Synthetic 2-stroke oils??

[ShoerFast]

May I suggest explaining to Ben the difference between indicated air speed and true airspeed and the correlating temp/altitude parameters? Did I say that pretty enough?
Andy...you can answer this one if you want to.

That was pretty!

Is it safe to assume that he knows those things? He did make the statement.

 

[Gologit]

That was pretty!

Is it safe to assume that he knows those things? He did make the statement.

LOL...Probably Googling like a madman even as we speak. Go Ben go.

 

[Lakeside53]

May I suggest explaining to Ben the difference between indicated air speed and true airspeed and the correlating temp/altitude parameters? Did I say that pretty enough?
Andy...you can answer this one if you want to.

Na.. I'll wait for Ben... Might have already given the show away in post 74 anyhow..

 

[ShoerFast]

LOL...Probably Googling like a madman even as we speak. Go Ben go.

Yup Yup !

Wildthinggy is, the more he comes up with, the further away he is getting!

 

[bwalker]

Before you get all flustered, if I may ask, what is the airspeed of an AC trimmed out for level flight at 5000' , compared to the same AC, same trim at 10,000' flying level. if I may ask?

The word I was trying to type was "analogous".
I am not talking about speed but aerodynamic drag vs HP in the case of the plane. And the drag of the wood vs. hp in the saw.
The plane at cruising altitude is under less load, due tot he thinner air, no? Hence the reason airlines fly so high.

To clarify. In the case of the plane as operating altitude goes up HP of the motor falls, but so does the thickness of the atmosphere the plain is flying in lessening the effect. To what degree these factors even out I am not sure, but there is something to the relationship I described.
The saw on the other hand loses HP at altitude, but the job its required to do stays the same. The operator may keep the saw in its happy RPM range, but its still taking longer, IE higher load to do the same job.

 

[precaud]

bwalker's analogy is correct. You can experience this for yourself with a car. Drive it at sea level, then come up here to 7,000 ft and see the difference. Much less power, but much greater fuel efficiency, due to the lessened drag thru the thinner air. I'm always shocked when I drive to sea level and feel all that low-rpm torque but also see the gas mileage drop 20%.

 

[Tzed250]

Actually Ben, most aircraft make max HP at high and low altitudes (recip) due to forced induction. Commercial engines have torque meters on them so the Pilot knows what power level each engine is making.

 

[PES+]

Error

The increase in MPG is due to less density of the air which the car's computer senses and delivers less fuel accordingly

A completely different ball of feathers

Take a saw tuned at sea level and take it up to 7000 feet and it will use the same amount of fuel per unit of time but be severly over rich and blubber all over itself

Now....you cut as fast as the saw will allow and tuned for the best possible running at the altitude you are cutting. The load is slightly less and it takes more time to get the whole job done so the work done per unit of fuel is a wash

Maybe we could look into the lower air resitance to the chain cutters and the chips

 

[ShoerFast]

The word I was trying to type was "analogous".
I am not talking about speed but aerodynamic drag vs HP in the case of the plane. And the drag of the wood vs. hp in the saw.
The plane at cruising altitude is under less load, due tot he thinner air, no? Hence the reason airlines fly so high.

To clarify. In the case of the plane as operating altitude goes up HP of the motor falls, but so does the thickness of the atmosphere the plain is flying in lessening the effect. To what degree these factors even out I am not sure, but there is something to the relationship I described.
The saw on the other hand loses HP at altitude, but the job its required to do stays the same. The operator may keep the saw in its happy RPM range, but its still taking longer, IE higher load to do the same job.

It was almost a trick question, but fell in line with your statement, the "air" speed stays the same, as it takes that much air to keep afloat so to speak.

The HP ( bottom line, thrust) has to always equal the drag for a fixed speed.

Jets and augmented engines are a different story, if you can keep a turbine engine cool, there HP , or the better word thrust can be bought more efficient, and will go up at altitude , sort of a rule, it's like -20 bellow at a good cruise altitude. (warm air in, hot air out, a little gain,,,, very cold air in, hot air out, efficacy)


What I found at chainsaw altitude, just to keep the efficacy there, in this case, chain speed, is to not get so aggressive with the depth gauges, and jump to skip chain sooner then you might have to on flat land. Yes it takes longer.

Plug in a 90 deg day, 29.92"hg an 85 deg dew point (bad day weather) @10000" here :

http://wahiduddin.net/calc/calc_hp_dp.htm

take a 7.0 HP saw, by the relative HP%,,,,, I come up with an MS-660 equal to an MS-361 on a good day on flat land?

A catch 22 that works for saws at altitude is that the cooling fan is less efficient, (noticeably less sideways air) but so are the cooling fins demand to get rid of the heat is lower at a bigger rate (engine efficiency seem to drop of faster then the fans ability).

To me, what that would have to do with the oil, other then burning clean/deposits, is lessan the demands, a good thing.

 

[ShoerFast]

bwalker's analogy is correct. You can experience this for yourself with a car. Drive it at sea level, then come up here to 7,000 ft and see the difference. Much less power, but much greater fuel efficiency, due to the lessened drag thru the thinner air. I'm always shocked when I drive to sea level and feel all that low-rpm torque but also see the gas mileage drop 20%.

You may have what they call "new cam syndrom" people that install a good milage gaining cam sometimes dont see the effect, till theu get there foot out of all the extra TQ?

 

[Steve128]

Ben's point

Are the engines even working in the same manner? I thought plane engine's are more of limited r.p.m. use and chainsaws vary considerably.

