Question to Physicists? Engineers? Anybody?
09-14-2005, 01:12 PM
#42
Drifting
Originally Posted by mp3car
I hope you're joking about the atomic clock in our cars.... right??? 
(we do of course have "atomic time" available to us though (those of us with Nav)... from the multiple atomic clocks on board each gps satelite, which i think are even sychronized regularly to an even more accurate atomic clock back on earth.)
(we do of course have "atomic time" available to us though (those of us with Nav)... from the multiple atomic clocks on board each gps satelite, which i think are even sychronized regularly to an even more accurate atomic clock back on earth.)
09-14-2005, 06:31 PM
#43
WDP Director of R & D
Originally Posted by Legend2TL
In relative terms we all have pressure in the manifold.
All depends what it is compared to (atmosphere pressure at sea level, 0 torre,...)
All depends what it is compared to (atmosphere pressure at sea level, 0 torre,...)
And that is what mp3car was referring to - more vacuum usually results in higher gas mileage.
09-15-2005, 12:51 AM
#44
Instructor
Join Date: Jul 2004
Location: Jacksonville, FL
Age: 60
Posts: 230
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by mp3car
No, 2750 in 6th gear is using more gas. Laws of physics require it.
The question is whether this mechanical friction loss is greater than the loss due to aerodynamic drag at the speeds of the higher gear.
Plus, if you check the original question, it's not about a comparable RPM in both gears. The question compared an absurdly high RPM in second to a low RPM in a higher gear.
09-26-2005, 08:56 AM
#45
Power = (Work / Time)
Work = (Force x Distance) (Work has to have displacement. If you drove 1 mile east then 1 mile west, you have done no work)
==>Power = (Force x Distance)/Time
Case A : 25 MPH @ 5000 RPM in 2nd Gear
Case B : 65 MPH @ 2750 RPM in 6th Gear
Let say for the sake of arguement, we both drive for 1 hour in both situations. In 1 hour,
Case A will travel 25 Miles in 1 hour
Case B will travel 65 Miles in 1 hour
Taking the Gear ratio of 2nd and 6th gear and final drive ratio of of a 2006 TL 6 speed, it is 2.48, 0.77 and 3.29 respectively. By multiplying the the gear ratio and the final drive ratio, you get total drive ratio (considering the same wheel size)The ratio is multiplied by the torque to aquire the "total work" the engine can do. So in second gear you have a total drive ratio of 2.48x3.29=8.1592 in 2nd gear and .77x3.29=2.533 drive ratio. So in 2nd gear, the "total work" the engine can do is 8.1292x233ft.lbs=1894ft.lbs. In 6th gear, the "total work" is 2.533x233ft.lbs=590ft.lbs. (Assuming the torque 233 ft.lbs is flat and pretty much constant over those rpm values). So multiplying Work & Distance gives us
Power = 47350 (ft.lbs.mile)/hour in 2nd gear
Power =38350 (ft.lbs.mile)/hour in 6th gear
% Difference = (47350-38350)/38350 = 23%
*The units of power above aren't converted to any standard....any other numerical factor that I left out is similar to both cases and will cancel out in the end so I just left it out.
The friction from the tire to the ground is the same in both cases, the air drag is different and the internal friction of the engine I have left out since there is no easy way of measuring it.
Some of you might bring out the point that I didn't use the RPM in my calculations. The RPM doesn't need to be calculated because it doesn't matter. becuase we already have the speed of 25 and 65 MPH. Reason : If you are in second gear @ 5000 RPM, you will always be @ 25 MPH, same goes for 65 MPH (considering you are on a flat surface for both conditions). So saying "I'm traveling at 25 MPH" and "I'm traveling in 2nd gear @ 5000 MPH" are one in the same, again, considering you are on flat surface and constant velocity.
So 25 MPH @ 5000RPM in 2nd gear USES more GAS then 65 MPH @ 2750 RPM in 6th gear, about 20% more gas.
