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BundyRumandCoke wrote:90%, not bad for someone who sorts mail all night. That must be why I am heading out soon to drive trains.
You can review your answers. Agree the engine one is a tad BS, if the piston wasnt going down, there would be no room for the atmosphere to force air in, so it really is the piston suction doing it, creating a vacumn.
Air is never sucked anywhere. It is always pushing out from a higher pressure region. Given a lower pressure area it will epand into it to fill it as it tries to equalise. Takes a big piston to reduce the pressure of the entire atmosphere :)
BundyRumandCoke wrote:90%, not bad for someone who sorts mail all night. That must be why I am heading out soon to drive trains.
You can review your answers. Agree the engine one is a tad BS, if the piston wasnt going down, there would be no room for the atmosphere to force air in, so it really is the piston suction doing it, creating a vacumn.
Air is never sucked anywhere. It is always pushing out from a higher pressure region. Given a lower pressure area it will epand into it to fill it as it tries to equalise. Takes a big piston to reduce the pressure of the entire atmosphere
Paul
They're talking diesels to, so no vacuum
Wanted: Car trailer or beaver tail truck, let me know what you got
-Scott- wrote:Q31 is *****! The diagram is poorly drawn. If it was accurate, the correct answer isn't there.
What was wrong with how it was drawn? And what would the correct answer be?
Doesn't show precisely where the mass acts. If CoG of each box is the centre of the box the lever ratio would (should) be 5:1. Their answer has the mass acting through the outer edge of the box (6:2 = 3:1).
me3@neuralfibre.com wrote:
96%
Q8 - Sun gear - wording is very poor - rotates vs turns (I got confused)
So did I - it referred to the sun gear "rotating" so I just hoped they were consistent with their terms.
me3@neuralfibre.com wrote:
Pulley questions - should say to neglect pulley friction
Never occurred to me.
me3@neuralfibre.com wrote:Q44 - Venturi - I don't beleive their answer. My spa bath shows very clearly water doesn't rise up the venturi tube. (second tube). First tube would rise due to static pressure before restriction.
That's the one I got wrong - got hung up thinking about Venturis, and forgot it's not a carburettor. In the example, the fluid at the entrance to the main tube is above atmospheric, in a carburettor it's (traditionally) below atmospheric. But I don't have a spa bath, either.
I got 80%, and I'm a student engineer, hah ha not good . Did it in 8 minutes though. the diagrams arn't the problem, I think some of the wordings in some of the multi-choice answers are not too clear. Oh also, I hate electrics, I blame that for my poor result.
Gwagensteve wrote:
zagan wrote:Are these EFI engines?
If so it'll depend on the map on the CPU as it depends on what map you use as to what the rpm will be.
an example
a bad map might be 3000rpm for 100klm chew up heaps of fuel.
A good map might be 1500rpm for 100klm and use very little fuel.
Gearing won't mean much if the engine has EFI.
can anyone troubleshoot this guy's efi though?
Steve.
I think its something to do with reletivity. If your map is rotating it changes the relative rpm of your engine with respect to your map. Why a 'good map' would rotate I dont't know? Don't know how this helps fuel economy either?
Unless its an auto and the map governs the torque convertor somehow...
Wheeling on completely wicked angles, without even looking stable.
-Scott- wrote:Q31 is *****! The diagram is poorly drawn. If it was accurate, the correct answer isn't there. :bad-words:
Answer should be 60kg shouldn't it?
Box A centreline is 1 bar from the pivot, weighs 300kg.
Box B centreline is 5 bars from the pivot, 300/5 = 60.
I got 88%, made easy cockups and couldn't go back. :oops: Will do it again later and take more than 8 minutes.
You are correct. Their diagram is poor. If you base it on the weight being on the outside edge of the box the ratio is 3:1
Typical multiple choice answer behaviour - choose the most correct answer.
bad_religion_au wrote:goit 80%, although i swear going back through them that the answer i clicked and the answer it said i clicked were completely different.
and the engine one... isn't the air drawn into the cylinder due to a difference in atmospheric pressure vs that of the cylinder? and what causes the difference (yes i got it wrong)
No, its pushed in by atmospheric pressure, Naturally aspirated
BUT atmospheric pressure can't push anything IF the cylinder was also at atmospheric pressure. the only reason the cylinder is at lower pressure than the atmosphere is the vaccum created by the piston moving down...
bad_religion_au wrote:goit 80%, although i swear going back through them that the answer i clicked and the answer it said i clicked were completely different.
and the engine one... isn't the air drawn into the cylinder due to a difference in atmospheric pressure vs that of the cylinder? and what causes the difference (yes i got it wrong)
No, its pushed in by atmospheric pressure, Naturally aspirated
BUT atmospheric pressure can't push anything IF the cylinder was also at atmospheric pressure. the only reason the cylinder is at lower pressure than the atmosphere is the vaccum created by the piston moving down...
