More reason to run higher oil to fuel ratio?

[CTYank]

Out load here but same ratio mix same RPM's but less fuel combustion so less heat so less friction right?

You folks are confusing yourselves. Without stratified scavenging, much more of the mix of air/fuel/oil goes RIGHT OUT THE EXHAUST serving no useful purpose in the engine.

My bet is that the fuel actually burnt and put to work is essentially the same.

No matter though- I'll trust the mfg's engineers first. They say 50:1, so be it. Seems to work fine.

 

[Stumpys Customs]

Yep!

The question is, are the stratos running on less fuel/oil volume for the same amount of work/time as an equivalent older design.

Say 361 vs 362.

Should be easy to check. Main jet size on each should tell the tale.
Anybody know off hand?

Stay safe!
Dingeryote

I'm gonna guess no. The only thing the fresh air does is take the place of the initial part of the transfer charge that in the regular style cyl would be air fuel & oil that just goes strait out the exhaust. It makes since in my mind. just not sure if it's comeing across here.
The strattos that I have checked the timing #'s on have had long tranfer durations. Meaning that if we say the tranfers open @ 114* on a stratto & the first 5-10 degrees are just fresh air. The fuel charge will start coming in at around 120* or so. That would be close to the same duration #'s as a conv type 2 stroke. These are not official #'s just hypathetical.

 

[Terry Syd]

A few years ago on the forum there was a fellow that had worked in one of the factories on oil ratios and engine temps. They decided on 50-1 as there was adequate lubrication and it produced lower EGTs than richer mixtures like 40-1. It was heat that fried the engines, not a lack of lubrication, less oil gave less heat.

If you take a look at Blair's work on engineering two-strokes, he comes to the conclusion that the vast majority of fuel is vaporised in the cylinder, very little is vaporised in the crankcase.

The area to check for adequate lubrication is on the surface of the rings. A large percentage of the heat from the piston crown is transfered to the cylinder through the contact of the ring/s. The rings are also pressed tightly against the cylinder by the gas pressure behind them. If the lubrication is breaking down you will see blue and/or brown spots on the rings. You can also find the same coloration at the top of the exhaust port where the rings are scuffing.

With the advent of synthetic lubricants, it has been decades since I have seen those tell tale spots on the rings of a properly set up two-stroke.

 

[saw dog]

Hi all
Years ago I felt as many of you seem to feal that using a higher persantage of oil in your mix did a better job of lubercating. This may well be the case as far as lubercation in the lower end, but when it comes to the combustion chamber, piston and rings there lies the problem. I found that I had a lot of carbon buildup and deposit. Carbon deposits become abrasives to the cylinder and pistons and lock up the rings. After coming to this conclusion and going with 50:1 mix I am getting much longer and better service life out of my saws. Since I have been using 50:1 mix my top ends seam to wear out at the same rate of the rest of the saw where as before I would go through two to three top ends before the rest of the saw was used up. Just my findings, safe cutting all.

 

[Aussie Dave]

The thing that confuses me,why do Husky recommend a richer oil mix in there big saws?
around 32/1 i think (that may not be exact my memory isnt the best )
I remember a while back Matt ( MCW ) talking about the same thing but know one gave a answer.

 

[flyboy553]

On an older saw, you will fry a piston long before a bearing gets roached, if the carb is set as lean as some of the Stratos run normally.
I forget who it was here, that recently discovered he had been running near 100:1 with Ultra. Hmmmm...

Stay safe!
Dingeryote

Uhm, that was me, Dinger, but it wasn't Ultra, it was Husky synthetic. This went on for 2 years! So, I am not going to
worry myself awake all night on oil mix in any saw!

Ted

 

[usmarinekurt]

Someone needs to.stop.laying in bed at night thinking about their saws

 

[zogger]

The thing that confuses me,why do Husky recommend a richer oil mix in there big saws?
around 32/1 i think (that may not be exact my memory isnt the best )
I remember a while back Matt ( MCW ) talking about the same thing but know one gave a answer.

---good question.

 

[c5rulz]

fuel /oil ratio is different to air/fuel ratio,most engines will tollerate varied oil/fuel ratios ,but get the air fuel ratio (Stoichiometric ratio ,Adjustable at the carb)wrong and an engine wont like for long

I agree.

From a mathematical standpoint, changing the fuel/oil ration is not near as significant as changing the Stoichiometric ratio. And we know what lean conditions do to a saw.

