Tree Monkey MS462 - PART 2

[tree monkey]

So there's more pumping and sucking going on in your average 2 stroke than a first year college dormitory[/B]

best explanation iv'e heard yet

 

[cus_deluxe]

And the strength of the negative pressure (vacuum, suction) dictates the speed at which a given volume is filled by ambient pressure. Both lines of thinking are correct IMO. Different ways to arrive at the same conclusion...chainsaws suck. Lol!

Agree, i guess the end of my point was that saying the piston does none of the work in this whole thing is not right, since its the thing that creates the vacuum which allows the atmospheric pressure to fill the case. It really is two sides of the same coin.

 

[XP_Slinger]

Agree, i guess the end of my point was that saying the piston does none of the work in this whole thing is not right, since its the thing that creates the vacuum which allows the atmospheric pressure to fill the case. It really is two sides of the same coin.

Yes sir it sure is Custer.

 

[retro]

I knew I was gonna open a can of worms. The filling process cannot be explained by saying it is two sides of the same coin though... that somehow drawing a column of air is the same as it being pushed. There is no drawing of air.

The piston does very little work while the motor is filling. Its swept movement increases the volume of the crankcase, which is almost immediately being filled at near the same rate as its volume is increasing, by pressurized external air, in accordance with its port timing events, port shape and port volume. Filling is initiated as a response to piston motion. Very little stretching of air molecules is taking place inside the crankcase, so the piston does not have to do much work during filling. A true pump must perform all of the work required for filling. So there is nothing to be gained by thinking of a motor as a pump.

Nitpicking I know... but look around and you'll find many, many folks who maintain a false pumping model in their minds. While modding for performance those folks typically resort to brute force tactics over time, attempting to create different variations of a pump... which can lead a person to repeat past mistakes while becoming one-trick ponies... because they cannot divorce themselves from false pump model concepts.

Can 'o worms, those damn motors are, regardless. But if you're gonna brute force a strato motor to behave as a conventionally scavenged motor, you're probably better off to begin with (or convert to) a conventional design in the first place. Got lemons...? Make lemonade.

Hope I'm not coming across as being a dick head. I'm not very good at this stuff.

 

[Deets066]

I knew I was gonna open a can of worms. The filling process cannot be explained by saying it is two sides of the same coin though... that somehow drawing a column of air is the same as it being pushed. There is no drawing of air.

The piston does very little work while the motor is filling. Its swept movement increases the volume of the crankcase, which is almost immediately being filled at near the same rate as its volume is increasing, by pressurized external air, in accordance with its port timing events, port shape and port volume. Filling is initiated as a response to piston motion. Very little stretching of air molecules is taking place inside the crankcase, so the piston does not have to do much work during filling. A true pump must perform all of the work required for filling. So there is nothing to be gained by thinking of a motor as a pump.

Nitpicking I know... but look around and you'll find many, many folks who maintain a false pumping model in their minds. While modding for performance those folks typically resort to brute force tactics over time, attempting to create different variations of a pump... which can lead a person to repeat past mistakes while becoming one-trick ponies... because they cannot divorce themselves from false pump model concepts.

Can 'o worms, those damn motors are, regardless. But if you're gonna brute force a strato motor to behave as a conventionally scavenged motor, you're probably better off to begin with (or convert to) a conventional design in the first place. Got lemons...? Make lemonade.

Hope I'm not coming across as being a dick head. I'm not very good at this stuff.

Motors are electric
Engines are gas

Hope I’m not coming across as a dick but your wrong

 

[retro]

Hope I'm not coming across as being a dick head. I'm not very good at this stuff.

I did stay at a Holiday Inn once tho...

 

[RI Chevy]

I knew some girls in HS and College that created nice vacuum! Like an old Hoover!

 

[cus_deluxe]

So what ur tellin me is...

