M-Tronic/Autotune & Oil Ratio Change?

[Haironyourchest]

It has oft been stated that changing the oil mix ratio requires re-tuning the saw, as the increase in oil will displace a bit of gasoline and therefore technically lean the air-fule mixture. This I understand.

My question is twofold, really:

1. In a manual carb saw, will going from 50:1 to 40:1 really lean the air fule mixture to any noticeable degree?

2. Will an electronic carb be able to sense that the air file mixture has changed and compensate accordingly? If so, does the carb remember this setting, or does it work off a default 50:1 baseline and adjust on the fly, each time the saw is run?

Anyone who understands the true workings of these electronic carbs on here?

 

[stihl86]

The system can sense temperature and rpm. It works mostly off rpm.
Anything that alters the predetermined map, load and altitude mostly, will
effect a change in the amount of fuel the engine is fed.
Many times a second.
The carb is a very conventional carb. What’s different is a switch on the choke to tell the system the choke is on and a electronic solenoid that controls fuel metering.
What I can’t comprehend, no matter how much research I do or as many Stihl factory training
sessions I attend, is why people think more oil is better.
Do you over fill your car or truck too?

 

[ammoaddict]

That's a good question. I hope you get some expert answers. I switched from 50:1 to 45:1 in my standard carb saws. I didn't retune them. They seemed to run the same. I tune mine a hair on the rich side anyway.

Sent from my moto g(7) power using Tapatalk

 

[sean donato]

I run 40 to 1 in all my saws, my 562xp has never missed a beat on it. The auto tune /mtronic as I understand sends a lean pulse every once in a wile and sees how the rpm reacts, and adjusts the fuel mix accordingly. Truth be told 50 to 1 or 40 to 1 it's not that big of a difference. And the 50 to one is largely because of emissions. And I also fill my 460 Ford 1 quart over full, from recommended level. Still ticking at 195k miles....(not that I think the oil level has anything to do with that)

 

[rogue60]

What I can’t comprehend, no matter how much research I do or as many Stihl factory training
sessions I attend, is why people think more oil is better.
Do you over fill your car or truck too?

What you have said here makes absolutely no sense lol the over filling of a sump on a 4T as a comparison had me ROFL
All you have done is laid out on the table for all to see that you know nothing about oil and what it's role is in two strokes less is not more that's fact.
Maybe doing some actual research on 2T engines and the role of oil in said engine might help.

 

[stihl86]

What you have said here makes absolutely no sense lol the over filling of a sump on a 4T as a comparison had me ROFL
All you have done is laid out on the table for all to see that you know nothing about oil and what it's role is in two strokes less is not more that's fact.
Maybe doing some actual research on 2T engines and the role of oil in said engine might help.

Right. My post was in question form you ******* *****.
I made no statement at all, about being an oil expert. Or anything for that matter. And work on the language. We speak English here.

 

[Storm56]

I have been running 2 MS 261 Motronic saws @ 40:1 for about 5 years now with 0 issues. One is ported by Mastermind. It is the only mix I use. Both saws run like the day I got them, which is to say very good!

 

[outdoortype]

To the OP,
Yes a higher oil ratio does create a more lean condition. I don't know if going from 50:1 to 40:1 will require an adjustment unless your close to max rpms anyway. In my experience, I didn't notice much difference in the sound of the saw. Someone please correct me if I am wrong, but other countries use the same saws at recommended 40:1.
Stihl86,
People want the higher oil ratios than 50:1 because a lot of folks started out back in the day with 32:1. The fact that chainsaws run much higher rpms than our vehicles without fluid cooling and no dedicated crankcase oil- It's understandable .

 

[DND 9000]

stihl86 is a professional in a workshop, he knows this all.

 

[sean donato]

To the OP,
Yes a higher oil ratio does create a more lean condition. I don't know if going from 50:1 to 40:1 will require an adjustment unless your close to max rpms anyway. In my experience, I didn't notice much difference in the sound of the saw. Someone please correct me if I am wrong, but other countries use the same saws at recommended 40:1.
Stihl86,
People want the higher oil ratios than 50:1 because a lot of folks started out back in the day with 32:1. The fact that chainsaws run much higher rpms than our vehicles without fluid cooling and no dedicated crankcase oil- It's understandable .

I thought some of the euro saws still speks out to run 32 to 1? (In the uk, not the states)
And heck I still remember my pop mixing gas with straight 30 weight engine oil for his old mcculloch.