Alright, i'll take the simple line (diesel not petrol) seeing as the site is about diesels, diesels do not creat vacuum, as they are open to atmoshpere all the time, they do not use butterfly's (yes I know their is a few that do, but most don't ), so if there is no vacuum, how does the air fill the void, when the piston moves down?? wouldn't be atmospheric pressure would it.............
Wanted: Car trailer or beaver tail truck, let me know what you got
cloughy wrote:
Alright, i'll take the simple line (diesel not petrol) seeing as the site is about diesels, ....
so if there is no vacuum, how does the air fill the void, when the piston moves down?? wouldn't be atmospheric pressure would it.............
HUH. Vacuum, by definition IS a VOID... if there is no vacuum there is no VOID to fill???
Also no motor i'm familiar with uses butterflies to control airflow into the cylinder, they use valves
Righto, following what you've written, a diesel engine does not produce vacuum FACT, how the fark does the air get in there hey??
How the fark can valves be use to CONTROL airflow, they are used to time it and for how long, the amount of airflow (air/fuel) on a petrol engine is REGULATED by a butterfly and as stated before, diesel's are open to full atmosphere all the time, just the valves let air in for the required time and duration
Fark I hate argueing with learned people bloody uni students
Wanted: Car trailer or beaver tail truck, let me know what you got
"Vacuum" in this sense just means pressure lower than atmosphere ie relative vacuum. Clearly it's not an absolute vacuum so in that sense no engine really produces an actual vacuum.
I think that question was out of whack with the others because it was about a technical definition of something, rather than the more practical "how it works" angle of all the others.
The answer would be the same for a petrol or diesel engine, it is technically atmospheric pressure (or boosted atmospheric pressure) that forces air into the cylinder as the piston moves down to make a space for it. In moving down it has to create a relative vacuum (again, lower than atmospheric pressure) for the atmospheric pressure to force air in there.
When we talk about "vacuum" with a petrol engine it's not true vacuum, it's just a lower-than-atmospheric-pressure body of air.
cloughy wrote:
Alright, i'll take the simple line (diesel not petrol) seeing as the site is about diesels, ....
so if there is no vacuum, how does the air fill the void, when the piston moves down?? wouldn't be atmospheric pressure would it.............
HUH. Vacuum, by definition IS a VOID... if there is no vacuum there is no VOID to fill???
Also no motor i'm familiar with uses butterflies to control airflow into the cylinder, they use valves
Righto, following what you've written, a diesel engine does not produce vacuum FACT, how the fark does the air get in there hey??
How the fark can valves be use to CONTROL airflow, they are used to time it and for how long, the amount of airflow (air/fuel) on a petrol engine is REGULATED by a butterfly and as stated before, diesel's are open to full atmosphere all the time, just the valves let air in for the required time and duration
Fark I hate argueing with learned people bloody uni students
my diesel has a butterfly....
[quote="Barnsey"]
Bronwyn Bishop does it for me.[/quote]
cloughy wrote:
Alright, i'll take the simple line (diesel not petrol) seeing as the site is about diesels, ....
so if there is no vacuum, how does the air fill the void, when the piston moves down?? wouldn't be atmospheric pressure would it.............
HUH. Vacuum, by definition IS a VOID... if there is no vacuum there is no VOID to fill???
Also no motor i'm familiar with uses butterflies to control airflow into the cylinder, they use valves
Righto, following what you've written, a diesel engine does not produce vacuum FACT, how the fark does the air get in there hey??
How the fark can valves be use to CONTROL airflow, they are used to time it and for how long, the amount of airflow (air/fuel) on a petrol engine is REGULATED by a butterfly and as stated before, diesel's are open to full atmosphere all the time, just the valves let air in for the required time and duration
Fark I hate argueing with learned people :roll: bloody uni students
my diesel has a butterfly.... :D
We had a storm here a few weeks back. When did it last flap it's wings?
