Oil Mix Ratios and Cylinder Head Temperatures

[North by Northwest]

I use a 45:1 mix with Motul T2 its full synthetic racing oil for air cooled engines. it has great film retention, lower flash point, viscosity. works well with high and lower temp applications (Idling). Saws used to cut lumber can face high temps close to 500 degree. When I first used this oil mix I noticed my MS880 was cooler at the end of 26" wide 10ft cuts. And always use premium non ethanol gas. And I don't use them if they're more than 10-12 months old. Don't be cheap on fuels and don't cut with dull chain Oh, and I would avoid mixes like 25:1 as it can cause your saw to run hotter. I see now the FT clone saws are now recommending 50:1 with their Nikasil cylinders and come with 6mo residential and 3mo commercial use warrantees. ???

44:1 is what commercial cutters use up North here . I use it in all my Pro grade saws due to higher compression & rpm range . My homeowner saws see 50:1 although both saw applications get Saber . I tested Motul T its a quality oil , I have a test of Dominator next month .

 

[OM617YOTA]

You really think 44:1 vs. 50:1 makes a difference? You actually keep separate gas cans with a drop of oil difference between them?

 

[North by Northwest]

You really think 44:1 vs. 50:1 makes a difference? You actually keep separate gas cans with a drop of oil difference between them?

There's a difference within rpm & work load within pro & homeowner saws with the new syn oil , not so much with the old dino oil . Your right its only a 1/2 ounce difference , however Amsoil recommends Saber no richer than 50:1 , technically I'am pushing the envelope lol. I use to run 32:1 & 40:1 when straight mineral oils were the norm . However when synthetics came out I followed the trend here with the commercial fellers I know . Also I use 50 :1 in all my other hand held blowers & trimmers . I have run 40:1 in my ported 357 xp during break in with Interceptor , but since retuning , I run it at the 44:1 along with the 346 xp 7910 & 5105H with Saber . I religiously ran my 660 milling saw at 32:1 for yrs on shell T but it also runs Saber @ 44:1 for the last 4 yrs .

 

[dando127]

I don't buy the "more oil = running lean". Does oil not cool like gasoline does?

The mixture is air to FUEL, not air to gas. And fuel for a chainsaw is a gas/oil mix. The oil burns.....it is part of the fuel.

 

[windblown]

I don't buy the "more oil = running lean". Does oil not cool like gasoline does?

The mixture is air to FUEL, not air to gas. And fuel for a chainsaw is a gas/oil mix. The oil burns.....it is part of the fuel.

So you disagree with the article you linked to? They clearly wrote that they opted to adjust the carb richer when testing the higher oil content fuel and that they did so to compensate for the increased percentage of oil to gas. (In other words, the higher oil content mix ran leaner and required a richer carb adjustment to correct).

If it were me I'd throw out the power results in the second test. They found the piston and cylinder heavily scuffed when they tore down the motor. That may have happened during the initial break in run. Regardless, the friction that created the scuffing had to reduce output power, not to mention probably didn't help the compression ratio or the motor any either.

Hats off to them for the exhaustive test though.

 

[dando127]

Ya....I guess I blew it.....I read the article after.....

The conclusion of the article is that more oil makes more power. It does also mention that while testing they had to give more fuel to compensate for more oil.

In my mind, that is only true if the oil doesn't burn. If the oil burns, then it is doing the same job as the gas.

 

[bwalker]

I don't buy the "more oil = running lean". Does oil not cool like gasoline does?

The mixture is air to FUEL, not air to gas. And fuel for a chainsaw is a gas/oil mix. The oil burns.....it is part of the fuel.

Carb settings are based on the amount of air and the amount of gasoline in a vapor state that is present when the spark plug fires.
In an ideal scenario air/pre mix leaves the carb and enters the engine as air and liquid droplets of pre mix. When it enters the crank case the gasoline component of the premix flashes to vapor and the oil is deposited on the rotating assembly and crank case. Gasoline vapor then makes its way to the combustion chamber where it can be burnt. The oil also makes it to the chamber but it's combusted after the gasoline charge burning ignites it. Remember the oil too must be in vapor form to combust.
Ever wondered why a choke must be used with a cold engine? It's because the charge entering the cold combustion chamber is so lean it can't be ignited. This is because there is very little vapor and lots of liquid fuel. The choke floods the engine with excessive fuel/air mixture to provide enough vapor that the plug can light it off. It's also why a two stroke smokes when cold. The engine combustion chamber isn't hot enough to change the oil into a vapor so it passes through the engine partially combusted(smoke) or un combusted(oily residue).

