2stroke motors instalment 1

[MajBach]

Re: 2stroke motors instalment 1

i have never heard of this before! and if it were true for premix, it would be more true for a vro system that is stored outside in the freezing temps. this really bothers me because i dont believe it! but after reading this i'm not going to risk it either. if anyone can validate this claim please step forward. i'm kinda freakin out now!<br />

I have heard/experienced this... to some degree.<br />About 15 or so years ago, Bardahl (I think owned by bombardier now) had a concentrated 2-stroke snowmobile oil. It was expensive but we used it on our new sleds for several weeks one winter. One day, we were out on the trails and two of the sleds' engine seized - within a few feet of each other! Both sleds had side mounted cooling fans and it was the outboard piston that had the trouble. The sled that survived had a center mounted fan. <br />Anyway, one of the guys owned a small engine shop and had determined (not entirely on his own) that the oil had congealed out of the pre-mix gas. This event BTW, happened after cold snap. He took his evidence and reports to the oil mfg. and surprisingly, the Bardahl paid the bills. Shortly after that, we noticed the oil no longer offered on the shelves and not long after that, there was a replacememt oil. The new oil was the same price but the quantity was a little over double from the previous can. However, one can still treated the same amount of fuel. <br />The verdict (from the oil mfg.) was that the oil did indeed not tolerate the cooler temperatures.<br />I know oil has come a long way in 20 years but ever since then, if I have pre mixed fuel lying around and it gets cold outside, I use the fuel for starting fires rather than running engines.

 

[Dhadley]

Re: 2stroke motors instalment 1

Just a comment here, but the fuel in the US and in England may be different. I dont know. The higher octanes here (US) used to burn cooler. Today they burn hotter. We see it all the time with motors on the dyno and running boats with EGT gauges. <br /><br />Just something to keep in mind...............

 

[sorrydog]

Re: 2stroke motors instalment 1

The higher octanes here (US) used to burn cooler. Today they burn hotter.

Whatya think that is from? More Toluene?<br /><br />Looks like we're about to start getting more ethanol in our gas though. That should cool'em down.<br /><br />I understand what geraint is saying about the heavier oil mixes, however, unless your motar is already on the bleading edge, I don't understand how my fuel that is 98%/2% fuel/oil at 50:1 versus a fuel mix at 40:1 that is 97.5%/2.5% fuel oil is going to lean out enough to raise cylinder temps.<br /><br />BTW- I always thought that hotter was better (from an efficiency standpoint-not reliability) because if the cylinder gases are hotter then you will have higher cylinder pressures since pressure and temp are proportional to each other. Tell me if this is wrong.<br /><br />This I do know- If you get a drum of something like Sunoco 110 they tell you if you keep it sealed in a controlled environment it will last years. If you put it in a gas can- you better use it fast.

 

[sinkingfast]

Re: 2stroke motors instalment 1

Read instalment 2 and hopefully that will answer your question. You are right about the motor if it is a bit too near the edge but consider something else..........<br /><br />A given volume of mix liquid contains given amounts of fuel and oil.<br />Increase the amount of one, you decrease the amount of the other.<br />Increase the oil,you decrease the amount of the gasoline.<br />Decrease the amount of the gasoline up goes the burn temp.<br />Higher burn temps and extra oil can lead to burnt tartar forming round the rings and lessen efficiency. If a ring sits proud when it passes a port and cant sit back, broken rings at least. We are trying to set safe standards.<br /><br />The manufacturer set an oils fuel standard.. stick to it.

 

[Forktail]

Re: 2stroke motors instalment 1

BTW- I always thought that hotter was better (from an efficiency standpoint-not reliability) because if the cylinder gases are hotter then you will have higher cylinder pressures since pressure and temp are proportional to each other. Tell me if this is wrong.

Well, yes and no. <br /><br />You are correct that heat will cause an increase in cylinder pressure, which in turn can create horsepower.<br /><br />But hotter is only better (more efficient) if the extra heat can be transformed into horsepower. Lost heat is not horsepower. Thus we see things like coated and insulated exhaust systems on 2-strokes.<br /><br />Think of an engine's thermal efficiency as how much of the burned fuel it converts to horsepower. Not how hot it runs. <br /><br />Keep up the good work geraint.