Advancing the Timing

[RES]

It seems that many saws run much better when the timing is advanced. If this is the case why doesn't the manufacturer make this obvious improvement on their new saws. I have heard that an engine with retarted timing burns cleaner, but I have always wondered why. It seems to me that if you get the spark to the mixture as early as possible there would be more burn time and more efficiency.

 

[w8ye]

You need to try this for yourself with timed cuts to determine top end power.

 

[mountainlake]

Couldn't advance it any more on my 044 as it already kicks back with a wimpy pull. Echo saws have electronic advance, 15* for starting- idling 30* wide open. Steve

 

[rupedoggy]

1. Most have trouble starting the saw with the timing where it is. Advance it and it will kick back if you "sissy" pull it. More hurt customers= more law suits.
2. Advanced timing will make a saw run hotter. Heat is an enemy of two strokes. They are on the ragged edge of reliability and longevity now. More heat would make more warranty issues.
3. Most saws have more power than neccessary for the causual user. There are more homeowners buying saws than pros. If you gave a homeowner more power he would be that much more likely to not stop and sharpen the chain or do other maintainence as it became neccessary. It is bad enough now.
4. More advance requires better fuel octane. Customers buy the cheapest fuel they can. "It's only a chainsaw!"
Anything else you were wondering about?

 

[w8ye]

From my experience 28 to 30 degrees is the best place for the timing at cutting speed.

I've played with the timing between about 25 and 32 degrees and there was barely enough difference to be able to measure?

Response will vary from saw to saw?

 

[RTK]

From my experience 28 to 30 degrees is the best place for the timing at cutting speed.

I've played with the timing between about 25 and 32 degrees and there was barely enough difference to be able to measure?

Response will vary from saw to saw?

I have had a similar experience with other two stroke engines but they run at a little lower rpm, 26,28,30 all seem the same until you start to push things then the 26 seems to detonate less and run a tad cooler, probably d/t pre-ignition from heat

 

[w8ye]

I was playing with a Mac plastic body saw some 13-14 years ago.

 

[RES]

My thoughts about advancing the timing mainly relate to my new MS201t. When Bsnelling advanced the timing by filing half the key away on a MS201t it made great improvements to the saw.

 

[chopperfreak2k1]

anybody have a link to Brad's thread? i'm not lazy, just couldn't find it. TIA

 

[Fifelaker]

I did not read the entire thread but iirc it in here http://www.arboristsite.com/chainsaw/180851.htm?highlight=ms201t

 

[blsnelling]

A lot of saws respond VERY well to advanced ignition timing. Some not so much.

 

[chopperfreak2k1]

thanks Fife!

brad if you can recall did you advance the 261 and how did it act for you afterwards?

 

[milkie62]

Husky advanced timing ?

Has anybody run advanced timing on a 372 or 394 Husky with any noticable improvements ?

 

[drkptt]

It seems that many saws run much better when the timing is advanced. If this is the case why doesn't the manufacturer make this obvious improvement on their new saws. I have heard that an engine with retarted timing burns cleaner, but I have always wondered why. It seems to me that if you get the spark to the mixture as early as possible there would be more burn time and more efficiency.

I'm not sure if any manufacturer actually retards timing to meet emission regs, but a late ignition typically does clean up the hydrocarbon in the exhaust. With a late spark the mixture is still burning when the exhaust port opens, EGT is hotter, and this sustains combustion in the muffler. So unburned fuel burns in the muffler, not in the cylinder. Same process was used in early Mazda RX-7s (rotary engine), they had a stainless-steel can called a 'thermal reactor' that was basically operated as a catalytic converter without any catalyst. Interestingly enough each rotor had two spark plugs and at higher speeds the ignition was killed on one plug to purposely put more unburned HC in the exhaust to keep the fire burning in the thermal reactor.

2. Advanced timing will make a saw run hotter. Heat is an enemy of two strokes. They are on the ragged edge of reliability and longevity now. More heat would make more warranty issues.

Depends on where you measure the temperature. As spark advances the cylinder head temperature increases but the EGT decreases. The cylinder wall is typically the hottest at the lower center of the exhaust port; overheating there is going to break down the oil film and streak the piston. So a retarded spark is usually more damaging to a 2-stroke, until the spark is advanced to the point that detonation starts to occur.

 

[blsnelling]

brad if you can recall did you advance the 261 and how did it act for you afterwards?

Yes I did. It's been a critical piece of almost every new Stihl I've worked on, read strato.

Has anybody run advanced timing on a 372 or 394 Husky with any noticable improvements ?

I tried it on my 372 and put it back to stock.

 

[tlandrum]

if a 372 is slow to spool up advancing the timing can help but i dont do it on my builds.

 

[WoodChuck'r]

Timing is more critical than most realize.


Lots of "stock saws" at races in the stock classes that have had their timing tweaked. You'd swear to god that the saws have transfer work done but they're most certainly stock. A timing adjustment can make some saws scream without doing anything else....

 

[walexa07]

Yes I did. It's been a critical piece of almost every new Stihl I've worked on, read strato.

If you don't mind, how much advancing did you use on the 261 - or rather, how much would you recommend on a stock 261 with MM?

Waylan

 

[milkie62]

How to

How is the timing actually advanced with an electronic ignition saw ?

 

[NPKenny]

If you don't mind, how much advancing did you use on the 261 - or rather, how much would you recommend on a stock 261 with MM?

Waylan

How is the timing actually advanced with an electronic ignition saw ?

I have been looking for this answer myself found it in the thread:


Members in Depth Review of a new MS261

His only minor complaint was about the throttle response of the 261. Here's what I told him.

I can help the throttle response on your 261. You need to lean the L out, nearly as much as you can and it still idle correctly. This will significantly help it. The rest of the fix is in advancing the ignition timing. This is done by removing the flywheel, and using a tiny square file and filing off 1/2 of the key, allowing the flywheel to spin CCW 1/2 of the key width. This will give you about 10° of additional timing advance. It will also give you about an additional 800-1000 RPMs. Tuning may be required. Thread a long drywall screw into the aluminum cap, and it will pull right out. Simply grind the ridge off of it and it will no longer be limited.