Two stroke fuel ratios

[MacAttack]

I get a headache thinking about this ****. I've run Amsoil Saber at 100:1 in customer's and my own saws, trimmers, blowers, and my paramotor for many, many years without ANY oil-related failures. I've seen nothing but benefits. Less mess coming out the exhaust, and less carbon to scrape off pistons and exhaust ports ... oh, and damned near ZERO wear under some very harsh conditions.

Everyone else can do what they feel is right. UNDISPUTED FACT: anything that is not fuel, displaces fuel. AIR displaces fuel. OIL displaces fuel. Moisture / humidity displaces fuel. If this were not true, then fuel screw tweaks would never be needed when ANY of these change.

Flame away!


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Yeah this subject has been absolutely beaten to death and really doesn't change people's minds too much.

I have to ask this though... if we are tuning saws to a fuel / air ratio (undisputed?)... how is oil not considered fuel in that equation? It combusts in the combustion chamber and in doing so uses oxygen, doesn't it?

That's my issue, and why I'm stuck in my ways.

Also... you're likely going to be verbally assaulted for the 100:1 mix comment, haha.

 

[MacAttack]

Looks like air fuel gauges are 35 bucks on eBay. The O2 sensor would have to be mounted on a pipe on the saw and powered by an outside power source.

Hmm.

Is this the one you found??

GoolRC Digital Air Fuel Ratio Gauge Kit 12V 2 in 1 Meter 52MM Narrowband Car Volmeter with O2 Oxygen Sensor Car Modification Acces White cover https://a.co/d/4ha1la2

Man.... I am so tempted....

I don't know anything about O2 sensors though to know if this would work on a chainsaw?

 

[Smitty Smithsonite]

Yeah this subject has been absolutely beaten to death and really doesn't change people's minds too much.

I have to ask this though... if we are tuning saws to a fuel / air ratio (undisputed?)... how is oil not considered fuel in that equation? It combusts in the combustion chamber and in doing so uses oxygen, doesn't it?

That's my issue, and why I'm stuck in my ways.

Also... you're likely going to be verbally assaulted for the 100:1 mix comment, haha.

Oil is nowhere near as flammable as gasoline. It's not going to burn nearly as good, or as completely, as gas. But, you've got to think about it BEFORE it burns, because that's where the fuel metering is. Oil is in the fuel, displacing said fuel, as it passes through the carburetor.

 

[huskihl]

Yeah this subject has been absolutely beaten to death and really doesn't change people's minds too much.

I have to ask this though... if we are tuning saws to a fuel / air ratio (undisputed?)... how is oil not considered fuel in that equation? It combusts in the combustion chamber and in doing so uses oxygen, doesn't it?

That's my issue, and why I'm stuck in my ways.

Also... you're likely going to be verbally assaulted for the 100:1 mix comment, haha.

I believe your thinking is correct, and if oil required the exact same amount of air as the fuel required for proper combustion, we may not need to retune.

 

[MacAttack]

Oil is nowhere near as flammable as gasoline. It's not going to burn nearly as good, or as completely, as gas. But, you've got to think about it BEFORE it burns, because that's where the fuel metering is. Oil is in the fuel, displacing said fuel, as it passes through the carburetor.

So the one argument that does make some sense to me is what you said about passing through the metering passages, it's reasonable that a higher oil ratio means higher viscosity and less fuel is drawn in.
But how much of a factor is that?? I have no idea... maybe significant? Maybe not?
Oil is less flammable definitely, but in the fuel / air equation it is still part of the fuel, it consumes oxygen, even if it burns poorly and slowly, which is exactly why a heavy oil ratio results in a saw etc that runs pig-rich, smokey and lazy. (personal experience... Not a lab experiment)
I need to go to bed haha....

 

[MacAttack]

I believe your thinking is correct, and if oil required the exact same amount of air as the fuel required for proper combustion, we may not need to retune.

I promised myself I wouldn't start debating this topic but here we are... haha.
We need that oxygen sensor test!
I've never had to retune for different ratios, I'm running a string trimmer with a fixed main jet at 32:1 when it calls for 50:1, no change in performance or 4-stroking that I can detect...

 

[MacAttack]

One last thing... if I don't wake up to a detailed and extensive retort from bwalker deconstructing my arguments, I will be very disappointed.

Peace out guys.

 

[muddy42]

These threads just keep on going! I've never seen a proper test where the carb is retuned between changing fuel mix. Everything else is just "I do XYZ and it works for me." What do I do? I am a huge fan of oil - I oil tools, I have the bar oil turned up to max, I replace 4 stroke oil every year, always over-oil everything. So I always mix 40:1 in small batches - using alkylate in the chainsaws, because I have a few and they might sit for a while and with fresh pump fuel in the strimmer/weed wacker, because it gets used so much for three months of the year. I do pay attention to engine note and retune the H whenever I have any concerns, RPMs kept rich and well below max.

 

[Lil'Skeet]

So is it reasonable to conclude that a given amount of oil actually requires more oxygen molecules to be combusted than the equivalent amount of gasoline? (you can see where I'm going with this...)

More heat|combustion would need more air to burn properly. Do optimal air|fuel ratios apply to 2cycles?
I'm not arguing over needing carb adjustments, just the fact that oil does burn hotter than gas. I'll link a video where a guy compares 25:1 to 50:1 and measures exhaust and head temps. I do not believe he made carb adjustments though. I don't know why. I don't think it sounded like he was running lean with the 25:1. Been a while since I've seen it but I'll watch it again at lunch.

