Ignition coil spark advance?

[chipper1]

Info on Stihl Coils has been posted in the past. It is not really a gradual increase, but more like a couple of steps are various RPMs.

The only important # is the total advance, and it is great to keep that in sync with any mods to the saw. Then you hope it remains easy to start, but it will not always happen that way! Sometimes, you just have to reach a balance.

I have even seen folks retard timing from the original position to make the saw easier to start. The thought makes me shudder, but I also hate a saw that bits me! Cool weather seems to magnify the problem. (thicker oil in the cylinder)

I remember back in the day I'd get the timing on my old Pontiacs set were I wanted for performance and they would burn up starters trying to hot start. My fix was a switch in the glove box to shut of the power to the coil, all I did was get it rolling over and flip the switch, worked like a charm.

@X_makina I have seen videos on youtube where they were using a timing light on a saw, pretty sure it was just last week.
I'll check my history and see if I see it.

 

[MustangMike]

I used to carry a distributor wrench in back of the front seat of my Mustang (a 68 390 GT, built). I would go down the road and hit it in first and second, then pull over, move the distributor a bit, and try it again. When it felt the strongest, I would remember where the vacuum advance line was pointing! For open headers, I would advance it some more, then put it back again.

Had a very aggressive solid lifter cam and 800 double pumper Holley, and damn that car was fast. Would eat up a 440 6 pack Super Bee (with headers) like it was sitting still! It was about the lightest body style that came with a Big Block! It is the only car I ever owned that never lost a race, and in the early 70s there were all manner of super cars on the street.

I put about 20 car lengths on a 383 Road Runner before I even hit 4th, and I beat a 455 GTO that had headers, gears, traction bars and MT rear tires in an 1/8 mi race, and I had 325 rear gears! He jumped me out of the hole, and I blew right by him. Once that engine got past 3,000 RPMs, it just pinned you to the back of the seat. It maxed out at 6,800, doing 70 in first gear. When you banged second, it jumped like a frog, gaining 3-4 car lengths on anyone you were racing. It was fun!

 

[MustangMike]

They assembled all the fasted cars at my college, and we were in an abandon parking lot and only had 1/8 mile to run. I had the only Ford. One of the guys with a really built 340 Cuda comes up to me and asks what engine I have. I told him it was a 390 and he said "390s don't run"! I said OK.

He asked what gears I had (325), posi (No) Traction Bars (No). He said "You know we are just running 1/8 mi, you don't have a F****** chance"! I said OK.

I beat all the other cars, the GTO twice, and the built 340 Cuda 3 times, they couldn't believe it! The Cuda and GTO would beat me off the line, and I would just blow right by them. Could only do 1st + 2nd, but that would get me to 90 MPH, fast!

 

[X_makina]

[/quote]@X_makina I have seen videos on youtube where they were using a timing light on a saw, pretty sure it was just last week.
I'll check my history and see if I see it.[/QUOTE]

I found a YouTube video from 5y ago, but you can't really see the timing light on the fins. He did
report that the initial timing on an MS461 was 8-deg BTDC, and advances to 16-deg BTDC. I can
not see how continuous the advance is. He also reports that an MS360 coil has fixed timing, at
12-deg BTDC.

I did not find specific data on AS, using a search for "ignition timing". It seems to me that AS should
be the go-to place for such data.

Part of the reason I wanted to find more data is my above findings with 3 diff saws. I also ran
into a problem which, as others have also reported, I seem to have narrowed down to an ignition
that will idle fine, but not throttle up. Husky seems to have many ignition modules for many
saws that look identical, but have diff part numbers and are not interchangeable.

 

[chipper1]

@X_makina I have seen videos on youtube where they were using a timing light on a saw, pretty sure it was just last week.
I'll check my history and see if I see it.[/QUOTE]

I found a YouTube video from 5y ago, but you can't really see the timing light on the fins. He did
report that the initial timing on an MS461 was 8-deg BTDC, and advances to 16-deg BTDC. I can
not see how continuous the advance is. He also reports that an MS360 coil has fixed timing, at
12-deg BTDC.

I did not find specific data on AS, using a search for "ignition timing". It seems to me that AS should
be the go-to place for such data.

Part of the reason I wanted to find more data is my above findings with 3 diff saws. I also ran
into a problem which, as others have also reported, I seem to have narrowed down to an ignition
that will idle fine, but not throttle up. Husky seems to have many ignition modules for many
saws that look identical, but have diff part numbers and are not interchangeable.[/QUOTE]
Great you found that video, the one I saw was not on a 461 so there's at least one more . I didn't look at my history, I'll look now.

