How does Auto-Tune or M-Tronic work?

[joecool85]

It's all in the coil and carb.

So it pulls power from the ignition coil?

 

[Chris-PA]

So it pulls power from the ignition coil?

More like the "ignition coil" is also a generator and control module for the carb. A big spinning magnet and coil of wire makes a generator.

 

[Stihlman441]

A few pics of the bits on a 241C

 

[Stihlman441]

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[hamish]

The software is the primary part, with the mapping being the key.

Think of your computer controlled auto trans in your truck..........just better to put er in drive and gas er, then think about too much.

Even if you work on the AT/MT saws regularily, the hardest part is still remembering it a simple chainsaw.

When the AT/MT system is not working right, its a good thing, for if it was an old school saw, in most hands it would be toasted.

When they come out with a version of the Autotune wife, i'm getting one.

 

[groundup]

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Great pics thanks for taking the time to capture them and provide something concrete to the thread.

 

[mweba]

Great pics thanks for taking the time to capture them and provide something concrete to the thread.

?

 

[hamish]

?

Perhaps it was like one of TK's replies,...........(joking Tom have a pint!)

If not, apart from the concrete coment as he is showing pics of a concrete saw, fuel injection has nothing to do with the AT system.
Stihl, well thanks for comming to the table, the little one over there, with the kids.

 

[LegDeLimber]

Can't wait to see what that high tech aftermarket solenoid core will cost.

Yes folks,
it's been lightened to improve throttle response times
and reduce thermal mass and turbo-cross drilled (copyright)
to expedite heat removal in the middle of the coil

act now and we'll include the patented reverberant swirly capillaries option
that gives a final extra super mixing action to the oil and gasoline!
It also provides turbulent liquid bearing action to reduce contact with the solenoid inner walls
Increasing their life by over 6 million cycles (on average, per independent lab tests)

All this and yet it still retains optimal magnetic hysteresis characteristics
(not to be confused with hysterical cow magnets on your fuel lines)
Which means it doesn't ruin your carefully built "F-you'll"(tm) mappings
(mappings, sold separately [sorry, DMCA requires that we sell them from Antigua] )

and don't forget to look in next year for the MARK III version.
Features are expected to include (patented) reverberant regenerative oscillation damping
in the MARK 111 solenoids to give an extra fuel boost carefully timed for
that "on the pipe" rpm zone that you'll want when running our HAWT PIPES!(tm)
tweaked to be twitchier than a mosquito on meth,
but good golly what a hit in the dyno!! when you're spooling in that power band
HAWT PIPES(tm) sold separately, see your local exclusive franchise owner for details today!

 

[sachsmo]

I know what it monitors and that it adjusts the carb, but how? Are there little screws and the computer activates servos to turn them? Some sort of fuel pump system and it adjusts the pressure? What's going on in there?

They are not voodoo like people think.

PID loops have been around for a long time, in fact they were developed for "auto pilot" on ships over a century ago.

Like said above there is very little going on since a saw is pretty simple. The engineers know where nominal is, and can set limits (high/low) to keep it in the ballpark.

To get best control of a loop, it needs to be tuned/programed right on the ragged edge of instability (tight upper and lower limits will keep it from going too far either way and becoming unstable)

No one will convince me they are true closed loop systems as there are simply too few inputs.

 

[sachsmo]

"so easy a caveman can do it"

http://www.cds.caltech.edu/~murray/books/AM05/pdf/am06-pid_16Sep06.pdf

 

[Chris-PA]

They are not voodoo like people think.

PID loops have been around for a long time, in fact they were developed for "auto pilot" on ships over a century ago.

Like said above there is very little going on since a saw is pretty simple. The engineers know where nominal is, and can set limits (high/low) to keep it in the ballpark.

To get best control of a loop, it needs to be tuned/programed right on the ragged edge of instability (tight upper and lower limits will keep it from going too far either way and becoming unstable)

No one will convince me they are true closed loop systems as there are simply too few inputs.

