Mastermind Revisits The MS261CM Type II

[Redbull661]

Thats incredible, thank you!

 

[wcorey]

Uh oh, dissent among the dividers.

Hope this isn't the start of the next popup wars...

 

[wcorey]

Does the carb divider have a shape or inclination, such like an aircraft wing, that would induce lower pressure on one side?

 

[Lightning Performance]

View attachment 90034

View attachment 90035

complete m-tronic system, can someone please show me all of the sensors

That black box on the bottom right is a super special mass air-flow sensor works off of "blow by" and is a dehumidifier and map sensor, "secret special" it needs no impulse hose or vacuum and it has a built in barometer and air density sensor plus it's a coil with a rev limiter plus timing retard, amazing I know. Your welcome

Questions?

 

[JMoney]

Just a couple amateurish questions that might help understand how m-tronic is working.

Would retarding the timing at WOT increase tolerance for an otherwise too lean condition at maximum RPM?

Is it possible that maximum RPM is not too lean for a computer that can react in a split second, and we don't tune to maximum RPM so that the motor doesn't suddenly become too lean if something changes?

 

[retro]

View attachment 90034

View attachment 90035

complete m-tronic system, can someone please show me all of the sensors

No sensors. One switch on the choke lever. Technically, you might label the two pole legs on the ignition coil and the rotating flywheel magnets as being a sensor, since those are all that is necessary for it to function.

It works by monitoring RPMs in real time... while it rapidly alters the ignition timing to provide an optimal RPM for each lean or rich mixture adjustment decision that it makes.

The algorithm provides 3 branch conditions (retard, advance, optimal) for the timing, and 3 branch conditions (lean, rich, optimal) for the fuel mixture. It seeks optimum WOT RPMs at all times and once found, maintains those optimums.

It "hunts" for optimal timing constantly, since timing affects engine speed immediately. Mixture alterations do not affect RPMs immediately (it takes a much longer time for air/fuel density changes to pass completely through the motor), so there is a brief delay programmed into the 3 mixture branches to allow for that.

While in operation, it "remembers" (due to the logic and path constraints inherent to the design of the algorithm) each lean/advance, lean/retard, rich/advance, rich/retard condition combination that it attempts, so that it ultimately knows whether advancing (or retarding) the timing might help or hurt optimal RPMs for each mixture condition that it attempts. In other words, it learns from its mistakes... in just miliseconds.

It saves the last known optimum settings for both timing and mixture on engine shutdown. When the engine is restarted, it bootstraps using those same last known optimal settings and begins to alter mixture and timing again, providing an optimum idle speed warmup mixture and WOT loaded operation.

It is very basic and simple... and very cheap. Yet is ingeniously designed and implemented IMHO.

 

[retro]

Just a couple amateurish questions that might help understand how m-tronic is working.

Would retarding the timing at WOT increase tolerance for an otherwise too lean condition at maximum RPM?

Is it possible that maximum RPM is not too lean for a computer that can react in a split second, and we don't tune to maximum RPM so that the motor doesn't suddenly become too lean if something changes?

No question is ever amateurish.

If a person manually adjusts the ignition timing by filing the key on the flywheel, the system will still seek to adjust (it will remain on the appropriate branch condition in the algorithm until it finds/overshoots optimum) the timing for optimum idle RPM and WOT RPM. And it will find optimum timing very quickly once it completes a relearning cycle. In other words, as long as the timing is not altered beyond the range that the coil legs spacing and flywheels magnets spacing provides, the system will correct for what that person has attempted to do.

Maximum RPM can not ever occur on an M-Tronic controlled engine while it is running lean. Can't happen while its running too rich either. Max RPMs occur in an engine only while the fuel mixture is stoichiometric AND while the ignition timing is optimal to attain max RPM.

