DC CDI ignition wired to any flywheel that has a magnet.

[Thepartsguy]

I spent $15 on a DC CDI ignition system to retrofit onto a briggs 5hp engine.

This is also a commen swap for when the stator goes bad and you just want spark from like a small 12v battery instead.

Once it’s wired up in the garage on the bench pass a magnetic screwdriver under the pickup to fire the ignition.

timed spark advance!

 

[Thepartsguy]

Photo of this on a OHV engine of some kind.. Found the picture while scrolling

 

[bob58o]

So it just uses the signal from magnet?
I’m not familiar with fancy electrodynamics.

Many of the sparky ‘puters I’ve stumbled across seemed to use some soft of missing tooth on gear to time the signal.

Can you explain the passing the screw driver under to find ignition advance?

if it uses the stock flywheel magnet, does it fire at the leading edge or trailing edge of magnet?

At the leg of the sensor or the middle?

Maybe I’m missing something, but if the dumb kid asks questions the whole class too scared to ask can learn.

 

[Denny]

Bob, it’s going to fire when it senses the magnetic field is the strongest. It’s firing about 90 times a second. A few milliseconds ain’t going to make a difference. The picture shown it looks like the timing would be retarded. Being your from Chicago politically correct term would be timingly challenged.

 

[Thepartsguy]

So it just uses the signal from magnet?
I’m not familiar with fancy electrodynamics.


Can you explain the passing the screw driver under to find ignition advance?

if it uses the stock flywheel magnet, does it fire at the leading edge or trailing edge of magnet?

At the leg of the sensor or the middle?

yes just the signal from the magnet.

Pass the magnetic screwdriver under the pickup to fire the spark at the spark plug.. like a briggs flywheel magnet passes under the magnetron to produce spark.

I do not know yet where to place the coil but have a 3hp and can make as many brackets as needed to find out.

 

[Thepartsguy]

Bob, it’s going to fire when it senses the magnetic field is the strongest. It’s firing about 90 times a second. A few milliseconds ain’t going to make a difference. The picture shown it looks like the timing would be retarded. Being your from Chicago politically correct term would be timingly challenged.

Any idea if it’s so retarded due to the cdi’s built in spark advance?? timing Needs whacked way back so it can advance correctly as needed? instead of being started statically to far advanced then advanced further through the cdi spark advance?? Knowing this would be helpful..

Guy I got the picture from isn’t responding..

 

[Denny]

I have no clue why he did it that way unless he was confused about engine rotation.
And I wish to make a correction it’s when the magnetic field is broken it fires. When it’s at the center it’s the strongest.

 

[BrownStainRacing]

This guy does alot with cdi ignition.

 

[Thepartsguy]

And I wish to make a correction it’s when the magnetic field is broken it fires.

@Denny thank you!! So if it fires when the magnetic field is broken then there can only be one single place the new pickup trigger can be placed!!

locking the crank after the magnets have just passed under the stock coil.. The new pickup must be placed at the edge of breaking the magnetic field. in the same exact spot the field was broke with the old coil.

 

[bob58o]

Wouldn’t it make sense to use the magnet on the flywheel to find timing at set advance?

I have no clue why he did it that way unless he was confused about engine rotation.
And I wish to make a correction it’s when the magnetic field is broken it fires. When it’s at the center it’s the strongest.

So would you say, with a standard lawn mower, that when the trailing edge of the magnet just passes the second leg of the coil?

When does it spark? I know I posted photos somewhere but can’t remember where or the position of magnet edge to coil leg.

 

[Denny]

Actually I’m not sure where the field would be broken. What I would do is hook up a timing light and figure out according to the light where it is firing. Then figure out degrees from there.

 

[bob58o]

This guy does alot with cdi ignition.

It looks like with that ignition and magnet the timing light show it fires when the the magnet is right about here. I have no idea why this video made me more confused. It doesn’t show the pickup does it?

 

[Thepartsguy]

It looks like with that ignition and magnet the timing light show it fires when the the magnet is right about here. I have no idea why this video made me more confused. It doesn’t show the pickup does it?

View attachment 145296

He has a programmable curve and can set the ignition coil way back to account for that I believe.

 

[Thepartsguy]

So lock The crank so the last magnet is at the cutting edge of breaking contact with the right leg on the coil..

GUY actually responded and confirmed that is how he set it up on three engines and it works. So that is how I will set it up.

This whole deal only made since to me because points don’t fire till the contacts broken and there open

 

[bob58o]

Bob, it’s going to fire when it senses the magnetic field is the strongest. It’s firing about 90 times a second. A few milliseconds ain’t going to make a difference. The picture shown it looks like the timing would be retarded. Being your from Chicago politically correct term would be timingly challenged.

if it’s programmable and only a reference point is needed, then it doesn’t matter.

At 3600 RPM…
3600 (rev/min) x 360 (degrees/rev) x 1/60 (min/sec) x 1/1000 (sec/millisec) =

21.6 degrees per milli sec.

 

[Thepartsguy]

The first magnet starts to pass under flywheel building power... last magnet has passed under the flywheel and breaks the connection sending spark. That is how he explained to me to set it up. He said he has had success on three engines that are on some nice bikes.

It’s a $100+ kit he probably programmed the whole deal so he can set the new pickup in close relation to the old coil. Pullstart shroud would go right back on without hitting etc..

 

[Thepartsguy]

 

[bob58o]

Ok I got it.
When the magnet’s trailing edge has just passed the right edge of the right leg of stock coil.

Then lock crankshaft in space.

then install new pickup
(centered where the right edge of right leg used to be?)

This will be at the left (trailing edge) of the magnet location once the crank was locked down.

 

[Thepartsguy]

Ok @bob58o I said your drawings didn’t look right but I was directly wrong.

your pictures are correct!

Sorry.

That is all

 

[Thepartsguy]

You CANNOT do this with an AC CDI...

You connect 12v to the coil post on an AC CDI it’s gonna go full Rico