Air density from temp is calculated in GT6

[KinLM]

I'll post with proof of this soon.

Basically, air density is calculated in GT6, and the temperature of the air does have an effect of this.

If you don't want to wait for my proof, try for yourself. Take the Tomahawk X to Route X. Do one run in the early hours of the morning before the sun comes up. Do another during the heat of the afternoon when the track is at its hottest.

See what speed you can reach in each run. You will notice a difference of a few MPH's on each run.

When I ran with the track at 80° F I was able to reach 423 MPH, however when I did another run at 64° F I was only able to reach 418. Both runs were done back to back with an oil change before each one.

I assume this is from the air being thinner when warmer, thus creating less resistance on the car? If so then hats off to PD, they may not have a perfect simulation but they definitely don't ignore some of the finer details.

 

[iName]

@sk8er913 - put this in your thread.

I'm guessing it's just a linear track temp-based system, but impressive none the less. PD is seriously under-appreciated sometimes.

 

[sk8er913]

@sk8er913 - put this in your thread.

I'm guessing it's just a linear track temp-based system, but impressive none the less. PD is seriously under-appreciated sometimes.

Under things well done?

Edit: added, good find.

 

[FoRiZon]

A question. Do this affects handling?

Because the last time I drove at different time and temp I notice the change of grip. More heat, more grip and vice versa.

 

[sk8er913]

A question. Do this affects handling?

Because the last time I drove at different time and temp I notice the change of grip. More heat, more grip and vice versa.

It should affect high downforce cars like LMPs at high speed, but it would be a very small difference that you probably wouldn't even notice.

 

[RobbiefromBC]

Thinner and hotter air would result in a loss of power, whereas if you were to run it at a cooler, thicker temp it would have more power...

 

[sk8er913]

Thinner and hotter air would result in a loss of power, whereas if you were to run it at a cooler, thicker temp it would have more power...

But it's less drag too, and at 423 mph there is A LOT of drag. Bernoulli's equation says that drag = velocity squared. So lets compare 200 mph to 400 mph.

1 drag = 1x1 mph
X drag = 200x200 mph
Y drag = 400x400 mph

X drag = 40,000
Y drag = 160,000


Unsurprisingly the drag resistance is 4 times stronger at 400 mph than 200 mph. But it is 160,000 times the drag felt at 1 mph. I'm sure this would negate any power loss, especially because the high speeds compress the air in front of the vehicle.






Could this have been wind speed?

 

[Johnnypenso]

But it's less drag too, and at 423 mph there is A LOT of drag. Bernoulli's equation says that drag = velocity squared. So lets compare 200 mph to 400 mph.

1 drag = 1x1 mph
X drag = 200x200 mph
Y drag = 400x400 mph

X drag = 40,000
Y drag = 160,000


Unsurprisingly the drag resistance is 4 times stronger at 400 mph than 200 mph. But it is 160,000 times the drag felt at 1 mph. I'm sure this would negate any power loss, especially because the high speeds compress the air in front of the vehicle.

Could this have been wind speed?

It also takes a lot of hp to push that much air out of the way at 400+mph. A loss of just a few % of hp from air reduced air density due to increased temperature would have a significant affect on top speed. Going from 30C to 20C for example is a loss of 3.5% of air density. I know there is at least one game that models volumetric throttle response for sure.

 

[KinLM]

Thinner and hotter air would result in a loss of power, whereas if you were to run it at a cooler, thicker temp it would have more power...

I hate to quote Top Gear for anything about science, but I do believe that I am correct in saying that when James tested the Veyron SS for outright top speed, Volkswagen specifically "had him wait until the middle of the day, when the air was at its thinnest." Yes the air in the engine would be less dense but at a speed like 400+ MPH I would believe that the air resistance would be so incredibly strong that the power lost in the engine would be overshadowed by the air resistance lost.

 

[sk8er913]

I hate to quote Top Gear for anything about science, but I do believe that I am correct in saying that when James tested the Veyron SS for outright top speed, Volkswagen specifically "had him wait until the middle of the day, when the air was at its thinnest." Yes the air in the engine would be less dense but at a speed like 400+ MPH I would believe that the air resistance would be so incredibly strong that the power lost in the engine would be overshadowed by the air resistance lost.

The increased speed would also increase compression in the front, leading to increased power... or in this case, equal power.

 

[YZF]

I hate to quote Top Gear for anything about science, but I do believe that I am correct in saying that when James tested the Veyron SS for outright top speed, Volkswagen specifically "had him wait until the middle of the day, when the air was at its thinnest." Yes the air in the engine would be less dense but at a speed like 400+ MPH I would believe that the air resistance would be so incredibly strong that the power lost in the engine would be overshadowed by the air resistance lost.

