oil mix

Dac · Post by **Dac** » Mon Sep 29, 2008 6:17 pm

ok, so i just read the hole article on premixing. Surprisingly good information. The way he put together the test its kinda hard to argue.

There test was 20:1 (recommended) vs 30:1 and 15:1. On a single cylinder Suzuki PE250.
Lets see if we can scale this to a honda Spree some. A sprees injector pushes 50:1. So lets compare 50:1 to there base line.
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50:1- 2.65 ounces to a gallon.
20:1- 6.4 ounces to a gallon.
that's a 2.5x difference.

so they say 30:1 is not that good.

30:1- 3.8 ounces to a gallon.
divide that by 2.5 = 1.52
1.52 ounces to a gallon is just about 75:1.

So following that math so far, the stock 50:1 is better then 75:1. i can see that.

But then they say 15:1 is the best.

15:1= 8 ounces to a gallon.
divide 8 by 2.5= 3.2
3.2 to a gallon - 40:1

So going by Gordon Jennings book, some basic math, and a oil-gas premix chart we can determine that 40:1 is the best for a stock spree.
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do i agree? Sort of. One on hand i do agree because the way the test was done was very professional, and they went though every step they did with great detail. And, during the test they did not push the motor WOT the hole time. So the motor they where doing the test on pushed probably about as hard as a stock spree at WOT. Another thing that makes this all add up.
They also explained why a company would make the mixture a hair leaner then what it should be. I can totally understand why honda would make a spree 50:1 when 40:1 is the best mixture.

But also the test was done on a 250cc endro. Thats 200 more "cc's" then a spree. even doing the math to the oil the maker recommends doesn't change the 200cc difference.

I guess if i was premixing a spree, i might go 40:1 just for the sake of experimentation. or i might go 50:1. i might even split the difference and do 45:1.

PimpinSpree · Post by **PimpinSpree** » Mon Sep 29, 2008 11:08 pm

i think your logic is a little off. changing the displacement isn't gonna change how good premix burns. I've heard you'll get optimal performance out of 18:1 and that guy says 20:1 is the magic number, i don't think that changes when you go to a spree.

Besides that, wasn't this argument about motor life, not performance. I figure if 25:1 is gonna give me better compression and better lubrication for longer motor life, i think thats a no brainer.

http://www.dansmc.com/2stroke_oil.htm

Arnadanoob · Post by **Arnadanoob** » Fri Oct 17, 2008 7:31 pm

In Hawaii nobody that I know of runs more than 32:1 which is 4oz to the gallon, this is ALOT of oil and will smoke out the back noticeably. The oil most modded moped riders use is Castor 927 which is a very thick premix oil that's mixed in at 32:1 per the label on the bottle. I personally use AMSOIL Dominator at 50:1 again per bottle label. Naturally I have zero experience in places that actually experiences all 4 seasons (Hawaii has a summer climate and a rainy climate only) so I can't say for certain if 25:1 is a good or bad thing, but it does seem to be excessive. You'd have to run very large jets to accommodate that ratio.

Now the oil/fuel theory, in a perfect world you only want to use only the amount of oil needed to maintain maximum lubrication, anything more will not only foul plugs but will cause a lot of extra carbon buildup and you'll naturally lose power. There is a point where you can/will exceed the limitations of the how much lubrication your engine can realistically use directly in relation to the kind of oil used. Think about it in terms of hydration for your health, there's a point where drinking extra water won't hydrate you any more since your body already is at the limit for absorption. Technically the better the lubricant, the less you'll need.

Too much oil = lean on fuel = possible seize. Keep in mind that oil is not your coolant, along with the fan shroud and fan (external cooling), the fuel is actually your internal coolant. When the oil burns inside along with the fuel, the oil turns into smoke which isn't a good heat carrier. Fuel burns into a hot gas which is carried down the exhaust out the muffler tip.

