Those Gall Durned, new Fangled Magnesium Pistons!

[Fellin Feller]

I did buy the Stihl MS 400 with the magnesium piston about 6 months ago and do like it. I run a 20" bar and have cut quite a bit of large oak firewood.

Just curious, why are there not more saws or other engines using magnesium pistons? Are these pistons going to last as long as the aluminum?

 

[bwalker]

Magnesium pistons are not new. Been around since the 20's. Even won a Indy 500.
They were called Dow Metal back then because Dow chemical was the Mfg.

 

[windblown]

I see Cosworth gave them a shot for a year or two in F1 back in the nineties.

The stuff gives up a fair bit compared to Aluminum based alloys with one exception, weight. I'm intrigued by the MS400 but the piston does give me some pause. I imagine if it becomes an issue the AM may step in with an aluminum replacement but then the question becomes will the bottom end hold up to the additional weight of a substantially heavier piston? If the bottom end was also lightened to take advantage of the lighter piston it might not like swinging a heavy aluminum one.

Hopefully Stihl did plenty of destructive testing and found it lasts just fine. I would be surprised if it would last as long as an aluminum one though. Less fatigue strength, less abrasion resistance (as I recall), and ground up into a powder makes a heck of a fire when lit! No more aluminum transfer to a plated cylinder, just *poof" instead. LOL.

 

[camel2019]

I see Cosworth gave them a shot for a year or two in F1 back in the nineties.

The stuff gives up a fair bit compared to Aluminum based alloys with one exception, weight. I'm intrigued by the MS400 but the piston does give me some pause. I imagine if it becomes an issue the AM may step in with an aluminum replacement but then the question becomes will the bottom end hold up to the additional weight of a substantially heavier piston? If the bottom end was also lightened to take advantage of the lighter piston it might not like swinging a heavy aluminum one.

Hopefully Stihl did plenty of destructive testing and found it lasts just fine. I would be surprised if it would last as long as an aluminum one though. Less fatigue strength, less abrasion resistance (as I recall), and ground up into a powder makes a heck of a fire when lit! No more aluminum transfer to a plated cylinder, just *poof" instead. LOL.

Can’t put out a magnesium fire that’s for sure.

 

[Canyon Angler]

Can’t put out a magnesium fire that’s for sure.

Not with water!

 

[user 122190]

I see Cosworth gave them a shot for a year or two in F1 back in the nineties.

The stuff gives up a fair bit compared to Aluminum based alloys with one exception, weight. I'm intrigued by the MS400 but the piston does give me some pause. I imagine if it becomes an issue the AM may step in with an aluminum replacement but then the question becomes will the bottom end hold up to the additional weight of a substantially heavier piston? If the bottom end was also lightened to take advantage of the lighter piston it might not like swinging a heavy aluminum one.

Hopefully Stihl did plenty of destructive testing and found it lasts just fine. I would be surprised if it would last as long as an aluminum one though. Less fatigue strength, less abrasion resistance (as I recall), and ground up into a powder makes a heck of a fire when lit! No more aluminum transfer to a plated cylinder, just *poof" instead. LOL.

I'm noticing that the warm up time of the 400 seems to be a lot longer then other Aluminum piston chainsaws.

 

[bwalker]

I see Cosworth gave them a shot for a year or two in F1 back in the nineties.

The stuff gives up a fair bit compared to Aluminum based alloys with one exception, weight. I'm intrigued by the MS400 but the piston does give me some pause. I imagine if it becomes an issue the AM may step in with an aluminum replacement but then the question becomes will the bottom end hold up to the additional weight of a substantially heavier piston? If the bottom end was also lightened to take advantage of the lighter piston it might not like swinging a heavy aluminum one.

Hopefully Stihl did plenty of destructive testing and found it lasts just fine. I would be surprised if it would last as long as an aluminum one though. Less fatigue strength, less abrasion resistance (as I recall), and ground up into a powder makes a heck of a fire when lit! No more aluminum transfer to a plated cylinder, just *poof" instead. LOL.

It's all just speculating without knowing the alloy.
This particular piston has some sort of coating on it as well. Maybe Ceramic?

 

[Chevboy0167]

Something but nothing on the coating...

https://www.stihl.com/stihl-technology-receives-award-of-excellence.aspx

 

[Chevboy0167]

A familiar name...

https://www.mahle.com/en/news-and-p...f-thermally-insulating-piston-coatings--62848
And a few different automotive style coatings...

https://www.jcmmachineandcoatings.com/coatings/pistons/

 

[bwalker]

Something but nothing on the coating...

https://www.stihl.com/stihl-technology-receives-award-of-excellence.aspx

With a little run time the coating turns a much darker color.

 

[RCamo]

My son bought one of these about a month ago for his landscape business. Saw ran great for several days, he said plenty of power with a 20" bar. It didn't make it to the 2nd week before it self destructed. Dealer told him the crank broke, but I'm not sure if they had actually disassembled and checked it at that point. I'll have to check back with him and see if they came up with what happened or sent it back to Stihl.

 

[bwalker]

I see Cosworth gave them a shot for a year or two in F1 back in the nineties.

The stuff gives up a fair bit compared to Aluminum based alloys with one exception, weight. I'm intrigued by the MS400 but the piston does give me some pause. I imagine if it becomes an issue the AM may step in with an aluminum replacement but then the question becomes will the bottom end hold up to the additional weight of a substantially heavier piston? If the bottom end was also lightened to take advantage of the lighter piston it might not like swinging a heavy aluminum one.

Hopefully Stihl did plenty of destructive testing and found it lasts just fine. I would be surprised if it would last as long as an aluminum one though. Less fatigue strength, less abrasion resistance (as I recall), and ground up into a powder makes a heck of a fire when lit! No more aluminum transfer to a plated cylinder, just *poof" instead. LOL.

I think your off base as far as strength goes. For starters the piston can be made thicker and still end up lighter and stronger than aluminum. Mag also doesn't lose strength with heat as fast as aluminum.
I would also suppose the coating found on the mag piston up its wear resistance.
Lastly, mag pistons haven't been know to catch on fire.

 

[bwalker]

My son bought one of these about a month ago for his landscape business. Saw ran great for several days, he said plenty of power with a 20" bar. It didn't make it to the 2nd week before it self destructed. Dealer told him the crank broke, but I'm not sure if they had actually disassembled and checked it at that point. I'll have to check back with him and see if they came up with what happened or sent it back to Stihl.

That's the kind of thing I expect from landscapers to be honest,lol.