Autolube vs Pre-mix

[MADDOG]

One very important point that needs to be taken into account. The oil is required to lubricate both the crankshaft bearings as well as the upper cylinder piston & rings.

Now the crankshaft bearings require more oil than the piston and rings for correct lubrication. With pre mix the oil ratio is a compromise in that in order too get enough oil on the crank bearing, too much oil ends up above the piston. This oil now has to be handled by the spark plugs during combustion. Plugs are hotter than ideal and need to be changed regularly otherwise they foul and you lose a cylinder. Many engine outs are caused by this. This fouling of the plugs is further agrivated by the cleanliness of the airfilters and the wear of the needlejet in the carb.

Autolube on the orther hand can inject the oil directly to the bearings (or as close as possible to them) without having to rely on the oil condensing out of the fuel mixture. This allows just the right amount of oil for bearing lubrication and thefore less oil gets up into the combustion camber resulting in less prioblems for the spark plugs to cope with and more safety margin for the air filters etc. Now you know why auto lube uses less oils than premix.

Many people say this is just one more thing to go wrong. This may be true, but well engineered technology has its benefits. My answer to nay sayers is why use watercooled engines, stick to 503's - heck why have 2 ignitions stick to single ones - heck run the risk of an engine out, delete the engine and stick to hang gliding - heck the pipes can break, stick the parasailing .......... Heck the electricity can go out ,stick too candles - Oh! we are here already. Thanks Eishkom!

It's your plane you make up your own mind while you still can. CAA will for your later!

[Morph]

Firstly, premixing has only one value, convenience, nothing else. There is no evidence whatsoever that it improves the life of the engine, reduces wear, reduces maintenance etc etc etc. IMHO if you bought a plane with it on, use it. However I would not buy it if I did not have it.

I have a strict regime ....I will leave it unmixed until I put it into the aerie

Me too. The only time I would actually mix the oil and petrol together is seconds before putting it in my plane. It is a ritual, and has zero chance of going wrong.

Premixing causes a lot of smoke at low revs and I know the consistency of the smoke by now so I always check the smoke after starting up.

DH, it would take a while to burn all the fuel in the pipes and filters and fuel bowls before starting to suck from the tank. At idling you are probably using 3l/h = 50ml per minute. Your carb bowl/filters etc prob hold double this. So it will take at least 2 minutes of running before you see the results of the new fresh petrol. What I am trying to say is don't rely on the first few seconds after starting, as this could be old fuel.

[Wargames]

One very important point that needs to be taken into account. The oil is required to lubricate both the crankshaft bearings as well as the upper cylinder piston & rings.

Please explain to me just how the oil gets to crank bearings from combustion chamber?? I dont quite get it, and my reconning of the rotax is that it has a prepack bearing on crankshaft.

Isn't the 2-stroke used as an agent to keep the tempreture of combustion down??

[Morph]

The oil get's injected into the crankcase directly instead of being mixed with the fuel.

Yes the oil, mixed with the fuel cools the motor.

The oil is still being mixed with the fuel, except now it actually gets to mix with the fuel inside the engine for the first time instead of before the carbs

[Slabfish]

Maddog , I hope some people see the after your explanation , I fully agree with you.

[MADDOG]

With premix the oil is held in solution (dissolved) in the petrol. This in tern is vapourised by mixing with air in the carb. When this vapour enters the engine crank case it will 'wet' the entire inside of the engine including the important crankshaft and con rod bearings through condensation. The oil ratio must be chosen to ensure sufficient oil condenses to lubricate the important bits. (Normally between 20 and 100 to 1 fuel oil ratio).

By using an auto lube - basically just a dosing pump - the oil is pumped directly into the crank case and in some engines directly to the crankshaft bearings. The oil is already small droplets and the fuel mixure is merely the wind that carries these drops onto the parts that are not directly fed from the pump.

All the mixture - air/fuel&oil vapour - in the crankcase is then fed into the combustion chamber through the transfer ports during the intake stroke and the spark plugs now have to deal with it.

During the compression stroke, the oil is somewhat squeazed out of suspension and condenses as small oil droplets on the coldest part of the combustion chamber - the spark plugs. This is why it is so important to check the plugs every 12 hours. (Notice the oil on them).With premix, there is more oil for the plugs to deal with.

Using premix, the oil gets into the engine through the carbs, and therefore the air fuel ratio will also effect the amount of oil present. A rich air fuel mixture will also result in a rich oil ratio present in the combustion chamber. As the carb needles vibrate in the needle jet, they wear resulting in the jet getting larger and the mixture getting richer. Also as the air filter begins clogging with dirt, the air fuel mixture gets richer. All of this adversly effects the spark plugs ability to spark.