Some reference I used.
http://tutor4physics.com/examplesworkdone.htm
http://en.wikipedia.org/wiki/Horsepower
Work = (Force x Distance) (Work has to have displacement. If you drove 1 mile east then 1 mile west, you have done no work)
==>Power = (Force x Distance)/Time
Case A : 25 MPH @ 5000 RPM in 2nd Gear
Case B : 65 MPH @ 2750 RPM in 6th Gear
Let say for the sake of arguement, we both drive for 1 hour in both situations. In 1 hour,
Case A will travel 25 Miles in 1 hour
Case B will travel 65 Miles in 1 hour
Taking the Gear ratio of 2nd and 6th gear and final drive ratio of of a 2006 TL 6 speed, it is 2.48, 0.77 and 3.29 respectively. By multiplying the the gear ratio and the final drive ratio, you get total drive ratio (considering the same wheel size)The ratio is multiplied by the torque to aquire the "total work" the engine can do. So in second gear you have a total drive ratio of 2.48x3.29=8.1592 in 2nd gear and .77x3.29=2.533 drive ratio. So in 2nd gear, the "total work" the engine can do is 8.1292x233ft.lbs=1894ft.lbs. In 6th gear, the "total work" is 2.533x233ft.lbs=590ft.lbs. (Assuming the torque 233 ft.lbs is flat and pretty much constant over those rpm values). So multiplying Work & Distance gives us
Power = 47350 (ft.lbs.mile)/hour in 2nd gear
Power =38350 (ft.lbs.mile)/hour in 6th gear
% Difference = (47350-38350)/38350 = 23%
*The units of power above aren't converted to any standard....any other numerical factor that I left out is similar to both cases and will cancel out in the end so I just left it out.
The friction from the tire to the ground is the same in both cases, the air drag is different and the internal friction of the engine I have left out since there is no easy way of measuring it.
Some of you might bring out the point that I didn't use the RPM in my calculations. The RPM doesn't need to be calculated because it doesn't matter. becuase we already have the speed of 25 and 65 MPH. Reason : If you are in second gear @ 5000 RPM, you will always be @ 25 MPH, same goes for 65 MPH (considering you are on a flat surface for both conditions). So saying "I'm traveling at 25 MPH" and "I'm traveling in 2nd gear @ 5000 MPH" are one in the same, again, considering you are on flat surface and constant velocity.
So 25 MPH @ 5000RPM in 2nd gear USES more GAS then 65 MPH @ 2750 RPM in 6th gear, about 20% more gas.
Some reference I used.
http://tutor4physics.com/examplesworkdone.htm
http://en.wikipedia.org/wiki/Horsepower
09-26-2005, 10:06 AM
#46
Originally Posted by mp3car
No, 2750 in 6th gear is using more gas. Laws of physics require it.
If I then walk those same number of steps again without the 100Lbs, this time taking larger steps, but at the same steps per minute, then I will go more than 100ft, in the same amount of time and my "rpms" were the same. It still took more overall energy for me to take the larger steps even though I still took the same number of steps in the same amount of time.
If I then walk those same number of steps again without the 100Lbs, this time taking larger steps, but at the same steps per minute, then I will go more than 100ft, in the same amount of time and my "rpms" were the same. It still took more overall energy for me to take the larger steps even though I still took the same number of steps in the same amount of time.
Let's hypothetically drop distance and velocity. Lets say you had a moutain bike with the 6 gears (2 front, 3 rear). Your first trial(A) will be in the bike's 1st gear, you will pedal 100 times/min. Your second trial(B) will be in the bike's 6th gear, you will pedal 100 times/min (both assuming you are starting at a constant velocity of that gear at that rate). Which one will you be more tired after doing? I would be tired doing (A)..meaning I used more of my power to complete the 100 revolutions of pedaling compared to the 100 revolutions of (B). (A) will cover less distance then (B). (B) did more work, but used less power then (A).