*sorry*
On a similar note, whose diesel has a vacuum reservoir tank full of vacuum......
cloughy wrote:
Alright, i'll take the simple line (diesel not petrol) seeing as the site is about diesels, ....
so if there is no vacuum, how does the air fill the void, when the piston moves down?? wouldn't be atmospheric pressure would it.............
HUH. Vacuum, by definition IS a VOID... if there is no vacuum there is no VOID to fill???
Also no motor i'm familiar with uses butterflies to control airflow into the cylinder, they use valves
Righto, following what you've written, a diesel engine does not produce vacuum FACT, how the fark does the air get in there hey??
How the fark can valves be use to CONTROL airflow, they are used to time it and for how long, the amount of airflow (air/fuel) on a petrol engine is REGULATED by a butterfly and as stated before, diesel's are open to full atmosphere all the time, just the valves let air in for the required time and duration
Fark I hate argueing with learned people bloody uni students
Your talking about vacuum (or relative vacuum as chimpboy rightly points out) in the intake manifold i assume. in the actual cylinder, the piston moving down creates a region of lower than atmospheric pressure, which leads to the pressure difference required to see air move into the cylinder.
with no pressure difference between the atmosphere and the cylinder interior, you'd get no air movement, unless you had a compressor pushing air in... which would be turbo'd
cloughy wrote:
Alright, i'll take the simple line (diesel not petrol) seeing as the site is about diesels, ....
so if there is no vacuum, how does the air fill the void, when the piston moves down?? wouldn't be atmospheric pressure would it.............
HUH. Vacuum, by definition IS a VOID... if there is no vacuum there is no VOID to fill???
Also no motor i'm familiar with uses butterflies to control airflow into the cylinder, they use valves
Righto, following what you've written, a diesel engine does not produce vacuum FACT, how the fark does the air get in there hey??
How the fark can valves be use to CONTROL airflow, they are used to time it and for how long, the amount of airflow (air/fuel) on a petrol engine is REGULATED by a butterfly and as stated before, diesel's are open to full atmosphere all the time, just the valves let air in for the required time and duration
Fark I hate argueing with learned people bloody uni students
Your talking about vacuum (or relative vacuum as chimpboy rightly points out) in the intake manifold i assume. in the actual cylinder, the piston moving down creates a region of lower than atmospheric pressure, which leads to the pressure difference required to see air move into the cylinder.
with no pressure difference between the atmosphere and the cylinder interior, you'd get no air movement, unless you had a compressor pushing air in... which would be turbo'd
Correct, lower than atmospheric pressure, not a true vacuum, hence there is no "real" suck, its a pressure differential, so the higher pressure, PUSHES the air in, it is not sucked in, for fark sake, maybe read some text on the matter, instead of me trying to convince you
I'm just telling you what the fact is, and why you got the question wrong
Wanted: Car trailer or beaver tail truck, let me know what you got
bad_religion_au wrote:goit 80%, although i swear going back through them that the answer i clicked and the answer it said i clicked were completely different.
and the engine one... isn't the air drawn into the cylinder due to a difference in atmospheric pressure vs that of the cylinder? and what causes the difference (yes i got it wrong)
No, its pushed in by atmospheric pressure, Naturally aspirated
BUT atmospheric pressure can't push anything IF the cylinder was also at atmospheric pressure. the only reason the cylinder is at lower pressure than the atmosphere is the vaccum created by the piston moving down...
Alright, i'll take the simple line (diesel not petrol) seeing as the site is about diesels, diesels do not creat vacuum, as they are open to atmoshpere all the time, they do not use butterfly's (yes I know their is a few that do, but most don't ), so if there is no vacuum, how does the air fill the void, when the piston moves down?? wouldn't be atmospheric pressure would it.............
Read the WHOLE thread maybe
Wanted: Car trailer or beaver tail truck, let me know what you got
In the example, the fluid at the entrance to the main tube is above atmospheric, in a carburettor it's (traditionally) below atmospheric. But I don't have a spa bath, either. 
How do you find out which ones you get wrong?
), so if there is no vacuum, how does the air fill the void, when the piston moves down?? wouldn't be atmospheric pressure would it.............
