V.3 M-Tronic Coils for the MS661 C / New Calibration Procedure

[PogoInTheWoods]

M-Tronic v3.0 ECU's (coils) are now being introduced domestically as replacements for MS661's with the last Gen 2 coils (1144-400-4720) no longer being restocked with 1144-400-4703 as the new part number. The main difference is the calibration routine has been greatly simplified and doesn't require any cuts. Additional enhancements relative to the MDG-1 diagnostics have also been introduced from what I understand, though I have no first hand knowledge of that.

The attached TI has been floating around since 2017 but hasn't been relevant until now since there haven't been any (or not many) v3.0 saws anywhere except Europe. It explains the procedure and the various compatibility designations, etc.

To date, the MS661 is the only saw I'm aware of that can currently be 'updated' to the v3.0 M-Tronic system here in the states. I'm sure it will be available to other saws as the v3.0 system will be around for a while and already applies to the fuel injected stuff as well as the MS462 and latest European MS362's. And while the new system is essentially just a software upgrade it still requires the replacement of the ECU and isn't something that can just be flash upgraded to an earlier M-Tronic coil.

Anyway, here's the calibration excerpt from the tech note and a vid of the calibration routine on a 661 I just rebuilt that needed a new coil and ended up with one of the first v.3's. We were using a phone stopwatch that wasn't very cooperative and it threw off the last part of the procedure. We should have gone straight to idle after the saw backed down from its 8 ~ 10 seconds of WOT instead of allowing it to go wide open a second time. I think it actually messed up the top end setting and the saw needs to be re-calibrated. Problem there is no readily available information yet about how to do a field reset on one of these coils. Will be tracking that down next week and will post anything I may find. And if anyone has a tech note or operator's manual for a Gen 3 M-Tronic saw, don't be shy about spreading it around for the field calibration procedure if nothing else..., provided there is one and these saws aren't relegated to needing the MDG1 system or some other type of dealer intervention to be reset from scratch. That would seriously suck.

Here's how the saw behaves during the process. That 30 secs at full throttle seems a little scary when you read it, but it actually only amounts to around 8 ~ 10 secs. Sorry for the lousy camera work. Was preoccupied with the stopwatch.
And the cuts weren't required for the calibration. Just wanted to see how the saw behaved. Shoulda ripped through that cottonwood a helluva lot faster imho..., and is why I think the calibration needs redone without the second WOT possibly having an effect on it.
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Hope some of you find this useful. And by all means, don't hesitate to offer any corrections or additions to any of this to keep it as helpful and accurate as possible.

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[Mike Greenwood]

After bar length change, is a reset necessary? Went from 24to36
Thanks

 

[PogoInTheWoods]

No, but you may want to crank up the oiler. LOL

Changing bars is no different to the ECM than going from a small branch to a stump with whatever size setup you happen to be running. The saw will obviously run differently with the 36"setup so don't expect it to run like it did with the 24. Should still run great, just not as snappy.

 

[Dave4610]

Is this still the procedure for the current model coil? I just bought the kit with the solenoid. How do I determine the coil version?

 

[WI_Hedgehog]

I wonder if the ECU is in "new saw mode" and needs 7-8 tanks run through it as "Total running hours" should read just a few minutes, similar with "Successful starting attempts."

 

[PogoInTheWoods]

How do I determine the coil version?

I'd start with the part number.

 

[Long Bar 60]

How does one know if they have V3.0 model? Serial number? I've had two M-Tronic 661's and they both ran so bad that I couldn't use them. Sold one of them and the other has been sitting on the shelf for a few years. I have a 661 with a regular carburetor and it runs perfectly.

 

[WI_Hedgehog]

@Long Bar 60 : They should run fine; from what I hear some of the first M-Tronic saws had some issues but STIHL rectified the problems and they should run strong after 7 to 8 tanks of fuel at 50:1 mix ratio. How many hours did you have on each? What altitude are you running at? What model year are they? Did you feed them ethanol fuel, and if so what % ethanol and what octane rating? What 2-stroke oil did you use? Have you had them in to a dealer? Would you take $300 for that P.O.S., shipped to Wisconsin?

 

[PogoInTheWoods]

Read the thread.

 

[Dave4610]

I'd start with the part number.

The kit number is 1144 007 1801 and it came with the white solenoid. I assume you want the actual number on the coil itself. I'll check in a bit and post it. My 661 was one of the very early ones. "D.O.M..03.14"

 

[Dave4610]

The new cool

I'd start with the part number.

The new coil is marked on one side 1144 400 4704B, DE22/36. The other side says 1144 4702 B, SMT, 2217.

 

[Dave4610]

I'd start with the part number.

The old coil just has markings on one side. 1144 4700 C, SMT, 1330

 

[PogoInTheWoods]

1144-400-4703 was the initial 661 v.3 ECU (ECM). (Read post #1) It replaced whatever was on the saw with the v.3 technology and brought the new calibration procedure with it -- which is still used. The latest solenoids can be white or green and one of the new orange fuel filters should also be used.

