Auto tune compensates for.....

[AKDoug]

All sorts of things involving running right, but if you don't have the latest software updates then you're up **** crick. Then Stihl Corp wants to be fuggin thugs and not allow other licensed saw shops to use their ipl's or software in an attempt to monopolize their brand.
Having to use a computer to work on a chainsaw makes me want to vomit my bones up, and I'm very computer literate.

Ok, rant over.

Every test that can be run with the computer can be done without the computer....for now.

 

[wde_1978]

I do not believe that a saw would run on bar oil. I call BS. It might run a minute while there was still gas in the carb system, but not indefinitely.

That's up to you if you believe it or not, but it's not BS. I was there and the saw ran on bar oil.

The carb switched from gasoline 2-stroke software to diesel 2-stroke software!
It arrested the ignition spark and raised compression, voila running perfectly fine.

 

[RIDE-RED 350r]

AT is more a product of environmental mandates than organic market demand, or coddling to the "lazy" as some seem to think. However, it is also touted as an improvement.. When you come out with something new, you are going to try and sell it... not tell your prospective customer that it's there because of EPA mandates on emission standards of your product line.

It has effected the snowmobile industry too..EPA mandates kept getting more and more stringent so you saw more and more 4-stroke sleds being produced..But Ski-Doo/Rotax came up with a 2-stroke direct injection system that meets the standards. It's all about EPA mandates on the product line folks.

 

[dogdad]

That's up to you if you believe it or not, but it's not BS. I was there and the saw ran on bar oil.

Looks like it's time for a repeat performance that is put on video...(?)

 

[Chris-PA]

AutoTune compensates for the lack of air corrector jets which are present in every other fixed jet carb. They couldn't figure out how to make an all position carb with air corrector jets, so they just got rid of them - which is why chainsaw carbs basically don't work. The result is a carb that cannot hold a constant fuel/air ratio as air velocity changes (like every other carb can), and pukes raw fuel out under almost every situation. It's gross.

Making a feedback carb that constantly adjusts is one way to address that problem, but there were other ways it could have been done. It should have been possible to make an all position CV carb , however it would have cost a few cents more and likely have been a little bigger. Also, it would have been difficult to tell people how to tune a saw without all the "4-stroking" blubbering and misfiring nonsense, and terminally rich WOT mixture. Although people manage with everything else.

 

[Termite]

It just so happens I ran our AT 550xp out of fuel today at work chasing down a tree that fell into one of our roads. I noticed that it quit with very little warning that it was running out of fuel. Not like older saws where you could see it coming and shut her down before it started wing-dingin. I revved it to make a cut and it quit almost instantly, out of the blue. I guess maybe the AT will compensate as the tank is getting down to the last little bit if fuel. Or maybe it was just a fluke.

I ran my 2253 dry yesterday and that is how it quit, just like ya turned the switch off.

 

[CascadeHusky]

The carb switched from gasoline 2-stroke software to diesel 2-stroke software!
It arrested the ignition spark and raised compression, voila running perfectly fine.

Its a common fallacy that you can simply expect the software to automatically run your saw on bar oil very well. It has to be taken to the dealer and programmed to arrest spark, also it intake/exhaust ports need some work for ideal duration.

Ideally you also move the handle heating element in the tank to thin your new fuel.

So while fergie is likely telling the truth about "his Buddy" running on bar oil, I highly doubt that saw could tow 4,000 lbs on a lewis winch and get 35mpg the way my properly-worked-over 562xp with the Detroit Diesel package can.

 

[Idahonative]

AutoTune compensates for the lack of air corrector jets which are present in every other fixed jet carb. They couldn't figure out how to make an all position carb with air corrector jets, so they just got rid of them - which is why chainsaw carbs basically don't work. The result is a carb that cannot hold a constant fuel/air ratio as air velocity changes (like every other carb can), and pukes raw fuel out under almost every situation. It's gross.

Making a feedback carb that constantly adjusts is one way to address that problem, but there were other ways it could have been done. It should have been possible to make an all position CV carb , however it would have cost a few cents more and likely have been a little bigger. Also, it would have been difficult to tell people how to tune a saw without all the "4-stroking" blubbering and misfiring nonsense, and terminally rich WOT mixture. Although people manage with everything else.

For the life of me, I just can't figure out how all my carb saws run so well. Maybe I just got lucky???

 

[CrufflerJJ]

For the life of me, I just can't figure out how all my carb saws run so well. Maybe I just got lucky???

You're probably running ethanol-free bar oil. Right?

 

[wde_1978]

I never adjusted my Dolmar PS-6400's carb till I got onto this site (2006. - 2014.) - that saw ran on a factory tuned carb throughout all weather conditions without any hiccups!
When I actually checked it with a tach the saw ran at a nice 13100rpm WOT, the coil is limited to 13500rpm.
This same saw is still my main go-to saw and it is running a carbon scored piston & piston ring for at least 14 months now - it puts out power to spare.

