Oil Mix Ratios and Cylinder Head Temperatures

[Smitty Smithsonite]

But what your bot considering is the change in 20 degrees of ambient temp has a much greater effect than a bit more oil in the fuel.
Most guys can't tune a carb to save their lives and are way rich anyway.
With the newer gen says with compensating carbs or FI your tuning is bang on all the time regardless of ratio.

I was just talking about the fuel mixture regarding premix. Tuning is an entirely different subject altogether.

 

[bwalker]

I was just talking about the fuel mixture regarding premix. Tuning is an entirely different subject altogether.

Yes, but what we are talking about is air to fuel ratio and the effect(minimal) that 1% more oil in your pre mix has on A/F ratio.

 

[Sepia]

OMG— me and my brothers all raced motorcycles back in the day, enduros and hare scrambles. Those Hodakas had a distinctive sound out in the woods, like swarms of angry bees coming down the trail.

Yeah and the clunk clunk clunk as they went by due to all the missing transmission gear teeth lol. But hey... when you are 14 and broke, who cares?! It beats walking!

 

[thenne1713]

It is hard to conclude anything definitive from that test. I don't know if it was the wood, the chain, the operator, the mix, or some combination thereof, but the saw struggled in the last large wood test - 57 seconds of cutting with 50/1 and 72 seconds of cutting with the 25/1. Until it reaches a terminal temperature, the longer a saw runs the hotter it should get.

Ron

There is a user (Tim Tatro) on other websites that experimented w/ 100:1, 50:1, 25:1, running each w/ new pistons/ rings for x-hours milling (= more constant load) and then teardown; his bottom line= confirmed 50:1=best lube w/ minimum deposits; he will continue w/ 50:1 mix. Interesting writeup. Your mileage may vary.

 

[North by Northwest]

OMG— me and my brothers all raced motorcycles back in the day, enduros and hare scrambles. Those Hodakas had a distinctive sound out in the woods, like swarms of angry bees coming down the trail.

Had a 1970 Hondaka Super Rat awesome little bike . Raced it successfully for 3 seasons . My cousin bought a Wombat he kept it for over 10 yrs . Never had a complaint .

 

[Wow]

More oil = less fuel so you compensate by setting the carb richer which equals more mix and more cooling. I would be surprised to see an appreciable difference in cyl. temp with different mixes.

fwiw, higher octane fuel burns more slowly - to prevent pre-ignition.

Here's my GUESS. Several years ago my Grandson and I (actually I raised him as my son) did some testing on various oils. Using a Propane Torch we dripped oil onto a heated piece of metal. Good Ashless 2/cycle oil vanished leaving no measurable amount of evidence. I contacted an Engineer and he told me ideally good 2/cycle oil "completely burns up with the gasoline". Several other oils left traces and even a tiny bit of residue. Automotive oils even Mobile1 eventually burned "mostly" up but it took more heat and more time. Back in the day,,1960 etc. I've mixed motor oil for 2/ cycle engines. NOTHING as good as todays engines. If we didn't make it smoke we needed more oil. . However, since GOOD 2/cycle oil DOES RAPIDLY burn ashless my GUESS would be using 2.6 ounces of oil per gallon vs 3.2 ounces of oil per gallon, on most engines probably wont hurt anything. BECAUSE, after carefully measuring exactly what gas pumps meter out, AND seeing some pumps NOT giving the same amount of gas on the pump as the 4 quart marks on my precisely marked container my GUESS is few people actually get precise mixes anyway. When it comes to precise mixes I'm a Paul. Peter and Dick took the day off and left me in charge. BECAUSE some of my weapons of work recommend 3.2 ounces of oil per 128 ounces of petrol ( should we include 3.2 ounces of oil with the 128 ounces of gas for a net total of 131.2 ounces of mix? ). Some do, so did that just change the ratio?. So to get closer than the hair on an old ladies lip. Where is your mind. and to make my life easy I simply but the oil with the 3.2 measurements on top. I buy a tad over a gallon of high octane NON SINFUL (that would be non ethanol, God hates ethanol and will beat me for using it in my saws), . Then I fill my mixing container two blond curly hairs BELOW a full gallon. Add my 3.2 ounces of Gods favorite oil ( I'm keeping that secret) and shake the container. Sometimes I also shake my body too. Once im contented and satisfied that the fuel is fully mixed I add Just enough gasoline To get the FULL gallon in my mixing jug. So far all my saws seem to be happy except that one time I parked my cs590 between a Stihl on one side of it and a Poulan on the other. They kept me awake fighting all night. Snobby Sthil. Even a Poulan snubs Chinese saws. Gotta keep them separated. This is experience, humor, opinion and a few facts. Have a great day. Stay calm. Tell a woman that and she'll smile and say thank you honey, here's your saw. The motor will probably be running. .

