Frank, in order for for the oil to combust(which it does) it HAS to evaporate.Crofter said:
Fuel/Oil mix
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Crofter
Addicted to ArboristSite
Dagger was talking about evaporative cooling of the piston by the charge prior to combustion. I dont contest that oil burning produces more btu energy than gasoline per unit volume ( I drive a diesel ) I am only talking about the analogy of a higher temperature to evaporate being equatable per se with a higher latent heat.
Stumper
One Man Band
Frank. I agree that Daggers point about evaporative cooling logically implies better cooling from Gas than oil in the mix-but how much difference does a little more oil make? After all the ammount of gasoline doesn't decrease in a properly tuned saw UNLESS the oil is functioning as fuel anyway. Right? I do see how having an oil coating on a piece of metal could impede flash cooling by the fuel;-but surely noone thinks that the metal parts should lack an oil film? I think that Dagger had a lot of knowledge-but that some of what he knew was incomplete or just wrong.
Blowdown1
ArboristSite Operative
OK, so still...if syn is better than dino, why can't that fact accomodate some of that "margin of error" or comfort cushion if you will and allow you to run the spec'd 50:1 without fear of problems?
I don't understand why someone would spend the extra money on syn and run it at the same higher than recommended ratio as dino simply for the sake of making sure you don't cook the saw.
I don't understand why someone would spend the extra money on syn and run it at the same higher than recommended ratio as dino simply for the sake of making sure you don't cook the saw.
Stumper
One Man Band
Blowdown1 said:
Simply for the sake of making sure you don't cook the saw. It is perfectly logical. We suffer lubrication paranoia.
Crofter
Addicted to ArboristSite
Stumper, I am not a fan of light on the oil mixes. I mix between 32 and 40 to one. I cant explain all the relationships between engine output, mixture ratio, fuel to air ratio, resistance to seizing etc. It is very complicated and dependant on specific test engines clearances, piston materials etc. I balk at having someone propound an explanation that is full of misconceptions about some pretty basic physics concepts such as specific heat, latent heat, latent heat vs boiling point, heat vs temperature etc. etc. Ben and I have been through this one before and I see he hasn't changed his mind either! Lol! I dont disagree with his results, but I dont agree with his explanation.
If someone were to look at the 2 cycle Kart air cooled forums.They would see they run 15-1 to 20-1. Or look at the 2 cycle motorcycle air cooled forums.They run 20-1 to 32-1 with yamalube semi synthetic a popular oil.
If you make more power and run cooler at 50-1 then someone should let them know.
Ray
Ken Dunn posted this in reference to Daggers post.
Hello dagger,
This post you wrote on 50-1 to 100-1 is just not correct. no engine manufacturer that builds 2-stroke engines or makes high quality 2-stroke engine oils recommend the
50-1 oil ratio,s. if you have a 250 motorcycle that doesn't operate over 7000 rpm maxima says you can use 50-1 if its synthetic oil. if you go to a 125cc motor and it turns over 10,000 they recommend 25-1 80cc engine that turns over10,000 they recommend 20-1. on yahama's kts-100 kart they recommend 15-1 on petroleum based oil and 25-1 with synthetic oil.In europe on the grand prix karts they are turning 22,000 rpm and making over 40 hp on the 125 shifter karts and they are using 100 percent synthetic at 12.5 to 15- 1 oil ratio's. They do this because their engines wont last at 40-1 or 50-1. they all tried the 100-1 and 50-1 when this was the craze 20 years ago but it didnt work .
the biggest reason you get varnish on a two stroke motor is because with a petroleum based oil . once you reach the 400 degree tempeture on the piston and cylinder wall it begans to break down and turn to a solid and becomes a varnish. Maxima 929 synthetic can be taken to 770 degrees before breakdown of the oil.
when you go on and on about 50-1 and 100-1 ratio's. you sound just like all the stihl factory instructors and factory reps i have ever talked to about oil. Isn't it strange that only the chainsaw, leafblower and weed wacker mfg's are hawking 50-1 ratio's. THey went over to 50-1 when the epa put in their emmision controls on thier motors. they pull engines right off the assembly line randomly and test them for emmisions. when they went to 50-1 is also the point in time that stihl started started having piston seisures on the 066's and husky started having big end rod failures
Sawracer works at a stihl-husky dealership here in california, they had a account that cut brush for PGE . they would buy ten saws at a time. first they lost almost all the big end bearings on the372 husky rods, then they bought 044 and 046 stihls and had piston/ barrels seisures. they finally went to 32-1 oil ratio and the problems were gone. I Dont Know of any engine builders and very few loggers that use 50-1. when You engineering guys design a motor or run all these tests then you need to go out to the dealers and see how this stuff works and what kind of problems are out there. talk to the mechanics, they give you the good data. of course that wont work on the oil ratio problem because stihl and husky are locked in to 50-1 because of the epa here in the usa
If you make more power and run cooler at 50-1 then someone should let them know.
Ray
Ken Dunn posted this in reference to Daggers post.