 

[PES+]

Now that old thread comes more clear eh?

With less air it follows that less fuel is needed for best performance

less fuel and less air = less torque

HP is a function of Torque over a set amount of time

Less torque means it takes longer to do the work hence lower HP

The loading is pretty close to the same or close to a wash

With less fuel and air you will never make the same HP

RPMs have nothing to do with it

 

[ShoerFast]

Are the engines even working in the same manner? I thought plane engine's are more of limited r.p.m. use and chainsaws vary considerably.

No, not faltering at all, good post really.

Constant speed props had a huge effect in keeping AC engines out put the same. Maybe easier to visualise on a helicopter, that roter needs to equal the weight perfectly in a hover, it can hover at 2000 feet, or at 10000 feet with the same roter speed and TQ setting, the pitch of the blades is just more at 10000 feet. but the engine is doing the same amount of work.

With a chainsaw, to me, there is no more, if you set the saw up to just barely burble out of the wood, but run clean in the wood, the in the wood speed will be slower because it can not scavage as well as it can at a lower altitude.

Just as the helicopter can hover with the same power setting (TQ) high or low, it can not climb as fast at altitude, chainsaws will burble / not burble at close to the same speed (4-cycle) , 13,300 on my 660, it still will not cut as fast, or work harder, taking more time is less work.

 

[sILlogger]

I Disagree!!

:greenchainsaw: :greenchainsaw:

The word I was trying to type was "analogous".
I am not talking about speed but aerodynamic drag vs HP in the case of the plane. And the drag of the wood vs. hp in the saw.
The plane at cruising altitude is under less load, due tot he thinner air, no? Hence the reason airlines fly so high.

To clarify. In the case of the plane as operating altitude goes up HP of the motor falls, but so does the thickness of the atmosphere the plain is flying in lessening the effect. To what degree these factors even out I am not sure, but there is something to the relationship I described.
The saw on the other hand loses HP at altitude, but the job its required to do stays the same. The operator may keep the saw in its happy RPM range, but its still taking longer, IE higher load to do the same job.

I just got to say this!!!! down here in the lower altitudes we(I in this instance) cut exclusively hardwood, this, being harder, cuts slower than softwood, therefore, even tho the saw is making more hp at lower altitudes it is having to cut a harder wood. The higher altitude saws, making less hp are cutting a softer wood, does this ever even out????? the world will never know?!!?!?!? just wanted to give someone a hard time--hadn't got to today!!!

p.s. i have noticed that you guys out west and up north can run longer bars on smaller saws in softwood than we could ever dream of down here. around here a 046 with a 28-36" bar would have an extremely tough time in hardwood,(i dont' run over a 20" on my 046BB):greenchainsaw:

 

[ShoerFast]

:greenchainsaw: :greenchainsaw:

I just got to say this!!!! down here in the lower altitudes we(I in this instance) cut exclusively hardwood, this, being harder, cuts slower than softwood, therefore, even tho the saw is making more hp at lower altitudes it is having to cut a harder wood. The higher altitude saws, making less hp are cutting a softer wood, does this ever even out????? the world will never know?!!?!?!? just wanted to give someone a hard time--hadn't got to today!!!

p.s. i have noticed that you guys out west and up north can run longer bars on smaller saws in softwood than we could ever dream of down here. around here a 046 with a 28-36" bar would have an extremely tough time in hardwood,(i dont' run over a 20" on my 046BB):greenchainsaw:

Being from Minnesota, did a lot of cutting there, and to get an idea, find a huge Basswood that is not hallow, or a Balsum Fir, you can even tell a little differance from a Suger Maple (hard) to a Silver Maple (soft) . But dig into an old onery Douglas Fir here, one from the windy side, 200 years old and almost 24" DBH, there may be that point that it evens out?

But your right, that Douglas Fir maybe cuts like a Red Elm there, give or take?

Get into a big Ponderosa Pine , cut it when it's so green that water runs out of it and you would think your saw has "happy gas" ,,,,, let it dry and toss it in your stove on a cold day, and you'll wonder why you cut it?

 

[Lakeside53]

do stays the same. The operator may keep the saw in its happy RPM range, but its still taking longer, IE higher load to do the same job.

Now I'm really confused.. it takes longer because it has a lower HP, not a higher load.

 

[ShoerFast]

Huh? Now you're talking ground speed.... but the engine doesn't know or feel how fast the ground is going by..

Sure the wood stays the same, but you, the user, still keeps the saw at max hp, but now it's MUCH less hp.. less heat and less stress (except maybe by the user working the clutch).

Boboak

Now thats pretty to

 

[59Billy]

:hmm3grin2orange: :hmm3grin2orange: :hmm3grin2orange: Didn't stop me:biggrinbounce2:

Now that I think of it, detuning-for-longevity provides an excuse for buying bigger and bigger saws...

 

[precaud]

Error

The increase in MPG is due to less density of the air which the car's computer senses and delivers less fuel accordingly

Well, this happened to my vehicles even before they had computers in them.

Take a saw tuned at sea level and take it up to 7000 feet and it will use the same amount of fuel per unit of time but be severly over rich and blubber all over itself

Yes, we see that all the time up here with out-of-state cars. It's simplistic to think that's the only factor at play. I don't.

 

[bwalker]

Now I'm really confused.. it takes longer because it has a lower HP, not a higher load.

Longer time to finish the cut= higher load.