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Bigger mag for more power?

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Mister_Fitz:
I run a n/a alcohol injected 350" sbc in my FED. Best et so far is 8.41sec 159.5mph. Planing to do some upgrades this winter to be able to go faster. My goal is a 7 sec run, which might be hard...
I have a Mallory SprintMag I, which never have been recharged during the 4 years I have raced with it.doing about 10-20 passes each year.
Engine is running good and feels strong. Can I expect any power gains if I have the mag recharged?
Or should I get a bigger mag? SuperMag IV would be nice since they do not need to be recharged.
Will a bigger mag help me make more power? Or will it just increase the losses since it takes more power to drive?
What mag is the best for my application?

Spud Miller:

 A Sprintmag is fairly comparable to a Vertex magneto except that it makes a little more current and voltage at the plug due to the external coil. You might notice a little power gain from recharging if the mag is way down on output. I'd be most concerned with reliability if you've not had anything done to it in that many years. Since mags generate ozone inside the cap, things can rust up pretty quickly depending on what climate you're in. Having it serviced every other year means it'll run its best and have plenty of poop. Your Sprintmag can be upgraded to a Sprintmag+ which makes about 3 amps (7 amps measured like a Pro-Mag) and that would have a rare earth magnet in it.

 The best thing about the Sprintmag is that it's a "constant duty" mag. You can run it all day and it won't get too hot and hurt itself.

 A Super-Mag IV would work great but they're bigger in diameter. Not sure if space is an issue. The power to drive them isn't going to be noticeably more than the Sprintmags. You probably wouldn't see a gain in HP for your application. A little nitro or a supercharger and you would. If you're drag racing, then a Super-Mag would be great for you. Anything bigger than a Super-Mag III gets too hot to run for a long time. Lake boats, hot rods or circle track guys need to stick with a Sprintmag or a Super-Mag II. A III will be ok if it's out in the breeze.

 The good news is the lower drive for your Sprintmag will also work on any Super-Mag if you decided to go that route. The coil would work too. You'd just need the generator and be up and running.

 For your application, I'd say the best mag is one that's "paid for" :) If you plan improvements in the future that would require more mag, upgrading to a Super-Mag at some point would be a good plan. Until then, your Sprintmag oughta work great with a little love.

 Spud


 

ricardo1967:
I'm not familiar with the mag lingo.... what does it mean 'recharging' a mag??

Spud Miller:

--- Quote from: ricardo1967 on October 05, 2014, 03:52:59 PM ---I'm not familiar with the mag lingo.... what does it mean 'recharging' a mag??

--- End quote ---

Many old magnetos use a ferrite based magnet. As the mag is used, the magnets slowly lose their magnetism. Sometimes they can lose as much as half their power. If a guy welds on his chassis, sometimes it can totally demagnetize the magnet if the mag is left on the car during the welding.

Any Vertex that hasn't had a "rare-earth" or Neodymium upgrade will slowly go dead. Sprintmag I and II, Super-Mag I, II, III all use ferrite based magnets. Sprintmag III and +, Super-Mag IV, V and + all use Neodymium magnets that don't lose their charge with use.

 We have a couple of big magnet chargers here in the shop that dump energy into big windings. The charging fixture is setup a certain way with these coils and the magnet/poleshoe/shaft assembly is mounted in it. When the coils of the charger are energized, the magnet is charged back to full strength again.

 It takes quite a lot of use for the magnets to discharge enough to have an issue with performance.

 Spud

ricardo1967:
Now I know! Many thanks Spud.

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