661 Oil Test 32:1 vs 40:1 vs 50:1 ?

[Trx250r180]

But it's not near that thick when thinned with gasoline. I would think the viscosity difference of pre-mix at various ratios would be nearly immeasurable. I could be wrong, but I can't see viscosity having anything to do with it. JUST MY OPINION. I believe it's because there's simply less fuel/volume.

Take a drink of a pepsi ,then take a drink of a milkshake out of the same straw ,now picture the straw as a jet ,the slower moving liquid will create a lean condition because it does not flow as fast so if that was your fuel ,less would be getting through ,does that make sense ? my atv engine builder told me this a long time ago for a comparison .

 

[mdavlee]

I can tune my 066 by ear and it will 4 stroke out of the wood @ 15,000
It makes its most power tuned to 13,200. I know this because this is where it holds the most RPM while cutting.

Anyone wanna guess how bad its blubbering at 13,200 ?

Can I, can I [emoji12]

 

[weedkilla]

Both the viscosity change and percentage of extra fuel when going from 32:1 to 50:1 are small. But either one or both factors is enough to need to adjust the tune on some saws.

 

[KG441c]

The smaller the saw and orfice the worse the effect

 

[Trx250r180]

Both the viscosity change and percentage of extra fuel when going from 32:1 to 50:1 are small. But either one or both factors is enough to need to adjust the tune on some saws.

I think 50 to 1 is 2.6 oz vs 4 oz at 32 to 1 for 1 gallon of gas that is enough to change tune to me ,some guys are just happy if it starts and cuts though

 

[bwalker]

But it's not near that thick when thinned with gasoline. I would think the viscosity difference of pre-mix at various ratios would be nearly immeasurable. I could be wrong, but I can't see viscosity having anything to do with it. JUST MY OPINION. I believe it's because there's simply less fuel/volume.

The mixture is made leaner by the extra oil displacing fuel. Very small effect.

 

[KG441c]

I think 50 to 1 is 2.6 oz vs 4 oz at 32 to 1 for 1 gallon of gas that is enough to change tune to me ,some guys are just happy if it starts and cuts though

Ya especially on smaller orfice and 1/8 to 1/16 of a turn is alot

 

[blsnelling]

I think it has more to do with oil having larger molecules affecting the flow than the actual viscosity difference itself. For the same reason, race gas typically runs much richer than pump gas.

 

[KG441c]

I think it has more to do with oil having larger molecules affecting the flow than the actual viscosity difference itself. For the same reason, race gas typically runs much richer than pump gas.

Yes. Thats what I had read before but couldnt remember it Brad. Ill look for the article though

 

[KG441c]

Also oil is a lubricant and although it burns its not fuel. If u add more oil means less fuel to burn per flow adjustment? Leans the engine until u increase the flow

 

[blsnelling]

Yes. Thats what I had read before but couldnt remember it Brad. Ill look for the article though

I just went looking to support or disprove my hypothesis.

In mineral based oil, molecule size and shape determine viscosity. The larger the molecule, the higher the viscosity.

However, in synthetic oil, the molecule size doesn't change.

Would this suggest that synthetic oil mix ratios should have less affect on tuning?

So on one hand we're arguing semantics. On the other hand, I prefer to think of reduced flow due to larger molecules, rather than being "thicker".

Here's a quote from another source.
"A typical example: you go from a 50:1 ratio to a 20:1 ratio. Your engine will now run leaner, and you’ll have to make jetting changes. You’ll need bigger (in number) jets because the oil molecules are thicker and the flow rate (the amount coming through the jet) is less."

 

[big t double]

Take a drink of a pepsi ,then take a drink of a milkshake out of the same straw ,now picture the straw as a jet ,the slower moving liquid will create a lean condition because it does not flow as fast so if that was your fuel ,less would be getting through ,does that make sense ? my atv engine builder told me this a long time ago for a comparison .

chocolate or vanilla? I like chocolate milkshakes best...plus, my milkshake brings all the boys to the yard...so, yea. church.

 

[KG441c]

I just went looking to support or disprove my hypothesis.

In mineral based oil, molecule size and shape determine viscosity. The larger the molecule, the higher the viscosity.

However, in synthetic oil, the molecule size doesn't change.

Would this suggest that synthetic oil mix ratios should have less affect on tuning?

So on one hand we're arguing semantics. On the other hand, I prefer to think of reduced flow due to larger molecules, rather than being "thicker".

Here's a quote from another source.
"A typical example: you go from a 50:1 ratio to a 20:1 ratio. Your engine will now run leaner, and you’ll have to make jetting changes. You’ll need bigger (in number) jets because the oil molecules are thicker and the flow rate (the amount coming through the jet) is less."

I agree with that reference. Probably why RB is seeing better results with 100% synthetic HP2

 

[KG441c]

Thicker or larger its still starving the engine of fuel if not adjusted though

 

[beaglebriar]

This thread makes my brain hurt. Excuse me while I go mix up some castor 927 and shoot myself.....

 

[nitehawk55]

"A typical example: you go from a 50:1 ratio to a 20:1 ratio. Your engine will now run leaner, and you’ll have to make jetting changes. You’ll need bigger (in number) jets because the oil molecules are thicker and the flow rate (the amount coming through the jet) is less."

^^ this right here , couldn't be plainer .

 

[KG441c]

"A typical example: you go from a 50:1 ratio to a 20:1 ratio. Your engine will now run leaner, and you’ll have to make jetting changes. You’ll need bigger (in number) jets because the oil molecules are thicker and the flow rate (the amount coming through the jet) is less."

^^ this right here , couldn't be plainer .

Pretty simple. Most guys think that just adding more oil they r protecting the engine more without make an adjustment though. Im not sure where the danger zone is if there is one but id say goin from 50to1 to 16to1 would deprive the engine pretty good if an adjustment isnt made for additional flow of fuel

 

[Trx250r180]

This thread makes my brain hurt. Excuse me while I go mix up some castor 927 and shoot myself.....

Castor in a saw ? Say it aint so .

 

[beaglebriar]

Castor in a saw ? Say it aint so .

Yeah....like it could never work right? Let's keep this pos thread rolling.......

 

[bwalker]

I just went looking to support or disprove my hypothesis.

In mineral based oil, molecule size and shape determine viscosity. The larger the molecule, the higher the viscosity.

However, in synthetic oil, the molecule size doesn't change.

Would this suggest that synthetic oil mix ratios should have less affect on tuning?

So on one hand we're arguing semantics. On the other hand, I prefer to think of reduced flow due to larger molecules, rather than being "thicker".

Here's a quote from another source.
"A typical example: you go from a 50:1 ratio to a 20:1 ratio. Your engine will now run leaner, and you’ll have to make jetting changes. You’ll need bigger (in number) jets because the oil molecules are thicker and the flow rate (the amount coming through the jet) is less."

Jets are a simple orifice. They meter based on volume of flow. More oil in the mix displaces fuel thus making the mixture run leaner.
I am not sure you could even measure the viscosity differance between 16 and 50:1.