Subaru to get heavy.
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- 96 Miata M-Edition, 2015 Mazda 3 Hatch
-pixy- said:
not gonna lie.. the miata is going to win unless there is 3 feet of snow on the ground
as well it should!
msp35, at steady highway speeds, weight is not nearly as important for mileage as drag. the problem is, you almost never drive at a constant speed. even on the highway, the ground isn't prefectly flat, so even w/ cruise, your engine is constantly having to adjust throttle position to maintain speed. every change in speed requires more fuel in a heavy car.
msp35, at steady highway speeds, weight is not nearly as important for mileage as drag. the problem is, you almost never drive at a constant speed. even on the highway, the ground isn't prefectly flat, so even w/ cruise, your engine is constantly having to adjust throttle position to maintain speed. every change in speed requires more fuel in a heavy car.
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- MP5T / 944
msp35 said:
Cars don't simply get up to speed and stay threre..
They are in a constant state of change.
I'm not sure about the legacy, but the impreza uses aluminum only for the hood, and that's only on the wrx and sti. I'm sure they'll continue aluminum use for at least for the sti, maybe the wrx. They can cut weight elsewhere to make up the difference easily.
I've also heard that the 07 models have lost the aluminum control arms, but this has not been confirmed yet.
I've also heard that the 07 models have lost the aluminum control arms, but this has not been confirmed yet.
eting_pro5
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- '03 Pro5
A) Friction = VehicleMass x FrictionCoefficient
This formula is written different than you'd find in a physics book, but it's basically correct. In reality downforce, lift or bumps would cause the friction value to be constantly changing.
The friction coefficient is an obscure number between 1 and 0. It comes from the two surfaces that are in contact, in this case the tires and the road.
As you can see, leaving the FrictionCoefficient the while raising the weight (driving a 4500 lb SUV vs a 2500 lb compact) increases the force of friction. Since friction is a force that acts in the direction opposite of movement, it's working against your car. More force working against the car means more energy is needed to overcome that force.
B) An object in motion does NOT stay in motion. Newton's (Second?) law states that an object in motion stays in motion, until acted on by an outside force. Friction is an outside force. Good luck driving a car and defying friction.
C) Larger car = larger engine. Larger engine = more gas
This formula is written different than you'd find in a physics book, but it's basically correct. In reality downforce, lift or bumps would cause the friction value to be constantly changing.
The friction coefficient is an obscure number between 1 and 0. It comes from the two surfaces that are in contact, in this case the tires and the road.
As you can see, leaving the FrictionCoefficient the while raising the weight (driving a 4500 lb SUV vs a 2500 lb compact) increases the force of friction. Since friction is a force that acts in the direction opposite of movement, it's working against your car. More force working against the car means more energy is needed to overcome that force.
B) An object in motion does NOT stay in motion. Newton's (Second?) law states that an object in motion stays in motion, until acted on by an outside force. Friction is an outside force. Good luck driving a car and defying friction.
C) Larger car = larger engine. Larger engine = more gas
eting_pro5 said:
technically correct (assuming the road is perfectly level), but also this kind of assumes the car is sliding along the ground, rather than rolling on tires, which changes the game and the analysis. the friction that really matters (at ~constant highway speeds) is drag, the formula for which escapes me at the moment, but which involves a coefficient (Cd), speed, and frontal area. that plays the biggest part in determining fuel use at constant speed...going faster, or driving a "larger, boxier" vehicle, increases drag and thus, the amount of energy (i.e., fuel) required to overcome that drag. of course, there is friction w/ the road surface (as well as internal friction) that also requires energy to overcome.
the formula that really comes into play is good ol' Force=Mass* Acceleration. more mass, same acceleration, more force required. that force comes from the tires pushing against the road (and the road pushing back via tire friction), and is a function of the torque created by the engine...which itself is a function of the force being exerted on the pistons. which increase in force, in simplest terms, requires more energy (i.e., fuel).
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Velocifero
Wham Bam thank you Ma'am
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- VRM MS6, Sunlight Silver MSP
Damn.... I thought the Subarus were getting heavy!
Velocifero
Wham Bam thank you Ma'am
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- VRM MS6, Sunlight Silver MSP
nah, I'll have to look for it, I havent read any mag lately, been trying to get back into shape physically, plus a new puppy has kept me pretty busy. Oh... and Call of Duty 3 too.dmitrik4 said:
Before the Petite LeMans here at Road Atlanta, at the local AM dealership they did demonstrations (insane full speed pits, and the crowd was only like 10 feet back, precision was amazing, and they did dough nuts for fun) and you could meet with everybody, very cool organization and very cool car. I had always liked them, but after meeting the drivers and stuff I found a new appreciation and was actually cheering them on during the ALMS. I really like the GT classes, competition is way better, I just wish Corvette would change so more cars would be in GT1, over seas that class is insane.
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- Protege5 2003
dmitrik4 said:
Drag due to interaction with air is proportional to speed^2. This form dominates at highway speeds.
Rolling and internal friction are proportional to speed. This form dominates at sub-highway speeds.
The air drag isn't affected by mass: a lead car and an aluminum car would have the same air drag if they were the same shape and size. However the rolling friction increases with mass, mostly due to deformation of the tires, and in some cases the surface under the tires (think "sand"). In addition, as others have pointed out, it takes more force to accelerate a heavier car because F=mA. More gas burned getting it up to speed, more energy wasted as heat when slowing it down. At speed slightly more energy used due to increased rolling resistance.
In an accident you'd probably be better off in the heavier steel clad car. Handling and mpg isn't everything.
The one thing I have not seen in this thread is the actual weight difference between the aluminum panels and the replacement panels. Anybody got a credible number, or estimate?