How does Auto tune work?

[TimberCutterDartmoor]

 

I'd also like to hear people's opinions on why they think that naturally aspirated saws are better than auto tune and vice versa.

 

Cheers

TKO

 

Autotune's aren't turbocharged.

[adw]

The tool once plugged in will as said give carb temp, rpm the last time it ran, it will test the the fuel vale function. Yes the dealer should really programme the customers name into the unit at sale, with the Stihl tool you can run the machine whist plugged in and get a graph of the rpm, the Husqvarna is a little more basic but gives all the information that is needed, like all new things it gets the blame for anythig that goes wrong with the saw, but you must accept it is still a two stroke engine, it has a cylinder and piston, it needs good two stroke oil, it has crank seals, it has pipes and filters, auto tune is here to stay, the days of carb screw drivers are numbered.

[Stubby]

Auto tune are naturally aspirated as well as non A/T saws . I think the Stihl saws run a version of Husqvarna s first generation A/T ( Husky sold it to them ) whilst Husqvarna are now on version 2 , possibly 3 ?

[Stubby]

The tool once plugged in will as said give carb temp, rpm the last time it ran, it will test the the fuel vale function. Yes the dealer should really programme the customers name into the unit at sale, with the Stihl tool you can run the machine whist plugged in and get a graph of the rpm, the Husqvarna is a little more basic but gives all the information that is needed, like all new things it gets the blame for anythig that goes wrong with the saw, but you must accept it is still a two stroke engine, it has a cylinder and piston, it needs good two stroke oil, it has crank seals, it has pipes and filters, auto tune is here to stay, the days of carb screw drivers are numbered.

 

The Stihl A/T is the basic one . Husqvarna sold it to them . Husqvarna are 1 or 2 versions ahead .

[Eddy_t]

The tool once plugged in will as said give carb temp, rpm the last time it ran, it will test the the fuel vale function. Yes the dealer should really programme the customers name into the unit at sale, with the Stihl tool you can run the machine whist plugged in and get a graph of the rpm, the Husqvarna is a little more basic but gives all the information that is needed, like all new things it gets the blame for anythig that goes wrong with the saw, but you must accept it is still a two stroke engine, it has a cylinder and piston, it needs good two stroke oil, it has crank seals, it has pipes and filters, auto tune is here to stay, the days of carb screw drivers are numbered.

 

 

And so much better for not needing screwdrivers! Although it makes a tachometer redundant too!

 

To answer the op's question, the throttle linkages has a magnet and 2 sensors on; idle and full throttle.

When the magnet is at idle (0% opening) the saw tunes the idle with a set logic - idle too high -> add more fuel, idle too low -> add less fuel

When the magnet approaches full throttle (>90%), the saw tunes the H with the same principles; rpm too high -> add fuel, too low -> less fuel.

It also does the tuning under load (when the saw is at WOT, but the rpm has dropped between 8-12k rpm, what it does here I'm not sure!

 

The Stihl m-tronic and gen 1 autotune are the same, which works on a start-up basis, tuning the idle and max rpm on initial start, it doesn't adjust during run-time (unlike the new gen 2 autotune on the 540xp, 545, 550xp, 555, 556, 560xp and 562xp).

[mowandgo]

Does this mean you can plug a laptop in if you get the right software and plug? My mate can do it on his Skoda Octavia. I think with machines less is best over complex auto tune will not stand the test of time. I doubt they will be saws running auto tune in 30 years time that was built today. The Made In West Germany 024 & 038 ect are still working today because there simple a d built & engineerd extremly well!

[TGB]

... My mate can do it on his Skoda Octavia ...

If the road vehicle is post '96inc., it's probably OBD II (On-board diagnostic) compliant.

[peatff]

Does auto tune only adjust the mixture ? If it doesn't do anything to the timing could you replace the auto carb with a manual one when it goes wrong ?

[Eddy_t]

Does auto tune only adjust the mixture ? If it doesn't do anything to the timing could you replace the auto carb with a manual one when it goes wrong ?

 

 

Someone in America has fitted a normal carb

[adw]

Not heard that Eddy, i know somebody has taken the unit apart and fitted a screw so to adjust the fuel flow, as i understand it you cannot change just the carb to a standard one as auto tune is controling the ignition, not too sure why anyone would want too?