Magneto ignition

[Russ Noble]

Hi guys.

Who can educate me on magnetos? /ubbthreads/images/graemlins/help.gif

My car will be racing under "classic regulations" which here in NZ basically means you can't run electronic ignition. I recall Caroll Smith in one of his excellent books saying that given a choice he would use nothing else. I note that most F5000's that I have looked at lately have been running it.

What do you need to watch when buying and using? I have only heard of two brands, Mallory and Vertex. I presume there any others worth considering? As always what's the best bang for the bucks? Do second hand ones (351W) come up on ebay very often?

A lot of questions but I'm coming from a zero knowledge base here.

Thanks in anticipation.

 

[Ron Earp]

Don't know a lot about them but I don't think that would be such a good idea. The magnetos are physically taller than a dizzy and that is one dimension you don't have any clearance on. Most magento systems I've seen are about 10" taller than a dizzy, with about the same diameter.

Neither Mallory or Vertex offer Ford applications. My Jegs catalog only shows Chevy magnetos. However, I'm sure there is one available, no doubt about that and it might be from these two companies and Jegs just doesn't show it.

I like the idea of a magneto on a pul start lawnmower, kick start dirt bike, airplane etc. where you want something dead reliable and simple. Planes have two independent mag systems and you check each one during runnup, lots of fun. I've never seen any lawnmower I've dealt with ever fail to produce a spark.

But, I don't know that I'd want a magneto on a street/track car because you are still going to have to have an alternator to power all your stuff, thus you aren't really saving anything by having a self-contained and stand alone ignition system like a magneto.

Besides, you still will need a battery to crank the thing, unlike some race cars with magnetos that use them to eliminate all the things like batteries, alternators, starters, etc. because they use a seperate starter and don't need accessory power.

 

[Howard Jones]

Mags work well in situations like sprint cars where the only thing that needs power is the ignition system. I have never heard of one being used on a street car.

I think I did see a sort of fake mag. that was a regular electronic distributor and coil system inside of a Mag looking big distributor body. It was for street rods/show cars that want to appear to be running a magneto.

I see no reason to use one on a GT40.

 

[John Fitzpatrick]

The advantage of a magneto is that it is self-generating and a mag ignition doesn't need a battery to function. That can be important when weight or reliability is critical. The old Piper Cub had no battery-that's why you had to hand pull the prop through to start it. Light and simple, but if your engine quit in a Cub, you WERE going to land! That’s why, as Ron said, aircraft use two mags. You can charge a battery with a magneto if you need power when the engine isn’t running-most modern light planes (and riding lawn mowers) operate that way.

I suspect magnetos rather than alternators are used in some racing and off-road vehicles because if the battery required for an alternator to work fails, the engine stops, and lead-acid batteries, sealed or not, do not like vibration.

I think you might avoid a magneto ignition primarily because it is much more efficient at producing a high voltage with low current. That’s great for ignition and, with regulation, charging a battery. No so much for headlights, fans, and power seats. I seem to remember Lucas made one that tended not to work when the lights came on, but that might have been a feature.
Just my $.02

 

[Russ Noble]

Re: Non electronic ignition

Thanks for the replies fellas.

Three negatives, no positives. Is there a trend showing up here?

Ron. Good thinking I will check out the height thing. That was something I hadn't even thought of.

There must be a reason, other than insurance against battery failure, that pre-electronic-ignition-computer-controlled race cars ran magneto's. Lets face it most cars use electric fuel pumps and battery failure will still stop the car. The period alternative, I think, would have been to have a twin point distributor.

What then must have been the perceived or actual disadvantage that ruled against the alternatives? Thinking about it, none of the F5000's run alternators therefore the battery does not get charged. Maybe the voltage drop affecting the ignition as the battery drains (fuel pumps, rain lights) is the reason the distributor was not used. The magneto would be unaffected by this and as a bonus could it also maintain a (smaller?) battery sufficiently to run the fuel pumps? Or maybe they didn't have electric pumps?

