Aerodynamics.. oh god why.

WanganWarrior

WanganWarrior

5
Antarctica
Antarctica
DRP_5N4K3
it has come to my attention testing ON REAL GRIP the NSX today, on stage 7, that the aerodynamics are completely different from gt5... and real life.. now, to give you all an example.

the honda/ acura nsx 1991 has roughly 250 hp. its top speed should be between 150-160 mph. that is around 260 km/h. my 1224 kg 451 hp nsx on racing soft tires ( no wing ) can barely hit anything around 290-310 km/h by itself. 260 km to 300 km/h comparison... with a 200 hp increase and 200 kg less..
MAKES NO SENSE TO ME. especially considering the nsx has much less air resistance than most cars.

so,
gt5- 425 hp 1100 kg = 200 mph/ 320 km/h or more.
gt6- 451 hp 1224 kg = 190 mph/ 300 km/h or more.

how does that even compute. makes perfect sense, yo.

for anyone that knows, most nsxs in japan on the wangan have been hitting around 180-200 mph in roughly 310-330 hp range with some sort of aero and possibly weight reduction.

does kaz hate the NSX or something? lmao ( no i dont suck at tuning my trans ) lol

MEANWHILE, MY FXX WITH NOS HITTING 485 KM/H WITH NOS ON STAGE 7

fix the aerodynamics! :C im assuming the fully tuned 1991 nsx should be hitting around 330-350 km/h.
and over all this game is just way too easy to go through air. there needs to be a noticeable barrier where you can tell the car is being slowed down by air resistance, not lack of hp output. if they're clever, they'll make air resistance different based on temperature at the track as well.

anybody else notice this? thanks for input!
 
WanganWarrior
for anyone that knows, most nsxs in japan on the wangan have been hitting around 180-200 mph in roughly 310-330 hp range with some sort of aero and possibly weight reduction.
Click to expand...

I'd like to see a NSX that can hit 200mph with only 330bhp... 170-180 sounds much more realistic for that sort of power.

You'd need c.450bhp for 200mph.
 
Stotty
I'd like to see a NSX that can hit 200mph with only 330bhp... 170-180 sounds much more realistic for that sort of power.

You'd need c.450bhp for 200mph.
Click to expand...


top end nsx team from japan?? their requirement was 180 mph for a car to join. their team average is 310 hp.
 
There's a massive difference between 180 and 200mph - you would need a pretty big increase in power to add the 20mph.

I don't believe you could get a NSX to 200mph with 330bhp in real life unless you did something very radical to the bodywork.

Your results seem realistic enough to me... the F40 (1st road car to break 200mph IIRC) needed 450bhp, and most modern cars need well over 500 to hit 200.
 
WanganWarrior
the honda/ acura nsx 1991 has roughly 250 hp. its top speed should be between 150-160 mph. that is around 260 km/h.
Click to expand...
Physics time!

The '91 NSX has a weight of 3035lb, a frontal area of 19.1sqft and a Cd of 0.31, making for a CdA of 6.13. This gives it an aero-limited top speed of about 166mph (267km/h):

3035lb = ~40.97lb rolling resistance
6.13 * 0.00256 * 166 * 166 = ~432.43lb air resistance
= 473.40lb total resistance

473.4 * 166/375 = 210whp = ~250hp crank
WanganWarrior
my 1224 kg 451 hp nsx on racing soft tires ( no wing ) can barely hit anything around 290-310 km/h by itself.
Click to expand...
Physics time!

For a 1224kg/2751lb NSX travelling at 310kmh/193mph, the required power is...

2751lb = ~37.14lb rolling resistance
6.13 * 0.00256 * 193 * 193 = 584.54lb air resistance
= 621.68lb total resistance

621.68 * 193/375 = 319whp = ~376hp crank

I'd suggest that with 451hp it should be able to reach around 205mph/330kmh (power required increases as a cube of the increase of speed. 451hp/376hp = 19.9% power increase; cube root = 6.3% speed increase; 193mph * 106.3% = 205mph).
WanganWarrior
for anyone that knows, most nsxs in japan on the wangan have been hitting around 180-200 mph in roughly 310-330 hp range with some sort of aero and possibly weight reduction.
Click to expand...
Physics time!

