661 Oil Test 32:1 vs 40:1 vs 50:1 ?

[bwalker]

Where are you two located? I've seen some ironwood up there (don't remember exactly where) that was in the 7-9in. category. I've never cut it, but I've heard that it's harder than your MIL's head!

Marquette county.

Here is a better one

Looks normal to me. Not that you can tell much by looking at a plug like this.

 

[bwalker]

Color looks pretty good to me. The wet goo probably doesn't hurt anything. How did the super M do? I may get some of it to try soon. It is local and cheap.

I was talking to a guy at a bike shop and he said HP 2 was good stuff. I've been meaning to try it out myself.

I find the smell of HP2 sickening.

 

[KenJax Tree]

I find the smell of HP2 sickening.

Uh oh[emoji53]

 

[bwalker]

Black cottonwood here is really hard on saws, especially old growth. Ask anyone that has salvage cut it after floods. Also I live at elevation here in the Cascades, and we are well above the 45th parallel. The seasons are not so long here. And if you want to talk about density, I will put western warm growing Eucalyptus, California live oak and Madrone up against your so-called dense cold growing hardwoods back east.

Madrone has the same BTU content as sugar maple. Our sugar maple is some of the highest density in the world. Hence the premier sports floors come from Upper MI. You can't compare out climate and growing conditions with yours

 

[CR500]

Marquette county.

Looks normal to me. Not that you can tell much by looking at a plug like this.

That is about what the plug looks like in the 441


Speaking of plug color I was doing some cutting with the 441 and I know M-tronic can leave different colors from time to time.... then I had a thought.

Could chain condition affect plug colour? In all respect when you have a dull chain the saw works harder making more heat thus lean conditions correct?

Also for giggles since plug colour is not the most accurate way of checking tune would piston wash be the way or am I worrying to much lol

Sent from my non internal combustion device.

 

[treedoc40]

Engine Basics: Detonation and Pre-Ignition

Written by Allen W. Cline

Reprinted from Issue 54 of CONTACT! Magazine, published in January, 2000

All high output engines are prone to destructive tendencies as a result of over boost, misfueling, mis-tuning and inadequate cooling. The engine community pushes ever nearer to the limits of power output. As they often learn cylinder chamber combustion processes can quickly gravitate to engine failure. This article defines two types of engine failures, detonation and pre-ignition, that are as insidious in nature to users as they are hard to recognize and detect. This discussion is intended only as a primer about these combustion processes since whole books have been devoted to the subject.

First, let us review normal combustion. It is the burning of a fuel and air mixture charge in the combustion chamber. It should burn in a steady, even fashion across the chamber, originating at the spark plug and progressing across the chamber in a three dimensional fashion. Similar to a pebble in a glass smooth pond with the ripples spreading out, the flame front should progress in an orderly fashion. The burn moves all the way across the chamber and , quenches (cools) against the walls and the piston crown. The burn should be complete with no remaining fuel-air mixture. Note that the mixture does not "explode" but burns in an orderly fashion.

There is another factor that engineers look for to quantify combustion. It is called "location of peak pressure (LPP)." It is measured by an in-cylinder pressure transducer. Ideally, the LPP should occur at 14 degrees after top dead center. Depending on the chamber design and the burn rate, if one would initiate the spark at its optimum timing (20 degrees BTDC, for example) the burn would progress through the chamber and reach LPP, or peak pressure at 14 degrees after top dead center. LPP is a mechanical factor just as an engine is a mechanical device. The piston can only go up and down so fast. If you peak the pressure too soon or too late in the cycle, you won't have optimum work. Therefore, LPP is always 14 degrees ATDC for any engine.

I introduce LPP now to illustrate the idea that there is a characteristic pressure buildup (compression and combustion) and decay (piston downward movement and exhaust valve opening) during the combustion process that can be considered "normal" if it is smooth, controlled and its peak occurs at 14 degrees ATDC.

Our enlarged definition of normal combustion now says that the charge/bum is initiated with the spark plug, a nice even burn moves across the chamber, combustion is completed and peak pressure occurs at at 14 ATDC.

Confusion and a lot of questions exist as to detonation and pre-ignition. Sometimes you hear mistaken terms like "pre-detonation". Detonation is one phenomenon that is abnormal combustion. Pre-ignition is another phenomenon that is abnormal combustion. The two, as we will talk about, are somewhat related but are two distinctly different phenomenon and can induce distinctly different failure modes.

