Will Strato charged motors be less reliable long term?

[Moparmyway]

yes they are strato. separate air valve. just had 6 more dropped off this morning with at least one of them needing a crankshaft

 

[fordf150]

i have posted pics of the bad cranks before seeking answers and didnt get anywhere. Stihl and the local Stihl dealers tells me it is operator error. Which is basically what everyone told me in the original thread i started on these. http://www.arboristsite.com/community/threads/stihl-261-and-362-crank-problems.260773/ If it turns out that this one has a bad crank i will post pics of it. Not sure yet jsut going off of the owners diagnoses. @fastLeo151 has them on the bench right now so we will see what he comes up with when they get torn down

 

[bikemike]

No, because I have talked to the engineers that have designed them. Oh, but that makes me a ******* moron here, right? Because a garage hack thinks he knows more than the Stihl engineers that designed the saws. Yah, I have heard that argument.

Trial n error its the only way to work bugs out of something

 

[bikemike]

i have posted pics of the bad cranks before seeking answers and didnt get anywhere. Stihl and the local Stihl dealers tells me it is operator error. Which is basically what everyone told me in the original thread i started on these. http://www.arboristsite.com/community/threads/stihl-261-and-362-crank-problems.260773/ If it turns out that this one has a bad crank i will post pics of it. Not sure yet jsut going off of the owners diagnoses. @fastLeo151 has them on the bench right now so we will see what he comes up with when they get torn down

To bend a crank on a rev limiter stock coil stihls should cover that a bad bottom end bearing from lack of lube thats a consumer issue.

 

[Chris-PA]

I have posted it here several times before, to the blind it seems. Stihl calls the MS461 and the MS661 design "delayed scavenging" in their technical bulletins and emails to me, yes. From Stihl engineering: "...compared to the previous fresh air stratified two-cycle engine, the newer stratified scavenging on these saws uses exhaust rather than clean air." They say that the design of the carburetor and intake manifold are the same as those of previous conventional two stroke engine without fresh air stratified scavenging, but after the intake manifold the designs are different.

As for cooling concerns, that is exactly why they also added the 'Intake side ramp' in the crankcase. That is what the Stihl engineers call what you refer to as the 'cooling dohickey'. Its job is to shift the direction and velocity of the fuel charge for maximum cooling and lubrication. The design is not the same as the Tanaka engines. Call it what you want, but when the transfers open on the downstroke of the 461 and the 661, exhaust gases are stuffed into the transfers to create a stratified layer of exhaust gas between fuel charges. Its that simple.

Frankly I do not comprehend the bone-headed insistence about this, but WTF. Everyone is an expert here, and the Stihl engineers apparently do not know shiit about the saws that they design. Typical non-technical understanding of the world. They told us that the Tomahawk cruise missiles that we designed and built at GD would not work I the first Gulf War, but they did. Then the advanced cruise missile program that I was working on was cancelled. The Navy said, "we don't need it."

I understand the concept, and the effect described happens in every 2-stroke to some extent. If the residual combustion pressure in the cylinder exceeds the case pressure when the transfers open, then some exhaust will flow down the transfers. I was looking some evidence that Stihl had enhanced this effect, but none has been discovered. Something like a shorter blowdown angle or an obvious increase in exhaust back pressure for example.

I've certainly never said the Stihl engineers don't know what they are doing. However, I have seen that Stihl marketing has a history of making fancy technical looking documents describing what are actually standard industry design practices (like quad transfers) and/or giving them fancy names (like "Intellicarb"), so their description of typical exhaust blowdown was not remarkable or particularly convincing.

 

[mdavlee]

575xp when they first came out had several bearing failures. My husky dealer friend hated those. He said the 576 was much better but the 372 still outsold them both.

 

[windthrown]

You have "talked to Stihl engineers". I read that as you have read emails from Stihl. Nice try. All you're doing is regurgitating Stihl talk. Doesn't sound like you've every even been inside of one of these saws. For what you're saying to be true, there would have to be some kind of change in the port timing. THERE IS NOT. If the 461 is strato charged, then so is the 460, 046, 026, 066, you name it. Bottom line is, you don't really know what you're talking about. You're just repeating what you've been told.

