Du4 bosch mag???

[Buzz68]

First off my 12 metz I getting mag rebiult had question or to

First can  add an impulse  but there no room add one?

or find a duplex ( dual) ignition mag make starting easier I found DU6 duplex wonder if that can be turned into du4??

Also mag I took off my car how can I test it I spin it and don't get arc from plug wire to base?

Is there a better mag to replace du4 altogether

[JV Puleo]

No, you can't make a 6 into a 4 but a DU6 is about 10 times more desirable than a DU4, which is probably the most common 4-cylinder magneto around. The impulse starter wasn't in general use in 1912. A form of it had been invented but the version we are familiar with didn't come around until later - they were most common on tractors long after magnetos were gone on American cars.

[Buzz68]

Looking at as an option a dual or ( duplex ) type magneto

Although serveral told me du4 if set up right should fire on pull up vs spin type  start?

[JV Puleo]

Bosch terminology can be very confusing. The DU4 was intended to work with a separate coil & battery for starting, switching over to the high tension mag when running. They will start without the battery or an impulse starter but this usually involves spinning the crank. "Spinning the crank" is commonly seen in the antique car world but isn't the way they were intended to work and you'd never be able to do it with a big engine.

 

I think - and I'm not sure about this - that the "duplex" version had two sets of points and was intended for cars with two plugs in each cylinder. Those are very rare and valuable and would be useless on your car in any case.

 

I'm not sure you need the Bosch dual switch - which for some reason always seems to be more valuable than the mag...you may be able to use a free-standing coil but I've never been able to get a straight answer to my questions about what will work and will have to do my own experiments. I've attached the DU4 external wiring diagram. The switch is connected to the terminal on the points cover as described in the text.

 

[Buzz68]

This wire diagram for duplex or dual mag 

This allows start on battery and switch mag for hard to start engines 

 

Edited March 22, 2021 by Buzz68 (see edit history)

[Buzz68]

JV yes your wire diagram is correct or at least what I seen but dual mag appears to be second circuit for battery

No sure how the current separates at the mag but 

Yes dual mags are twice the price as are the switches and reading the mag switch be fitted with trember coil not sure what that is unless it's referring to buzz coil

[Mark Shaw]

12 hours ago, JV Puleo said:

The DU4 was intended to work with a separate coil & battery for starting, switching over to the high tension mag when running. They will start without the battery or an impulse starter but this usually involves spinning the crank. "Spinning the crank"

The original separate coil and battery starting systems in Buicks used low tension REMY mags that could not produce enough spark without the coil to increase voltage. A DU4 high tension mag can easily start the engine without spinning the crank if fuel delivery and timing are correct.  Several early cars also used battery ignition only for starting because early mags produced weak spark when hand cranked.  The impulse coupler installed on a DU4 mag eliminates the need for battery starting and will start the engine with a quarter turn pull on the crank when fuel is available to burn.  

[Layden B]

Low tension magnetos such as the Remy, Splitdorf and others ( timers and coils as well) have the benefit of hot spark at low hand cranking speed as Mark has stated. They also have the advantage that when on battery they will spark the plug without the engine turning at all. When set up properly they often fire the cylinder charge and start the engine without hand cranking. In the era this was called " starting on the spark". If you are not familiar with it, ask any Model T Ford owner!

[1912Staver]

Not sure if it is clear or not but as far as I know there are 4 basic types of DU 4 .

1} the plain DU4

2} DU4 Duplex

3} DU4 Dual

4} DU4 with impulse

 

The plain DU4 seems to be the most common.  You can use it for hand crank engines, many cars and trucks used it on crank start . The most practical unit for your Metz.

 

The DU4 Duplex seems to be an early improvement . A reference like Dykes explains it best. Not seen very much these days , and probably not worth the extra trouble  / expense compared to a regular DU4.

 

DU4 Dual is the best and most desirable. Quite expensive. Used with the dash switch / coil unit and a battery. As JV says, the dash switch assy is very sought after and expensive. Used on the highest quality Mag. ign. cars.   Total overkill on something small like a Metz.

 

And finally the impulse units. Usually on tractors and non - electric start 1920's trucks. Uncommon for car use.