KEY DEFINITIONS Detonation: Detonation is the spontaneous combustion of the end-gas (remaining fuel/air mixture) in the chamber. It always occurs after normal combustion is initiated by the spark plug. The initial combustion at the spark plug is followed by a normal combustion burn. For some reason, likely heat and pressure, the end gas in the chamber spontaneously combusts. The key point here is that detonation occurs after you have initiated the normal combustion with the spark plug.

Pre-ignition: Pre-ignition is defined as the ignition of the mixture prior to the spark plug firing. Anytime something causes the mixture in the chamber to ignite prior to the spark plug event it is classified as pre-ignition. The two are completely different and abnormal phenomenon.

DETONATION Unburned end gas, under increasing pressure and heat (from the normal progressive burning process and hot combustion chamber metals) spontaneously combusts, ignited solely by the intense heat and pressure. The remaining fuel in the end gas simply lacks sufficient octane rating to withstand this combination of heat and pressure.

Detonation causes a very high, very sharp pressure spike in the combustion chamber but it is of a very short duration. If you look at a pressure trace of the combustion chamber process, you would see the normal burn as a normal pressure rise, then all of a sudden you would see a very sharp spike when the detonation occurred. That spike always occurs after the spark plug fires. The sharp spike in pressure creates a force in the combustion chamber. It causes the structure of the engine to ring, or resonate, much as if it were hit by a hammer. Resonance, which is characteristic of combustion detonation, occurs at about 6400 Hertz. So the pinging you hear is actually the structure of the engine reacting to the pressure spikes. This noise of detonation is commonly called spark knock. This noise changes only slightly between iron and aluminum. This noise or vibration is what a knock sensor picks up. The knock sensors are tuned to 6400 hertz and they will pick up that spark knock. Incidentally, the knocking or pinging sound is not the result of "two flame fronts meeting" as is often stated. Although this clash does generate a spike the noise you sense comes from the vibration of the engine structure reacting to the pressure spike.

One thing to understand is that detonation is not necessarily destructive. Many engines run under light levels of detonation, even moderate levels. Some engines can sustain very long periods of heavy detonation without incurring any damage. If you've driven a car that has a lot of spark advance on the freeway, you'll hear it pinging. It can run that way for thousands and thousands of miles. Detonation is not necessarily destructive. It's not an optimum situation but it is not a guaranteed instant failure. The higher the specific output (HP/in3) of the engine, the greater the sensitivity to detonation. An engine that is making 0.5 HP/in3 or less can sustain moderate levels of detonation without any damage; but an engine that is making 1.5 HP/in3, if it detonates, it will probably be damaged fairly quickly, here I mean within minutes.

Detonation causes three types of failure:

1. Mechanical damage (broken ring lands)

2. Abrasion (pitting of the piston crown)

3. Overheating (scuffed piston skirts due to excess heat input or high coolant
temperatures)

Fantastic article to share...

 

[redbull660]

That is about what the plug looks like in the 441


Speaking of plug color I was doing some cutting with the 441 and I know M-tronic can leave different colors from time to time.... then I had a thought.

Could chain condition affect plug colour? In all respect when you have a dull chain the saw works harder making more heat thus lean conditions correct?

Also for giggles since plug colour is not the most accurate way of checking tune would piston wash be the way or am I worrying to much lol

Sent from my non internal combustion device.

Everything plays into the temp of the saw....

Tune
ported or not ported
oil ratio - more oil or too little oil can make the saw run hotter.
kind of bar
length of bar
time in the cut
type of chain and condition
octane of gas
air filter plugged up or clear
chain tension
wood - type and condition it's in
list could go on and on

As far as oil goes...my bottom line is finding the best out there. Then finding how much (the more the better) oil I can run in my saw with out hindering performance. And the amount of oil does affect the temp and the time. BUT it's saw specific. Cuz all the conditions vary.

Biggest differences I've found are - length of cut, bar, and oil/gas mix.

Is there a ratio that is safe for all? I doubt many saws have been lost at 40:1.

 

[Bwildered]

Discounting the past with ignorance of the present and how we got there is the height of stupidity.

We can all look up to you in that respect then. LOL
Thansk

 

[bwalker]

Fantastic article to share...