But hey, I am a noob.:msp_smile:

 

[sps3172]

That is an interesting point but if the strato saw uses less fuel then it is more lean.

This simply isn't true. The reason the 'strato' engine uses less fuel is because it wastes much less unburned fuel out the exhaust port. The mixture inside the combustion chamber during ignition doesn't automatically 'have to' be 'leaner' just because the engine uses less fuel.

That being said, the bottom end of the standard 2-cycle does 'see' the extra fuel and oil (on it's way to be wasted out the exhaust port).

 

[jbighump]

i run 50:1 stihl ultra in everything and no problems here,,,i even run it in older stuff requiring 32:1

 

[lone wolf]

Just thinking out loud here:

With the strato saws using much less fuel per amount of work done, that means they are also using much less oil (in the fuel).

I know the oil threads get old, just throwing a new twist out there to think about. Sorry if this has been put out there before.

Waylan

My MS200T uses less mix than my 046 but that dont mean i should put more oil in it.The smaller saw also uses less air what can you do?

 

[3000 FPS]

I'm gonna guess no. The only thing the fresh air does is take the place of the initial part of the transfer charge that in the regular style cyl would be air fuel & oil that just goes strait out the exhaust. It makes since in my mind. just not sure if it's comeing across here.
The strattos that I have checked the timing #'s on have had long tranfer durations. Meaning that if we say the tranfers open @ 114* on a stratto & the first 5-10 degrees are just fresh air. The fuel charge will start coming in at around 120* or so. That would be close to the same duration #'s as a conv type 2 stroke. These are not official #'s just hypathetical.

Ok I get it now and that makes sense. These saws do not run on a leaner mix they just do not throw unburnt fuel away when the first part of the transfer occurs by using unmixed air instead. So then the saw does not use as much fuel and it does not pollute as much. Thanks

 

[walexa07]

Wow, way more attention than I expected, but then again - I know oil ratio on this forum is like politics and religion, lol. Reason I started this thread is because some guys like to run more oil than 50:1. And if any saw really justifies it, I figured it would be the strato saw.

Thinking through, it does seem as if there is always the same ratio of fuel/oil in the crankcase, regardless of whether it is being replaced as quick as the non-strato saws. Hmmmm........

 

[BloodOnTheIce]

Race saws get 32:1 or richer
Ported work saws get 40:1
Stock saws 50:1

The more modified the more safety barrier you remove, the more oil you have to add.
This is what I personally run. A current production saw is designed to run 50:1, if you run
a good fuel, and good oil, no reason to run a richer mix than that.

 

[brncreeper]

Not rocket science, bearings need oil and engines that run WIDE OPEN like pro chain saws, milling saws and motocross bikes need 2 stroke racing oil and 32:1 mixing ratio.
Too much oil will cause excessive smoking and spark plug fouling, too little oil will cause engine damage or premature wear.

 

[VTWoodchuck]

It seems like nobody trusts the engineers working for these saw companies. I tend to think that some folks WAY smarter then me have figured out all that crap so I don't have to. I get the EPA chokehold that occurs but it cant be that bad. I put a cold air intake and aftermarket exhaust on my trucks but never mess with the fuel injection. Seems to work fine.

 

[lone wolf]

Stratos burn less fuel because thier carbs flow less mix, I.E. run on less fuel/oil. In effect OP is correct.

Less fuel/oil is reaching the bearings for the same amount of time, under the same load, making similar or more power.
Which is why the Stratos make the Hippies and EPA smile in the first place....fewer emissions.

If the volume of mix/oil getting to the bearings was similar, fuel consumption would be similar, and it is not. Stratos sip.

With all things oil related, it is a matter of engineering the bearings to do the things they do.
Coatings, alloys, dimensional considerations and that sort of thing. I also have to suspect that modern 2cycle oils and thier superior propertys come into play as well.

On an older saw, you will fry a piston long before a bearing gets roached, if the carb is set as lean as some of the Stratos run normally.
I forget who it was here, that recently discovered he had been running near 100:1 with Ultra. Hmmmm...

Stay safe!
Dingeryote

So Strato = Hippie saw

 

[splitpost]

Stock 660 with muff modd

Took these pictures of my MS660 combustion chamber,saw running on 25:1 stihl/castrol oil,89octane unleaded,carb tuned fat up top
this saw gets run hard,
after all the talk on mix ratios and carbon build up i was expecting something else

 

[splitpost]

I can't see the pic.

Waylan

fixed it