Veyron SS ? I think it was standard Veyron

 

[KinLM]

Veyron SS ? I think it was standard Veyron

The standard Veyron was tested initially, and then in a later episode he also tested the SS. Should be on YouTube if you haven't seen it

 

[Famine]

I hate to quote Top Gear for anything about science, but I do believe that I am correct in saying that when James tested the Veyron SS for outright top speed, Volkswagen specifically "had him wait until the middle of the day, when the air was at its thinnest." Yes the air in the engine would be less dense but at a speed like 400+ MPH I would believe that the air resistance would be so incredibly strong that the power lost in the engine would be overshadowed by the air resistance lost.

Nope. That's basically what turbochargers are for - though turbocharger efficiency and temperature will change depending on intake conditions.

 

[MatskiMonk]

I did some testing on this a while ago... can't remember which thread... but in order to negate power, I took the veyron upto 250mph, then coasted till 30mph. Then did the same with different ambient temperature. If air resistance would have been higher, that car should have have reached 30mph sooner. But I put the equations into MoTeC with the the Cd and frontal area of the car etc. to get a curve of air resistance as well as deceleration. Both were virtually identical.

Edit: at 250 the Veyron was using something along the lines of 950hp to overcome Air Resistance IIRC.

 

[eran0004]

A question. Do this affects handling?

Because the last time I drove at different time and temp I notice the change of grip. More heat, more grip and vice versa.

Good point. The difference in speed may be because of increased grip rather than decreased air density.

Edit: Wheel spin seems to be the same though. So it could very well be air density that has changed.

 

[Aussie_HSV]

Personally, I believe that the BHP and torque figures of individual cars are static figures.
ie. Not influenced by cooler temp., which in turn creates denser air, therefore delivering more O2 / cm3, therefore more bang for your buck.

Warmer (thinner) air, being a lighter fluid to push through, and therefore resulting in a higher max. speed .. ??
I've not gone to the lengths of testing, so I have no clue.

 

[kolio]

A question. Do this affects handling?

Because the last time I drove at different time and temp I notice the change of grip. More heat, more grip and vice versa.

It should affect high downforce cars like LMPs at high speed, but it would be a very small difference that you probably wouldn't even notice.

I am not sure about it exactly affecting handling or not, however, I have seen the temp affect lap times on tracks that do not have time variable.

Example:
2010 Nascar #48
Racing Softs
453 Horse power
Motegi Super Speedway
Lowest Temp - 66 Degrees F.
Highest Temp - 75 Degrees F.
[These are the lowest/highest temps I have seen]

I cannot remember the exact times, however I do remember they varied by at least .050 on average.

This data was retrieved Online Gameplay with the following conditions.
- Tire Wear on Normal
- Grip on Real
- No Driving Aids (Including ABS)
- Game Version was Pre 1.18
(I think temps are always the same now in online at Non-variable tracks [Not 100% sure on that though])

I hope this provides helpful information!

 

[Lewis_Hamilton_]

Wasn't this advertised as one of the features before the game came out? That temperatures and humidity would be calculated and affect performance and handling?

I'm not sure whether the increased power from colder air or the reduced air resistance from warmer air is a bigger factor at either 400+mph or in this game, but all I know is that at the drag strip (Santapod), they always say that cold air gives the quickest runs. Those Top Fuelers also produce a huge amount of downforce and achieve 330+mph like the Tomahawk X.

 

[YZF]

The standard Veyron was tested initially, and then in a later episode he also tested the SS. Should be on YouTube if you haven't seen it

Yes, you are right. There was another episode 2 years later.

Btw, GT6 physics also calculate tyre slip quite accurately, going at the high speed. I.e. the faster car runs, the more tyre slip there is. This is also a great detail which is implemented.

So if not for the BUG (yes, flawed top seeds is a bug, they did not want that to happen) then overall physics engine is quite good. Not real sim, but still good.

 

[eran0004]

I'm not sure whether the increased power from colder air or the reduced air resistance from warmer air is a bigger factor at either 400+mph or in this game, but all I know is that at the drag strip (Santapod), they always say that cold air gives the quickest runs. Those Top Fuelers also produce a huge amount of downforce and achieve 330+mph like the Tomahawk X.

As for top speed, the increase in drag is linear with the increase in air density. If air density goes up by 1%, the force of drag goes up by 1%.