09-27-2005, 12:34 AM
#47
TLover
Join Date: Feb 2004
Location: Brooklyn, New York
Age: 41
Posts: 723
Likes: 0
Received 1 Like
on
1 Post
iam too lazy to read all the posts so i dont know if this wwas said.
just b/c both speeds is at 2750rpm doesnt meant that the car is using the same fual. when you are going 75mph the engine has to use more gas to get you to the same rpm then at 25mph.
just b/c both speeds is at 2750rpm doesnt meant that the car is using the same fual. when you are going 75mph the engine has to use more gas to get you to the same rpm then at 25mph.
09-28-2005, 09:57 AM
#48
Advanced
Join Date: Aug 2005
Age: 62
Posts: 79
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by TLXLR8S
iam too lazy to read all the posts so i dont know if this wwas said.
just b/c both speeds is at 2750rpm doesnt meant that the car is using the same fual. when you are going 75mph the engine has to use more gas to get you to the same rpm then at 25mph.
just b/c both speeds is at 2750rpm doesnt meant that the car is using the same fual. when you are going 75mph the engine has to use more gas to get you to the same rpm then at 25mph.
09-28-2005, 10:23 AM
#49
Advanced
Join Date: Aug 2005
Age: 62
Posts: 79
Likes: 0
Received 0 Likes
on
0 Posts
Huh, more work using less gas? Can you write us the equations for this? I'm sure we would all like to get our cars to do more work using less gas.
It's not just about power or torq, you have to look at the net energy used to do that work.
It's not just about power or torq, you have to look at the net energy used to do that work.
Originally Posted by AcuraTLFan
When comparing 2750 in 2nd gear and 2750 in 6th gear, yes...the 2750 in 6th gear will DO MORE WORK, but doesn't necessarly use more gas. Since at 2750 at 2 different gears will yield two differnt displacements.
Let's hypothetically drop distance and velocity. Lets say you had a moutain bike with the 6 gears (2 front, 3 rear). Your first trial(A) will be in the bike's 1st gear, you will pedal 100 times/min. Your second trial(B) will be in the bike's 6th gear, you will pedal 100 times/min (both assuming you are starting at a constant velocity of that gear at that rate). Which one will you be more tired after doing? I would be tired doing (A)..meaning I used more of my power to complete the 100 revolutions of pedaling compared to the 100 revolutions of (B). (A) will cover less distance then (B). (B) did more work, but used less power then (A).
Let's hypothetically drop distance and velocity. Lets say you had a moutain bike with the 6 gears (2 front, 3 rear). Your first trial(A) will be in the bike's 1st gear, you will pedal 100 times/min. Your second trial(B) will be in the bike's 6th gear, you will pedal 100 times/min (both assuming you are starting at a constant velocity of that gear at that rate). Which one will you be more tired after doing? I would be tired doing (A)..meaning I used more of my power to complete the 100 revolutions of pedaling compared to the 100 revolutions of (B). (A) will cover less distance then (B). (B) did more work, but used less power then (A).
09-28-2005, 10:50 AM
#50
41 43 55 52 41 20 54 4C
okay, there have been a lot of replies to thing's I've said, too many to respond to, but i will restate some things...
when i said 2750 in 6th uses more gas than 2750 in 3rd or whatever, i meant more gas as far as real-time, or more gas per unit time, not per mile... which, yes, deviated slightly from the topic of this thred, which started out as economy (if i can remember right).
And when i said pressure, as Legen2TL said, you could call a vacuum pressure... if you wanted, but yes, it could cause some confusion... does something get sucked out of a plane if a "hole" suddenly occurs at altitude? or does it get blown out? The correct answer obviously is blown out, but i wouldn't exactly say that if someoen said it got "sucked" out was wrong, as long as they actually know that, again as Legend2TL said, it's the differences... i suppose I could have said negative pressure :p If you are in a plane and the cabin suddnely loses pressurization, does the air in your lungs get blown out or sucked out?
when i said 2750 in 6th uses more gas than 2750 in 3rd or whatever, i meant more gas as far as real-time, or more gas per unit time, not per mile... which, yes, deviated slightly from the topic of this thred, which started out as economy (if i can remember right).