If something happens to the motor causing it to lean out (monkey snot/banana peel patch falls off from a chewed carb boot?) suddenly, the system immediately retards the timing and keeps adjusting toward a corrected fuel/air ratio until it runs out of adjustment range. It either corrects the lean (or rich if its flooding with fuel) problem immediately or the motor slows and barely runs... or has stopped already due to retarded timing.

Only my answers are amateurish, no worries.

 

[retro]

Does the carb divider have a shape or inclination, such like an aircraft wing, that would induce lower pressure on one side?

The venturi provides for the pressure/velocity differentials in the carb. Other than splitting the incoming volume of air into two columns, the divider has very little influence on that.

 

[CR888]

Threads like this are kinda good for those who fear the 'computer saw' and refuse ownership of them. Once they see how few working parts are involved and how it works in easy to understand words it can be reassuring to folks. What will be driving us around soon with driverless car tech is truly complex and amazing.

 

[weedkilla]

After 13 pages how is the biggest mystery the internal workings of mtronic and no one has asked how come Mike - after years of telling us that the lightest saw you'd ever need is a 10mm 044 (or maybe a 362) - has bought a 261.

 

[Ronaldo]

how it works in easy to understand words

I am still waiting for this.

 

[breese]

I have been reading all the documentation I can find on this including the patent info.
From what I see, there must be some type of ECM / Chip within the casting of the coil.
I would like the part # and possible costs for this coil.
Being a long time hacker, I would love to Dig into this coil and see what is going on.

From the patent info, this is all the hardware locations associated to this and its notable that there are more than 2 Possible Solenoid locations.

 

[Mastermind]

Uh oh, dissent among the dividers.

Hope this isn't the start of the next popup wars...

No worries Bill.

I think we are all way past having a "war" over how we build a saw.

Many ways to skin a cat.....and they all end up with a skinned cat.

After 13 pages how is the biggest mystery the internal workings of mtronic and no one has asked how come Mike - after years of telling us that the lightest saw you'd ever need is a 10mm 044 (or maybe a 362) - has bought a 261.

I never judge, I just enable.

 

[Mastermind]

@retro

Thanks for breaking that down for us. You made it very easy to digest.

 

[blsnelling]

No worries Bill.

I think we are all way past having a "war" over how we build a saw.

Many ways to skin a cat.....and they all end up with a skinned cat.




I never judge, I just enable.

 

[Mastermind]

No worries Bill.

I think we are all way past having a "war" over how we build a saw.

Many ways to skin a cat.....and they all end up with a skinned cat.




I never judge, I just enable.

I've been using a popup in a couple models too....

Hahaha

 

[MustangMike]

After 13 pages how is the biggest mystery the internal workings of mtronic and no one has asked how come Mike - after years of telling us that the lightest saw you'd ever need is a 10mm 044 (or maybe a 362) - has bought a 261.

I believe you are mis quoting me, and have not been following recently.

If you can only take one saw with you, the 60 + 70 cc saws are the most versatile and can do anything, I will stand by that. My 60 + 70 cc saws are my work horses and get the most usage.

However, have you not been hearing my comments about my MOFO 026 Lightning Limber??? Love that little saw for the limbing duties, and now it will have a "partner in crime". The small saws are also more convenient to take along on the ATV. Was considering getting a 241, but when Stihl made the Ver II 261 lighter, I decided to go with that. A lot more grunt for a little extra weight.

I have been re arranging my saw portfolio, in an attempt to have 2 saws in each size from 50 to 90 cc (I count the 77 cc saws as 80 cc). I like to have a back up for every saw in case I rock a chain, etc. I currently have 3 066/660s, but one of them is spoken for. Since I have the 90 cc saws for milling, I sold two ported 77 cc saws (still have 2).

 

[T.Roller]

I've been using a popup in a couple models too....

Hahaha

And that is @blsnelling fault for sure

 

[Mastermind]

And that is @blsnelling fault for sure

That damn Brad.....

 

[T.Roller]

That damn Brad.....

Bastard