You are a broken record. It is subtle, and obviously beyond your comprehension. You are like the Ape spreading disinformation because you cannot figure it out. You have a theory that is based on nothing but conjecture and after the fact observations. You are just displaying your stubbornness and lack of mechanical ability to THINK.

My father was a lawyer from Brooklyn, NY. He used to tell me, "Son, never get into a fight with someone with nothing to lose." Well, Brad, I have nothing to lose here. I am not making money off of fools sending me saws to do pop-up mods on (which I believe are inferior to cut squish mods, but that is another topic). You are simply wrong. Nothing you have claimed has convinced me otherwise, and everything I have seen from Stihl makes perfect sense to me. And unlike you, I was a rocket scientist. Or rather, engineer. Yes, I delve in the virtual world of design using computer simulation, modeling, prototyping, theory, science and math. I am very good at it. I have multiple engineering and science degrees from multiple respected universities. I know that does not resonate herein the world of blue collar hacks, but I really do not care. I have time to refute your claims, as I will continue to do. I say in your face, Bubba. You are wrong.

 

[Deleted member 83629]

So who had the 4 mix trimmers first? Shinny or Stihl?

not sure but i seen the valve train problems with the 4 mix along with burnt exhaust valves and snapped camshaft.
seen the many piles of br600 blowers were the valve fell out of the head and mangled the engine broken timing belts etc....etc

 

[windthrown]

I understand the concept, and the effect described happens in every 2-stroke to some extent. If the residual combustion pressure in the cylinder exceeds the case pressure when the transfers open, then some exhaust will flow down the transfers. I was looking some evidence that Stihl had enhanced this effect, but none has been discovered. Something like a shorter blowdown angle or an obvious increase in exhaust back pressure for example.

I've certainly never said the Stihl engineers don't know what they are doing. However, I have seen that Stihl marketing has a history of making fancy technical looking documents describing what are actually standard industry design practices (like quad transfers) and/or giving them fancy names (like "Intellicarb"), so their description of typical exhaust blowdown was not remarkable or particularly convincing.

The difference is in the transfers, and that is all you really have to do to make the effect work. Well, that and the intake side ramp to keep them from overheating and keep them lubricated. If you look at all the crap required to make a fresh air stratified saw work, this is a breakthough in engineering. It is subtle, but subtle can make a huge difference. Seemingly it is beyond anyone else here. My challenge would be to remove the ramp (the doohickey) from a stock saw and see how long they last before burning up. If they are the same as pre-EPA saws, as Brad claims, they should run forever w/o the ramp in there.

 

[blsnelling]

You are a broken record. It is subtle, and obviously beyond your comprehension. You are like the Ape spreading disinformation because you cannot figure it out. You have a theory that is based on nothing but conjecture and after the fact observations. You are just displaying your stubbornness and lack of mechanical ability to THINK.

My father was a lawyer from Brooklyn, NY. He used to tell me, "Son, never get into a fight with someone with nothing to lose." Well, Brad, I have nothing to lose here. I am not making money off of fools sending me saws to do pop-up mods on (which I believe are inferior to cut squish mods, but that is another topic). You are simply wrong. Nothing you have claimed has convinced me otherwise, and everything I have seen from Stihl makes perfect sense to me. And unlike you, I was a rocket scientist. Or rather, engineer. Yes, I delve in the virtual world of design using computer simulation, modeling, prototyping, theory, science and math. I am very good at it. I have multiple engineering and science degrees from multiple respected universities. I know that does not resonate herein the world of blue collar hacks, but I really do not care. I have time to refute your claims, as I will continue to do. I say in your face, Bubba. You are wrong.

You should try reading your own writing and apply it to yourself. You're doing a fantastic job of describing yourself. Your silence is deafening on how many of these you have been into. BTW, your not the only engineer in this conversation...not that it matters.

 

[fordf150]

nothing to post pics of. lots of P&C carnage but no crank failures but it does show how many of these saws have had crank problems when the owner makes the guess that it needs a crankshaft.

 

[bwalker]

I understand the concept, and the effect described happens in every 2-stroke to some extent. If the residual combustion pressure in the cylinder exceeds the case pressure when the transfers open, then some exhaust will flow down the transfers. I was looking some evidence that Stihl had enhanced this effect, but none has been discovered. Something like a shorter blowdown angle or an obvious increase in exhaust back pressure for example.

