

Here is a picture showing the older Mallory Super Mag setup in the Bruce Larson Sentry Funny Car from 1989-90-91.

And here are a couple of more recent MSD Pro Mag 44 setups from the 2000's, the last pic is from one of the Worcham family's CSK Funny Car from 2008-9 and it's pretty much how it still looks today

[shift13]

Love this thread!!!!!! Can we get it pinned?

[johnbuzzed]

As far as I know, a magneto creates it's own power. Grab the plug lead on a lawnmower while someone pulls the starter rope- you'll see what I mean. The coil in a car without a magneto acts a transformer to convert the normal 12 V power from the electrical system (battery, then generator or alternator) to a much higher voltage; the distributor then distributes that high voltage to the spark plugs. The step-up is limited by the amount of turns in the coil of wire that is in that transformer. I'm not sure as I have no schematics but the coil and magneto setup might somehow use the coils to step up the voltage created by the magnetos, then return it to the mags for them to distribute the current. I'm just a technician so I can't wrap my head around that setup. Any engineers out there who can clarify that?

Edited August 1, 2014 by johnbuzzed

[NJJeff]

i'm diggin' the smiley face on the blower belt....

:-)

[Ace-Garageguy]

Any engineers out there who can clarify that?

Yup. This is somewhat simplified, but it's the general drift. What makes a magneto special is that it has an internal "generator", and supplies its own current without the need for a battery. The internal "generator" is also often capable of delivering more primary current than a conventional battery-generator system, so in part because of that, the resultant spark is hotter. On many older mags, the "coil" is internal, and works like a conventional coil, more or less. Mags also have internal points, or electronic analogs of points that control when current is cut to the primary coil windings.

When the mag points open (determined by a small cam, as in a conventional point-type distributor) a relatively small current through the primary windings of the coil is cut off. This makes a magnetic field that has been established (while the points were closed) around the primary windings collapse, and as the collapsing magnetic flux-lines move through the secondary windings, they induce a higher-voltage current that is directed out to the plugs by a rotor and cap that function just like a familiar distributor cap. That hot, fat current is strong enough to jump the gap at the plug, making a spark.

Remember: It's the collapsing magnetic field in both the "coil" windings in a magneto and in a regular coil that produces the high voltage, as the moving magnetic flux lines of the collapsing field move across the secondary windings. Remember science class? A wire moving through a magnetic field will produce a flow of electricity through it (through the wire). This is how ALL electricity is generated, from car generators and alternators, up to big power plants that light your home. Moving the magnetic field relative to the wire, whether the wire moves, or the field moves, has the same effect.

Mags are more complicated than just a combination of a generator and an ignition system, but the analogy holds true for simplified explanation purposes.

External coils can be added that step up the available voltage more than the space-limited internal coils might be able to do, and for competition cars, having an external coil makes replacement quicker than it might be with an all-encompassing unit.

A significant difference between internal-coil mags and external-coil mags is that the external-coil unit has a cap with an extra terminal that connects the coil output to the "distributor" cap. Internal-coil mags lack the center terminal on the cap because the connection is, of course, internal.

Here's a schematic of an external-coil mag, with optional coil setups.

Magnetos can also be built where the mag generates the primary current and controls the timing of the ignition event, but a capacitive-discharge unit creates the spark, instead of the more familiar coil. Many variations and combinations of the various functions are possible. The whole mess may also be controlled electronically, with the mag still supplying the primary current to run it all, and supplying possibly a speed-reference for the control unit, or the timing may be varied by a small computer that gets its engine-speed-signal from a crankshaft sensor.

Edited August 2, 2014 by Ace-Garageguy

[booboo60]

Good pics and reff! Thats why I love this site

[gtx6970]

The style of and where you mount the coil ( or coils ) depends A LOT on the era of build your trying to replicate.

[Force]

Yes it does, that's why I showed pictures from the two eras with dual mags we have had so far.

They started to use the dual magneto setup in the nitro classes in the late 80's and Mallory Super Mag's was what almost everyone used back then, before that only one magneto were used in the nitro classes.

Later on in the mid 90's they switched from the Mallory Super Mag's to the more efficient MSD Pro Mag 44's and that's what they still use today...MSD started to develope a 66 amp Pro Mag back in 2002 but it was never permitted for use in the NHRA.

Edited August 3, 2014 by Force

[Ace-Garageguy]

Yes it does, that's why I showed pictures from two eras with dual mags.

They started with dual magneto setup in the late 80's and Mallory Super Mag's was what they used, before that only one magneto were used in the nitro classes.

Later on in the mid 90's they switched from the Mallory Super Mag's to the more efficient MSD Pro Mag 44's and that's what they still use today.

VERY helpful, too. I haven't stayed current with drag-racing technology, and your pix help fill a significant gap in my knowledge.

This site is becoming more and more a one-stop resource for the builders who want to get the details right.

Edited August 3, 2014 by Ace-Garageguy

[johnbuzzed]

Thanks for the info, Bill. That's one of those things which, until you see it, makes sense but doesn't.