Pre-Mix ratios

[Shonuff]

I cant remember what ski, engine, and mods you have.... if you run 60:1 dominator with no issues in a similar setup as mine-->that would definately give me good feelings of running 50:1 or maybe even 60:1 in mine... what do you have?

Stock SX-R and Group K big bore SX-R.

 

[kevbo]

A racer could realize an advantage from expensive oil. The guys that spend most or their time doing tricks or jumping do not need much in terms of quantity or quality. Cheap TCW-3 protects against corrosion better than anything expensive. The only skis that found the limits of cheap oil were the most powerful sitdowns that ran full throttle all the time tank after tank. I could not tell any difference between mixing 3oz/gal or 5oz/gal.

 

[w-nut]

i run 50/1 in all my skis . cheap valaline oil never had a problem yet

 

[Ericfox]

I run high quality oil because I paid too much damn money for everything... so why stop now?

 

[showmepro1200]

I believe Alexander Graham Bell achieved the most power at 20:1. (I'm not 100 percent sure on this, but I know he was using a ton of oil.) Why he reached the most power at this mixture, I do not know.

Did AGB ride a SJ or a Kawi? Just wondering :biggrin:

 

[Ericfox]

he was a smart guy... he rode a superjet

 

[Odd Duck]

so the cylinder get no lube at all?

Of course it does. As the mixture goes through the cases, then into the cylinder, it gets lubed from both ends. The oil is part of the fuel/air mixture.

I have an old weedeater that the shaft is broken on.

I wish I had some way to measure its power, Id do some tests starting at 16:1 and ending at 100:1 just to see.

I really dont understand how 32:1 can make more power than 50:1.

there is more LUBE, for less friction, and better ring seal, but there is also LESS fuel to burn and push the crank around?

can someone explain this to me?

IM not trying to argue at all, just trying to get my head around the concept.

Remember, it is important in the testing that was reported, that they were very careful to keep the air:fuel mixture consistent. They did this by adjusting jetting or whatever else they needed to do.

You will only get more power IF the fuel/air (not fuel/oil/air) ratio is maintained during the process of comparing the oil ratios. So, think back to the white/black/red marble analogy. If your fuel/air ratio lets, say, . . 20 black marbles with every 100 white marbles through the jet as the standard for your fuel/air ratio in any given time frame. [I don't know what the number or ratio actually is, obviously, just using easy numbers so we can compare {the number of molecules is NOT the same as the volume ratios we use, ie 50:1, 40:1, etc}]

So, let's just pick a number and say that at 50:1 there will be 5 red oil marbles/molecules that will fit through the jet at the same time as the 10 black and 100 white marbles. If we increase our oil in the ratio to 40:1, let's say that means there are 7 red oil marbles plus 10 black and 100 white marbles. That means we would need to increase our jet size slightly to get all the marbles through in the same amount of time. If we increase our oil again to 32:1, let's say this means that there are about 10 red along with our black and white marbles. You can see that we need a larger jet to get the same number of black and white marbles through along with the red marbles. As we keep increasing red marbles, we need to keep increasing the jet orifice to maintain the same black (fuel) and white (air) amount.

Make sense so far? That's the rich/lean/jet size theory.

Now, if we suppose that we are burning some of that oil in the mixture along with the fuel and air, then IF we are still burning the same amount of fuel and air, then the extra power comes from burning oil (the only other possible source of combustion). We likely save a little power from loss via friction as we increase oil in our mixture, along with saving power via better ring seal, but apparently there is enough increased power that some of it must come from burning the oil.

At least, this is my interpretation from what my genius hubby explained to me. If there is another genius out there that thinks of it differently, or if I'm completely full of BS, by all means, let us know.

 

[Mouthfulloflake]

I understand the marble and jet ratio thingy OddDuck.

My gut feeling though, is that I cant see how burning OIL, ANY oil, could produce more power.

if burning oil made more combustion power, a worn out 4 stroke, with leaky ring seal would have increasing power output as it declined.

BUt in real life, a worn out 4 stroke, smokes more, and makes less power.
Much like a 2 stroke, running on an overly rich mixture.

IN fact, I contend, that a 2 stroke engine designed in such a a way as to have pressurized oil lube to the crank bearings and NOT inculding ANY lubrication oil in the combustion mix would make better power, and burn NO oil.