 

[Deleted member 117362]

Ran and run my 562xp el-46 ported, 550xp, 550xp mk2, 572xp all on 40:1 with no problems, carbed saws run on it also. Oil ratio threads crack me up, buy the oil you like, mix it how you like, ethanol or e-free, shake the can fill your saw and run it, it's all on you. If mine blows up, will blame it on manufacturer or neighbor, but in the end it's all on me.

 

[OM617YOTA]

I run 40:1 Trufuel. Somewhere one can of 50:1 Trufuel got grabbed. When I burned that one can of 50:1, it was enough different that I had to retune significantly richer.

I know that more oil in a given volume of fuel mix means less gasoline and in theory that means a leaner mix, so my leaner oil ratio should have meant more gasoline and made the saw run richer, but that's only if the oil isn't burning and contributing to the overall fuel volume. In this case it certainly was, and I had to go richer w/ 50:1.

 

[NeSurfcaster]

Too much oil in a truck/car engine can make the crank whip it into foam. Obviously oil doesn't lube to well when it's half air. I just got a 562xp and run 36:1 in all my saws. I also just had my 562 muffler gutted completely. I cut oak logs for a full tank, but right off the bat it was still 4 stroking doing the ear test before cutting. Also when lifting in a cut it would 4 stroke, so the auto tune adjusts pretty fast.

 

[stihl86]

stihl86 is a professional in a workshop, he knows this all.

Thank you for those kind words ( I think lol) But I have a brand new MS 261 CM in for warranty work on my bench. It has 1 hour on it. And it’s making me feel like the cave man felt when he first met fire. I thought I had a pretty good understanding of this mtronic system. Turns out I know 0
Going to try the newest of the new solenoid.
This one will be a pretty green.

 

[sean donato]

So you guys dont just swap a new carb in, just the solenoids?

 

[stihl86]

So you guys dont just swap a new carb in, just the solenoids?

The carbs are very similar to any other. The main reason the solenoid fail is 1) Design 2) Dirt.
They are on the third generation. so they are trying
If a mtronic starts but won’t idle, or won’t run in “Start”, it will start but not run, good chance it’s the solenoid
No need to replace the whole thing.
But only after your sure the power head is intact.
I’ve replaced them on 201t’s without hesitation when those symptoms appear with positive results.

 

[sean donato]

Ah ok good to know. Makes sense.

 

[stihl86]

To the OP,
Yes a higher oil ratio does create a more lean condition. I don't know if going from 50:1 to 40:1 will require an adjustment unless your close to max rpms anyway. In my experience, I didn't notice much difference in the sound of the saw. Someone please correct me if I am wrong, but other countries use the same saws at recommended 40:1.
Stihl86,
People want the higher oil ratios than 50:1 because a lot of folks started out back in the day with 32:1. The fact that chainsaws run much higher rpms than our vehicles without fluid cooling and no dedicated crankcase oil- It's understandable .

Yes. More oil = leaner running. That’s true. So add more oil to compensate for the added heat that you just created by adding more oil to better lubricate your saw.
Octane is much more critical to the health of a two cycle than 10% more/less oil.
Some on here sing the praises of 100-1. They must be stupid? Or are the 40-1 crowd? Are they wrong?
I don’t know and care even less.
My performance secret is a correctly sharpened chain.
Quality modern oils are more than capable of lubricating you saw at the recommended ratio.
So why not listen to the people who design and built the tool instead of being a closet scientist?

 

[outdoortype]

Yes. More oil = leaner running. That’s true. So add more oil to compensate for the added heat that you just created by adding more oil to better lubricate your saw.
Octane is much more critical to the health of a two cycle than 10% more/less oil.
Some on here sing the praises of 100-1. They must be stupid? Or are the 40-1 crowd? Are they wrong?
I don’t know and care even less.
My performance secret is a correctly sharpened chain.
Quality modern oils are more than capable of lubricating you saw at the recommended ratio.
So why not listen to the people who design and built the tool instead of being a closet scientist?

No one is being a closet scientist. Saws ran for years on specified 40:1, 32:1 ratios. When 50:1 became specified, most people associated that change was influenced by emissions standards. It's not unreasonable to assume that it's compromising the wear/longevity of the saw. In reality, 50:1 might have been acceptable all along. Before emissions standards changed, there was no need to test it.
How and why is octane so critical? Saws have low compression ratios and don't have the risk of detonation as much as other engines.

 

[echomeister]

I thought the issue with running lean was lack of oil in the cylinder with high speeds and light loads. Now I don't know anything but wouldn't more oil be ... more oil despite what it does to fuel ratio?