180mph in a stock NSX requires ~320hp crank. 200mph in a stock NSX requires ~440hp crank. Weight reduction doesn't do much to change this (as you'll see from the numbers above).
 
Including tire friction, along with surface bumps, cars aerial downforce how many kg's it gain pressure against road, and what's clipping speed when airflow under car kills downforce and car starts "flying"..

I give props to GT6 physics, like adding "flatfloor" to car increases a lot downforce, and same time decreases top speed, less powered cars lose easily 30 km/h of its speed.
Increasing downforce reduces top speed, until reaching clipping point when tire friction is running out and to maintain acceleration you need more downforce, and as increasing it you loose speed, and you have increase drastically power on car to get even on speed loss and to go over it.
 
Famine
Physics time!

The '91 NSX has a weight of 3035lb, a frontal area of 19.1sqft and a Cd of 0.31, making for a CdA of 6.13. This gives it an aero-limited top speed of about 166mph (267km/h):

3035lb = ~40.97lb rolling resistance
6.13 * 0.00256 * 166 * 166 = ~432.43lb air resistance
= 473.40lb total resistance

473.4 * 166/375 = 210whp = ~250hp crankPhysics time!

For a 1224kg/2751lb NSX travelling at 310kmh/193mph, the required power is...

2751lb = ~37.14lb rolling resistance
6.13 * 0.00256 * 193 * 193 = 584.54lb air resistance
= 621.68lb total resistance

621.68 * 193/375 = 319whp = ~376hp crank

I'd suggest that with 451hp it should be able to reach around 205mph/330kmh (power required increases as a cube of the increase of speed. 451hp/376hp = 19.9% power increase; cube root = 6.3% speed increase; 193mph * 106.3% = 205mph).Physics time!

180mph in a stock NSX requires ~320hp crank. 200mph in a stock NSX requires ~440hp crank. Weight reduction doesn't do much to change this (as you'll see from the numbers above).
Click to expand...


i didnt realize i put the rear diffuser on it and that it made a difference. im going to test that here in a second,

my bad! but i was close :embarrassed: wow,

180mph in a stock NSX requires ~320hp crank. 200mph in a stock NSX requires ~440hp crank.
120hp just to go 20 miles an hour faster..

you're the man!
 
WanganWarrior
180mph in a stock NSX requires ~320hp crank. 200mph in a stock NSX requires ~440hp crank.
120hp just to go 20 miles an hour faster..
Click to expand...
Physics is cruel like that.

Air resistance increases by a square of the rate of increase of speed and power required increases proportionally, so you need to cube the speed increase to work out the power increase.

The maths said that the 250hp crank car could do 166mph before it ran out of power to overcome the air resistance - rolling resistance is fairly steady, though it'll decrease a little as lift comes into play or increase a little if you have aerodynamic aids. So to get the same car to 180mph it'd need to increase the power by a cube of the increase of speed:

180/166 = 8.4% (or 1.084)
1.084 ^ 3 = 1.274 (or 27.4%)
250 * 1.274 = 318.7hp

To push on to 200mph:

200/180 = 11.1% (or 1.111)
1.111 ^ 3 = 1.372 (or 37.2%)
318.7 * 1.372 = 437.2hp
 
Famine
Physics is cruel like that.

Air resistance increases by a square of the rate of increase of speed and power required increases proportionally, so you need to cube the speed increase to work out the power increase.

The maths said that the 250hp crank car could do 166mph before it ran out of power to overcome the air resistance - rolling resistance is fairly steady, though it'll decrease a little as lift comes into play or increase a little if you have aerodynamic aids. So to get the same car to 180mph it'd need to increase the power by a cube of the increase of speed:

180/166 = 8.4% (or 1.084)
1.084 ^ 3 = 1.274 (or 27.4%)
250 * 1.274 = 318.7hp

To push on to 200mph:

200/180 = 11.1% (or 1.111)
1.111 ^ 3 = 1.372 (or 37.2%)
318.7 * 1.372 = 437.2hp
Click to expand...
I hear Adrian Newey is looking for an assistant.
 