 

[Deets066]

So what ur tellin me is...
View attachment 154528

Yes

 

[Deets066]

So what ur tellin me is...
View attachment 154528

Carbs are run by low atmospheric pressure... which is definitely not created by the piston.

 

[RI Chevy]

Smoke and mirrors! [emoji106]

 

[huskihl]

Air is like golf balls

 

[XP_Slinger]

I knew I was gonna open a can of worms. The filling process cannot be explained by saying it is two sides of the same coin though... that somehow drawing a column of air is the same as it being pushed. There is no drawing of air.

The piston does very little work while the motor is filling. Its swept movement increases the volume of the crankcase, which is almost immediately being filled at near the same rate as its volume is increasing, by pressurized external air, in accordance with its port timing events, port shape and port volume. Filling is initiated as a response to piston motion. Very little stretching of air molecules is taking place inside the crankcase, so the piston does not have to do much work during filling. A true pump must perform all of the work required for filling. So there is nothing to be gained by thinking of a motor as a pump.

Nitpicking I know... but look around and you'll find many, many folks who maintain a false pumping model in their minds. While modding for performance those folks typically resort to brute force tactics over time, attempting to create different variations of a pump... which can lead a person to repeat past mistakes while becoming one-trick ponies... because they cannot divorce themselves from false pump model concepts.

Can 'o worms, those damn motors are, regardless. But if you're gonna brute force a strato motor to behave as a conventionally scavenged motor, you're probably better off to begin with (or convert to) a conventional design in the first place. Got lemons...? Make lemonade.

Hope I'm not coming across as being a dick head. I'm not very good at this stuff.

So explain the vacuum pulse that actuates the fuel pump diaphragm in the carb. I’m not trying to be combative on this either but I definitely do not see things the way you do. If the motion of the piston doesn’t create vacuum then I seriously need to go back to the drawing board on what I thought I knew about combustion engines. That and GM put “vacuum” lines on engines just to piss us all off in the 80’s...lol!!!! If this ends up going too far around the barn shoot me a PM so we don’t kill Scott’s thread.

 

[huskihl]

So explain the vacuum pulse that actuates the fuel pump diaphragm in the carb. I’m not trying to be combative on this either but I definitely do not see things the way you do. If the motion of the piston doesn’t create vacuum then I seriously need to go back to the drawing board on what I thought I knew about combustion engines. That and GM put “vacuum” lines on engines just to piss us all off in the 80’s...lol!!!! If this ends up going too far around the barn shoot me a PM so we don’t kill Scott’s thread.

In the scientific world, there is no such thing as a vacuum. Only positive or negative pressure. Positive pressure pushes air into an area with lower pressure.

 

[Gary Courtney]

And the strength of the negative pressure (vacuum, suction) dictates the speed at which a given volume is filled by ambient pressure. Both lines of thinking are correct IMO. Different ways to arrive at the same conclusion...chainsaws suck. Lol!

When I was pumping the engine hooked to a hydrant I continuously watched my gauges,for some systems I could pull the water out of the water mains and collapse them.

 

[Gary Courtney]

In the scientific world, there is no such thing as a vacuum. Only positive or negative pressure. Positive pressure pushes air into an area with lower pressure.

Cabin of an airplane at high altitudes is an example of + ,- pressures. When William Shatner saw a gremlin on the wing of the plane he learned about negative pressure real quick !

 

[XP_Slinger]

In the scientific world, there is no such thing as a vacuum. Only positive or negative pressure. Positive pressure pushes air into an area with lower pressure.

You’re right, I used the wrong term. But my point remains that without a negative pressure differential (mistakenly referred to as vacuum) ambient pressure would not move through the intake to fill the case. And this pressure differential IS produced by the upward movement of the piston. I’m spent...lol

 

[Fruecrue]

Girls, You’re all pretty.

 

[Deets066]

Girls, You’re all pretty.

Too much of that *s-word, somebody has to be the loser

 

[AlfA01]

Girls, You’re all pretty.

I laffed.