 

[bwalker]

Ya....I guess I blew it.....I read the article after.....

The conclusion of the article is that more oil makes more power. It does also mention that while testing they had to give more fuel to compensate for more oil.

In my mind, that is only true if the oil doesn't burn. If the oil burns, then it is doing the same job as the gas.

The oil does burn, but not in the same manner as the fuel air mix and it effects mixture because it effects how much fuel flows through the carb.

 

[John Walsh]

I didn't have the patience to sit through a 15 minute video. Did he retune the carb? If not it's kind of bogus because of course you'd tune the carb properly for each ratio.

Gordon Jennings (motorcycle tuner and writer) did a oil ratio test where he held the engine temp constant on a dyno and saw slightly higher power for the highest oil ratio: www.bridgestonemotorcycle.com/documents/oilpremix6.pdf

Since power and temperature are related when all other factors are the same, you can deduce that the highest oil ratio would run slightly cooler at the same power.

 

[bwalker]

I don't know if you can say that or not.
Regardless, worrying about minute differences in temperature is silly.

 

[North by Northwest]

Ya....I guess I blew it.....I read the article after.....

The conclusion of the article is that more oil makes more power. It does also mention that while testing they had to give more fuel to compensate for more oil.

In my mind, that is only true if the oil doesn't burn. If the oil burns, then it is doing the same job as the gas.

The theory that more oil produces more power has been understood for yrs . Its at what cost & to what extent . A ounce of proper tuning can resolve a pound of improper mix ratio ! Properly mixed oil ratio's and tuning will provide maximum energy (power) from the fuel charge , allowing adequate lubrication of vital engine components & reducing any residue within the combustion chamber , pistion crown & rings . Understanding the dynamics of your engine & its operating perimeters will assist in what oil type & mixture is most beneficial to your saws intended use .

 

[North by Northwest]

The oil does burn, but not in the same manner as the fuel air mix and it effects mixture because it effects how much fuel flows through the carb.

Its a pure density & volatility relationship .

 

[dando127]

I get that there is alot going on inside an engine and a carb. But I don't think it's a straight division. The spark doesn't discriminate between gas and oil, and niether does the carburetor. And when talking about tuning, I think we are only talking about one screw depending on throttle position....it is complex but it is also very simple.....

 

[bwalker]

Its a pure density & volatility relationship .

Right, gasoline is very volatile and can be ignited by the park plug. Oil needs the heat of the gasoline combusting to flash it into a vapor so it can be combusted.

 

[bwalker]

I get that there is alot going on inside an engine and a carb. But I don't think it's a straight division. The spark doesn't discriminate between gas and oil, and niether does the carburetor. And when talking about tuning, I think we are only talking about one screw depending on throttle position....it is complex but it is also very simple.....

Spark only ignites gasoline thats in a vapor state. The oil is in a liquid state. As such the oil isn't ignited by the spark.

 

[bwalker]

The theory that more oil produces more power has been understood for yrs . Its at what cost & to what extent . A ounce of proper tuning can resolve a pound of improper mix ratio ! Properly mixed oil ratio's and tuning will provide maximum energy (power) from the fuel charge , allowing adequate lubrication of vital engine components & reducing any residue within the combustion chamber , pistion crown & rings . Understanding the dynamics of your engine & its operating perimeters will assist in what oil type & mixture is most beneficial to your saws intended use .

Indeed it has, but don't tell Amsoil,lol.
The only negative to running something like 32:1 and 50:1 is cost. Performance, cleanliness, etc are all better with a bit more oil.
And yes tuning matters. Until you know how to set a carb properly worrying about oil, gasoline, or temperature is a fools errand.

 

[North by Northwest]

Indeed it has, but don't tell Amsoil,lol.
The only negative to running something like 32:1 and 50:1 is cost. Performance, cleanliness, etc are all better with a bit more oil.
And yes tuning matters. Until you know how to set a carb properly worrying about oil, gasoline, or temperature is a fools errand.

I promise Ben , I won't t whisper a thing to Amsoil !

 

[bwalker]

I promise Ben , I won't t whisper a thing to Amsoil !

Ha ha!