stihl's mtronic

[mdavlee]

Yeah......I tried that too. lol

Going to have to have some fooling in the pickup sensor to trick it to let it turn more rpm.

 

[Duane(Pa)]

Yeah......I tried that too. lol

Randy, you have been all through these things; there simply isn't any TPS, temp sensor, map sensor etc. Right?

 

[longbowch]

What then is the difference between M-tronics and Autotune? I have both and the Stihl seems to adjust better.

 

[Stackowood]

From the tech manual:

"By monitoring of the engine temperature and speed, the control unit continually checks the operating state of the chain saw..." "The microprocessor detects that the micro switch has been actuated and thus the choke shutter is
closed and computes the necessary amount of fuel and the ignition timing for the start."


So it looks like there is a temp sensor, but no throttle position sensor other than the micro switch that closes when the lever is in the start position.

Autotune senses carb temp, RPM, and throttle position, but my limited use of M-tronic (MS261C-M) says that M-tronic works better on start-up and acceleration.

 

[mdavlee]

I still haven't seen the sensor for throttle position.

 

[Duane(Pa)]

I think the only switch senses the position of the choke shutter?

 

[cease232]

If tune changes with temperature wouldn't monitoring rpm and temperature be the same thing in a round about way.


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[jmssaws]

The switch is on top of the selinoid
Pull the rubber inspection cover on the side and there it be.

Any change in altitude or temperature or gas or muffler or porting will affect rpm and it will adjust the ignition and fuel metering to suit just like it says.

I think it's a incredible thing to port the crap out of one and from stock to ported you will never hear the difference in tune.
I like it enough that I'm building a mtronic 066 flat top.

 

[jmssaws]

When you put a regular carb on one you have to push the switch with a screwdriver or something or it won't fire.

 

[Tbrown]

If it were looking for max rpm it would run lean and burn up.

Max rpm in the cut requires a proper tune. Too lean and you loose power, then rpm drop.

 

[RD35]

If tune changes with temperature wouldn't monitoring rpm and temperature be the same thing in a round about way.

That's what I think they are saying. This system doesn't care about altitude, temperature, weather, fuel quality (to a point) or much of anything else. It doesn't even care how much dirt is in the air filter. All it does is adjust to maximum rpm's whatever the conditions. Now I will add this 2-cents. We all know that if you adjust a carb to maximize unloaded rpms the saw will be too lean. I believe they simply must have taken that into account with their program map. I'm thinking the program temporarily finds max possible rpms and then adds a little fuel to get the correct air/fuel mix. So if you mod the muffler, deck the jug, do port work, or just install a new air filter, the system doesn't care one bit. It just adjusts for those new conditions and keep on going.
After reading the manual (Thanks Duane) I am not at all afraid of one of these now. Very simple design. I will buy one the first chance I get.

 

[Mastermind]

Randy, you have been all through these things; there simply isn't any TPS, temp sensor, map sensor etc. Right?

No TPS on the Stihl system. The Husky AT system does have a TPS.

 

[cease232]

What do you guys think about limitations, improvements?


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[MustangMike]

I believe M-Tronic limits max RPMs with timing changes. Otherwise, the saw would blow itself up. (I don't remember where I saw that, but I don't think they do it with fuel).

Also Dan, when you cut the key I believe you change the range in which it can operate. For example, maybe it can move timing 10 degrees, from 5 to 15. You cut the key, now it is 10 to 20. I don't think the range it can adjust is unlimited.

 

[paragonbuilder]

I believe M-Tronic limits max RPMs with timing changes. Otherwise, the saw would blow itself up. (I don't remember where I saw that, but I don't think they do it with fuel).

Also Dan, when you cut the key I believe you change the range in which it can operate. For example, maybe it can move timing 10 degrees, from 5 to 15. You cut the key, now it is 10 to 20. I don't think the range it can adjust is unlimited.

Yes, but if the timing was modulated based on feedback, if you advance the timing, it would be trying to retard the timing the whole time.
So it must have a set timing curve that like you said, when we advance it, it advances the entire curve.



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[MustangMike]

I will politely disagree. If it can only advance to a certain limit, and you change that limit, along with mods that call for more timing, I believe it will respond.

 

[paragonbuilder]

I will politely disagree. If it can only advance to a certain limit, and you change that limit, along with mods that call for more timing, I believe it will respond.

[emoji41]
I see what you are saying, but that would indicate that on a stock saw with no porting, the mtronic would try to resist the timing advance, but it responds well to them like most saws do.
So this tell me you are sliding the whole preset curve toward advanced, rather than the timing being controlled by feedback.




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[mdavlee]

I think it has a set amount of advance. When you move the flywheel it changes that range.

 

[MustangMike]

Well, I do not definitely know the answer, but even if the stock timing range is conservative, a feedback system would still allow it to change on a stock saw. It is also possible that you cut the key to allow an additional 6 degrees of advance, but based on feedback it only provides 3 addl degrees??? I guess if we over advance one, we would know.

 

[paragonbuilder]

Well, I do not definitely know the answer, but even if the stock timing range is conservative, a feedback system would still allow it to change on a stock saw. It is also possible that you cut the key to allow an additional 6 degrees of advance, but based on feedback it only provides 3 addl degrees??? I guess if we over advance one, we would know.

I think redbull did just that.


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