 

Greg

[Layden B]

Just a couple of notes on Greg's post.

1. Duplex also uses a battery like the dual system.

2. A battery assisted system to " start on spark" or just to assist in starting can be very useful on any engine without a starter if your back is not up to the job!

3. The use of an impulse will get a hotter spark at lower speed but I never recommend it on a car or truck. Antique vehicles need all the spark retard that you can get when going down steep hills because they usually have minimal brakes. An impulse drive has a built in spark advance so full retard is unavailable.

 

 

[JV Puleo]

31 minutes ago, Layden B said:

... An impulse drive has a built in spark advance so full retard is unavailable.

 

Thanks! That is a really good piece of information that I confess I did not know.

[F&J]

20 hours ago, Buzz68 said:

Although serveral told me du4 if set up right should fire on pull up vs spin type  start?

Decades ago, I had a 1913 Metz and then followed later by a 1912 Metz.  Both were dry barn-stored relics since way before WW2. (Meaning not older or newer restorations).   I did not rebuild either engine, but recall having at least one head off for minor valve work, maybe both engines, not sure now. 

 

One mag was shorted or something, so I took it apart to learn how they work and somehow fixed it.. Neither mag was sent out for magnet recharging, and both cars would start very easy on the first pull "up", (after the one pull up that I always did first, to pre choke).

 

I'm nearly 100% positive they both had "DU4" stamped on the bases. 

 

My only point is, Metz engines do start very easy if nothing is wrong.

 

.

[Terry Harper]

19 minutes ago, JV Puleo said:

 

Thanks! That is a really good piece of information that I confess I did not know.

 

That is good info! 

[JV Puleo]

3 hours ago, 1912Staver said:

And finally the impulse units. Usually on tractors and non - electric start 1920's trucks. Uncommon for car use.
 

 

The earliest type of impulse starter I have found was first patented by Unterberg & Hleme around 1906 but was only available on their magnetos. They had a later US patent dated 1915 as well. The original design was patented in the US as well as in Europe and it appears that the impulse starter we are familiar with did not appear until WWI.  It may have taken time to design something that circumvented U&H's patent or, perhaps the patent protection was nullified by the declaration of war.  Certainly American Bosch was making them in 1918 because I've seen a National Archives photo of them being tested. U&H's patent would have protected the idea at least until WWI, at which point it may have fallen under the aegis of the Alien Property Custodian - this was the government agency that seized the assets of the German Bosch company and sold them - the origin of "American Bosch" which is not connected with the German company. The same thing happened to Bayer Aspirin...the American company is completely separate from the original German company.

[Layden B]

True about a Metz should be among the easiest cars to hand crank. When hand cranking what you effectively feel at the crank is only one cylinder at a time. Some of the toughest are one cylinder cars! One cylinder Curved dash Oldsmobiles have a reduction ratio between the hand crank and the crankshft because it takes so much to get those cubic inches over top all at once. 

[MochetVelo]

Metz used the Bosch DU4 magneto. Other than the engine, it was the most expensive part of the car. It is a common magneto today, and is very well made. No pot metal or fiber parts. The magneto on the Metz did not have adjustable spark timing. Once set to the timing gears, there is no adjustment to the magneto spark. The advantage there is you never break your arm by forgetting to retard the spark. The disadvantage is you can't adjust the spark! You can use a DU4 with adjustable timing, but the Metz engine runs well with this system, as did many cars of the era. The Metz should start on the first or second crank, as the Bosch provides plenty of spark. If you pull out your plugs and lay them on the cylinder head, you'll see. In other words, you should not need an impulse unit.

 

Phil

Edited April 27, 2021 by MochetVelo (see edit history)

[Buzz68]

Thanks my mag was weak last time it ran so I was told but it's dead now.

Just looking for options as I have brass frame DU4 I sent out to rebiuld and I'm barrowing duplex mag I can buy if I want

I thank you all on the info and advice I had du4s on a speedster but they where harder to start then ford coils

[Mark Shaw]

On 3/22/2021 at 12:13 PM, 1912Staver said:

And finally the impulse units. Usually on tractors and non - electric start 1920's trucks. Uncommon for car use.

Certainly not uncommon in many of the hand crank cars with magnetos that I have seen on tour.