Modifying M-Tronics or Autotune saws...

[mikefunaro]

I've asked the same questions, but I'm not particularly into modded saws so it doesnt keep me up at night.

I'm repeating a lot of what has been said, most likely but, the way I see it there are two immediate limitations on either Autotune (AT) or M-Tronic (MT).

A. Restriction through firmware, software, or physical setting on the module/device.
B. Restriction through physical capacities of carburetor on the device.

My guess would be that A has a narrower range than B, and that A has been determined by the engineers for what the saw could reasonably encounter. Presumably, in time, someone will actually "hack" a saw and then you'll get widened A, perhaps as wide as the range of B will allow.

The real problem that I see is that I dont think the majority of the builders here have an ability to analyze in a dynamic sense the changes which are being made to the engines--the actual functional amount by which intake volume is increased, and the corresponding change needed in fuel supply. Who knows how sensitive these devices are to timing, etc. I cant really blame the builders for that, and could obviously be wrong, but this seems highly highly advanced.

 

[sachsmo]

I've asked the same questions, but I'm not particularly into modded saws so it doesnt keep me up at night.

I'm repeating a lot of what has been said, most likely but, the way I see it there are two immediate limitations on either Autotune (AT) or M-Tronic (MT).

A. Restriction through firmware, software, or physical setting on the module/device.
B. Restriction through physical capacities of carburetor on the device.

My guess would be that A has a narrower range than B, and that A has been determined by the engineers for what the saw could reasonably encounter. Presumably, in time, someone will actually "hack" a saw and then you'll get widened A, perhaps as wide as the range of B will allow.

The real problem that I see is that I dont think the majority of the builders here have an ability to analyze in a dynamic sense the changes which are being made to the engines--the actual functional amount by which intake volume is increased, and the corresponding change needed in fuel supply. Who knows how sensitive these devices are to timing, etc. I cant really blame the builders for that, and could obviously be wrong, but this seems highly highly advanced.

I think you're right there Mike.

Seems they are operating on several closed loops, depending on the few inputs the system has.

I just hate the idea of being dependent on someone else having the device to "flash" my system.

Stihl needs to make an app,,,,,,,,,,,,,,,,,,,,,Think that would ever happen?

 

[mweba]

I've asked the same questions, but I'm not particularly into modded saws so it doesnt keep me up at night.

I'm repeating a lot of what has been said, most likely but, the way I see it there are two immediate limitations on either Autotune (AT) or M-Tronic (MT).

A. Restriction through firmware, software, or physical setting on the module/device.
B. Restriction through physical capacities of carburetor on the device.

My guess would be that A has a narrower range than B, and that A has been determined by the engineers for what the saw could reasonably encounter. Presumably, in time, someone will actually "hack" a saw and then you'll get widened A, perhaps as wide as the range of B will allow.

The real problem that I see is that I dont think the majority of the builders here have an ability to analyze in a dynamic sense the changes which are being made to the engines--the actual functional amount by which intake volume is increased, and the corresponding change needed in fuel supply. Who knows how sensitive these devices are to timing, etc. I cant really blame the builders for that, and could obviously be wrong, but this seems highly highly advanced.

All of my knowledge is based off fuel settings I've read, either from ported models or models with inherit air leaks. All the saws I build get hooked up before and after mods to note the fuel changes. That being said, most of the gains I've achieved come from a change in duration which doesn't necessarily change the fuel setting (richen the needle).

 

[SawTroll]

....
My concern is that they may end up getting modified beyond their ability to cope. The reason I started this thread is that I've never read much about the operating parameters of these systems and am curious to know just how far they can be pushed before they can't compensate anymore.

I suspect there are quite a few that is in the same situation, and also suspect that there may be only one way to find out - pushing the limits, and see what happens (= trial and error)? :msp_confused:

 

[sachsmo]

C'mon Troll,

you know the reason they are going to AT/MT?

Keeps everything in check emissions wise.



Only time will tell, but judging by the guys who use them the things work pretty well.

There will never be a way for a regular joe to mod them (legally).

If the EPA can fine you for putzing with a muffler???????????????????????????????????????

 

[Stihlman441]

Wheres Brad.
I think he will have some valuable information on this topic.

 

[TK]

Here's a theory - a ported saw doesn't necessarily need the carb to be richened up a whole lot more than a stock saw. The combustion chambers are smaller (typically) when finished. Where the difference is in fuel usage you'll find is probably more so in the increased RPM's that the saw can maintain. Sure more power most of the time means more fuel. But when you're running a saw 2k rpm faster than before, you're naturally going to use more fuel. At an idle I doubt a ported saw would run out of fuel much sooner than a stock saw.

I would bet the saw parameters would change more going from 100*F to 0*F than from stock to ported with no temp change.

 

[mikefunaro]

Here's a theory - a ported saw doesn't necessarily need the carb to be richened up a whole lot more than a stock saw. The combustion chambers are smaller (typically) when finished. Where the difference is in fuel usage you'll find is probably more so in the increased RPM's that the saw can maintain. Sure more power most of the time means more fuel. But when you're running a saw 2k rpm faster than before, you're naturally going to use more fuel. At an idle I doubt a ported saw would run out of fuel much sooner than a stock saw.

I would bet the saw parameters would change more going from 100*F to 0*F than from stock to ported with no temp change.

excuse my naivete, but what ultimately governs speed with an autotune saw? The coil? The AT module? Can you swap in an unlimited coil? does it do any good?