 

[Gabriel1982]

I'm looking for real-life empirical data showing the relationship between oil mix ratios and cylinder head temperatures. We've all heard statements like: more oil in the mix means less fuel -- so the air/fuel mixture is leaner and that makes more heat". Or: "I run 32:1 oil to provide more lubricity and I've never had a saw fail due to a lean mixture condition". I would like to see a real-world scientific evaluation that documents the cylinder head temperature change when running 50:1 vs. 40:1 vs 32:1. Same saw. Same base fuel. Same oil. Same ambient temperature. There seems to be a lot of strong opinions on this matter, but I wonder how much of the various opinions are anecdotal, hearsay, or culturally motivated. Myth or Fact? This might be a good test for Project Farm on YouTube.

JQ

I use Motul 2T 800 offroad in a brand new(first tank of gas barely used up) Makita EA6100P, 30ml to 1 liter of 95 octane gas . Barely gets warm(about 5 degrees Celcius here in Romania),revs easy,revs fast, smokes a bit only when revved from idle. Some unburned oil can be seen dripping on the stainless steel exhaust.Still have to figure out how to do the "break in " of the engine...
As for temperature of cylinder head... Either it never reaches operating temperature or this is the NORMAL operating temperature, I can hold my hand/fingers on the side cylinder aluminum fins..
Am curios how hot it will be after cutting a few 20 inch diameter logs in small slices one thing is for sure: I will use only fully synthetic premix oil Motul 2T 800 offroad in the 95 octane gas. Just to be sure at least everything inside the engine is lubed!

 

[Tomos770]

Just to inform you.....

Motul 800 is superb oil.....but....if you can hold your finger on its cylinder.....you are obviously not running your saw @WOT alot....

Motul 800 needs higher temperatures to burn off completely.....so you will only acumulate unburnt oil in its muffler!

Reconsider you oil choice(s).....Shell ultra 2t..... Elf moto 2t tech.....Motul 710 2t.....

 

[NSEric]

I've always used left over premix from my 2 stroke dirt bike in my saws.
You have to run a saw really really hard to get motul 800 or amsoil dominator to burn clean, its made for motors that run a lot harder and hotter. It never hurt the saw but never stopped smoking or drooling out if the muffler either.
I switched to the cheap/easy to get lucas semi synthetic in both the bike and the saws at 32-1. It's nothing to right home about, there's better oils for sure but it burns clean, there's no oil drooling out the muffler and nothing has blown up in the 7-8 years I've been running it.
Since I sold the 2 stroke bike, I'll likely switch to a cheaper saw only mixing oil when I run out of mix as I dont need an oil that works in both my saw and bike anymore.

 

[Gabriel1982]

Just to inform you.....

Motul 800 is superb oil.....but....if you can hold your finger on its cylinder.....you are obviously not running your saw @WOT alot....

Motul 800 needs higher temperatures to burn off completely.....so you will only acumulate unburnt oil in its muffler!

Reconsider you oil choice(s).....Shell ultra 2t..... Elf moto 2t tech.....Motul 710 2t.....

Well, it's a new chainsaw, a few hours of engine running,I think... Haven't counted. Just burned about 700-800ml of fuel. What was in the gas tank, first fill.But it will get full use ,soon. Was wondering how long break in should last...

 

[North by Northwest]

Well, it's a new chainsaw, a few hours of engine running,I think... Haven't counted. Just burned about 700-800ml of fuel. What was in the gas tank, first fill.But it will get full use ,soon. Was wondering how long break in should last...

A few tanks normally is more than adequate , after you 1st tank run it like you stole it . Let it idle after use for a few minutes , to let it cool down prior to shutting it off . Enjoy your new saw , ensure to keep your air filter clean & chain sharp , to protect your investment .

 

[Gabriel1982]

A few tanks normally is more than adequate , after you 1st tank run it like you stole it . Let it idle after use for a few minutes , to let it cool down prior to shutting it off . Enjoy your new saw , ensure to keep your air filter clean & chain sharp , to protect your investment .

