Shebs

The F10 is not prejeduced, I test drove it for two days.

As for top speeds, it is a pretty simple equation that depends on frontal surface area (A) and Cd (Coefficient of Drag) and is not related to car's weight.

The force on a moving object (car) due to a fluid (air) is:

FD = 1/2 * ? * u^2 * Cd * A.

where

FD is the force of drag, which is by definition the force component in the direction of the flow velocity,
? is the mass density of the fluid (air),
u is the velocity of the object relative to the fluid,
A is the reference area, and
Cd is the drag coefficient ? a dimensionless constant, e.g. 0.25 to 0.45 for a car.

Now since the F10's Cd is higher than the E60's Cd by 0.02 on average, and the frontal surface area of the F10 (A) is larger than that for the E60, it is inevitable that an F10 equipped with the same hp as an E60 will have a lower top speed due to the higher aerodynamic force generated on the car. That is not my personal opinion, it is basic physics.

As a proof for the equation above, the E60 LCI 523i had 190 hp and achieves higher top speed (237 km/h[236 km/h Auto]) while the new F10 has 204 hp and achieves 234 km/h manual and auto. This is not related to weight, top speed is based on fluid dynamics since Newtonian acceleration plays no role at top speed.

Furhtermore, the F10 is not faster at high speeds acceleration as per Edmunds Inside Line where the E60 obtained 1/4 mile at 14.0 s and 100.4 mph while the F10 did 14.3 and 95.1 mph. So as I mentioned earlier, this debate can go forever.

Comparing the F10 535i to the E60 535i puts the F10 at a disadvantage due to both cars having nearly the same hp and the F10 having higher weight. The F10 compensates by having an 8 speed gearbox that will bracket the engine rpm in higher average power.

C&D had tested the E60 535i and the F10 535i and the results for chassis and acceleration will not appeal to you. I will start a new thread for the C&D tests now.

tadtaggert

Saying acceleration plays no role at top speed is misleading, top speed is determined when the force of drag equals the force of acceleration. You talk of top speed, then throw out an equation for FD.

While I don't really disagree with your logic (which is part of the reason I think the N55 is a poor match for the F10), if you're going to throw the physics in...

Shebs

The force of drag you are referring to is FD that I mentioned in my post above.

You misunderstood what I wrote, by Newtonian acceleration I meant the effect of gravity (which Newton discovered) on the car's acceleration. The force needed to move the weight (which is due to gravity) of the car on tires is the called the "force due to rolling resistance" of car tires, Frr, where:

Frr = Crr * m * g

where Crr is the rolling resistance coefficient of the tires, m is its mass, and g is the acceleration due to gravity. For a car we can assume Crr is around 0.01 for simplicity.

To push a car that weighs 1500 kg , i.e. roughly 15000 N (assuming g = 10 m/s^2 for simplicity), by yourself you need F = Crr * m*g = 0.01 * 15000 = 150 N which is quite achievable by a human being. That is why you are able to push your car on a horizontal surface.

Now once the car starts gaining speed the air resistance starts adding to the equation. Now the force needed to move the car will be

Fcar = Frr + FD = Crr*m*g + 1/2 * ? * u^2 * Cd * A.

FD is the force of drag,
? is the mass density of the fluid (air),
u is the velocity of the object relative to the fluid,
A is the reference area, and
Cd is the drag coefficient ? a dimensionless constant, e.g. 0.25 to 0.45 for a car.

At top speed (u), u is so large that the Frr part of the equation can be considered negligible when compared to the FD.

Let's assume that a car's top speed (u) is 252 km/h, i.e 70 m/s and its frontal surface area is 3 m^2 (i.e width = 2m and height = 1.5 m, like the F10). FD is now = 1/2 * ? * u^2 * Cd * A = 1/2 * 1.2 kg/m^3 * 70 m/s ^ 2 * 0.29 * 3 m^2 = 2646 kg.m i.e 2646 N. Compare that to Frr of 150 N that we obtained earlier and you will see that Frr can be considered negligible.

Now, if the same car was going at 54 km/h (15 m/s), FD would be 117.45 N only which is less than than Frr of 150 N that we obtained earlier. At low speeds we can not neglect Frr, on the contrary, FD is zero when the car speed is zero, so at low speeds FD is the force to be considered negligible.

At top speed, (FD + Frr) is equal to F-engine. That is why we are not able to achieve any acceleration and the car stops at that speed.

Take a look at this link:

Ferrari 360 Modena Vs. Ariel Atom 2. Both cars have very close acceleration times up to 200 km/h. Suddenly the lower powered Ariel Atom 2 (241 hp) with superior hp/kg (0.38) stops accelerating at 245 km/h, while the higher powered Modena (395 hp) with inferior hp/kg (0.21) continues to accelerate up to 295 km/h.

At top speed, the FD part of the equation is so high for the Ariel to handle due to the low force generated by its 241 hp engine, while the FD part of the equation for the Ferrari is handled with its more powerful engine 395 hp regardless of the fact that it weight is three times that of the Ariel since Frr became of low influence at top speed.

I hope I made things clear.

Note: The equations above do not take into consideration the downforce from aerodynamics adding to the normal force on the car, neither does it take into consideration the alteration of Frr at higher velocities, but these equations do give an indication of the fact that at top speed the drag force FD is the bigger player when compared to Frr which depends on gravity (which I referred to as Newtonian acceleration in my earlier post).

bm323

0-809.3 90-9011.4 11.20-10013.9 13.80-11018.4 17.60-12022.221.6

Quarter mile14.1 sec @ 100.6 mph 14.1 sec @ 101.0 mph


Did you notice the above? right column for the F10. Read more: http://www.motortrend.com/roadtests/...#ixzz11ucf2pQ7
Prejudiced in the sense that you say they must be similarly equipped. The cars generally improve as they age, and imo shouldn't be compared this way. Should the a tested F10's engine be substituted with the older engine if the newer engine is an improved one http://www.fastestlaps.com/compariso..._BMW_530d.html the F10 with the improved engine is 1.6 seconds faster on the Autozeitung, and taking into account the figures you mentioned, is this significant or not?

The maximum speed which you are referring to as the top speed has nothing to do with the equations as the cars are speed limited.

Shebs

The F10 and E60 523i are not speed limited, and my reference to the top speed in my post above is legitimate as it shows the cars ability to accelerate at high speeds. Despite the 14 hp advantage of the F10 523i it was not able to overcome the maximum speed of the E60 523i. That is due to the worse Cd and it is very simple if you try to read the equations.

I can't believe that after all of these discussions you thought that I did not know that both 535i were speed limited

You are comparing the pre LCI 530d with 0-100 of 6.9 s (not 6.7, check the original brochures) to the F10 530 d with 0-100 of 6.3 s. Of course the F10 would lap the track faster. If you remember from the lap times thread discussions we had, I compared the E60 535d to the F10 because they had the same elasticity and acceleration times, which is not the same in your case. The E60 5ir30d Autozeitung test was done in 2005 and unfortunately the acceleration and elasticity data are not available on their site for accurate comparison.

The E60 had the option of adding ARS, and I am sure you know this, so it is not unique to the F10. The uniquness of the F10 comes at the VDC, which is an achievement on its own.

bm323

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bm323

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