 

[X_makina]

I just took some data on my favorite small rear-handle saw, which I use quite often, a
Shindaiwa 377. The data were surprising. I have a video, too, but I need to edit before
posting on YouTube. The link will be coming.

I got an initial advance of 17-deg BTDC at about 3300RPM, and a final advance of 13-deg BTDC
at 9900RPM. Initial advance was at idle, and it gradually DECREASED to the final advance
number. Test condition was under no cutting load, but chain installed, fully warmed up. The
blackened fin was used as the crank position indicator. The engine barely 4-strokes at full
throttle, and the spark is very steady throughout the speed range.

 

[chipper1]

I went through a bunch of my history and couldn't find the video, pretty sure it was within the last two weeks, but there's a lot in my history .

 

[X_makina]

I just took some data on my favorite small rear-handle saw, which I use quite often, a
Shindaiwa 377. The data were surprising. I have a video, too, but I need to edit before
posting on YouTube. The link will be coming.

I got an initial advance of 17-deg BTDC at about 3300RPM, and a final advance of 13-deg BTDC
at 9900RPM. Initial advance was at idle, and it gradually DECREASED to the final advance
number. Test condition was under no cutting load, but chain installed, fully warmed up. The
blackened fin was used as the crank position indicator. The engine barely 4-strokes at full
throttle, and the spark is very steady throughout the speed range.
View attachment 629570

Here is a link to my video, "Shindaiwa 377 chainsaw ignition timing":


Also, I just took some data on a 12yo Husqvarna Rancher 455:
initial advance: 23-deg BTDC @ 3300RPM
final advance: 21-deg BTDC @ 10000RPM
The advance changes just slightly at full throttle. Essentially, this is a fixed-advance ignition.
I bought this saw new, and the only modification is spark-arrestor delete.

 

[captain dangers]

I have never thought about if the ignition coil (module) also having the ability to advance the spark?
--I have assumed that if there is no spark then the coil is bad? ----I think I have a echo coil that is
bad because the motor will not accelerate. Starts fine but will not rev over 4000 rpm. I have done everything
except replacing the coil. --- Does the coil on never model saws ect. have electronics to control spark advance?

I know fro experience that the early echo were very sensitive to coil gap, they don't like business card gap, they like a really narrow gap like paper folded twice or thrice as far as my memory goes. it may be the problem or at least one problem to tick off the list ? CD

 

[spyder62]

I remember back in the day I'd get the timing on my old Pontiacs set were I wanted for performance and they would burn up starters trying to hot start. My fix was a switch in the glove box to shut of the power to the coil, all I did was get it rolling over and flip the switch, worked like a charm.

@X_makina I have seen videos on youtube where they were using a timing light on a saw, pretty sure it was just last week.
I'll check my history and see if I see it.

What did you have goats?

 

[ncfarmboy]

Mitch Weber & Tree monkey have videos of using timing light on a saw on YouTube IIRC.

Shep

 

[X_makina]

If anyone has a link to a video showing measuring ignition timing on a chainsaw with
a timing light, please post. On YouTube, I found only the one I mentioned above, using searches
that included ignition timing with chainsaw, timing light, etc. I have not yet checked Vimeo.

Anyway, I tested another brand today: Tanaka. I got 17-deg BTDC initial advance (2800RPM), and
a smooth increase to 25-deg BTDC at 7000RPM. This is a TCS3401, and needs a load to run at
max RPM. This saw gave me an advance curve that I expected. It also has a 2-pole coil, vs. all
the others I have mentioned above, with 3-pole coils.

 

[ncfarmboy]

Mitch Weber Timing light on chainsaw
Shep

 

[X_makina]

Yeah, that's the 5yo video (mweba1) that I mentioned above, and where I got the Stihl data
for 2 saws. Too bad you can not see close up. He has many many good videos posted over many
years.

 

[X_makina]

Here are more data on an aftermarket ignition from Hong Kong. It has a brand stamp, and it is sold
for the Husqvarna 362 371 372 372XP. Sadly, many aftermarket ignitions are listed for sale, saying they
work on a whole slew of Huskies, from the 141 all the way up to the 390, and everything in between.
That is decidedly NOT correct, as I found out the hard way.