This site is making people worry about things that don't matter that much.
Then again, this site also offers a huge knowledge base about stuff that does matter!
One just needs to sort out one from the other.

 

[Jules083]

I never adjusted my Dolmar PS-6400's carb till I got onto this site (2006. - 2014.) - that saw ran on a factory tuned carb throughout all weather conditions without any hiccups!
When I actually checked it with a tach the saw ran at a nice 13100rpm WOT, the coil is limited to 13500rpm.
This same saw is still my main go-to saw and it is running a carbon scored piston & piston ring for at least 14 months now - it puts out power to spare.

This site is making people worry about things that don't matter that much.
Then again, this site also offers a huge knowledge base about stuff that does matter!
One just needs to sort out one from the other.

I was the same way. Bought my 55 Rancher in 2000, ran it up until whenever my join date is there and never touched the carb. Now it's muffler modded and tuned in a little better, and I've learned how to sharpen chain more better.


I think the auto-tune is a good thing. I can't think of anyone off the top of my head that knows how to 'correctly' tune a carb. Including my local Husqvarna dealer, and the local Stihl dealer. Not to mention box stores like Lowes and Tractor Supply, both of which sell saws.

I used to work at a Hardware store that sold Husqvarna in 2000-2002. Right when I bought my 55. The mechanic shop in the back didn't know how to tune carbs. When someone bought a new saw the store owners policy was that a 'mechanic' had to check the saw over, run it, and install the chain. They did not touch the carb, at all, ever. No tachometer in the shop that I know of. The mechanic would put the bar and chain on, run the saw to make sure it seemed ok, and send it out the door.

The Stihl dealer seems about the same. I have an 021, and I used to have no clue how to work on saws. It wouldn't run from sitting too long when I got it, I brought it to the dealer. They decided that it needed a new carb, after first trying to sell me a new saw because mine 'probably isn't worth fixing'. When I got the 021 back, $100 later, it still didn't run right. They told me that they don't know what is wrong but they put the new carb on and it still isn't right. I got on here, learned how to adjust a carb, and was cutting wood 20 minutes later.

 

[Chris-PA]

For the life of me, I just can't figure out how all my carb saws run so well. Maybe I just got lucky???

Congratulations, you can tune a saw. Me too. Your saws still misfire badly and puke raw fuel out the exhaust at almost every operating point (fuel that makes no power and that you breathe) - unless you have it set to perfect under max load, in which case that is the only point at which it is correct. It gets called "4-stroking" and such, but it's a misfire from an excessively rich mixture. People think nothing of adjusting the mixture of their saw by using a tach - essentially adjusting the point where the fuel mixture is so rich the saw cannot rev any higher.

It's not like setting the mixture on some cheap lawn mower carb, where it will mostly hold a constant F/A mixture as rpm changes. Here the F/A mixture is a curve that changes massively with rpm (and everything else). You can set it at a point, but it will be wrong everywhere else. They all dump raw fuel out the exhaust because they are designed to, and you cannot correct that by turning the screws - it's not a matter of tuning skill, it's just how they work.

And AT is a carb, a very simple one pretty much the same as they've always been. It just has a small microcontroller adjusting the mixture more-or-less continually, or at least as often as possible.

 

[Idahonative]

Congratulations, you can tune a saw. Me too. Your saws still misfire badly and puke raw fuel out the exhaust at almost every operating point (fuel that makes no power and that you breathe) - unless you have it set to perfect under max load, in which case that is the only point at which it is correct. It gets called "4-stroking" and such, but it's a misfire from an excessively rich mixture. People think nothing of adjusting the mixture of their saw by using a tach - essentially adjusting the point where the fuel mixture is so rich the saw cannot rev any higher.

It's not like setting the mixture on some cheap lawn mower carb, where it will mostly hold a constant F/A mixture as rpm changes. Here the F/A mixture is a curve that changes massively with rpm (and everything else). You can set it at a point, but it will be wrong everywhere else. They all dump raw fuel out the exhaust because they are designed to, and you cannot correct that by turning the screws - it's not a matter of tuning skill, it's just how they work.

And AT is a carb, a very simple one pretty much the same as they've always been. It just has a small microcontroller adjusting the mixture more-or-less continually, or at least as often as possible.

Yep, carb saws "puke raw fuel" all over the place...it's "gross"...hahaha. I'm throwing all my saws in the dumpster and I suggest everyone else do the same. They are disgusting, man and earth killing machines. It sounds like all two-stroke machines are dangerous and I'm not sure why you'd want to own one. I will say one thing Chris, you sure do tickle my funny bone.