Check out Evinrude E-tec outboard motors, I beleive they operate in this manner.

I mean, if burning oil increased the power, wouldnt drag racers dump a quart of 10w30 in the tank on race night?

 

[Odd Duck]

Ya got very good points there, and that I can't answer, as I'm not the genius mechanic, only interpreting what the genius told me. To me, even though it is clearly NOT efficent to burn oil, it still makes sense that burning a small amount of oil (even a very high oil ratio is still a fairly small amount of oil) would add to the overall total of burned compounds.

The 4 stroke that is worn out would, I think(?), be past any margins of efficiency that make it a not very realistic comparison. Not to mention that oil inside the chamber on a 4 stroke increased detonation which robs power.

As far as your point with the E-tec, I would love to see . . strike that, I would love for my hubby to see (and interpret for me, cuz he could make more sense out of it) how they would do with a similar experiment that was done on the older type of 2 stroke that was in the studies the hubby has read. IE, what would happen if there WAS oil in the mix, what would happen with the power, etc, what would happen if they converted an older 2 stroke to run w/pressurized oil delivery and no oil in the fuel, etc.

Why don't you set up that study, Lake and let us know what you find out? :biggrin:

We're all curious, now.

 

[cookerq62]

I mix 16oz to 5gallons cus its easy and comes out to 40:1. I read some where that a test was done and more oil made more power to a point. Some where around 30:1. The reasoning was reduced friction/less heat. After a certain point the oil starts displacing air/fuel and the power drops off. This was on dirtbike motors so the magic number probably varries for different motors.

 

[Mouthfulloflake]

thats pretty much what I was thinking cooker, I would be surprised if it was actually that rich though, but maybe so!

the 50:1, and 100:1 stuff comes from EPA pushes Im sure, the put power output, and engine longevity secondary to emissions.

which is cool and all, since we can basically disregard those 'recomendations' when mixing our own fuel.

Until someone can prove to me that 32:1 makes more power than 50:1

Ill be running castor 927, and walmart or whatever is handy tcw3 oils mixed randomly at 50:1

I mix 16oz to 5gallons cus its easy and comes out to 40:1. I read some where that a test was done and more oil made more power to a point. Some where around 30:1. The reasoning was reduced friction/less heat. After a certain point the oil starts displacing air/fuel and the power drops off. This was on dirtbike motors so the magic number probably varries for different motors.

 

[cookerq62]

the 50:1, and 100:1 stuff comes from EPA pushes Im sure, the put power output, and engine longevity secondary to emissions.

Kind of off topic but my owners manual for my 2007 Tacoma says the oil my truck needs is 0w20. It is imposible to find at regular auto parts stores and is super expensive. It even says that you can use 5w20 but its not recomended. So I take it to the dealer for my first oil change cus it was $20 and they put 10w30 in. I asked them why they didn't put the recomended oil in and they said thats what the service manual says. Turns out they recomend that oil to boost fuel economy but the high cost of the hard to get synthetic oil totaly negates any fuel savings.

 

[Mouthfulloflake]

right.

I recall in the early 80s when many truck manufactureres started recommending ATF in the transfer cases, and later the manual transmissions of trucks, because it offered less drag.

apparently that old Hypoid 80w90 just made stuff last too long.

hahahaha

Kind of off topic but my owners manual for my 2007 Tacoma says the oil my truck needs is 0w20. It is imposible to find at regular auto parts stores and is super expensive. It even says that you can use 5w20 but its not recomended. So I take it to the dealer for my first oil change cus it was $20 and they put 10w30 in. I asked them why they didn't put the recomended oil in and they said thats what the service manual says. Turns out they recomend that oil to boost fuel economy but the high cost of the hard to get synthetic oil totaly negates any fuel savings.

 

[kevbo]

Many years ago motorcycle tuners found that peak power increased with oil content. The problem is that it only occoured at peak PRM, the extra oil hurt throttling and low rpm performance. Im not sure how well this phenomenon applies to jetskis. I have ran as much as 25/1 and noticed a difference only after idling through long no-wake zones.

 

[cambo au]

i am no expert but i do remember a mate telling me that a 2 stroke oil made by red line was banned in f1 boat racing either here in oz or overseas and it was the best oil he had ever run in a motor but it was really expensive so some oils must have performance gains