Yes, especially so since many on this board and else where do not understand what pre ignition and detonation really are, and as such often confuse the two.

 

[bwalker]

Everything plays into the temp of the saw....

Tune
ported or not ported
oil ratio - more oil or too little oil can make the saw run hotter.
kind of bar
length of bar
time in the cut
type of chain and condition
octane of gas
air filter plugged up or clear
chain tension
wood - type and condition it's in
list could go on and on

As far as oil goes...my bottom line is finding the best out there. Then finding how much (the more the better) oil I can run in my saw with out hindering performance. And the amount of oil does affect the temp and the time. BUT it's saw specific. Cuz all the conditions vary.

Biggest differences I've found are - length of cut, bar, and oil/gas mix.

Is there a ratio that is safe for all? I doubt many saws have been lost at 40:1.

Once you have seen a two stroke ran when equipped with an EGT gauge you realise how little things really effect the load on the motor.

 

[KenJax Tree]

I mixed up some Honda HP2 42ish:1 today and in the bottle it smells awful but has minimal smell when burning. Mufflers are still pretty dry and nothing has blown up so it appears to work.[emoji1]

 

[KenJax Tree]

Anyone got a spec sheet on this HP2 or know what its compared to? I looked but can't find anything.

 

[mdavlee]

I wonder how hot is too hot for the cylinder and piston? I know on diesel trucks with aluminum Pistons 1500 and 2000 degrees is ok for short bursts.

 

[huskihl]

I wonder how hot is too hot for the cylinder and piston? I know on diesel trucks with aluminum Pistons 1500 and 2000 degrees is ok for short bursts.

@bwalker had some snowmobile egt's posted awhile back. 15-1600 I'm thinking is the high limit

 

[brockhaskins]

Color looks pretty good to me. The wet goo probably doesn't hurt anything. How did the super M do? I may get some of it to try soon. It is local and cheap.

I was talking to a guy at a bike shop and he said HP 2 was good stuff. I've been meaning to try it out myself.

We've run about 3.5 gallons of Super m in the last week. Haven't pulled any saws apart as I don't do that unless necessary. I like the way it runs. Everyone one the crew noticed throttle response seemed a little better and power may seems up a little. Was using lucas before.

 

[RedFir Down]

Fellas all I have to say is this is weird.... Im mean alot here are trying different oils at different ratio's and not a single saw has grenaded!!!! Whats going on here?

 

[bwalker]

@bwalker had some snowmobile egt's posted awhile back. 15-1600 I'm thinking is the high limit

I set mine to alarm at 1225 IIRC. But the number is meaningless unless one know the distance from the piston that the probe is placed at.

 

[Whitespider]

Fellas all I have to say is this is weird.... Im mean alot here are trying different oils at different ratio's and not a single saw has grenaded!!!! Whats going on here?

And here I thought no one else had noticed‼
*

 

[CR500]

Pulled the cylinder on the 7900 tonight after about 5 gallons of fuel mixed with K2 and I had carbon....
Not a huge thing to me lol

None the less the crank was coated in a real nice coat of oil. If it looks like that to me I can see the saw living a healthy life.


I really don't tear down a saw for this, I was more interested in how the saw came apart and to see how tight the crankcase is on these saws (holy cow there is no room in that case lol how does the7900 run so good ????)

I'm very pleased with how K2 and 32:1 are doing so far. Yamalube is next to try. Looking forward to purple fuel haha

I know 5 gallons is minor but none the less I had a some stress reliving fun lol
Sent from my non internal combustion device.

 

[huskihl]

Pulled the cylinder on the 7900 tonight after about 5 gallons of fuel mixed with K2 and I had carbon....
Not a huge thing to me lol

None the less the crank was coated in a real nice coat of oil. If it looks like that to me I can see the saw living a healthy life.


I really don't tear down a saw for this, I was more interested in how the saw came apart and to see how tight the crankcase is on these saws (holy cow there is no room in that case lol how does the7900 run so good ????)

I'm very pleased with how K2 and 32:1 are doing so far. Yamalube is next to try. Looking forward to purple fuel haha

I know 5 gallons is minor but none the less I had a some stress reliving fun lol
Sent from my non internal combustion device.

Yea they're not bad to work on. At first, I thought it resembled a cross between husky and stihl by the way they're put together.