stihl's mtronic

[tree monkey]

lets discuss how it works.

there are 2 sets of magnets on the flywheel.
there is a processor in the coil that does a few things.
it works as a tripper to collapse a magnetic field in the primary windings that produce a high voltage pulse to the spark plug. this has to happen at the right time.
it also send a signal to the carb to supply fuel.

lets look at the magnets on the flywheel. 2 sets, 180 degrees apart. one set has a poll arrangement north- south, the other set is south-north. the processor reads the magnetic fields. the system does not spark twice, or feed fuel twice per revolution of the flywheel.

the only information given to the processor is flywheel rpm. so it has to simple and "fixed",

ign timing is advanced at a "fixed" rpm somewhere between 5&7 thousand rpm. If I remember right.

I feel that the fuel delivery side of the processor is "fixed" as well. it delivers a "fixed" amount of fuel at a given rpm. it also floods the engine when it gets over a "fixed" rpm.

I don't see how the system can "learn" when the only info it is given is rpm.

 

[Chainsaw Jim]

So who's gonna be the hero who builds an app for programming carb chips?

 

[dall]

 

[Stackowood]

Does the M-tronic system read throttle opening and carb temp?

 

[tree monkey]

no, only rpm

 

[Dub11]

Ive have wondered about these systems my self you would thing at the very least they would need an O2 sensor in the exhaust to work.

 

[Moparmyway]

there are 2 sets of magnets on the flywheel.
there is a processor in the coil that does a few things.
it works as a tripper to collapse a magnetic field in the primary windings that produce a high voltage pulse to the spark plug. this has to happen at the right time.
it also send a signal to the carb to supply fuel.

lets look at the magnets on the flywheel. 2 sets, 180 degrees apart. one set has a poll arrangement north- south, the other set is south-north. the processor reads the magnetic fields. the system does not spark twice, or feed fuel twice per revolution of the flywheel.

the only information given to the processor is flywheel rpm. so it has to simple and "fixed",



I feel that the fuel delivery side of the processor is "fixed" as well. it delivers a "fixed" amount of fuel at a given rpm. it also floods the engine when it gets over a "fixed" rpm.

I don't see how the system can "learn" when the only info it is given is rpm.

You're not going to see how it learns if you believe that fuel is fixxed

What does the N/S magnet do ?
What does the S/N magnet do ?

 

[drf256]

no, only rpm

What do you mean by "Floods when it gets over a 'fixed' rpm"? Is that a limiting coil? Do they use the carb as an rpm limiter?

 

[drf256]

Flywheel magnet polarity is an interesting topic. I had an MS270 on my bench with no spark. After a lot of swapping and cussing, it finally came down to the flywheel magnets which certainly had magnetism but the polarity of one or both had switched, likely from a hit from the coil legs. I still have the bad flywheel here.

 

[Marshy]

Is there a throttle position sensor of any kind?

We can learn things about the processor and what's happening by understanding the error codes that the computer can generate... Might be worth looking into.

 

[Tbrown]

I feel that the fuel delivery side of the processor is "fixed" as well. it delivers a "fixed" amount of fuel at a given rpm. it also floods the engine when it gets over a "fixed" rpm.

I understood that at any given time in the cut it adds/pulls fuel to try to max rpm. These parameters are what are learned.

 

[jmssaws]

It can't be fixed or it could keep itself in tune.
It adjust for temperature and elevation and is limited by the coil and the carb.
Not spark limited I don't believe but fuel.

 

[jmssaws]

A fixed amount of fuel at say 12k wouldn't work once you knock a big hole in the muffler.
It would lean seize

 

[Moparmyway]

Ive have wondered about these systems my self you would thing at the very least they would need an O2 sensor in the exhaust to work.

My 2017 KX250F has 2 fuel injectors and the ECU has different maps for fuel and ignition............ no O2 sensor

 

[Moparmyway]

A fixed amount of fuel at say 12k wouldn't work once you knock a big hole in the muffler.
It would lean seize

It would also lean sieze when you run a long bar in a big cut, and/or it would be pig studdering rich in a small cut

 

[Tbrown]

It adjust for temperature and elevation and is limited by the coil and the carb.
Not spark limited I don't believe but fuel.

It only knows rpm, it adjust fuel to control rpm. It's that simple. Tuned for max rpm under a given load is an optimal tune.

 

[CR888]

A fixed amount of fuel at say 12k wouldn't work once you knock a big hole in the muffler.
It would lean seize

Would it not run richer due to the venturi effect from the carb? I thought the way carburetors worked was the more air that went through them the more fuel they drew. Am I missing something? Do you always need to richen a carb after a MM? I thought you'd perhaps need to lean it out.

 

[Mastermind]

I can readily admit that I have a lot yet to learn.

I'll be over here in my corner studying everything I can find on the subject.

 

[Dub11]

Maybe its Voodoo? Or magic

 

[Duane(Pa)]

Hear Yugo Boyz...