Sharpening the chain will be the most complicated thing for me, to be honest. I'll probably spend a day reading and trying things out with the chain tools and chainsaw...

 

[North by Northwest]

Sharpening the chain will be the most complicated thing for me, to be honest. I'll probably spend a day reading and trying things out with the chain tools and chainsaw...

Get the proper sized files & practice , practice , practice . Be patient & don't over think it , lots of backyard videos on the net or Buckin Billy has some good technique & amusing video's on utube . Good luck !

 

[Wow]

Sharpening the chain will be the most complicated thing for me, to be honest. I'll probably spend a day reading and trying things out with the chain tools and chainsaw...

I remove my chains sometimes. Seldom sharpen in the field. When I do sharpen one on the saw I tighten the chain a little tighter than what it's set for cutting. That helps with the wobble. I LOCK the brake, sharpen with saw bottom Up. I made a guide. 6 inch + o - , out of Aluminum Angle. Using a metal saw both ends are cut angled 30 degrees. Holding that to the bar above the tooth slightly forward or behind gives a visual to assist and steadiest the chain. Wear gloves. I'll send you a photo of the jig in my shop. Chain is on the jig not saw. I file from tip aft chain facing aft tooth AWAY from tip.. The correct file needs to stick up above the top of the tooth a little bit. Learn how to lower the rakers. Good luck.

 

[bwalker]

There is a user (Tim Tatro) on other websites that experimented w/ 100:1, 50:1, 25:1, running each w/ new pistons/ rings for x-hours milling (= more constant load) and then teardown; his bottom line= confirmed 50:1=best lube w/ minimum deposits; he will continue w/ 50:1 mix. Interesting writeup. Your mileage may vary.

Happen to have a link to this test.

 

[windblown]

Agree that without re-tuning the carb the results don't mean much. Chainsaws when properly tuned for WOT run the AFR on the rich side of Max power AFR to keep no load RPMS from going thru the roof, which also provides a bit of cooling effect from the unburned gas. Jump from a saw tuned for 50:1 to using a 25:1 mix without adjusting the carb and the motor will run leaner. Not enough leaner to get the AFR so lean it starts to cool the combustion though, in fact it will lean it just enough to climb the scale towards max combustion temps.

Interesting video below regarding AFR and combustion temps. At first one may get the impression the maker is claiming lean runs cooler, and he is from a strictly mathematical/theoretical perspective. However he then goes on to explain why the math/theoretical </> real world and in fact what we would call "to lean/hot" actually isn't mathematically lean yet, and it does result in higher real world combustion temps.

 

[bwalker]

Agree that without re-tuning the carb the results don't mean much. Chainsaws when properly tuned for WOT run the AFR on the rich side of Max power AFR to keep no load RPMS from going thru the roof, which also provides a bit of cooling effect from the unburned gas. Jump from a saw tuned for 50:1 to using a 25:1 mix without adjusting the carb and the motor will run leaner. Not enough leaner to get the AFR so lean it starts to cool the combustion though, in fact it will lean it just enough to climb the scale towards max combustion temps.

Interesting video below regarding AFR and combustion temps. At first one may get the impression the maker is claiming lean runs cooler, and he is from a strictly mathematical/theoretical perspective. However he then goes on to explain why the math/theoretical </> real world and in fact what we would call "to lean/hot" actually isn't mathematically lean yet, and it does result in higher real world combustion temps.

In theory a overly lean engine will run cooler. In practice not so much. All sortsnofnbad things start to occur once you start to run a two cycle lean. Especially in performance engines with high BMEP, of which the baddest mod saw is not.

 

[North by Northwest]

In theory a overly lean engine will run cooler. In practice not so much. All sortsnofnbad things start to occur once you start to run a two cycle lean. Especially in performance engines with high BMEP, of which the baddest mod saw is not.

I believe this video is more intended for 4 cycle applications , agree with Ben , two stroke chainsaws require a rich fuel to air mixture in real world usage !

 

[cookies]

All internal combustion piston engines require a rich fuel to air mixture, the initial burn temp may be lower but the piston crown temp will skyrocket until preignition occurs without the quench effect. I have seen pistons that have melted through the crown down the side, through the rings from running lean, pistons swollen to the point they seized in the bore and the connecting rod broke. Nox peaks at stoich because there is more fuel burning to make it. Some of his info in his videos is malarkey since he seems to just copy whatever he can find to the point of plagiarism then writes it all over a white board as if he is teaching from experience.

 

[randallpacific]

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. ???