I'll have another close look at some more F5000's at Teretonga this weekend and take note. I'll also see if I can find out what actual battery charging output is available from the magneto.

A non registered lurker has emailed me about a relevant article in EAA Sport Aviation Dec 2005 (thank you Dennis) but he doesn't have a scanner. I will see if I can find a copy here in NZ. Otherwise maybe someone who's got it could scan it for me?

As a mainly race only car, even with only minimum electrics it could be that I will still need to run an alternator, in which case the best ignition option under classic race regulations would be the twin point distributor? Any opinions on these, or better non electronic alternatives?

As you can see I'm woefully lacking in my knowledge of V8 ignition systems. Thanks Ron, Howard and John for your replies to date which have helped to clarify and focus the issues.

BTW John. It is a feature of Lucas systems that many things don't work when you switch them on. /ubbthreads/images/graemlins/banghead.gif

Regards

 

[Ron Earp]

Re: Non electronic ignition

Hi Russ,

One thing to consider is many race cars run a loss system, which I think you covered. But, in plain terms they use the magneto to provide ignition since it is self contained and a small battery can provide whatever other electrical power is needed. There is no alternator to charge the battery in some of these cars because the races are less than 2 hours in length or so.

I've always wanted to use a mechanical pump on my GT40 since they worked back in the day and modern blue printed pumps are plenty reliable. If you combined that, with a magneto ignition, you'd have a dead reliable machine except for the battery to turn the starter, which I suppose could peter out.

 

[John Fitzpatrick]

Re: Non electronic ignition

Here's a magneto ignition system which also keeps a pattery charged. It isn't automotive, but you get the idea.

John

 

[Howard Jones]

Re: Non electronic ignition

Russ, Nothing wrong with mechanical fuel pumps and point/coil ignition systems. A lot of races have been won with them. The main reason for electric pumps on race cars in redundancy and more than one fuel tank. Electronic ignitions have come from the extreme RPMS modern race engines run at. A good ol SBF running at 7000RPMS will be fine with a well maintained duel point and quality coil.

It should be added that there are some very good small and light batteries available today as well as alternators.

Even starters have come way down in weight. If you limit the current load to only what you need in a race car, brake lights, gages/sensors, ignition, starter, you should be able to get by with a very small race alternator and battery.

 

[Jac Mac]

Re: Non electronic ignition

Russ, The T142 Ford 302 powered 5000 at teretonga had recently been fitted with a magneto and had to be push started or assisted with a jumper battery. A case of the Hi- torque starter simply not turning the engine fast enough. Aircraft use an impulse system on one mag to aid startup. Use the standard Ford distributer converted to twin points, fit the later large dia cap from the electronic dizzy if it will clear your manifold to reduce the crossfire risk.(We are talking USA Autolite,not Aussie Borshe) The standard Autolite has one of the easiest and most bulletproof centrifugal weight setups around,is simple to change springs and alter curve on.Just remember to fit a bronze gear if you use a roller cam. Any further problems you know where I live. Regards Jack.

 

[Paul]

Re: Non electronic ignition

The only down side about using mechanical fuel pumps is having to turn the engine over enough to prime the the carb's if they are dry. The good thing is that if the engine stops turning the fuel supply stops unlike an electric pump. /ubbthreads/images/graemlins/flamed.gif
Paul

 

[Russ Noble]

Re: Non electronic ignition

Jack,

You're just a fountain of knowledge! /ubbthreads/images/graemlins/flehan.gif I'll take your advice on that one and go that way.

One of many things I've recently learnt about mags is they need to run relatively small plug gaps. That came as a surprise!

Thanks for the look through your place at the weekend, if the guys on here knew what you can do, have done and are doing, they would be amazed. As I was. A real understated Kiwi achiever. /ubbthreads/images/graemlins/banana.gif

Yeah, thanks for the offer, I know where you live, but could I find it again? /ubbthreads/images/graemlins/lol.gif

Regards

 

[Ron Earp]

Re: Non electronic ignition

Hi Russ, it sounds you are going to run a magneto system, so can you share what you'd learned and how one is setup?
Thanks,
Ron