 

[bucketofguts]

I would think the new fuel injected saws would have an O2 sensor. I have not seen many gauge clusters on chainsaws. But you could run a tach an O2 sensor, and a temp gauge Might help the people with hearing loss keep it in the green.

 

[OM617YOTA]

Is this the one you found??

GoolRC Digital Air Fuel Ratio Gauge Kit 12V 2 in 1 Meter 52MM Narrowband Car Volmeter with O2 Oxygen Sensor Car Modification Acces White cover https://a.co/d/4ha1la2

Man.... I am so tempted....

I don't know anything about O2 sensors though to know if this would work on a chainsaw?

Yep something like that. A pipe would have to be fabbed up to attach to a saw and mount the O2 sensor, a power supply for the electronics figured out, the system powered and the saw run for awhile to get the O2 sensor up to temp and able to sense, and then test cuts and readings made, then re-done for every fuel type and tune.

Quite a bit of hassle, but if an established forum member wants to do this, document their results, maybe put together a video, I'll buy the sensor and have it sent to them.

@Vintage Engine Repairs Is who came to my mind, let me know if you're interested. Also wouldn't blame you for not wanting to wade into this mess at all.

Also open to others.

 

[Vintage Engine Repairs]

Yep something like that. A pipe would have to be fabbed up to attach to a saw and mount the O2 sensor, a power supply for the electronics figured out, the system powered and the saw run for awhile to get the O2 sensor up to temp and able to sense, and then test cuts and readings made, then re-done for every fuel type and tune.

Quite a bit of hassle, but if an established forum member wants to do this, document their results, maybe put together a video, I'll buy the sensor and have it sent to them.

@Vintage Engine Repairs Is who came to my mind, let me know if you're interested. Also wouldn't blame you for not wanting to wade into this mess at all.

Also open to others.

Sorry mate I don’t get what test you are hoping for? If more oil makes an engine go lean? I think a constant load engine would be better than a saw to test this, for example a leaf blower. The load will never change and will make the process easier and more accurate. A chain will dull, knots in the wood will load the saw up more etc. It will be hard to get anything consistent with a saw.

 

[OM617YOTA]

Sorry mate I don’t get what test you are hoping for? If more oil makes an engine go lean? I think a constant load engine would be better than a saw to test this, for example a leaf blower. The load will never change and will make the process easier and more accurate. A chain will dull, knots in the wood will load the saw up more etc. It will be hard to get anything consistent with a saw.

I envisioned running the saw on the standard fuel, getting readings, then changing the oil ratio, NOT retuning, running the saw, and seeing how the readings change. Then tune to the new oil ratio, run the saw, get readings, and see how the readings on changed oil ratio + tuned for the new ratio compare to tuning for the previous oil ratio. Or maybe no difference at all?

I was thinking saw, because that's what we're discussing and using, but your thoughts on the blower for constant load are good too. Just something that can be tuned manually, and specifically not M-tronic or EFI, so the person doing the testing has control of the test parameters.

 

[Vintage Engine Repairs]

I envisioned running the saw on the standard fuel, getting readings, then changing the oil ratio, NOT retuning, running the saw, and seeing how the readings change. Then tune to the new oil ratio, run the saw, get readings, and see how the readings on changed oil ratio + tuned for the new ratio compare to tuning for the previous oil ratio. Or maybe no difference at all?

I was thinking saw, because that's what we're discussing and using, but your thoughts on the blower for constant load are good too. Just something that can be tuned manually, and specifically not M-tronic or EFI, so the person doing the testing has control of the test parameters.

This is about as good as I could do. Not sure if it really answers any of your questions, but I found oil ratio didn’t much much if any difference

 

[OM617YOTA]

I saw that when you did it, and it didn't answer any of my questions. That is why I thought of you for this test, though.

 

[Vintage Engine Repairs]

I saw that when you did it, and it didn't answer any of my questions. That is why I thought of you for this test, though.

No worries, it would be a cool test! Though I’ll let someone else take it on. Thanks for the offer though

 

[MacAttack]

I envisioned running the saw on the standard fuel, getting readings, then changing the oil ratio, NOT retuning, running the saw, and seeing how the readings change. Then tune to the new oil ratio, run the saw, get readings, and see how the readings on changed oil ratio + tuned for the new ratio compare to tuning for the previous oil ratio. Or maybe no difference at all?

I was thinking saw, because that's what we're discussing and using, but your thoughts on the blower for constant load are good too. Just something that can be tuned manually, and specifically not M-tronic or EFI, so the person doing the testing has control of the test parameters.

What if I got my hands on a spare muffler from a junk Poulan 4218, attached the sensor into the body of the muffler with a 12v battery and made a series of cuts in a large log?

Do you think a saw's exhaust would be within the heat and oxygen levels that the sensor would work?

 

[OM617YOTA]

Four wire O2 sensors are electrically heated, so in theory it would be fine temperature wise, even after a relatively short period running. Not sure if the electrically heated sensors get hot enough on their own to sense on electricity alone, or if the electric heat just shortens the time it takes to heat up. Might take some run time to get readings. Our saws definitely get hot enough, the rest I don't know. A wideband O2 sensor might be a good idea.

 

[Lil'Skeet]

The burnt and unburnt oil is going to be hell on the O2 sensor, but will work for what we are trying to find.

 

[Lil'Skeet]

Here is the link to the guys 25:1 vs 50:1 temperature test.