Timing Advance s- When \ When Not To Do - Questions

[mdavlee]

They make a different sound when it's too much advance. You know it quick.

 

[Mastermind]

Great thread Greenthorn.

 

[jmssaws]

I've never had a stihl pop in the cut like a husky, I will say a 394 or 395 likes it alot and a 390 likes it a little and a 372 likes it none.

 

[Hedgerow]

I've never had a stihl pop in the cut like a husky, I will say a 394 or 395 likes it alot and a 390 likes it a little and a 372 likes it none.

I got one that will when the conditions are right.

 

[tickbitintn]

great thread, sounds like baby steps on amount of advance is the best route....
Thanks all for some good info.

 

[jmssaws]

I messed with my 066 today,probably changed the amount of advance 5 or 6 times and from 030 to 050 I can't tell a bit of difference. From 020 to 030 there's a noticeable gain, also I've noticed that a aluminum flywheel 066 likes more than a poly saw.

 

[SixGun]

I usually start with 1/3 of the key, this works on many saws. 026, 192, older 201, 044 and others.
Saw will run a little hotter but a dual port muff will balance it out.

 

[Cobby08]

I think it's useful on non MT/AT saws but from my knowledge on the MT system at least makes me wonder on the advance. I know Mike says he thought it made a difference on his 362 but the advance on the 661 didn't seem to different other then non advanced other then it starts like a miserable hag. I know that on an MT saw you still have a mechanical limit for your idle but you "fine" adjustment is all based on timing. Makes me wonder if the same is done at the high side. I'm trying to understand more daily so I'm not saying to write any of this in stone.

 

[half_full]

Maybe I'm over simplifying this. But, could I use a piston stop and degree wheel to measure advance? Mark flywheel and case for original and move it to 5 or 6 degrees?

 

[Magic_Man]

Maybe I'm over simplifying this. But, could I use a piston stop and degree wheel to measure advance? Mark flywheel and case for original and move it to 5 or 6 degrees?

Yes you can, most accurate way to do it actually.

 

[Brewz]

Digging up an older thread to ask a few questions as opposed to a new one.....

I am interested to know what effect timing advance can have when you change bar lengths to extremes.

Eg.

Stihl 066
Timing advance 5 or 6* and tuned out to about 13500 rpm for best result running a 20 to 25" bar for cutting firewood.
I bolt on a 42 or 50" bar and want to mill with the saw........ will the advanced timing cause issues with the extra load?

If I change the bar length, I always re-touch the tune but when going to a really long bar, will there be a different optimal ignition timing point?

 

[MustangMike]

IMO, the timing should be in sync with the mods to the saw, not the bar length.

The tune should always be checked when any conditions change.

 

[czar800]

This is some great popcorn!

 

[Brewz]

So timing wont make any difference to what length bar I run given that I tune appropriately?

 

[drf256]

So timing wont make any difference to what length bar I run given that I tune appropriately?

IDK,

I could see a longer bar causing more heat buildup and wanting less timing.

You can increase or decrease the coil to flywheel gap for a minor change.

 

[MustangMike]

I've run a 36" bar on my ported 460 w/o changing anything, and it pulled it just great.

Always pay attention to what the saw is doing, but I would not change it. Just don't "over" lean on it.

 

[David Young]

So timing wont make any difference to what length bar I run given that I tune appropriately?

Think of ignition timing like hitting a baseball, it is about anticipation when it will reach you to deliver the most power timing must be spot on. There is only one right timing for peak performance. It depends on how fast the pitch is and how fast the bat comes off your shoulder.

you have to anticipate when the pitch will be in your sweet spot. you may start swinging when the ball is 30 feet out (26 btdc). If you wait until the pitch is over the plate (tdc) you have completely missed. If your timing is a little later than optimum you are not capturing all the power you could. If you swing too early or fire the ignition to early the peak of the explosion is before tdc and is actually fighting the piston coming up and robbing the motor of power. you can kind of mask this by a rich fuel mix because the rich mixture will delay peak cylinder pressure.

Back to saws. if a saw was designed to run at 9000 rpm and we mod it to turn 11000 rpm. it is moving faster like an 87mph fastball to a 95mph fast ball.
so there is a good chance that we need to swing a little sooner or..... advance the timing.

but there are other variable like the speed of our swing or trigger response time of our ignition circuit.


just a guess some coils may saturate at a certain point (rpm) or produce weaker fire or misfire.

 

[srcarr52]

A timing light with advance can help alot, more like a boatload.
Just dial in the advance as you are running untill you match up the TDC mark, then read the light for total advance

Dial back timing lights are for 4 strokes, so take the number on the dial x2 to get your real timing before TDC.

 

[Moparmyway]

Dial back timing lights are for 4 strokes, so take the number on the dial x2 to get your real timing before TDC.

Ive got an electronic one that gives RPM and a choice of 2 or 4 cycle .................. but this is the first Ive heard of timing advance being affected by cycles.
In my mind, the timing light does not know the difference between a 2 stroke or 4 stroke, it only lights when the plug fires.

 

[srcarr52]

Ive got an electronic one that gives RPM and a choice of 2 or 4 cycle .................. but this is the first Ive heard of timing advance being affected by cycles.
In my mind, the timing light does not know the difference between a 2 stroke or 4 stroke, it only lights when the plug fires.

It doesn't know the difference. It knows the time between the last two pulses and then flashes light X/720 seconds before a predicted pulse. It's 720 because the spark plug only fires once every two revolutions on a four stroke. For a two stroke it would have to be X/360 seconds before or you can just multiple the dial number X by 2.