# co drag of the R34



## GTR-Zilla (May 17, 2005)

anyone know what it is? not seen any figuers for the R34, only R32 and R33..


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## kingsley (Aug 26, 2002)

make sure you know the frontal area too - the Cd is only half of the story


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## GTR-Zilla (May 17, 2005)

but when testing for overall Cd isnt the frontal area taken into consideration??


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## ExScoobyT (Jan 6, 2004)

Cd is the coeffecient of drag.

Aero power is frontal area * Cd


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## kingsley (Aug 26, 2002)

GTR-Zilla said:


> but when testing for overall Cd isnt the frontal area taken into consideration??


no - ExScoobyT is right.

Cd is the drag coefficient. To get the drag, you multiply this by the frontal area, the square of your speed and the density of the air and then divide by 2:

drag force (N) = (d * v^2 * Cd * a) / 2

Where:
d = air density (typically about 1.29 kg/m^3 at sea level on a 15C day)
v = velocity (metres per second)
Cd = Drag coefficient
a = frontal area

Some old figures I've dug out (not official figures, don't know whether they're right) says that the Cd of an R34 is 0.34 and the effective frontal area is 2.4276m^2 ... though I don't know whether these figures are for a GTR with all of the spoilers, wide body and tyres or one of the other models.

The R33 has a Cd of 0.35 and the R32 is 0.40, though the R32's frontal area is smaller than that of the R33 (don't know how much).

I wrote a spreadsheet some time ago where you could put in constants such as air density, frontal area, Cd and a nominal rolling resistance for tyres and it'd show you in 5mph increments how much power would be required to get the car to go that fast.

With R34 drag factor and area, an air density of 1.29kg/m^3 and a 200N (wild stab in the dark) guess at rolling resistance, my spreadsheet came up with these figures (remember the power will be power required at the wheels, not flywheel):



```
mph	drag(N)	bhp required
		
5	203	1
10	211	1
15	224	2
20	243	3
25	266	4
30	296	5
35	330	7
40	370	9
45	415	11
50	466	14
55	522	17
60	583	21
65	650	25
70	721	30
75	798	36
80	881	42
85	969	49
90	1062	57
95	1160	66
100	1264	76
105	1373	87
110	1487	98
115	1607	111
120	1732	125
125	1862	140
130	1998	156
135	2139	173
140	2285	192
145	2437	212
150	2594	233
155	2756	256
160	2924	281
165	3097	307
170	3275	334
175	3458	363
180	3647	394
185	3841	426
190	4041	461
195	4246	497
200	4456	535
```


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## liquidculture (Apr 19, 2004)

Im suprised the 33's cd is higher than the 34's, seems a better shape why is that? or is it more to do with the way the air travels over the car?


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## Piggaz (Sep 5, 2002)

It was only a couple days that i saw this after not knowing myself for years on end.
Off the top of my head the R34 GTR Cd with the rear wing at 0 Degrees is 0.36. With it at 10 degrees it was 0.37, 20 it was 0.38 and 30 it was 0.39
Ill try and dig up the link.

Come to think of it i think i saw it on this video.

http://video.google.com/videoplay?docid=1971073009473255092&q=GT-R

59 minutes of those crazy nutters thrashing 3,33 and 2 34's

Enjoy.


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