 

[TK]

excuse my naivete, but what ultimately governs speed with an autotune saw? The coil? The AT module? Can you swap in an unlimited coil? does it do any good?

The coil and the AT unit work together. As far as rpm is concerned, they are limited via coil. As far as power under load is concerned, that is the porting. Swapping in an unlimited coil would break the communication between the coil and the AT unit and render the saw useless. Conventional saws do not hold rpms in the wood higher than the cutoff of the limited coil so swapping one out is a moot point. Really the only reason people swap them out now is so they can tune a saw out of the wood. With AT you don't need to worry about that.

 

[indiansprings]

I'll try to find out some parameters, they are pretty broad on Mtronics, altitude will have no affect, works with barometric pressue, don't have the manual here at the house, I know you can cut an intake boot and I'm talking a big cut and it will compensate for it, just from what I've seen it would take some wild azz mods for it not to be able to compenstate. The true digital fuel injection may let us get even more extreme.

 

[Chris-PA]

The coil and the AT unit work together. As far as rpm is concerned, they are limited via coil. As far as power under load is concerned, that is the porting. Swapping in an unlimited coil would break the communication between the coil and the AT unit and render the saw useless. Conventional saws do not hold rpms in the wood higher than the cutoff of the limited coil so swapping one out is a moot point. Really the only reason people swap them out now is so they can tune a saw out of the wood. With AT you don't need to worry about that.

I had not thought of that - with traditional saw carbs the mixture will get so rich it limits the max no load WOT rpm. With MT/AT they really needed some other way to limit the rpm.

 

[TK]

I'll try to find out some parameters, they are pretty broad on Mtronics, altitude will have no affect, works with barometric pressue, don't have the manual here at the house, I know you can cut an intake boot and I'm talking a big cut and it will compensate for it, just from what I've seen it would take some wild azz mods for it not to be able to compenstate. The true digital fuel injection may let us get even more extreme.

I don't think the "extreme" nature of saw mods will be out of the parameters of any of these saws. Neither will fuel injection. The only thing that really matters with 99% of these saws is performance at WOT, one position of throttle under load. Race saws, well that's their problem lol.

AT and MTronic do a great job. The only way I would see FI being an improvement is if it is able to perform better, while at the same time being simpler without adding any weight or cost. There's no point in this application to go FI unless it is less expensive or saves weight. Of course there's the whole EPA thing. If FI is ultimately the next step in the emissions race then we have no choice. If they have it their way we'll be back to buck saws in no time.

 

[Chris-PA]

I don't think the "extreme" nature of saw mods will be out of the parameters of any of these saws. Neither will fuel injection. The only thing that really matters with 99% of these saws is performance at WOT, one position of throttle under load. Race saws, well that's their problem lol.

AT and MTronic do a great job. The only way I would see FI being an improvement is if it is able to perform better, while at the same time being simpler without adding any weight or cost. There's no point in this application to go FI unless it is less expensive or saves weight. Of course there's the whole EPA thing. If FI is ultimately the next step in the emissions race then we have no choice. If they have it their way we'll be back to buck saws in no time.

I suspect the big advantage of crankcase FI would be if it gets a competitor around Husky's patents on strato and AT. I doubt it would work much different.

 

[Jacob J.]

A. Restriction through firmware, software, or physical setting on the module/device.
B. Restriction through physical capacities of carburetor on the device.

You've nailed it on A., and Husqvarna has already made three generations of Auto-tune modules. The third generation can be turned up the highest and that's the module currently on the 562XP and 562XPW.

 

[MCW]

Hey thanks for the input guys.
It looks like the systems should be able to compensate for most things we can throw at it.
If these setups can go pretty hard with fuel delivery then many builders may not have scratched the surface yet with their full potential.
My concern with modifying these saws has been that nobody really seems to truly know their limitations (apart from Stihl and Husky) and I was concerned that maybe in the odd case buliders have exceeded the capability of the system.
Everybody knows carbies, but not too many people have ever talked about the limitations that these systems may or may not present.

I remember a story from a while ago involving modified cars that showed at WOT the old side draught Weber carburettors were producing more peak HP than a similar EFI setup. Of course the driveability was less but an interesting comparison nonetheless.

 

[Tzed250]

The AT on my 550XP compensated for a significant air leak. This was on a saw that was ported and muffler modded. After fixing the air leak the saw ran fine. The last time I ran it the air temp was below freezing. No problems. From all this I gather that the system parameters are wide enough to handle any reasonable mods.

 

[TK]

I suspect the big advantage of crankcase FI would be if it gets a competitor around Husky's patents on strato and AT. I doubt it would work much different.

That is very true, I didn't look at it from a patent workaround or a financial standpoint.

 

[MCW]

The AT on my 550XP compensated for a significant air leak. This was on a saw that was ported and muffler modded. After fixing the air leak the saw ran fine. The last time I ran it the air temp was below freezing. No problems. From all this I gather that the system parameters are wide enough to handle any reasonable mods.

Lucky I've just pulled the trigger on a 550XP then...

 

[Stihlman441]

Look out you will get hooked.

 

[TK]

One drawback would be the characteristics of the carburetor itself, Venturi and bore size. The original 365 zama could feed my saw just fine. Perhaps the walbro hd12 even better. The tillotson from a 385 maybe better. A walbro off a 394xp.... Etc etc etc. it changes the way the fuel is delivered, the effort required and whole bunch of other stuff I don't really know about. The smaller carb sure can supply it. But it runs better with a bigger carb on there. Can't do that with the AT and Mtronic. Perhaps modify the carb, but not replace it.