I've certainly never said the Stihl engineers don't know what they are doing. However, I have seen that Stihl marketing has a history of making fancy technical looking documents describing what are actually standard industry design practices (like quad transfers) and/or giving them fancy names (like "Intellicarb"), so their description of typical exhaust blowdown was not remarkable or particularly convincing.

There is no residual pressure because the combustion chamber would be at atmospheric shortly after the exhaust port opens. Then the transfers open and blast residual exhaust out of the combustion chamber.
I can't see how the 461 can be considered a strato saw without dual barrel carb and duct setup, but I haven't inspected one either.

 

[Deleted member 83629]

like a echo 590 it has no cat muffler and a single barrel carb and yet it meets emissions.

 

[Chris-PA]

There is no residual pressure because the combustion chamber would be at atmospheric shortly after the exhaust port opens. Then the transfers open and blast residual exhaust out of the combustion chamber.

At 10,000rpm the transfers open 333microseconds after the exhaust port. I'd place bets on residual combustion pressure, especially if there is much muffler back pressure.

I would like to see some data though.

 

[bwalker]

At 10,000rpm the transfers open 333microseconds after the exhaust port. I'd place bets on residual combustion pressure, especially if there is much muffler back pressure.

I would like to see some data though.

You ever seen exhaust deposits in the transfer ports? I sure havent.
And also keep in mind that even prior to the exhaust port opening pressure has been reduced by a great degree.

 

[Chris-PA]

You ever seen exhaust deposits in the transfer ports? I sure havent.
And also keep in mind that even prior to the exhaust port opening pressure has been reduced by a great degree.

I'm sure cylinder pressure vs. crank angle data exists, but I don't have any so there's no point debating it.

Edit: I just looked at an old cylinder, and yes it does have exhaust deposits in the upper transfers. I also re-read a document about modeling transfer flow on a strato, and it describes flow of exhaust gas into the transfers when the transfer ports first open. Unfortunately it doesn't say how long this lasts, but the implication is clearly that it does not delay the fresh charge very long compared to the column of fresh air in the transfer runners.

 

[STIHLTHEDEERE]

While I don't see the need for either, compare a flip out handle on a screw cap to the Stihl quarter turn flippy cap - what is the relative parts count?

was it a copy of stihl or not? the flippy cap is only an issue for those who are too simple minded to figure them out..................... i am guessing husky simplified it becuase they knew the average husky operator would just stand there dumb founded. after they ran through the initial tank of fuel, the saw may just set there unused until they figured the ever so complicated cap out. it is just a fuel cap, if a guy cant figure it out, then he should probably leave the chainsaw to someone that is a little less challenged with such things.

 

[STIHLTHEDEERE]

yes they are strato. separate air valve. just had 6 more dropped off this morning with at least one of them needing a crankshaft

wow, you have more 362 repairs in this thread than my shops have seen in a couple of years. i guess i never knew it was such a problematic model for stihl. i will look today and see how many crank assemblies BRYAN EQUIP. has warranted in the last couple of years.

 

[Andyshine77]

was it a copy of stihl or not? the flippy cap is only an issue for those who are too simple minded to figure them out..................... i am guessing husky simplified it becuase they knew the average husky operator would just stand there dumb founded. after they ran through the initial tank of fuel, the saw may just set there unused until they figured the ever so complicated cap out. it is just a fuel cap, if a guy cant figure it out, then he should probably leave the chainsaw to someone that is a little less challenged with such things.

You're one arrogant little sob.

I've had flip caps fall apart, have had a few tanks that deformed so the cap would no longer fit, and the cap on my fs110 was recalled. It's simply another part Stihl prioritized. Stihl flip caps are absurd and needlessly over engineered pos. A stupid design for stupid homeowners that use their equipment once a year. aka you!!

 

[ArcticOverland]

was it a copy of stihl or not? the flippy cap is only an issue for those who are too simple minded to figure them out..................... i am guessing husky simplified it becuase they knew the average husky operator would just stand there dumb founded. after they ran through the initial tank of fuel, the saw may just set there unused until they figured the ever so complicated cap out. it is just a fuel cap, if a guy cant figure it out, then he should probably leave the chainsaw to someone that is a little less challenged with such things.