Timing Advance

[Frogfarmer]

Question for the builders. In my experience advancing the timing is a benefit. Why doesn't the OEM send them out this way? I have modded 026 Stihls but nothing else besides mufflers. Is any particular model of Stihl saw more responsive to timing advance. Will an 028 gain RPM to run more like an 026? Same question for an 038 vs 044. Thanks in advance.

 

[hotshot]

"Tough on your knuckles" starting & to prevent broken ropes & recoils is why.

A better question is why they never built in a centrifugal timing advance like the
LawnBoys or small outboard engines. Cost & weight penalties?

 

[Chris-PA]

There are a lot of variables. Some saws have ignition timing that is fixed in terms of degrees, and some have a curve where the timing varies with rpm. You advance the timing because you want to get the burning going so that the cylinder pressure peaks at the right time. If the timing is fixed then moving the working rpm up will require more advance, as the propagation time is largely constant - at higher rpm you have to start sooner to get done at the right time.

Combustion chamber shape plays a role too - if the flame propagates quickly you may not need as much advance. Fuel mixture problems can slow the pressure rise too. In a way you can look at the need to spark advance as an indication that the combustion chamber design and/or fuel mixture is poor.

Not all saws benefit from spark advance. I've been doing less lately as some of my saws had that strange light popping sound under load, which I've come to think is a symptom off too much advance.

 

[blsnelling]

Many saws have a timing advance curve built into them. This is to aid starting. Typically, the timing is only retarded at very low RPMs. As soon as throttle is applied, timing jumps to its max. If the factory wanted them with more timing they would have. They would simply set the advanced point to a higher value.

 

[blsnelling]

I do advance the ignition timing on many saws. However, not all saws like it. You simply have to try it.

 

[2tone]

Brad,

Have you advanced the timing on an 026 pro?
If so did it like it?

 

[MustangMike]

In my experience advancing the timing is a benefit. Why doesn't the OEM send them out this way?

In answer to your question, when you open the muffler, uses a less restrictive air filter, etc, the saw will benefit from a little more timing advance. A factory chocked up muffler will not! All the mods to your saw must stay in sync.

044/440, 046/460, and 066/660 all seem to benefit from timing advance in conjunction with muff mods and low restriction air filters.

 

[Frogfarmer]

Brad,

Have you advanced the timing on an 026 pro?
If so did it like it?

Sorry not Brad but I have advanced the timing on several 026 and 026 PRO models. I opened the muffler up to go along with the advance. All responded well but some more than others. I have one that is getting tired and it gave the most noticable increase on that saw. All saws have the fully adjustable carb.

 

[Termite]

In my limited experience, timing advance is an individual saw thing not a model specific thing. The timing from the manufactures varies from saw to saw and can be optimized for each individual saw. So, you may see gains in performance or you may not.

 

[Ozhoo]

Here's 3 timing curves for SEM ignitions. You can see by looking at them that advancing them all by a couple degrees will have a much different result.

 

[2tone]

Thanks for the individual saw and not model specific comments.

 

[mountainlake]

You don't want to advance the timing on a 044, it already kicks back unless you pull it real good.. Echo saws have a 30 degree built in advance for years, makes for easy starting and good power. Steve

 

[MustangMike]

I've had 2 044s and a 440 and I took .020 off each key to provide addl advance. They all started fine and run strong.

Here is my unported 044 with base gasket delete and timing advance, it will almost keep up with ported 460s:

 

[blsnelling]

In answer to your question, when you open the muffler, uses a less restrictive air filter, etc, the saw will benefit from a little more timing advance. A factory chocked up muffler will not! All the mods to your saw must stay in sync.

I'm not following you, Mike. Can you explain? Thanks.

 

[MustangMike]

Just like with a car, if you mod your saw to flow more air/fuel in and out, it will usually benefit from a timing advance and turn more RPMs.

 

[blsnelling]

Just like with a car, if you mod your saw to flow more air/fuel in and out, it will usually benefit from a timing advance and turn more RPMs.

I'm thinking the saw would anyway.

 

[MustangMike]

It may, but it will even more with the mods.

 

[Little Al]

I have a guy who brings his saw for service & his chains sharpened ,he is an electronics geek in his daytime job, he built a test rig to plot the advance curve on saw coils the local Stihl dealer lent him half dozen of the same model new coils. No 2 showed the same advance curve. 1 produced the correct advance curve related to that model of coil ,2 produced .5 of a degree more advance over the curve 1,1degree of advance, & 2 produced .75 & 1 degree less advance than should have so this would point to different performance with advance of timing & it suggests a suck it & see in regard to the advance amount Please don't ask me any questions regarding this as it is around 15ft above my head I' m more a hammer & chisel man but none the less it was an interesting exercise

 

[Ted Jenkins]

I work at 6,00 feet which makes a big difference compared to some one who lives near sea level. Rule of thumb will tell you that the more condense the air is the less timing you need. More advanced timing will increase torque at a lower RPM at the sacrifice of over all power. For some one living at 3500 feet will likely achieve some increase in performance if they increase timing one or two degrees. At higher altitudes with less air pressure the fuel burns a little slower so a more advance timing will try to recover some of the lost performance. Thanks

 

[JonCraig]

I have a guy who brings his saw for service & his chains sharpened ,he is an electronics geek in his daytime job, he built a test rig to plot the advance curve on saw coils the local Stihl dealer lent him half dozen of the same model new coils. No 2 showed the same advance curve. 1 produced the correct advance curve related to that model of coil ,2 produced .5 of a degree more advance over the curve 1,1degree of advance, & 2 produced .75 & 1 degree less advance than should have so this would point to different performance with advance of timing & it suggests a suck it & see in regard to the advance amount Please don't ask me any questions regarding this as it is around 15ft above my head I' m more a hammer & chisel man but none the less it was an interesting exercise

I'm an electronics geek, so this makes sense to me. And the variance within the same model makes sense. There are tolerances in solid state electronics manufacturing for the different components that go into the coil. The tolerances stack. They stack one way & you end up with a degree or two more than you intended. They stack the other way & you get a degree or two less. Up to the Quality Control to define & verify that the coils are within a certain spec.

Makes me wonder what would happen if you started comparing OEM to aftermarket coils on your buddy's rig?