Magic Data Discussion

Prblanco schrieb:
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Great news to hear that!

CC-cars yielding their position much too early is really a stupid and an anoying issue in GP4 to me. This is the reason, why I recommend to set desc73= "Track sector after which AI cars stop being cautious on 1st lap" / "in-line start range" allways to zero, no matter what track you drive. I do this since several years and never had any problems with that. With a value of zero, the starts are so more realistic!

Hello everybody,

slipstream will still be a recent topic in the next few days. Nevertheless, in the meantime I made some further tests about desc45= "Temperature (degree C) - top speed only affected, minimal effect in corners / acceleration? (17 - 31)".

The question was, whether a hotter air would also influence things like tyre degredation, water temperature, etc. as one would expect in real life. Here are the results:

- Obviously the air temperature is not at all affecting the water temperature at all. Even unrealistic high values don't seem to impress the cooling water, neither it's standard temperature, nor it's rate of change.
- Also, the tyre wear is not influenced by the air temperature. So, there is no need to change soft or hard tyres appropriate to the air temperature.
- As written in the descition text by TomMK, the top speed is quite highly influenced. Just to get a feeling for it, I had the following top speeds at these air temperatures (°C):
0°: 327 km/h
35°: 341 km/h
80°: 355 km/h
- A side effect of the air temperature is that it also affects the grip level. It's maybe a bit crazy, but the hotter the air is, the less grip you have. At "normal" values you will probably just feel a very slightly difference, but at a temperature of 1,000°C your car will swim all across the track. Beside that, it's really no problem for the car to drive at a temperature, that probably no motor would survive .
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Further findings (not really related to magic data) about water temperature:
- It's not affecting the water temperature, if a car is driving in an other car's slipstream or not. In real life, it would have a high impact on the water temperature, when a car is driving closely behind another car. But in GP4, the temperature (sadly) is unaffected.
- Next question was, whether a high water temperature would affect the engine power in any way. That would be very realistic, as we know that a high temperature is decreasing the engine power clearly. But here - sadly once again - there is no influence on the top speed, as well.
- In my opinion, the two findings before really raise the question:
Why the hell did Geoff Crammond implement the water temperature at all? Obviously there is no function of it, except it will give you an engine failure after making a few donuts.

Quote
klausfeldmann
- As written in the descition text by TomMK, the top speed is quite highly influenced. Just to get a feeling for it, I had the following top speeds at these air temperatures (°C):
0°: 327 km/h
35°: 341 km/h
80°: 355 km/h

The rationale for this is that hot air is less dense than cold air - so there is less air resistance/drag in hotter temperatures.

Quote
klausfeldmann
- A side effect of the air temperature is that it also affects the grip level. It's maybe a bit crazy, but the hotter the air is, the less grip you have.

So maybe there is some kind of track temperature simulation hidden in there as well.


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80 °C is 353 K, which is 29% warmer than 0 °C, so according to the ideal-gas law the air density should be 29% less.
As the engine power required to overcome air resistance increases with the cube of speed, top speed increases with the cube root of the reduction in air density, which is about 9%. This quite accurately matches the observations (at 80 °C the top speed is indeed 9% higher).

At the same time, the reduction in air density also reduces downforce and therefore cornering speeds. This effect will be most noticeable in high-speed corners. In reality, engine power (and cooling) is negatively affected by the reduction in air density, so cars tend to go faster when it's cooler, but this aspect is not modeled in the game (this is where the power factors are for). Engine cooling is only affected by the change speed in the engine temperature menu in GPxPatch (in the GPxLap tab). It's better not to change this parameter, as it can easily cause the engines to overheat.

Wow, very accurate physical statements. Thank you for these background information!

Hey there. What values determine consistency of the laptimes shown by drivers? Obv tyre degradation and amount of fuel are affecting the laptimes, as well as driving errors, but what overall determines whether the driver (all of them, all the AI/Comp Controlled cars) matches the identical time every time or does the different each lap with the tyre degradation, fuel consumption and driving errors set to 0?

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In the magic data, there are these two values:

; desc63= CC random performance range min
; desc64= CC random performance range max

But, currently, I don't know whether this random value is determined just once at the beginning of a session or every time newly lap by lap. There was any user, who investigated it and wrote the result anywhere into the 17 pages of this thread. Maybe someone still remembers it.