261 M-Tronic - What makes it tick.....

The temp reading is just for tuning right? i.e. use the temperature to lean it for best power w/o cooking things?
We were tuning the saws on the dyno using the RPM reading w/o the brake applied, but the extra load the disc has on it made it so when the saw came off the dyno the tune would be different when just tuning by ear against WOT.

I'm curious what the diag cable does -- convert their comm (dallas 1 wire?) to USB serial? It would be nice if a cable could be made instead of spending the dollars for the Stihl one.

If a scope can determine bits from the data that would be a huge step. Here at the office we have one that can decode most protocols to show hex -- that would be nice to help figure out how bits are encoded on the data / power wire.
Very interesting!

 

Maybe a cable could be borrowed?????

 

This is part of what I do know... From 2010.
http://www.google.ch/patents/US8428847?hl=de&cl=en

According to the invention, in the operating state of the work apparatus, the short circuit line is configured as a bus line, especially as a LIN-bus. On the bus line, an exchange of information takes place between the ignition module and the external control apparatus and/or the intelligent sensors or even passive resistors as consumers. That is, data are transmitted and received in both directions.

Disturbance pulses are generated in the bus line with the triggering of the ignition sparks at the spark plug because of the ignition. For this reason, in accordance with the invention, the ignition module is connected as the master of the bus line so that the ignition module permits data communication on the bus line only when there is a minimum crankshaft angular distance A or B at an ignition time point of the ignition module. The minimum crankshaft angular distance A after an ignition time point is greater than the minimum crankshaft angular distance B ahead of an ignition time point. This is due to the fact that after an ignition, the disturbance pulses must first decay before a data packet can be sent on the bus line.

Each data packet lies in a time-dependent communication slot whose start lies after the minimum crankshaft angular distance A after an ignition and whose end lies at a distance ahead of a next ignition, which distance does not lie less than the minimum crankshaft angular distance B ahead of an ignition. In this way, data packets can be transmitted over a crankshaft revolution of 360° crankshaft angle at specific points in time or crankshaft angle positions, in which the disturbance pulses have decayed or have not yet occurred.

 

When your engine gets too lean, the skyrocketing temperature you see on an engine head is probably not really an indication of hotter combustion. Most likely it's a warning sign of DETONATION. Detonation is the collision of two flame fronts inside the combustion chamber, where there should be just one, and it's the single biggest cause of heat related engine failures.
So the use of a thermo couple within the exhaust chamber gives a faster reading there-by allowing for a better tune.

My guess is you are applying more brake than is normally applied to a saw within a cut. I can understand high breaking as a measurement for HP and RPM, but maybe not as a tuning method.

 

Interesting -- perhaps we could make a portable RPM (was looking at circuits to pickup RPM from the coil like fast tachs use) and exhuast temp reader that would allow a user to tune the saw by ear + RPM + exhaust temp. For limited coils it would be cool to see RPM and exhaust temp while in the cut so you can lean it to where you are comfortable for power and not risk scoring and do it by more than just listening for 4 cycling. On the dyno the temp monitor could be an add-on. There are like 7 AtoD's on the beaglebone I've used to sense battery voltages over a range of 0 to 17 volts w/ at least 0.05 volt precision or something we can calibrate accordingly for a thermocouple that you shove in your muffler. Want to learn how much cooler your saw runs after that muffler mod you did? Very cool (literally!).

When applying the brake with the motorcycle dyno @wcorey Bill could chime in on what point the caliper + pads loading the saw would seem mostly like cutting oak versus lugging it so much that the RPMs fall off (which we would usually do on each dyno run) I have an option in the dyno graphs to plot the RPM as a third line against time to make it easier visually to see what it's doing. My thought (which could be totally wrong is that when the brake is lugging the saw to the 8000-11000 RPM powerband area on the dyno (which is only a second or two as it lugs down) this area is pretty comparable to the saw cutting some wood and holding somewhere around 9500-10500 as you cut and try and stay in the saw's powerband to win that cant race We certainly aren't lugging it long enough w/ the motorcycle brake to get the head heating up like it would on a long cut w/ 32" bar buried in petrified 2 year+ old oak you might find at @paragonbuilder site LOL. Dangit now I want go visit Dan again and play in the petrified wood....