But the impact of drag increases exponentially with speed, so if the denser air feeds more oxygen to the engine the acceleration at low speeds will increase, and that's probably enough to make the total run faster.

 

[sk8er913]

As for top speed, the increase in drag is linear with the increase in air density. If air density goes up by 1%, the force of drag goes up by 1%.

But the impact of drag increases exponentially with speed, so if the denser air feeds more oxygen to the engine the acceleration at low speeds will increase, and that's probably enough to make the total run faster.

Well said, that's what I was trying to explain earlier.

Wasn't this advertised as one of the features before the game came out? That temperatures and humidity would be calculated and affect performance and handling?

I'm not sure whether the increased power from colder air or the reduced air resistance from warmer air is a bigger factor at either 400+mph or in this game, but all I know is that at the drag strip (Santapod), they always say that cold air gives the quickest runs. Those Top Fuelers also produce a huge amount of downforce and achieve 330+mph like the Tomahawk X.

Most of that run though they are running a lot slower than 330 though, we are talking about sustained high speeds. NASCAR at Daytona may be applicable.

 

[ScottPuss20]

This is an interesting find - I was unsure weather temperature had an effect on the game.

 

[cjr3559]

I'm guessing that altitude also has something to do with engine performance as well; higher altitudes (the Alps tracks) should result in higher engine power than lower altitudes (Route X, Daytona) but don't quote me on that.

 

[Exorcet]

You tend to lose power with increasing altitude because of a drop in air density.

Interestingly at the speeds of the fastest cars in GT6 Mach effects start to appear. With lowered temperature they appear at lower speeds, so the change in top speed with temperature could go one way with "fast" cars and the opposite direction with "slow" cars.

 

[sk8er913]

You tend to lose power with increasing altitude because of a drop in air density.

Interestingly at the speeds of the fastest cars in GT6 Mach effects start to appear. With lowered temperature they appear at lower speeds, so the change in top speed with temperature could go one way with "fast" cars and the opposite direction with "slow" cars.

Test a miata! it should be slower in lower temp.

 

[sk8er913]

Uh oh! New data does not seem to support our theory!

Tomahawk X confirmed no wind at route X.

The results:
Mazda Mx5: 69F = 151 MPH; 81F = 153 MPH
Tomahawk X: 69F = 370 MPH; 76F = 372 MPH; 82F = 373 MPH

The gap in the miatas top speeds are worrying I predicted it to do 150, not 153. I'm too lazy to do the math. Can someone else do it? Also I suggest using an Electric Vehicle, because they don't lose power with decreased air pressure. But the batteries transfer voltage more quickly at higher temps, dont use tesla model S because it redlines at 134 MPH

 

[iName]

Uh oh! New data does not seem to support our theory!

Tomahawk X confirmed no wind at route X.

The results:
Mazda Mx5: 69F = 151 MPH; 81F = 153 MPH
Tomahawk X: 69F = 370 MPH; 76F = 372 MPH; 82F = 373 MPH

The gap in the miatas top speeds are worrying I predicted it to do 150, not 153. I'm too lazy to do the math. Can someone else do it? Also I suggest using an Electric Vehicle, because they don't lose power with decreased air pressure. But the batteries transfer voltage more quickly at higher temps, dont use tesla model S because it redlines at 134 MPH

Like I said before, it's probably just a linear track temp-based system. Goes faster when track is warm, goes slower when track is cold.

 

[LeGeNd-1]

If this is true then I would need to retest my Tomahawk X. I got up to 730 km/h (456 mph) at Route X going downhill, drafting and with perfect gearbox tune, but I did it in the wee morning hours. Let's see if I can squeeze a few more km/hs.

Anyone knows what time gives the hottest temp at Route X?

 

[sk8er913]

If this is true then I would need to retest my Tomahawk X. I got up to 730 km/h at Route X going downhill, drafting and with perfect gearbox tune, but I did it in the wee morning hours. Let's see if I can squeeze a few more km/hs.

Anyone knows what time gives the hottest temp at Route X?

At 15:00 it is about 82F.


Maybe we can ask PD in a future interview?

 

[eran0004]

I'm guessing that altitude also has something to do with engine performance as well; higher altitudes (the Alps tracks) should result in higher engine power than lower altitudes (Route X, Daytona) but don't quote me on that.

You tend to lose power with increasing altitude because of a drop in air density.

Two things occur when you get to higher altitude:

1. The air density drops because of lower pressure.
2. The air density increases because of the lower temperature.

The first is bigger than the other, so the net result of going to higher altitude is a decreased air density, which means that the engine gets less oxygen and produces less power.