The biggest problem with M-tronics in general was the early solenoids. The 661 ECM programming disasters didn't help much either with that particular saw. The other early M-tronics did much better with significantly fewer problems, though the solenoids still sucked and required frequent replacement until refinements in manufacturing were made.

Any M-tronic 661 can be upgraded to the latest version with the kit. An upgrade doesn't need to be broken in nor does the control module come pre-tuned for x amount of tanks of fuel, yada, yada, yada. It learns the saw and performs accordingly from the first start till the last and every other one in between.

Today's version of the MS661C-M is a reliable and solid running saw. Any upgraded one should also be -- barring any other issues already present.

 

[Long Bar 60]

@Long Bar 60 : They should run fine; from what I hear some of the first M-Tronic saws had some issues but STIHL rectified the problems and they should run strong after 7 to 8 tanks of fuel at 50:1 mix ratio. How many hours did you have on each? What altitude are you running at? What model year are they? Did you feed them ethanol fuel, and if so what % ethanol and what octane rating? What 2-stroke oil did you use? Have you had them in to a dealer? Would you take $300 for that P.O.S., shipped to Wisconsin?

I probably had around 1000 hours on each of them before I got tired of throwing money at them and set them aside. Depending on the job I cut as low as 2500' up to around 6500'. I bought both of them in 2018. No ethanol, 89 octane and Stihl synthetic at 50:1. My dealer is sick of them. A lot of hardcore Stihl guys around here switched to Husky's because of the M-Tronic. I started using 461's and 500i's most days but would break out the old 084 in bigger wood. I wouldn't feel right selling the one I have to you. I sold the one to a friend with a mill and told him if it gave him any trouble I'd refund his purchase. There's a big difference between using a saw once in a while and using it in daily production cutting.

 

[WI_Hedgehog]

I probably had around 1000 hours on each of them before I got tired of throwing money at them and set them aside. Depending on the job I cut as low as 2500' up to around 6500'. I bought both of them in 2018. No ethanol, 89 octane and Stihl synthetic at 50:1. My dealer is sick of them. A lot of hardcore Stihl guys around here switched to Husky's because of the M-Tronic. I started using 461's and 500i's most days but would break out the old 084 in bigger wood. I wouldn't feel right selling the one I have to you. I sold the one to a friend with a mill and told him if it gave him any trouble I'd refund his purchase. There's a big difference between using a saw once in a while and using it in daily production cutting.

Those saws "should" have 2,000 good hours left in them, but it does sound like something is up. It's unfortunate one's a shelf-sitter, i hate to hear that, though it sounds like you gave them a good life and for some reason they turned out to be bad apples.

 

[singinwoodwackr]

Wow, that’s just nuts. I have one of the first 661s to hit Cali. I ran it about 2 weeks and sent it to Brad for his full treatment…might have been his first, don’t remember. The saw has never had 1 issue since then. I’ve had 2 later 661s in the shop that got solenoids swapped out to white. I followed the old recalibrate procedure on both and both are stihl running perfectly after nearly a year of hard use at a firewood yard. Go figure…

 

[Dave4610]

1144-400-4703 was the initial 661 v.3 ECU (ECM). (Read post #1) It replaced whatever was on the saw with the v.3 technology and brought the new calibration procedure with it.

So, just to be clear, the 1144 400 4704B coil uses the calibration procedure in the video? I don't want to mess this up. I messaged the seller and he claims a tool is needed to program the new coil.

 

[Dave4610]

I probably had around 1000 hours on each of them before I got tired of throwing money at them and set them aside. Depending on the job I cut as low as 2500' up to around 6500'. I bought both of them in 2018. No ethanol, 89 octane and Stihl synthetic at 50:1. My dealer is sick of them. A lot of hardcore Stihl guys around here switched to Husky's because of the M-Tronic. I started using 461's and 500i's most days but would break out the old 084 in bigger wood. I wouldn't feel right selling the one I have to you. I sold the one to a friend with a mill and told him if it gave him any trouble I'd refund his purchase. There's a big difference between using a saw once in a while and using it in daily production cutting.

How do you like the 500i? On paper it has the same power as the 661 and weighs less.

 

[Dave4610]

Wow, that’s just nuts. I have one of the first 661s to hit Cali. I ran it about 2 weeks and sent it to Brad for his full treatment…might have been his first, don’t remember. The saw has never had 1 issue since then. I’ve had 2 later 661s in the shop that got solenoids swapped out to white. I followed the old recalibrate procedure on both and both are stihl running perfectly after nearly a year of hard use at a firewood yard. Go figure…

Do you notice a big difference in performance after Brad is done with them? I was considering sending mine to him.

 

[singinwoodwackr]

Do you notice a big difference in performance after Brad is done with them? I was considering sending mine to him.

I believe he stopped building saws years ago