And when i said pressure, as Legen2TL said, you could call a vacuum pressure... if you wanted, but yes, it could cause some confusion... does something get sucked out of a plane if a "hole" suddenly occurs at altitude? or does it get blown out? The correct answer obviously is blown out, but i wouldn't exactly say that if someoen said it got "sucked" out was wrong, as long as they actually know that, again as Legend2TL said, it's the differences... i suppose I could have said negative pressure :p If you are in a plane and the cabin suddnely loses pressurization, does the air in your lungs get blown out or sucked out?
09-28-2005, 04:02 PM
#51
Aaaarrrggghhhh!
Originally Posted by toynaround
Clearly the physics change when you install a flux capacitor and travel at 88mph 
09-28-2005, 06:04 PM
#52
WDP Director of R & D
[QUOTE=mp3car]okay, there have been a lot of replies to thing's I've said, too many to respond to, but i will restate some things...
when i said 2750 in 6th uses more gas than 2750 in 3rd or whatever, i meant more gas as far as real-time, or more gas per unit time, not per mile... which, yes, deviated slightly from the topic of this thred, which started out as economy (if i can remember right).
And when i said pressure, as Legen2TL said, you could call a vacuum pressure... if you wanted, but yes, it could cause some confusion... does something get sucked out of a plane if a "hole" suddenly occurs at altitude? or does it get blown out? The correct answer obviously is blown out, but i wouldn't exactly say that if someoen said it got "sucked" out was wrong, as long as they actually know that, again as Legend2TL said, it's the differences... i suppose I could have said negative pressure :p If you are in a plane and the cabin suddnely loses pressurization, does the air in your lungs get blown out or sucked out?[/QUOTE]
Depends on whether your mouth/nose is open or not..... :-)
And if they are closed, like every other cavity in your body, the air in your lungs would/will "expand".
Spent many an hour in altitude chambers witnessing it physically and visually..
Good analogy.
when i said 2750 in 6th uses more gas than 2750 in 3rd or whatever, i meant more gas as far as real-time, or more gas per unit time, not per mile... which, yes, deviated slightly from the topic of this thred, which started out as economy (if i can remember right).
And when i said pressure, as Legen2TL said, you could call a vacuum pressure... if you wanted, but yes, it could cause some confusion... does something get sucked out of a plane if a "hole" suddenly occurs at altitude? or does it get blown out? The correct answer obviously is blown out, but i wouldn't exactly say that if someoen said it got "sucked" out was wrong, as long as they actually know that, again as Legend2TL said, it's the differences... i suppose I could have said negative pressure :p If you are in a plane and the cabin suddnely loses pressurization, does the air in your lungs get blown out or sucked out?
[/QUOTE]Depends on whether your mouth/nose is open or not..... :-)
And if they are closed, like every other cavity in your body, the air in your lungs would/will "expand".
Spent many an hour in altitude chambers witnessing it physically and visually..
Good analogy.
09-28-2005, 06:44 PM
#53
Racer
Slightly off topic but since everybody talks about fuel economy & speed.....
I have a quick question, has anybody tried from their "experiences" or little mpg indicator which constant speed would yeild to the best fuel economy (mpg) including all the factors (same wind speed or not at all)? Assuming constant speed at the best gear ratio, 45mph would yeild less mpg than 50mph and I believe it has a upside down parabola curve. Anyone knows the maximum point (constant speed vs. mpg). Sorry,I only have 2g tl, so no mpg indicator.
I have a quick question, has anybody tried from their "experiences" or little mpg indicator which constant speed would yeild to the best fuel economy (mpg) including all the factors (same wind speed or not at all)? Assuming constant speed at the best gear ratio, 45mph would yeild less mpg than 50mph and I believe it has a upside down parabola curve. Anyone knows the maximum point (constant speed vs. mpg). Sorry,I only have 2g tl, so no mpg indicator.
Thread
Thread Starter
Forum
Replies
Last Post
wusty23jd
3G TL Audio, Bluetooth, Electronics & Navigation
4
09-24-2015 11:41 AM
Billu99tl
3G TL Problems & Fixes
1
09-13-2015 11:30 AM
