Update based on latest testing:
Code:
+--------+-------------------------------+--------+---------+--------+---------------------------------+
| Offset | Field Purpose | Ford | Mercedes| Honda | Notes |
+--------+-------------------------------+--------+---------+--------+---------------------------------+
| 0x00 | fuel_consumption_rate | 6282 | 6282 | 6282 | Lower = less fuel used |
| 0x04 | rpm_upshift_point | 6500 | 6500 | 6750 | Used for autoshift |
| 0x08 | rpm_downshift_point | 3900 | 3900 | 4100 | Used for autoshift |
| 0x0C | engine_power | 1290 | 1236 | 1180 | Higher value = more power |
| 0x10 | engine_power2 | 8675 | 8308 | 7637 | Lower value = more power |
| 0x14 | unknown | 0 |2000000 |1000000 | ??? |
| 0x18 | rpm_limit | 6500 | 6500 | 6750 | Slightly lower than engine blow |
| 0x1C | fuel_consumption_unknown | 18 | 18 | 18 | 0x120000 >> 16 |
+--------+-------------------------------+--------+---------+--------+---------------------------------+
(05-04-2025, 05:16 AM)kakukri Wrote: [ -> ]Nice findings.
It seems the number is then half of the RPM value, Ford and Mercedes is known to shift at 13000 RPM, while Honda at 13500. As for the second number, the engine does not actually blows at that RPM, might it be the value when the RPM light in the cockpit lights up?
Yes, I think there is code in there that allows for some additional revs before blowing the engine.
I think chassis parameters are in this block of code, close to the engine parameters. This is at 004f3b8c in Windy.
Code:
+-------------+-----------+-----------+-----------+
| Parameter | Chassis 1 | Chassis 2 | Chassis 3 |
+-------------+-----------+-----------+-----------+
| Param 1 | 7500 | 7550 | 7550 |
| Param 2 | 33000 | 33000 | 33000 |
| Param 3 | 28000 | 28000 | 28000 |
| Param 4 | 255 | 255 | 255 |
| Param 5 | 260 | 260 | 260 |
| Param 6 | 43691 | 43691 | 43691 |
+-------------+-----------+-----------+-----------+
If I change the first parameter to 500, the car feels relatively normal from a standing start until around 100 mph when it starts accelerating incredibly fast. It then feels like I have unlimited downforce through the turns even at 250+ mph at Michigan, it is stuck to the ground like an arcade game.
EDIT: Here's something else I found from looking at the code that loads the parameters. The game will load Param 1, and then it will then load Param 2 and Param 4 for non-speedways, or Param 3 and Param 5 for speedways. And then it will load Param 6 in all cases.
I might take another wild guess that the parameters are weight, front downforce, rear downforce and drag. In which order, I am not sure.
(05-05-2025, 03:32 PM)checkpoint10 Wrote: [ -> ]................It then feels like I have unlimited downforce through the turns even at 250+ mph at Michigan, it is stuck to the ground like an arcade game......
There is a setting in the text file that does this also- I can't think of it right now. I remember trying it Darlington once and it was so easy to catch it when I got loose.
Look at you getting deep into reverse engineering now... I'm Jealous!
I'm at vacations and far away from my PC but I'm very encouraged by this discussion and findings
(05-05-2025, 06:13 PM)Pavel 69 Wrote: [ -> ]I'm at vacations and far away from my PC but I'm very encouraged by this discussion and findings
You could be back at your PC in no time, just change your engine lookup table value. At 272 MPH, you will get back home very quickly
For sure, my next step is going to be making a basic tool for changing all the values I mentioned above. I would like some test drivers to help experiment with the values to better understand what they do to the car physics.
(05-06-2025, 02:30 AM)checkpoint10 Wrote: [ -> ]For sure, my next step is going to be making a basic tool for changing all the values I mentioned above. I would like some test drivers to help experiment with the values to better understand what they do to the car physics.
I don't know... alternate physics could be dangerous... I could spontaneously combust or atomize at any random moment!
Just playing - I would be glad to help.
What you're doing is just like adjusting "magic data" in gp2 except it is not track specific. GP2LAP is a program that will change things in memory so you can run with a modified game.
Here's the editor, both compiled and Python source.
https://github.com/skchow03/icr2_physedit
BACK UP YOUR ICR2 EXECUTABLE FIRST
Put the program in your ICR2 folder and run at the command prompt: icr2_physedit INDYCAR.EXE
Let me know if this works!
EDIT: Don't edit the last engine parameter for now. I think it is expressed as a 2-byte value instead of 4 bytes.
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