Lower oil ratio's increase hp - tested with dyno

[mowoodchopper]

So the way the world spins has changed since 1978?

So they should not have corrected the A/F ratio?

So oil is not burnt?

:notrolls2:




Seems to me dirt bike racers and karters have a better handle on it than some posts here suggest!



Can we have a little higher level of output please - like say 40:1 :monkey:

Your on the right track! The super lean ratio = more power is BS. There is plenty of reading and more recent test with the new super oils like Amsoil that will got the same results. For the most part it comes down to anything leaner than 50-1 = more heat ,less lubrication, less ring seal, less power, more engine wear.

 

[BobL]

The mention of tuning hits close to the mark I think, but not as referenced. The increase in oil volume (lower ratio of mix) is reducing the volume of fuel getting to the chamber (increased A/F mix) so of course the jetting needs retuning to compensate...

Any further thoughts?

Not this old chestnut again.
This idea applies to older type saws that run below 25:1 mix ratios but had little relevance to modern saws that use 25:1 or higher ratios.

Changes in air pressure due to changes in weather are around 4%. This means that weather changes can vary the gas/air ratios by 4% and most saws are designed to accommodate this. On top of this the gas/air ratio that saws get is significantly altered by how clean the air filter is. Most saws will keep running (maybe not well but they will keep running) even with very dirty air filters further demonstrating the gas/air ratio (heading in the richer direction) does not make as significant a difference as one thinks.

Here's a table that shows the "Mix ratio", and then the "% of gas in the mix" in the middle column, and then the "change in the % of gas in the mix" from a 50:1 ratio.

Many people have a limited idea what lube/gas ratios mean. Then think if they change the mix ratio from 40:1 to 20:1 that they have substantially reduced the amount of gas in the mix where as it changes from 97.6 gas to 95.2% gas so the change is only 2.4% ie hardly anything and most saws will not notice this.

To change the gas/air ratio by more than 4%, for a given atmospheric pressure, the mix ratio needs to be changed over a range between 50:1 to 16:1 - see yellow colored entry in table.

Of course a saw is unlikely to accommodate i) changes wide in air pressure, ii) wide changes in mix ratio, and ii) changes in air filter cleanliness, but most should be able to cope with changes from 50:1 to 30:1 without any problems and certainly without changing jets.

If there are any issues it comes from going the other way.
If a saw is tuned with dirty filter, low mix ratios, and at low atmospheric pressure and the same saw;
- has it's air filter cleaned
- is fueled with a substantially higher mix ratio
- in higher atmospheric pressure clean
Then that is asking for trouble.

 

[Jonsered2095]

Hello,
Reread the article. The reason they chose castor over some other oil type is because it is flexible with is mix ratios. They mention that some of the other oils are limited to a certain ratio range. Granted modern oils are much improved but I think it still applies.

bullittman

My bet? Same test with new oils & current power plants? Same results with one exception. Less gooey unburned Castor Bean oil oosing out the exhaust port.

I think some still use Castor oil. Why don't they run 'super' synthetic? So I guess they think it still applies.

Hello,
I've re red the article and it does not specifically say why the heavier oil mix makes more power but I'd wager it is the result of better ring seal. That's all I can figure.

As far as exhaust smoke and cleanliness all of that is more a function of tuning than mix ratios. I used to work for a public municipality as seasonal help and part of my job duties was to keep the sidewalks clean. There were over 2 miles of side walk at least 8 feet wide that we cleaned twice a week in the summer. We used echo back pack blowers to do this. I mixed my own fuel with what ever cheap oil they bought. What ever it was was elcheapo petroleum that simply said to mix to manufactures instructions. I didn't trust the oil and in an effort to be socially unacceptable I mixed the oil heavy. I wanted a lot of smoke. The more the merrier. I don't care too much for tourist. I would keep the carbs tuned so the blower made good power. The result, no smoke, no dirty exhaust, nothing. I got to the point I was mixing at more than 8:1 in my quest for a smokey mess. The blowers never did protest. In the 6 years I worked there I was the only one that touched the blowers. They never even needed a spark plug, and I never did cause my smoke screen.

bullittman

Thats sounds on par with the article! Whatever your intentions Maybe Echo built in more tolerance :taped:

No they don't say... And yes I think the better sealing is a common reason.