Anyway, this new ignition module yields 15-deg BTDC at idle (2800RPM), and a final advance of
about 28-deg BTDC on my 371K, a circular saw converted to chainsaw with big-bore kit. It was hard to get
data on this ignition since my timing light would kill the spark. I need to get an inductive light. The
saw did run fine with this module.

Above, I reported the advance curve of the Husky Rancher 455 (fixed at 23-deg BTDC). I wonder what
happens when you try the 372 module on the 455? My 371 would not throttle up reliably with
the coil for a 455.

 

[X_makina]

I just took some data on my favorite small rear-handle saw, which I use quite often, a
Shindaiwa 377. The data were surprising. I have a video, too, but I need to edit before
posting on YouTube. The link will be coming.

I got an initial advance of 17-deg BTDC at about 3300RPM, and a final advance of 13-deg BTDC
at 9900RPM. Initial advance was at idle, and it gradually DECREASED to the final advance
number. Test condition was under no cutting load, but chain installed, fully warmed up. The
blackened fin was used as the crank position indicator. The engine barely 4-strokes at full
throttle, and the spark is very steady throughout the speed range.
View attachment 629570

I notice that ACRESINTERNET reports the 377's timing as 28-deg BTDC fixed. I wonder who reported
that and where it came from. I suppose some repair manuals might list the advance #s.

I also checked a bunch of modern Stihls and Huskies on that site, and none are reported as having
variable advance. Many have "28-deg" fixed ignition advance listed on their data sheets.

 

[X_makina]

I just analyzed the advance curve for a Husqvarna 350, and I used a new inductive PU
automotive timing light, rated up to 9999 RPM.

Initial advance at idle (2400RPM) was 20-degrees BTDC, and final was about 23-degrees BTDC
at over 10K RPM. It was a small but smooth change in advance and this may be due to inaccuracies of
the timing light over 10K RPM.

The ignition module was the usual 3-pole Husky OEM unit, made buy "SEM AB", part # 537 16 21 01.

 

[LegDeLimber]

That's almost within the bounds of just being the, increasing, velocity of the magnet driving the circuit voltage to operation level a bit sooner.
Thus the slightly earlier trigger?

Just a little speculation my part, is all.

 

[dynodave]

Trying to follow the over all plot which is more then just the advance curve...if any. I'm trying to figure out how the spark is made/generated.
I had researched a few brands of saws which on twin pole flywheel the polarity sequence is N/S then on some brands it is S/N/ Now with a identical wrap direction of wire on either it will make a + then - single sine and a - then + on the other magnetic sequence. I researched and worked on and repair motorcycle ignitions. However they are battery driven coil and magnetic trigger only. The big key is in a magnet flywheel system, the flywheel/magnets must provide power as well as the trigger event.
Since most are 2 pole and as you state some are 3 pole....
So until I can see some wave shapes and circuitry diagrams I will still be in technical limbo. But I do know magnetic and therefore polarity sequence matters.

 

[X_makina]

Trying to follow the over all plot which is more then just the advance curve...if any. I'm trying to figure out how the spark is made/generated.
I had researched a few brands of saws which on twin pole flywheel the polarity sequence is N/S then on some brands it is S/N/ Now with a identical wrap direction of wire on either it will make a + then - single sine and a - then + on the other magnetic sequence. I researched and worked on and repair motorcycle ignitions. However they are battery driven coil and magnetic trigger only. The big key is in a magnet flywheel system, the flywheel/magnets must provide power as well as the trigger event.
Since most are 2 pole and as you state some are 3 pole....
So until I can see some wave shapes and circuitry diagrams I will still be in technical limbo. But I do know magnetic and therefore polarity sequence matters.

What interests me is how the spark is generated, but also, as the OP asked, do these small engines have an advance
curve? There is a lot of hearsay out there, but little first-hand data that I have found. I have heard numerous times
that some of these small 2-strokes had "retarded ignition timing", which I doubted. My data shows, mostly as predicted,
that all of my sample engines have advanced timing, some with a continuous curve.

Without access inside one of these modules, we can't reverse-engineer the circuit, or place an oscilloscope probe
on anything but the HT lead. I am still in the process of non-destructive de-potting of a Husky 3-pole module, but
it has been slow. So far, I can see two separate coils wound around one pole, and a pair of poles. I soak it
in lacquer thinner overnight, which allows me to scrape off about a half mm of epoxy at a time.

I tried for years to find aftermarket substitutes for OEM igniters for one-cyl ATVs with dead ignitions. Of course,
these required a battery and a fairly hi voltage pulse off the engine's stator.