Belray should not be used at less than 32:1 in any engine under 125cc.
Read the jug sir.
Had a nice long discussion with Belray Tech. The tech guy Andrew is awesome. I don't see what it could hurt posting it. So it's a long read but, pretty interesting and informative at least for me.
And i have to read through it again and digest and figure out some more questions.
---------------------------------------------------------
Redbull660 -
Hello, My friend (heavy into motocross) swears by your products. Wondering if you carry anything that would be good for my Stihl 661 91cc 7hp chainsaw?
-----------------------------------------------------------------------------------------------------------
BelRay -
We have many customers of ours using the H1-R ester 2-stroke oil in their chainsaws and other gas powered tools with a lot of success. That would definitely be my first recommendation for your Stihl. Its full name is H1-R 100% Full Synthetic Ester 2T Engine Oil, item number 99280. You can mix that at Stihl's recommended mix ratio, but if you see excess oil coming from the exhaust you may be able to switch to a leaner oil mixture over time for a cleaner burn. If you have any additional questions, let me know.
----------------------------------------------------------------------------------------------------------------------
Redbull660 -
So H1R ok. I'll pick some up. So stihl says like 50:1 in all their saws with their Stihl ultra synthetic 2 stroke oil. Would you start out that lean with the H1R? A little searching...I see a guy who has a ported MS661 (91cc) and runs your H1R at 32:1 ratio with 92 ethanol free gas. But with the porting he's running around 205-215psi compression. I think a stock MS661 ie. what I"m using is more around 170psi. I'm assuming that would make a difference?
-----------------------------------------------------------------------------------
Belray -
Based on that, I would suggest starting at 40:1 or 42:1 for normal use. I'm not sure how you are running the saw though, so if you are taking on some heavy pieces that you are running the throttle wide open for longer periods of time than average use, then the 32:1 might be the better way to go. The only thing that too much oil might do is foul a spark plug. So if you want to start at 32:1 and work your way up to the "sweet spot" ratio that might be a good idea.
---------------------------------------------------------------------------------------
Redbull660 -
I'll try 32:1 and 42:! and see what happens. My friend has a thermo gun (measure the cyl temp after the cuts) and I can do some long timed cuts with a 41" bar.
btw - I'm switching because I'm pissed that even when I tried the Stihl ultra syn at 45:1 and then 40:1 I still had hard black carbon build up on the piston head. My friend thinks with the Belray I won't be seeing any more build up? Maybe it has something to do with flash point? which has me asking this - Could you tell me a little about the importance of the flash point? I see the flash point on the H1R is 395F while I looked up the flash point on the Stihl ultra syn 2 cyl - at 222 F. Quite the difference.
http://www.stihlusa.com/WebContent/CMSFileLibrary/MSDS/Stihl_HP_Ultra.pdf
--------------------------------------------------------------------------------------------------
Belray -
The flash point does have to do with combustion but there are more important properties that contribute to carbon buildup. The H1-R should give you a much cleaner burn and result in far less buildup than the Stihl oil. The biggest factor in this is the base fluid. Because H1-R is made with all ester base fluids it burns very cleanly. The residue left behind after burning this type of fluid is almost negligible when actually burned where petroleum and some other types of synthetic oils will leave carbon deposits and ash when burned.
The flash point has more to do with how quickly the oil is consumed by the combustion process and how it affects the octane rating of the fuel.
--------------------------------------------------------------------------------------------------
Redbull660 -
Very interesting!
ok so I gotta ask...how would a low flash point affect the octane rating vs a high flash point temp?
---------------------------------------------------------------------------------------------------
Belray -
If the flash point is too high and the oil is able to interrupt the gasoline's combustion, you can have decreased combustion efficiency due to a portion of it being less flammable. If you have a very low flash point it can result in increased combustion, but you are sacrificing lubrication by doing so since your lubricant is burning off before it even reaches the piston. There is a balance point that is necessary to not effect the combustion but still make the lubricant robust enough to reach the surfaces.
Due to one of the certifications our H1-R carries, which is specified for Kart racing, we have tested the effect of H1-R on the octane rating of gasoline. There are two different testing protocols called the motor octane number (MON) and the research octane number (RON). The MON for H1-R is 0.2 increase in 86 octane fuel and the research octane rating is a change of 0 in 96 octane fuel.
-------------------------------------------------------------------------------------------------
Redbull660
well that makes a lot of sense.
hmm. This seems obvious. But i'll ask anyway... Well...
could you talk about how the combustion would change if one went from H1R 92
eth free 32:1 to say 50:1 ? what are the basic things that would happen
if you did that?
---------------------------------------------------------------------------------------------
Belray -
Going from a leaner oil ratio to a richer oil mixture just increases the amount of oil you are pumping into the combustion chamber. If you are running too rich you have excess oil that will just come in and go right out in the exhaust. It might also lower the power in the engine by just bogging the piston down with excess oil. Going from 32:1 to 50:1 though would lean out your oil mixture. There is potential is that you could under-lubricate and engine that way, but since your engine originally calls for a 50:1 mix so you should not have any problem there. The harder and hotter you are running your engine, the more oil you want because you need to replenish oil that is being burned off.
For instance, in Kart racing, they are running at about 16000 - 20000 rpms at full throttle for a whole race, so they often mix between 16:1 to 32:1 to compensate for the high speed and heat. In moto trials, they are running very low rpms for only short bursts or idling, so they often will run between 80:1 to 100:1 so that they do not have excess oil building up in the cylinder at idle speeds.
The effect on the combustion going from 32:1 to 50:1 will not be very noticeable, you may see differences over time if you are tearing the engine down and inspecting the piston and cylinders, but the combustion itself will largely be unaffected by that change.
-------------------------------------------------------------------------------------------
Redbull660 -
sounds good. makes a lot of sense now. So the Stihl 661 runs at 13k-13.5k (max throttle) and max throttle is used for most cuts, but most cuts are
only running on avg. maybe 20-30 seconds long. Then back to idle. So based
on that what mix ratio would you think would likely work best? Curious to what you think.
But...thinking it might be interesting to both of us if I mix up some 32:1,
42:1 and 50:1. Time the cuts and take the jug temp ...see if there is a discernable difference?
--------------------------------------------------------------------------------------------------
Belray -
That is not a bad plan. I think you will end up at the 42:1 ratio in the end, but by all means, test and figure out what works best for your machine.
------------------------------------------------------------------------------------------------
Redbull660 -
So the flash point on the stihl synthetic 2 cyl mix is 222F and the H1R is
395F. The highest I've ever recorded a cyl temp with my friend's thermo
gun is around 345F Obviously it would be hotter inside the cylinder. I
contacted Stihl and they couldn't give me an exact # ...but said the
operating range is between 375-425 F measured at the sparkplug. Not sure how
they do that. Anyway...would that mean that the H1R isn't actually burning
at all?
-------------------------------------------------------------------------------------------------
Belray -
The flash point only refers to a single measurement point where the vapors reach a combustible limit under special circumstances. It is used as a reference for general safety of transport and gives a general idea of the volatility of oils. All oil will "burn" at just any temperature, the only difference is the rate and how completely it burns (residues left behind). The H1-R does burn over time, which is what you want or else your crankcase would just fill with oil and overflow into the cylinder. Your mix ratio is set so that you should be introducing fresh oil at an equivalent rate to the burn rate of the oil in the case and cylinder.
----------------------------------------------------------------------------------------------------
.png "Love :heart:")
oil threads
Everything is setup though. So hoping for tomorrow.