He had one until McLaren bought him :lol:
WanganWarrior
damn. well, my friend has the 1991 nsx and he said his car hits 280 km/h. he has 279 hp. c:
Click to expand...
The beermat maths from the 250hp example says 279hp = ~277km/h. I'd say that's near enough.

Of course there's a few variables. Power for a start - his "279" might not be accurate as, even if measured on a braking dyno, it would only be good for wheel power in those specific conditions (of course wheel power is what actually moves you). It'd vary by several horsepower depending on local atmospheric conditions and fuel. There's also an estimate of air pressure built into the equations and that can vary too. Also it's only really useful for a level grade - you really CAN go faster downhill. WHile weight doesn't make much of a difference, it still makes a difference - shaving 50kg off could be as meaningful as taping up panel gaps.

I wouldn't be quibbling about +/- 5hp or +/- 2mph as a result - it's just good for reaching decent estimations that allow you to see gross trends.
 
Top Gear mentioned this, it was James May not Jeremy Clarkson so the information might be true.

The Bugatti needed 100s of more hp just to go an extra 10mph to 250. I have a 200hp Prelude, it maxes at 140, so if you double the hp then that would mean I can go 280? I wish, but as Famine said, -insert physics equations here- its a little bit more complicated.
 
andy0a
I have a 200hp Prelude, it maxes at 140, so if you double the hp then that would mean I can go 280?
Click to expand...
Nope. As speed increases, power must increase by a cube of the speed to overcome air resistance.

Double the power is 200%, so you would only be able to go the cube root of that increase - and the cube root of 200% is 26% - or 176mph.
 
Famine
Nope. As speed increases, power must increase by a cube of the speed to overcome air resistance.

Double the power is 200%, so you would only be able to go the cube root of that increase - and the cube root of 200% is 26% - or 176mph.
Click to expand...

Haha it was a rhetorical question, but no doubt an informative response. Its nice to know the GTplanet has all my GT information, but now that I'm in college, it can help me with physics. :)
 
WanganWarrior
so,
gt5- 425 hp 1100 kg = 200 mph/ 320 km/h or more.
gt6- 451 hp 1224 kg = 190 mph/ 300 km/h or more.
Click to expand...

What the heck are kg and km/h?
Here in 'Merca we don't speak that language.

{This is joke/funny response...but probably true for a lot of my fellow 'Mercan's}
 
Rionmoon
What the heck are kg and km/h?
Here in 'Merca we don't speak that language.

{This is joke/funny response...but probably true for a lot of my fellow 'Mercan's}
Click to expand...

Nah here in 'Merica, we measure it in fast food. How much does that fancy wancy, whaddya call it, Askin Martin weigh?
Whats 1600 kilograms, oh you mean 12800 quarter pounders? Nice.
 
Physics time 2 ;-).

If you want to calculate the power you need for a certain velocity just solve this equation.

v³ * (0,6 kg/m³ * cd * A) + v * (m * g * F_roll) - P = 0

with

v = velocity in m/s
cd = drag coefficient
A = reference area of the vehicle in m²
m = vehicle mass in kg
g = gravitiy of earth = 9,81 m/s²
F_roll = rolling resistance coefficient = 0,008 (car tire on asphalt on average)
P = vehicle power in kW
 
Gf2k2
Physics time 2 ;-).

If you want to calculate the power you need for a certain velocity just solve this equation.

v³ * (0,6 kg/m³ * cd * A) + v * (m * g * F_roll) - P = 0

with

v = velocity in m/s
cd = drag coefficient
A = reference area of the vehicle in m²
m = vehicle mass in kg
g = gravitiy of earth = 9,81 m/s²
F_roll = rolling resistance coefficient = 0,008 (car tire on asphalt on average)
P = vehicle power in kW
Click to expand...

Don't forget to tell them to multiply the kW # by 1.34 to get hp :sly:
 
Eww, watts are for power stations and household lighting, not cars.

(Although a 370 Veyron SS's can power Guelph during it's yearly peak.)
 

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