"People think nothing of adjusting the mixture of their saw by using a tach - essentially adjusting the point where the fuel mixture is so rich the saw cannot rev any higher."

This statement makes me question whether you even understand saw carbs. "So rich the saw cannot rev any higher"? I think you've got that backwards. If the saw is that rich, it will be on the low end of the rpms.

 

[Idahonative]

I think the auto-tune is a good thing. I can't think of anyone off the top of my head that knows how to 'correctly' tune a carb. Including my local Husqvarna dealer, and the local Stihl dealer. Not to mention box stores like Lowes and Tractor Supply, both of which sell saws.

I'm gonna give you a heads up...there will be ALOT of guys, rolling on the ground laughing, when they read this.

 

[pro94lt]

The autotune and mtronic really shine for me, let me explain my daily operations. I own a tree service have a dozen saws in the truck ranging from a ms150t 200t ms241 346xp 543xp 550xp 562xp 357xp 2 372xps 390xp and a 395xp when I get done today the temp will be mid 70s Monday morning high 20s so tuning all them carbs will probably need to be done except on the autotune... Saves me a lot of time

 

[CascadeHusky]

Yep, carb saws "puke raw fuel" all over the place...it's "gross"...hahaha. I'm throwing all my saws in the dumpster and I suggest everyone else do the same. They are disgusting, man and earth killing machines. It sounds like all two-stroke machines are dangerous and I'm not sure why you'd want to own one. I will say one thing Chris, you sure do tickle my funny bone.

"People think nothing of adjusting the mixture of their saw by using a tach - essentially adjusting the point where the fuel mixture is so rich the saw cannot rev any higher."

This statement makes me question whether you even understand saw carbs. "So rich the saw cannot rev any higher"? I think you've got that backwards. If the saw is that rich, it will be on the low end of the rpms.

Its Christmas, be nice, no one is going to throw anything away around here.

What he means, and you know it, is "as many revs as possible without the possibility of a lean condition (what a bit of 4 stroking indicates you don't have)

Its no secret that a 4-stroke engine is more fuel-efficient than a two-stroke, while a two stroke has a better power to weight ratio.

If you think that when exhaust gas leaves the cylinder it isn't taking some intake out with it(raw fuel) you have a lack of understanding how these engines work. Minimizing this wasted fuel is to the advantage of the user, independent of the EPA.

Now, when you question "is it worth it to have a saw with a feature I can't troubleshoot and costs more initially as well?", I can understand that line of thinking.

I sure don't like knowing that if I have an auto-tune problem I am dependent on a dealer.

 

[Chris-PA]

Yep, carb saws "puke raw fuel" all over the place...it's "gross"...hahaha. I'm throwing all my saws in the dumpster and I suggest everyone else do the same. They are disgusting, man and earth killing machines. It sounds like all two-stroke machines are dangerous and I'm not sure why you'd want to own one. I will say one thing Chris, you sure do tickle my funny bone.

"People think nothing of adjusting the mixture of their saw by using a tach - essentially adjusting the point where the fuel mixture is so rich the saw cannot rev any higher."

This statement makes me question whether you even understand saw carbs. "So rich the saw cannot rev any higher"? I think you've got that backwards. If the saw is that rich, it will be on the low end of the rpms.

Your hysterical response is typical and why I rarely post here any more. You failed to address anything I wrote, other than one demonstration that you have no understanding of how the carbs work (my quoted statement was correct), and jumped directly to irrelevant straw-man nonsense. If you don't need your saws then throw them away - I need to cut wood so I must use them even though they do indeed emit a large amount of unburned fuel out the exhaust (I cannot afford an AT saw yet).

Can you give any explanation of how carbs work, or the phenomena of "4-stroking" and setting the mixture via WOT rpm that does not involve producing excessively rich fuel mixtures? Can you provide any references that show breathing gasoline vapors is not bad for your health?

For others who might be interested in (and capable of) understanding how it works: At wide open throttle the air velocity through the carb venturi is mostly proportional to rpm. Even if you set the H screw for a perfect mixture under load in the cut, if the rpm goes up the mixture gets very rich very fast. Only a minor lift/rpm increase causes a massive misfire ("4-stroking"). At some greater rpm the mixture becomes so rich the rpm will not increase any higher - it is effectively a rich mixture governor.

The relationship between the fuel mixture at that high rpm and under load in the cut is not linear, but it is at least consistent/repeatable. The factory works out the correct mixture under load and then measures the WOT no load rpm. If the saw has not been modified, then they can tell you to set the WOT no load rpm to that same value (by changing the H mixture screw), and then it will also be correct under load in the cut. There is no other purpose/meaning to the WOT no load rpm (it tells you almost nothing about power or performance under load), and if you've modified the saw in any way then it is meaningless.