Your on the right track! The super lean ratio = more power is BS. There is plenty of reading and more recent test with the new super oils like Amsoil that will got the same results. For the most part it comes down to anything leaner than 50-1 = more heat ,less lubrication, less ring seal, less power, more engine wear.

Yes! I think most would agree 50:1 is the least oil they would add; but its not proof of course just accepted wisdom (right or wrong).


Speaking of Amsoil; would you run this @ 100:1 in your favorite saw:

I'm sure its 'good' but would you (anybody?) I think it has more to do with (as eluded to by bullittman281) social and/or environmental acceptability.

Not this old chestnut again.
This idea applies to older type saws that run below 25:1 mix ratios but had little relevance to modern saws that use 25:1 or higher ratios.

Changes in air pressure due to changes in weather are around 4%. This means that weather changes can vary the gas/air ratios by 4% and most saws are designed to accommodate this. On top of this the gas/air ratio that saws get is significantly altered by how clean the air filter is. Most saws will keep running (maybe not well but they will keep running) even with very dirty air filters further demonstrating the gas/air ratio (heading in the richer direction) does not make as significant a difference as one thinks.

Here's a table that shows the "Mix ratio", and then the "% of gas in the mix" in the middle column, and then the "change in the % of gas in the mix" from a 50:1 ratio.

Many people have a limited idea what lube/gas ratios mean. Then think if they change the mix ratio from 40:1 to 20:1 that they have substantially reduced the amount of gas in the mix where as it changes from 97.6 gas to 95.2% gas so the change is only 2.4% ie hardly anything and most saws will not notice this.

To change the gas/air ratio by more than 4%, for a given atmospheric pressure, the mix ratio needs to be changed over a range between 50:1 to 16:1 - see yellow colored entry in table.

Of course a saw is unlikely to accommodate i) changes wide in air pressure, ii) wide changes in mix ratio, and ii) changes in air filter cleanliness, but most should be able to cope with changes from 50:1 to 30:1 without any problems and certainly without changing jets.

If there are any issues it comes from going the other way.
If a saw is tuned with dirty filter, low mix ratios, and at low atmospheric pressure and the same saw;
- has it's air filter cleaned
- is fueled with a substantially higher mix ratio
- in higher atmospheric pressure clean
Then that is asking for trouble.

Hi BobL, good info but wouldn't further calculations need to be addressed?

Like what is the change in actual fuel charge taking into account cfm etc?
What is the difference in calorific value of any two charges?
Does the interaction of different oil ratios change the dynamics, velocity, burn temp, or duration?
Timing is another issue. And yes of course the environment would have to be controlled.

0.4% change in fuel quantity (50:1 to 40:1) does not seem much but is it? A small change in VE makes a difference, a change in exhaust flow makes a difference.

 

[Jonsered2095]

I thought I missed a reply last night; damn multi quote.

Agreed that jetting needs to be adjusted. This results in more total mix getting into the cylinder, correct?

I believe so.

What I was trying to understand is why richer oil mix creates more power in that situation. The article didn't really get into that. Is it more cooling? Better ring seal resulting in higher compression?

Good question. No it didn't say.

Can 0.4% increase in fuel account for over 10% increase in hp on its own? I doubt it like BobL said but there is so much more going on; having said that my opinion is pure conjecture.

Seems like theres a trade off - potential for more power or running cooler vs. plug fouling & deposits forming (with today's oils)

Maybe. Lots of different grade oils using different detergents etc. As bullittman281 has re-emphasized; thats why they used Castor oil. Modern tests would have to identify all ingredients and know their individual limits. So I guess you couldn't just cast a blanket over all of them.

Seems like quite a few guys run 32:1 with no issues so I maintain that poor tuning could potentially cause more issues than different mix ratios.

I agree. Tuning first.

bullittman281 said he ran 8:1

 

[mowoodchopper]

Not this old chestnut again.
This idea applies to older type saws that run below 25:1 mix ratios but had little relevance to modern saws that use 25:1 or higher ratios.

Changes in air pressure due to changes in weather are around 4%. This means that weather changes can vary the gas/air ratios by 4% and most saws are designed to accommodate this. On top of this the gas/air ratio that saws get is significantly altered by how clean the air filter is. Most saws will keep running (maybe not well but they will keep running) even with very dirty air filters further demonstrating the gas/air ratio (heading in the richer direction) does not make as significant a difference as one thinks.

Here's a table that shows the "Mix ratio", and then the "% of gas in the mix" in the middle column, and then the "change in the % of gas in the mix" from a 50:1 ratio.