Cheers.

 

@breese you want the link for the custom programmable 4-mix ecu?

http://motorsaegen-portal.de/viewtopic.php?f=1&t=102324

I put the link in this thread, so everybody could have part of it.

I will only some confidential things per PM, cause these annoying Stihl guys with their copyright *B-S...., have some good lawyers

 

come on down...

 

This is exactly the way some propeller-powered fighter aircraft fired the pilot-operated machine gun "through" the rotating propeller blade plane. A mechanism timed the machine gun cycling with engine rotation and prevented you from shooting your own propeller off.

ps
A long time ago I wrote a onewire driver which is now in use in tons of PIC microcontroller applications.
https://www.ccsinfo.com/forum/viewtopic.php?t=19520

That said, it is not likely that Stihl used a straightforward adaptation of Dallas' ubiquitous onewire protocol. Possibly, yes. Likely, no. At the manufacturing volumes that Stihl is playing with, they would have gone for the lowest cost solution -- and that means minimizing die area, minimizing IP licensing fees, and so on. This leads to an in-house proprietary platform development. Hence, discovery regarding how the protocol is structured and how the timing and data capture are implemented requires a week or so of benchtop time -- unfortunately with a running saw or a reasonable facsimile of one. The latter can possibly be emulated by back-driving a pistonless engine with an electric motor. Nevertheless, a even a trivial Xor-based 'encryption' of the data packets means you first have to spend a fair amount of time discovering and understanding how the data obfuscation was implemented.

Or, the entire M-tronic system is based on commodity Dallas onewire parts and you can build a decoder in an afternoon. You can then build an emulator (first via SW, in then HW) which sends "different" data to the OEM Stihl microcontroller, which then results in different performance characteristics on the engine itself. The next step then is to figure out the best way to massage the data *on the saw itself* while in operation. Anf of course, the holy grail is to update/augment the controller firmware to remap engine behavior.

There is one other option available which must be considered as well. Engine control algorithms are not rocket science. The various mappings (timing advance vs RPM, etc) can be implemented in a DIY microcontroller; mated with the existing OEM, or alternatively a DIY sensor set, the DIY uC takes on engine management responsibility and there is no reliance on Stihl hardware nor any need to decode their IP.

wrooster

 

I did a quick read and that is Very Interesting...
We need to talk more in detail.
At this point I believe the chip in the coil pack is for Stihl only. I have yet to find a LIN protocol Dual Row 30 pin IC.
At the same time I have documents that show they are using the true LIN protocols.

 

A truely captivating thread Bob thanks for sharing your knowledge with us here my friend

 

If the name fits Randy

 

Thank you....
While it has been a little bit since I posted anymore on this, I am still working on it.

 

So... you got this thing all reprogrammed and done yet? tick toc...

 

Lol.... Still looking for a saw..
starting to think about getting the board from a 501 (seeing it is different).

 

A "live wire" would be good.

 

Today some new part lists showed up.
Stihl replaces all the M-Tronic machines ECUs.
They will show the M-Tronic Version on the brake handle.

First was the MS 362 now the MS 661 with new ECUs.
M-Tronic Version 2 and higher cant be resetted to factory default.

You have to do a calibration run just like the MS 462.

 

Are we talking version 2 now or version 3?

 

MS 462 = Mtronic Version 2.1
MS 362/661 = Mtronic Version 3

I think they will update the MS 261 to Mtronic Version 3 too.

 

Cool. Thank you for the information sir.

Do we know what the changes do to the saw?
Stronger? Faster? No difference?

 

Not yet.
But i think it is just the next step to software updates for the Mtronic.
You can swap Mtron 1 and Mtron 3 coils on those MS 661s without any problems.

Here is a picture from a Mtronic 2.1 saw (MS 462).
I dont know when i get te first Mtronic 3 saw to my place.