Voltage to ignition coil

[Robban 54]

In order to get higher primary voltage to the ignition coil, especially at start when the battery voltage drops and also during normal operation, is there any disadvantage or other problem to use a DC voltage converter?

[mag2555]

If a properly charged battery ( above a static 12 volts ) is not enough to throw a hot enough spark to fire over a motor then you have other problems going on.

A spark coil is nothing more then a step up transformer ( more windings on the spark plug side then the 12 volt side) so using a higher KV rated coil is the same thing as using a DC to DC converter.

Also power IE wattage is a combination of voltage and current, so when you step up voltage by means of a transformer you loose current which in turn produces less wattage, IE power.

As you have heard before there is no such thing as a free lunch.

Better then trying to use a dc to dc converter would be a ignition system that can throw multiple sparks at low rpms as when cranking.

[Tuner]

For sure, your plan will increase ignition energy. 30+ years ago some circle track outfit was marketing a system that ran the HEI coil at 24 V with the module at 12 V (24 V kills the module). I rigged this on the bench and can report it works. Crazy hot spark and increased spark output at high RPM, but not worth the effort when the standard HEI makes more than enough energy when it is fed sufficient amperage through 10 ga. wire from a standard charging system 13-14 V.

You who have no experience with points ignition missed all the fun .....

[rebelyell]

^^^ this ^^^ y'all missed it!

[RCJ]

FYI ,I was working on a 460 ford and the voltage at the hei plug was 9.8. While cranking. That was not the problem , but it .ight be why everything has to be perfect for it to start.

[Tuner]

FYI ,I was working on a 460 ford and the voltage at the hei plug was 9.8. While cranking. That was not the problem , but it .ight be why everything has to be perfect for it to start.

Are you using a HEI distributor with a regular GM HEI pickup and module inside the coil-in-cap housing, or a Ford magnetic distributor to trigger an HEI module?

At engine speed below about 500 RPM (250 distributor RPM) the Ford pickup and reluctor triggers most HEI modules several degrees advanced, so may cause an engine to fight the starter as if the timing is too far advanced -- because it is. When running above 500 or 600 RPM the trigger point will retard back to the actual position of the advance mechanism. If you use a timing light as the engine cranks and idles very slow you will see this phenomenon of Ford reluctor vs. HEI module.

This characteristic of the Ford magnetic pickup is why the Ford ignition boxes have a built-in retard function. Early boxes were caused to retard by a 12V signal from the starter solenoid, later and all new boxes sense RPM and retard when low RPM cranking.

[Robban 54]

When I bought this T-23 21 years ago it was a 327 sbc 69 year model with points so I've had some fun with those.
Nowadays it is a 383 World block with the same distributor but an Ignitor 2 module and flamethrower ignition coil and a second strik box.
In that case, I was thinking of connecting the DC voltage converter to the ignition coil directly from the main switch and the Ignitor over the ignition lock.
Not that I have any starting problems now but it would be good to know that the ignition coil gets full voltage even at start.
Can you tell if the DC voltage converter in the picture is capable of powering the ignition coil?

[Tuner]

If you can check with the manufacturer, find out if it can tolerate the high voltage flyback from the ignition coil, which can be as high as 400 V, depending on turns ratio of the coil and maximum voltage rating which can be reached if a plug wire is not connected when the spark fires.

[Robban 54]

I hadn't thought of that. I think it's difficult to get that information, it's bought from China.
Can it be protected with a diode?

[Tuner]

I hadn't thought of that. I think it's difficult to get that information, it's bought from China.
Can it be protected with a diode?

Yes, you can limit the flyback voltage in the primary with a zener diode, but shunting the primary to ground at some arbitrary voltage limits the output of the coil by diverting the stored inductive energy to ground instead of letting the oscillations ring and discharge that energy to the plug gap.

There are some electronics savvy people on this board who can explain it better than that, but I think that is the basics of it.

Some California Corvette restoration parts supplier makes a gizmo that that suffers from exactly this. The thing is supposed to replace the original transistors and components and hide in an old GM MagnaPulse amplifier so the original wiring harness is retained for a true original restoration.

Unfortunately, the gizmo has a zener diode that shuts off the spark discharge and limits the arc duration and spark energy such that maximum engine speed is about 5500 RPM, which ain't enough for solid lifter Chevy engines equipped with that ignition system, such as 435 HP 427 Corvettes, etc.

.... "We haven't had any complaints."

... "Well, you suckered this guy into buying two of them, and we have three here and they all do it. "You can see this on an oscilloscope, plain as day. "A stock MagnaPulse box with new transistors runs just fine, all on the same original wiring harness. "We would like our money back."

.... "You say they all run, so there is nothing wrong with them, and no refunds on electrical parts."

No RPM, no joy, and no money back, slimy bastard. It is so easy to repair the original MagnaPulse I don't know why anybody would go to all the trouble to make a gizmo that doesn't work.

[Robban 54]

I guess I'll plug it in temporarily and just drive around the block to see what happens, maybe measure some current and voltage.

[Robban 54]

Now I have been able to test drive a bit (no snow) with direct plus to the ignition coil. Cable 2.5 mm2 from the main switch with 20 amp fuse. The DC voltage converter will have to wait a bit
Probably think that the cold start was better able to idle earlier.
Maybe some better throttle response.
Could there be any advantage to a thicker cable also from the minus on the ignition coil to the ignitor?
And a proper grounding of the distributor?

[Tuner]

How long is the wire from the minus on the coil to the Ignitor 2 ? If it is only a few inches the wire supplied attached to the Ignitor 2 is large enough.

The improvement on the positive side is accomplished because the larger wire direct to the coil eliminates several feet of wire in a primary ignition circuit from battery through vehicle wire harness to ignition switch and from ignition switch to coil.

The Pertronix Second Strike is an interesting device.

Have you noticed any effect from adjusting the crank angle delay of the second (CD) strike ?

For those who are not familiar with the Second Strike, it is a CD system arranged to follow the discharge of the original inductive system with a capacitor discharge second strike. The timing, or "offset" of the second CD strike after the inductive strike, is adjustable in two degree steps over a range of several crank degrees.

[rebelrouser]

In order to get higher primary voltage to the ignition coil, especially at start when the battery voltage drops and also during normal operation, is there any disadvantage or other problem to use a DC voltage converter?

If you want a lot of voltage at the coil use a capacity discharge type ignition, like an MSD, I remember many years go trouble shooting a MSD for the first time, trying to use a test light at the coil like a normal ignition system, the test light blinks one time really bright.

[Robban 54]

The cable from the ignition coil to the ignitor is spliced to about twice the length with the same area as the original cable.
I haven't noticed any difference with second strike from zero degrees (off) to max.
On the other hand, the speed controller works perfectly.

Of course, it's fun when the test lamp works as a photo flash.