Hello dagger,
This post you wrote on 50-1 to 100-1 is just not correct. no engine manufacturer that builds 2-stroke engines or makes high quality 2-stroke engine oils recommend the
50-1 oil ratio,s. if you have a 250 motorcycle that doesn't operate over 7000 rpm maxima says you can use 50-1 if its synthetic oil. if you go to a 125cc motor and it turns over 10,000 they recommend 25-1 80cc engine that turns over10,000 they recommend 20-1. on yahama's kts-100 kart they recommend 15-1 on petroleum based oil and 25-1 with synthetic oil.In europe on the grand prix karts they are turning 22,000 rpm and making over 40 hp on the 125 shifter karts and they are using 100 percent synthetic at 12.5 to 15- 1 oil ratio's. They do this because their engines wont last at 40-1 or 50-1. they all tried the 100-1 and 50-1 when this was the craze 20 years ago but it didnt work .
the biggest reason you get varnish on a two stroke motor is because with a petroleum based oil . once you reach the 400 degree tempeture on the piston and cylinder wall it begans to break down and turn to a solid and becomes a varnish. Maxima 929 synthetic can be taken to 770 degrees before breakdown of the oil.
when you go on and on about 50-1 and 100-1 ratio's. you sound just like all the stihl factory instructors and factory reps i have ever talked to about oil. Isn't it strange that only the chainsaw, leafblower and weed wacker mfg's are hawking 50-1 ratio's. THey went over to 50-1 when the epa put in their emmision controls on thier motors. they pull engines right off the assembly line randomly and test them for emmisions. when they went to 50-1 is also the point in time that stihl started started having piston seisures on the 066's and husky started having big end rod failures
Sawracer works at a stihl-husky dealership here in california, they had a account that cut brush for PGE . they would buy ten saws at a time. first they lost almost all the big end bearings on the372 husky rods, then they bought 044 and 046 stihls and had piston/ barrels seisures. they finally went to 32-1 oil ratio and the problems were gone. I Dont Know of any engine builders and very few loggers that use 50-1. when You engineering guys design a motor or run all these tests then you need to go out to the dealers and see how this stuff works and what kind of problems are out there. talk to the mechanics, they give you the good data. of course that wont work on the oil ratio problem because stihl and husky are locked in to 50-1 because of the epa here in the usa
Crofter
Addicted to ArboristSite
What are the piston clearances on those cart motors that they are running 16 to one. I have seen the charts that showed the dyno outputs to be highest with the stronger oil mix. I have also read that they dont make many trips without being pulled down.
Stumper
One Man Band
Discussion is Dunn. KD Hotsaw has spoken.
Frank, The clearance on the KT 100 shifter is comparable with a saw. The clearances that a 125 shifter(LC)runs would be tighter.
Blow down, the idea that a synthetic allows you to run less oil is laughable and is proclaimed by companies like Amoil and Opti that are less than reputable. Read the fine print.
Blow down, the idea that a synthetic allows you to run less oil is laughable and is proclaimed by companies like Amoil and Opti that are less than reputable. Read the fine print.
Al Smith
Addicted to ArboristSite
In answer to the Kart engine thing,and bare in mind,it's been years for me.In my McCulloch stuff,it shows setting kart engines up a lot looser than saw engines.I'm thinking 5 or 6 thou,piston clearance,but might be wrong.When I fit the piston to my 125,I used 31/2 thou.I might have been a little too tight,but it runs ok.My buddy ,that had a national kart ranking in the 70's,would only get 6 to 8 races between a rebuid.Some of his "short track" 101 Macs,would hit close to 15 thou rpm.They had shaved flywheels,and would get hot.He ran alkie,and synthetic oil,but I don't know the mixture.He just started out with stock blocks[a lot of them],and when they finally blew,and they did,they really had some big bores in them,because of the amount of rebores.An old saying"that,that runs fast,does not run long"
Crofter care to pick apart my tea spoon analogy?Crofter said:
Its a fact that oil or fuel for that matter has to vaporise in order to combust. Its fact that oil requires more heat to vaporise than fuel. In a IC engine where does this heat come from?
Latent heat (of vaporisation in this case) would simply be a measure of the energy required to change the oil from a liquid to a vapor. Boiling point is the temperature at which boiling starts. Heat vs temp? Heat measures transfer and temperature is the measure of kinetic energy. I had physics also....
BTW your diesel analogy is a little flawed. Viscosity and BTU content are not always intertwined. Rather the specific carbon and hydrogen make up of the fuel has more influence on BTU output. High energy components exist that increase the BTU content of a fuel, but are the same viscosity as mo gas.
Isn't this fun... I thread with info.
dang
ArboristSite Lurker
Pre-mix oil doesn't burn worth a crap - no matter what kind or brand. So think about it, the more oil you ADD to your gas the less actual fuel is going through your jets (pilot, main etc.) so if less actual fuel is going through you jets, guess what? You're leaning out your motor / just like putting a smaller main jet in it. As I am sure you all know when you lean out a motor it gets hot. Come on engine builders in here, whats up? this is old and common knowledge. You should have known this.
Al, technology and MFG techniques have changed alot since Mac kart motors where in vogue.
P_woozel
ArboristSite Guru
40:1 is just fine. :blob5: :umpkin:
Of course you are makeing the ASSUMPTION that the fuel/air ratio is not altered by the user when switching to a richer mix. Any mix ratio has to be tuned properly(or oil brand for that matter) and if done correctly there is no differance in the amount of fuel going through the motor.dang said:
dang
ArboristSite Lurker
Yea no kidding but how many of these guys do you think are swapping mains whenever they make an adjustment do thier pre-mix ratio.
Stumper
One Man Band
bwalker said:
Maybe if we keep saying this different ways it will sink in.
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