Part Five: Ignition Timing

[Deets066]

I really liked the swap to the 272 on the solo. I just couldn't get the timing where it felt right with the stock coil. It sounded the best with the stock setting, it didn't like any advance at all on the stock coil

 

[Al Smith]

Depends on the saw .I've advanced 10 series Macs with points ignition and had good results .Case in point a 70 cc 6-10 that free throttles at over 15,000 RPM . They tell me it helps on lower compression saws and maybe not on higher compression engines .Stock McCullochs are at 26 degree advance ,Stihls at 27 .Old Lombards such as the AP 42/Comango are at 30 advance . I have a 5 degree off set key in one of my Mac 125's that came from California .They say in the day this was a popular thing to do .Go kart stuff ya know . So depending on how the points are set it could be 31 advanced .All I can say about that is it has plenty of power but then again it is a 125 Mac, it's supposed to .

 

[Hedgerow]

How are you checking the timing? Just looking where the magnet lines up with the last leg of the coil or are you actually putting a timing light on it?

I'll buy a timing light right after I buy a pop off pressure tester.
Lol..
I looked at it and mathed the hell out of it.

 

[Simondo]

Should be sparking BTDC even from the factory. Just not "optimal".
I think they do it to give the saw better manners for starting purposes.

Im a bit of a fan of the "Datum" in most things ...much more confident and comfortable when I have the designed standard start point so i can repeat or return things to that "Datum" if i want. With many engines you get specs to give you what the factory set is ...i suspect the spec information is out there ..somewhere .

 

[Hedgerow]

What didn't you like about the 272 coil?

Never had that rip your head off power. Mike dinked with it.. I dinked with it..
I finally put the "good" limited coil on, advanced it 1 key width, and BAM!!
The mutt was back in action.

 

[Mastermind]

Should we do a part on blowdown and primary compression.......or do y'all feel like we covered that well enough in the transfer section?

 

[Stump Shot]

Should we do a part on blowdown and primary compression.......or do y'all feel like we covered that well enough in the transfer section?

Nothing ventured, nothing gained.

 

[Mastermind]

rip your head off power

Pics of the dead kittens after the heads being ripped off?

 

[Stump Shot]

From what I can tell, you take an advance type coil, it has a starting/idle degree to fire and run, and an advanced degree to fire when the engine is revved up, it also may be limited. The older counterpart unlimited coil is usually split in the middle. (Remembering) Stihl I think was firing at like 8 degrees BTDC to start idle and advance to 16 degrees BTDC revved up, its older counterpart comes in at around 12 degrees BTDC. So if you put an older unlimited coil in to gain more RPM you just went backwards 4 degrees of total advance. This is why everything is so muddled up and confusing to folks that just want to take .020" off the key and call it a day(like me)
What's really truly needed here is a way to electronically alter these coils or trick them somehow into going past their preset limits. As the advance feature is a good one and would be nice to somehow keep. Any Electronical Geniuses in the house?

 

[mdavlee]

Same guy that told me every saw should get an "aftermarket heavy duty crankshaft".

You forgot big bore

 

[Mastermind]

Any Electronical Geniuses in the house?

Is "Electronical" even a real word?

 

[ny15]

Is "Electronical" even a real word?

It is now

 

[Motorhead]

Can't use it in scrabble

 

[Chainsaw Jim]

Has anyone ever been able to make adjustments to the timing while the saw is running? Could it be possible to invent a coil with an adjustable dial on it?
Or hook up a computerized ignition program to the spark plug while the saw is hooked up to a dyno to determine maximum performance?
Maybe this technology already exists?

 

[RIDE-RED 350r]

In and of itself a timing advance does not as much good unless a expected rise in RPM is expected. So I believe it's part of the whole package and helps everything work together kind of a thing. As the faster an engine goes the more advance is required.

As a side note, I am working on a fast, simple, easy and accurate way to measure actual timing in a modern power saw(modulated coil). If proven correct and true, I will share it with all you guys.

Excellent post and very true I think!

Look at old outboard motors. I have a 1960 Johnson 18hp on my rowboat. When you twist the throttle, with the cowl off, you can see that the actual throttle in the carb is wide open quite early in the hand throttle range. I want to say at about 1/3 of the hand throttle range, @XP_Slinger correct me if I'm wrong here... The rest is solely ignition advance.

 

[Stump Shot]

Is "Electronical" even a real word?

If W could make up all the words he did can't I do just one?

It is now

Exactly.

Can't use it in scrabble

You will if you're playing with me. Lol



But you all knew what I was talking about though anyway, didn't ya? Look for more, better made up words in the future...

 

[Stump Shot]

Excellent post and very true I think!

Look at old outboard motors. I have a 1960 Johnson 18hp on my rowboat. When you twist the throttle, with the cowl off, you can see that the actual throttle in the carb is wide open quite early in the hand throttle range. I want to say at about 1/3 of the hand throttle range, @XP_Slinger correct me if I'm wrong here... The rest is solely ignition advance.

Yes, outboard engines work that way. Look at the really old cars with the hand throttle on one side the advance on the other. Or the old motorcycles one twist grip for throttle the other for advance. So it's been known from the early days of engines.

 

[RIDE-RED 350r]

Amazing the influence the ignition timing has

 

[Stump Shot]

Has anyone ever been able to make adjustments to the timing while the saw is running? Could it be possible to invent a coil with an adjustable dial on it?
Or hook up a computerized ignition program to the spark plug while the saw is hooked up to a dyno to determine maximum performance?
Maybe this technology already exists?

I think you just described the future, that is if Randy quits squabbling about wordage and go out and find us an electronical genius. Like everything the trick would be making such a thing A) small enough to fit in a power saw and B) tough enough to withstand the vibration.
Surely if the Military can build a shell that can be fired out of a 155mm cannon that has electronic guidance inside, and take that kind of shock. So it would seem something could be worked out. Can we get a budget for this? There really isn't much to the module inside of a coil, or look at the NOVA II modules, pretty small. Surely this could be worked out, after all a rev limiting and single stage advance coils already exists, proving that the signal can be modified.

 

[moparnut88]

On the coils with a timing advance curve built in what is the amount of timing it can advance automatically?


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