But a closed loop system requires only one input. The closed loop system in your car uses primarily one sensor (the upstream oxygen sensor), and all the other inputs serve to modify the response to that sensor or are used when the engine is running open loop.

Here, the carburetor is still a carburetor, so it is creating a mixture that it pretty close, and the AT system just has to tweak the mixture based on the lean out test.

No doubt the mixture could be made more accurate yet, but this is a good compromise that provides good mixture control (at WOT at least) with a minimum of mechanical complexity and weight. It is an elegant solution and the engineer in me approves. For the same reason I find Stihl's fuel injection system appalling. I don't like complexity for the sake of complexity.

 

[naturelover]

I guess my question is which way is Stihl planning on going with this?

I figure the FI system will perform as well as, or better than the MT system, but seems kind of odd to be coming out with new models of saws with M-Tronic, then FI on cut-offs. Seems like it would be most cost effective, and advantageous in other ways, to concentrate on one system.

Some have said that the FI system is the replacement for MT, but if that is the case, wonder why Stihl would go through all the trouble and costs for the 241 and 661, why not put the FI system on them?

Course maybe the 441C was the test base, and it performed better than they expected, but they already had the FI system ready to go? Is the FI system better with respect to emissions than the MT?

I guess it boils down to, does one wait for the 661C or the 661i....

 

[Chris-PA]

I guess my question is which way is Stihl planning on going with this?

I figure the FI system will perform as well as, or better than the MT system, but seems kind of odd to be coming out with new models of saws with M-Tronic, then FI on cut-offs. Seems like it would be most cost effective, and advantageous in other ways, to concentrate on one system.

Some have said that the FI system is the replacement for MT, but if that is the case, wonder why Stihl would go through all the trouble and costs for the 241 and 661, why not put the FI system on them?

Course maybe the 441C was the test base, and it performed better than they expected, but they already had the FI system ready to go? Is the FI system better with respect to emissions than the MT?

I guess it boils down to, does one wait for the 661C or the 661i....

My bet is they will drop the FI system. As far as I have been able to tell from the recent thread with pictures and the video, there is no input air sensor nor any means of feedback on it, except for probably something like the lean out test on AT/MT. What can it do that AT/MT cannot?

 

[sachsmo]

But a closed loop system requires only one input. The closed loop system in your car uses primarily one sensor (the upstream oxygen sensor), and all the other inputs serve to modify the response to that sensor or are used when the engine is running open loop.

Here, the carburetor is still a carburetor, so it is creating a mixture that it pretty close, and the AT system just has to tweak the mixture based on the lean out test.

No doubt the mixture could be made more accurate yet, but this is a good compromise that provides good mixture control (at WOT at least) with a minimum of mechanical complexity and weight. It is an elegant solution and the engineer in me approves. For the same reason I find Stihl's fuel injection system appalling. I don't like complexity for the sake of complexity.

The point is people think this system is much new technology. it has been around for decades, even a century.

Really, how much does the carburetor on a chainsaw do?

Like I've said in the past,

"it just enables the manufacturer to produce and sell 2 strokes within EPA specs" (for now)

Everyone knows "Lean is Mean"

 

[sachsmo]

The longevety of these saws is unproven.

The coatings on the cylinders these days are pretty stout, but the technology of the bearings has changed little. (perhaps less robust these days?)

Running these lean settings over time will tell. I aint' Miss Cleo, but would lay odds on some bottom issues rearing their ugly head in the future.

 

[XSKIER]

Yeah, I know...

View attachment 285127

 

[Mastermind]

Yeah, I know...

View attachment 285127

Hey that's my pic. It ain't from an autotune either.....

 

[XSKIER]

Yeah, I know...

 

[Jlhotstick3]

If these saws automatically compensate , could you mod the muffler and would it compensate for the differences in pressure?