Many people have a limited idea what lube/gas ratios mean. Then think if they change the mix ratio from 40:1 to 20:1 that they have substantially reduced the amount of gas in the mix where as it changes from 97.6 gas to 95.2% gas so the change is only 2.4% ie hardly anything and most saws will not notice this.

To change the gas/air ratio by more than 4%, for a given atmospheric pressure, the mix ratio needs to be changed over a range between 50:1 to 16:1 - see yellow colored entry in table.

Of course a saw is unlikely to accommodate i) changes wide in air pressure, ii) wide changes in mix ratio, and ii) changes in air filter cleanliness, but most should be able to cope with changes from 50:1 to 30:1 without any problems and certainly without changing jets.

If there are any issues it comes from going the other way.
If a saw is tuned with dirty filter, low mix ratios, and at low atmospheric pressure and the same saw;
- has it's air filter cleaned
- is fueled with a substantially higher mix ratio
- in higher atmospheric pressure clean
Then that is asking for trouble.

:agree2: 100 %

 

[mowoodchopper]

Yes! I think most would agree 50:1 is the least oil they would add; but its not proof of course just accepted wisdom (right or wrong).tor oil. Why don't


Speaking of Amsoil; would you run this @ 100:1 in your favorite saw:

I'm sure its 'good' but would you (anybody?) I think it has more to do with (as eluded to by bullittman281) social and/or environmental acceptability.


I wouldnt run amsoil at 100:1 in anything period! I would run it at 40:1 though. MOWOOD

 

[Tzed250]

Unfortunately, I don't think that article pertains to our oil uses. I'd love to see an in depth scientific study done that does.

Say why Brad.

The bike is an air cooled two-stroke, and so is a chain saw.

Better pack a lunch if you are going to refute Jennings.


.

 

[BobL]

Hi BobL, good info but wouldn't further calculations need to be addressed?

Like what is the change in actual fuel charge taking into account cfm etc?
What is the difference in calorific value of any two charges?
Does the interaction of different oil ratios change the dynamics, velocity, burn temp, or duration?
Timing is another issue. And yes of course the environment would have to be controlled.

0.4% change in fuel quantity (50:1 to 40:1) does not seem much but is it? A small change in VE makes a difference, a change in exhaust flow makes a difference.

Yep all very good points and I agree my calcs are overly simplified.

But just getting back to the weather, which can have a ~4% difference - apart from racers, I'm not seeing anyone retuning for changes in the weather.

I also agree that varying oil/gas is different than changing mix to air ratios but todays lubes seem to cover for a multitude of problems over a very wide mix range, including reduced plug fouling, reduced smoking, better cooling, and better overall performance. What I see is people still using 25:1 because that's what dad used, which is quite unnecessary and all they really do is foul the air with more gunk.

For all practical purposes on more or less stock saws I can't see varying mix ratios using todays lubes making anywhere near the differences it did in the past. Even though I'm only a weekend warrior I work saws very hard (milling in big hardwood Aussie logs) I've used mix ratios ranging from 32:1 up to 50:1 (usually 40:1 for milling) without retuning and haven't worried at all about doing so.

If someone does some tests to demonstrate a significant difference using todays lubes I'm quite prepared to eat their smoke.

 

[Jonsered2095]

Yep all very good points and I agree my calcs are overly simplified.

But just getting back to the weather, which can have a ~4% difference - apart from racers, I'm not seeing anyone retuning for changes in the weather.

Apart from altitude, I agree. Practical use might not see many (or any) estimating the weather before they cut, although if you tune frequently (mix to mix, bar changes, or what your cutting) you may be inadvertently doing just that?

My point though was that the tests were controlled and without re-reading the article I think the increase in hp was significantly more than the weather you have said (14%??); that would be a 10% increase over any weather fluctuations.

I also agree that varying oil/gas is different than changing mix to air ratios but todays lubes seem to cover for a multitude of problems over a very wide mix range, including reduced plug fouling, reduced smoking, better cooling, and better overall performance. What I see is people still using 25:1 because that's what dad used, which is quite unnecessary and all they really do is foul the air with more gunk.

I agree with the first part. But what if more oil does increase performance?

For all practical purposes on more or less stock saws I can't see varying mix ratios using todays lubes making anywhere near the differences it did in the past. Even though I'm only a weekend warrior I work saws very hard (milling in big hardwood Aussie logs) I've used mix ratios ranging from 32:1 up to 50:1 (usually 40:1 for milling) without retuning and haven't worried at all about doing so.