There are special exceptions to this like if your bore is scored (from a previous seize), you may need to use more oil to maintain compression. Is your 2 stroke engine at risk of damage when you run too much oil? The answer is yes, don't think that just because you run extra oil your motor is any better than running too little. Think about just how much harder your ignition system has to work trying to light that spark across a very oily fuel mix (your coil will work harder, your plug wire and plug will naturally have to work harder).

Hope this helps.

scooterwerx · Post by **scooterwerx** » Sat Oct 18, 2008 2:37 am

all i know is 50:1 is no good for WOT for long periods of time, at least with repsol race synthetic. of course ill rejet, but im going to run as much as it will fire through...20:1? 15:1? holy smokes

Kenny_McCormic · Post by **Kenny_McCormic** » Sat Oct 18, 2008 9:47 am

25 will be fine, you dont need 16 till your spinning a go kart race engine at 17K.

PimpinSpree · Post by **PimpinSpree** » Mon Oct 20, 2008 8:45 pm

Arnadanoob wrote:In Hawaii nobody that I know of runs more than 32:1 which is 4oz to the gallon, this is ALOT of oil and will smoke out the back noticeably. The oil most modded moped riders use is Castor 927 which is a very thick premix oil that's mixed in at 32:1 per the label on the bottle. I personally use AMSOIL Dominator at 50:1 again per bottle label. Naturally I have zero experience in places that actually experiences all 4 seasons (Hawaii has a summer climate and a rainy climate only) so I can't say for certain if 25:1 is a good or bad thing, but it does seem to be excessive. You'd have to run very large jets to accommodate that ratio.

Now the oil/fuel theory, in a perfect world you only want to use only the amount of oil needed to maintain maximum lubrication, anything more will not only foul plugs but will cause a lot of extra carbon buildup and you'll naturally lose power. There is a point where you can/will exceed the limitations of the how much lubrication your engine can realistically use directly in relation to the kind of oil used. Think about it in terms of hydration for your health, there's a point where drinking extra water won't hydrate you any more since your body already is at the limit for absorption. Technically the better the lubricant, the less you'll need.

Too much oil = lean on fuel = possible seize. Keep in mind that oil is not your coolant, along with the fan shroud and fan (external cooling), the fuel is actually your internal coolant. When the oil burns inside along with the fuel, the oil turns into smoke which isn't a good heat carrier. Fuel burns into a hot gas which is carried down the exhaust out the muffler tip.

There are special exceptions to this like if your bore is scored (from a previous seize), you may need to use more oil to maintain compression. Is your 2 stroke engine at risk of damage when you run too much oil? The answer is yes, don't think that just because you run extra oil your motor is any better than running too little. Think about just how much harder your ignition system has to work trying to light that spark across a very oily fuel mix (your coil will work harder, your plug wire and plug will naturally have to work harder).

Hope this helps.

all this oil talk is just theory imo, but imo, i think your deffinitly on track. But i think the point where your talkin about is more like 18:1. Any more oil than 20:1 and its not going to burn as well. But 25:1 will burn just as good as 32:1. IMO the perfect mix for a scooter motor that is held wot for long periods of time is somewhere between 25:1 and 32:1 and therfore ive been mixing at 28:1

i think 50:1 is just barely enough to keep things from not seizing, but certainly not enough

Kenny_McCormic · Post by **Kenny_McCormic** » Mon Oct 20, 2008 9:19 pm

Dyno tests and respectable 2 stroke tuners beat theory. Read some of Jennings stuff.

scooterwerx · Post by **scooterwerx** » Tue Oct 21, 2008 2:03 pm

so...i have been running 20:1 in my motor since i got it back together three days ago, its got a badly scored 70cc malossi cylinder, 21mm carb, all sorts of transmission mods, carbon reeds, case porting etc...and this thing is faster than its ever been! wheelies like its a trials bike, 60mph top speed, keeps up with 125cc scoots all day...plug looks fresh and clean, like light chocolate...and it doesnt smoke!!! im sold...