Part Five: Ignition Timing

[Terry Syd]

Let's give it a try -

 

[Adirondackstihl]

Mitch Weber is an electronical genius IMO.
Sadly....he not hang out wif us nomo

 

[Time's Standing Stihl]

Mitch Weber is an electronical genius IMO.
Sadly....he not hang out wif us nomo

Yup, builds a fine saw too. I think the forums burnt him out....

 

[Mastermind]

That worked Terry.

 

[Terry Syd]

Yeah, too easy! There's some good information in there about saw ignition systems. I never knew how the flywheel was constructed with the magnet. The document cleared that up.

 

[jake wells]

usually something with advanced timing is going to be harder to start.
so naturally i chose not to advance anything that i own.
now is part 6 fuel oil ratio mix?

 

[MattG]

Picking up from Terry's upload, if anyone's interested, here's a patent document with an enclosed circuit diagram and (admittedly very terse) explanation of function. I saved this file from a post from an AS forum member some moons ago.

Bear in mind that this is from an early discrete component design; but of course the fundamental principles remain the same today.

 

[Al Smith]

I've got the theory of operation for the SEM self advance coil used on the Stihl 042 and 048 .I might add it is the only example I've ever seen that explains how it works .It's a couple of pages long .

Now two problems exist .Firstly Stihl claims to have intellectual rights over copying printed material .Secondly even if you know the operation it's an epoxy encapsulated system ,you can't change or modify the internal components . So in a nut shell it either works or it doesn't .you can't repair it with one exception perhaps .

On an Echo weedwacker which used three magnets,one mag was weak,can't remember weather it was a positive or negative .I pepped it up using a strong rare earth mag by stroking it with same .Once it held some magnetism it was okay but the retentivity of the magnet was low and it lost the charge over the winter for some reason .So at least in that example the problem was the flywheel and not the coil .

 

[MattG]

,you can't change or modify the internal components . So in a nut shell it either works or it doesn't .you can't repair it with one exception perhaps .

There is actually a thread on AS (I've still got it on my watch list, I can PM anyone if they are interested), where some guy hacks up a busted 056 ign unit and changes the blown capacitor. A labour of love, yes, but I guess that's the case with a lot of these projects.

 

[Terry Syd]

usually something with advanced timing is going to be harder to start.
so naturally i chose not to advance anything that i own.

Yeah, I had the kick-back issue with a 029/390 I built. You had to go through a ridiculous starting drill (like starting a 064) to avoid problems. I got lazy and it kicked back when I was out cutting and stuffed up the plastic starting mechanism, I had to use my back-up saw to finish the session.

I put on an 066 (660??) ignition with a 4 degree retard on starting. Fixed the the kick-back. Now, with the de-comp and retarded ignition, I can just pull it and go. Works for a old bloke like me, never had a kick-back since.

 

[Mastermind]

usually something with advanced timing is going to be harder to start.
so naturally i chose not to advance anything that i own.
now is part 6 fuel oil ratio mix?

Part six is gonna be on mufflers and tuned piped.

I think we have an oil thread of epic proportion already.

 

[Stump Shot]

Part six is gonna be on mufflers and tuned piped.

I think we have an oil thread of epic proportion already.

Biggest understatement of the year.

 

[XP_Slinger]

Biggest understatement of the year.

Of the decade lol

 

[Mastermind]

And stuff.

 

[Mastermind]

http://opeforum.com/threads/part-six-the-exhaust-system.7372/

 

[MattG]

Randy, my take on it is this. When we cut the squish band two things happen. One, we increase compression. Two, we improve flame travel in the chamber. We know compression makes the fuel/air charge more flammable and explosive. So it makes sense that a fuel mixture that's more explosive, and has a chamber design that the flame can travel faster would need less timing.

If we are creating a situation where combustion is more efficient (i.e. making the squish band closely to optimal - less f/a mixture is wasted, and more is compressed in the combustion dome) then it seems likely that the charge will burn slightly quicker, and thus less advance of ignition timing would be required.

 

[Magic_Man]

If we are creating a situation where combustion is more efficient (i.e. making the squish band closely to optimal - less f/a mixture is wasted, and more is compressed in the combustion dome) then it seems likely that the charge will burn slightly quicker, and thus less advance of ignition timing would be required.

Yea, what I said, only fancier and more proper and stuff. Lol

 

[Al Smith]

There is actually a thread on AS (I've still got it on my watch list, I can PM anyone if they are interested), where some guy hacks up a busted 056 ign unit and changes the blown capacitor. A labour of love, yes, but I guess that's the case with a lot of these projects.

If I'm not mistaken the 056 uses the same type SEM coil a 2100 Husqvarna uses which are very costly to find in OEM . When I was looking for one they were around $200 .I found one from Bryce in Washington state for $50 that the shut off circuit didn't work .I just taped into the high voltage lead and used a kill switch .

 

[MattG]

If I'm not mistaken the 056 uses the same type SEM coil a 2100 Husqvarna uses which are very costly to find in OEM . When I was looking for one they were around $200 .I found one from Bryce in Washington state for $50 that the shut off circuit didn't work .I just taped into the high voltage lead and used a kill switch .

PMd you dude.

 

[Chainsaw Jim]

There is actually a thread on AS (I've still got it on my watch list, I can PM anyone if they are interested), where some guy hacks up a busted 056 ign unit and changes the blown capacitor. A labour of love, yes, but I guess that's the case with a lot of these projects.

That might be the same guy I talked to from bend Oregon. This guy I talked to was assigned to ignition coils for his job in the military and learned everything about them. He told me the main thing that goes bad in 056 type coils is one little tiny wire that burns out and that they can be repaired.
I may get lucky and find him if my email inbox archive goes back 2 years.