If someone does some tests to demonstrate a significant difference using todays lubes I'm quite prepared to eat their smoke.

Yep we got some of that Aussie stuff here too.


Have you read http://www.arboristsite.com/showthread.php?t=6104

Dagger and bwalker trade several posts with some good info from post #41 on.

Thank you Fish!

 

[Denman123a]

More oil produced more horsepower: nobody (unless I missed it) mentioned that oil has more energy per volume than gas, so if the oil is burning at these temps then there's some of the increased HP. Also as mentioned above, more oil would give better sealing between piston and cylinder therefore higher compression. Just my $.02

 

[Terry Syd]

Mixture

Take a look at the piston crowns. The 15 to 1 piston is considerably darker than the other two. I expect that it was actually running a bit richer than the other two. The engine was on a dyno and heat builds up quick under that situation. A hot piston crown directly affects the fuel mixture below it.

The extra fuel would tend to cool the internals and allow a denser cylinder charge. More fuel mixture in the cylinder, more power.

The 30 to 1 showed scuffing, so there was obviously a friction component that has to be factored in. The more oil, the more lubrication - just like on a chain.

They were running a two ring piston. I doubt that the oil contributed very much to cylinder sealing at the higher rpms.

 

[Jonsered2095]

More oil produced more horsepower: nobody (unless I missed it) mentioned that oil has more energy per volume than gas, so if the oil is burning at these temps then there's some of the increased HP. Also as mentioned above, more oil would give better sealing between piston and cylinder therefore higher compression. Just my $.02

Everyone missed it.

So the way the world spins has changed since 1978?

So they should not have corrected the A/F ratio?

So oil is not burnt?

But at what point does the oil not burn (to the point of being a problem)?

Take a look at the piston crowns. The 15 to 1 piston is considerably darker than the other two. I expect that it was actually running a bit richer than the other two. The engine was on a dyno and heat builds up quick under that situation. A hot piston crown directly affects the fuel mixture below it.

The extra fuel would tend to cool the internals and allow a denser cylinder charge. More fuel mixture in the cylinder, more power.

The 30 to 1 showed scuffing, so there was obviously a friction component that has to be factored in. The more oil, the more lubrication - just like on a chain.

They were running a two ring piston. I doubt that the oil contributed very much to cylinder sealing at the higher rpms.

Why did they test @ 30:1 before 15:1

More oil also causes a longer burn duration I believe. Was timing adjusted accordingly? This could be the 'richer' mix you refer to.


Great couple of posts!

 

[mowoodchopper]

More oil produced more horsepower: nobody (unless I missed it) mentioned that oil has more energy per volume than gas, so if the oil is burning at these temps then there's some of the increased HP. Also as mentioned above, more oil would give better sealing between piston and cylinder therefore higher compression. Just my $.02

:bang: 100% correct , I have stated this a few times in the past. For the the most part people dont understand oil does make power not just lube. Just like most people dont understand diesel has more power per gallon in it than gas. As you keep refining oil down to diesel and then gas you lose power but gain clean burning quality's. If you can properly burn the less refined fuel , meaning diesel which is dirtier, more oil etc there is more power potential there. The more oil you can burn EFFECENTLY the more power you can produce , the key is you have to burn it all!

 

[Terry Syd]

Air/fuel

What limits power is how much air you can get in the engine. It is real easy to keep adding more fuel (whatever kind it is), but getting the air in to burn that fuel is the problem.

An air-cooled two-stroke can loose up to 20% of its power when it gets hot. That's why water-cooled two-strokes make more power. Another way to get liquid cooling is to fatten up the mixture and flush out some heat with the extra fuel.

The 15 to 1 mixture made more power, that means more heat and pressure in the combustion chamber. Yet, the piston crown shows less effect from the heat.

IMO, that engine was running a lot richer on the 15 to 1 mixture than the other mixtures. As a result the extra fuel was flushing a lot of heat out and allowing a more dense cylinder charging. The extra cylinder charging is what gave it the extra power.

What surprises me is that Gordon Jennings wrote the article.

 

[teacherman]

was he referring to astro glide?

You mean Ben Dover's research?

Oh, man. Good ol' Ben. He was in my class at the old JDC last year. Really was a distraction to the other boys.