Using autolube, the oil ratio is only relative to engine RPM. Poor carb and air filters condition will not effect the oil ratio.

[Wargames]

Thanks Maddog.

And so I will go to sleep tonight knowing that I did learn something new today.

Regards,

[Biggles of Africa]

As everyone has said, there are pro's and con's to both ways of getting oil into the engine, and it is a matter of personal choice.
Way back when granny was a pin up and I was racing motorcycles and life was good, I would only pre-mix, and if the bike came with an auto lube system, it would be blanked off and removed, my thinking was, if you pre-mix, thae as long as the engine is running, its getting oil.
But technology has come a long way, and the auto lube systems today are super reliable, and as I remember if you did have a cable break the arm is spring loaded to default to full rich max flow.
You pay's your money and you take's your choice. :D
It was also the days when Bel-Ray launched thier synthetic two stroke oil on the market, and the okes where bragging about how you only mixed this wonder stuff 100:1, being a firm believer and staunch supporter of Castrol Super Chainsaw, mixed at 20:1, yerra, we didn't know too much about this 100:1 stuff

And on that subject, I have always used, and swear by Castrol Super chain Saw, as the way I see it, it was developed to work under the harshest conditions and protect the motor.
Like the chainsaw that has been lying in the snow all night, and Phinias, fires it up, straight to red line and immediately starts to push it through a 200ft Red Ceadar.
PS Castrol/Mobil can't remember, suffer from CRAFT

[MADDOG]

Ja Boet - brings back memories.

I ran all sorts of Rotax engines pulling 85 hp out of 250cc reving 14000 rpm.
Also never had the balls to try 100:1 but stuck to Shell Sport S at 20:1.

Broke lots of engine things over the years but taking Potters in EL flat out 270km/h was good for the cholestral

[Biggles of Africa]

Ah yes MADDOG, memories indeed, I still hold my pen like a dremel tool, throwback from too many midnight porting jobs, working out 7 pages of expansion box formula to try and get it to fit on the bike, should have listened to wise advise the first time "If you get the exact formula you need for the motor, the pipe won't fit on the bike." never a truer word spoken, pre-mixing and then jetting the auto-lube system to feed all manner of other go fast juices into the crankcase, modifying rotary valves, balsa under the piston to increase crank case pressure, fiting Yamaha FS1 motors with Honda MB5 barrels so you could run duel carb (1 on the crank case, rotary valve and one reed valve on the barrel, oh yeah and DUNLOP RACING'S
Rickman fairings, and battery ignitions, running single rings, and butchering the skirts off the pistons to lessen the internal drag.
Sitting in front of the TV at night with a piece of glass and fine water paper, getting that head surface as true as a die, to bump up the compression.

Ah yes, and trying to get beasts like the Kawasaki KH trip's and the Suz T500 around corners

Good memories indeed, now excuse me while I pull my walking ring closer and shuffle off to empty my bladder, that has not been emptied in the last 15 minutes :D

[Byron]

Any idea what the autolube system weighs?

[Biggles of Africa]

hi Byron
Very little, it is a tiny little pump and a cable and a piece of tubing, you would save more weight by removing your wallet before flying :D
The wieght of the system is very negligable, but the oil tank when filled with 2 liters of 2 stroke oil will come in at a kilogram or more, SG of 2 stroke oil....anyone?

[IceAge]

Maddog,

I too have heard many different opinions on the good and the bad of both. I bought my trike with autolube, ie. 582 blue top, and have been flying approx 50 hours without problems.

The question now is what needs to be checked/serviced/etc. to ensure good working of the autolube system. I dilligently replace the two stroke filter every 15 hours as with the plugs and petrol filter. Is this good or overkill?

I have heard that over time the oil forms a thick 'goo' in the fliter which results in less oil being fed to the engine, ie. leaner mix. Is this true?

I have also heard that over time the 'gear', which apparently is plastic, that feeds the oil to engine in the correct amounts gets worn over time resulting in a similar situation. Is this true and if so what needs to be checked/services to prevent this from happening?

Thanks

[MADDOG]

Hi Ice Age

I would not like to suggest which is best but merely try and point out the pros and cons of each. My 618 autolube has 250 hours but I have only done 100 of those. I have changed the oil filter once before a long Hazyview trip. I have not heard of a gear problem, but I will include this check when I do the crankshaft major check. I will scout around and see if I can pick up more info on this.

Cheers

[Wargames]

Hi guys,

I know this topic it done and dusted, but I came across this nice little insert that shows exactly how a 2stroke engine works. I am posting it as a nice little tutorial for those that don't quiet get the grip of it. I was one.

http://www.youtube.com/watch?v=LuCUmQ9FxMU