I notice the HP change in one of my Cars in GT3 (Subaru Impreza WRX STi Ver. VI). The HP may rise but due to the fact that the HP was recorded before ever driven, you are still legal.
Various "bolt on" parts such as Performance mufflers, turbo kits, and intercoolers should be bought to get the best HP/per ton out of your vehicle.
The rating of the HP should be recorded before taking your vehicle on the track or test track. So record your HP and vehicle weight before driving. You should go to Machine Test, and change parts to get the closest HP/per ton on your vehicle with various "bolt on parts that you have bought. Try different combinations to get the most out of your vehicle but not exceed your HP limit.
Weight Reduction
The more weight you have, the more HP you can have. The less weight you have, the less HP you can get. If you want to maximize overall grip level, you'll have to sacrifice some HP for weight reduction. If you want lots of HP, dont' perform weight reduction at all and get the most power of you can get that doesn't exceed your HP limit. You have either choice of performing different stages or not. You can do only stage 1, up to stage 2, full weight reduction or none at all.
Finding your HP per ton
When you have made a choice of weight reduction, you take .2 * vehicle's new weight. It will give you your HP limit of how much HP you can have. You CANNOT go over your HP limit even if it's .5-1hp difference.
Due to No Racing Modification available in GT3, GT4 Class Regulations have to be somewhat similar to the GT Class.
GT4 Class: All vehicles are at or below 400 hp per ton. Vehicles in this class are able to be equipped with all modifications. Power mods are free to go but hp must not exceed the hp per ton limit of 400hp/per ton. A list of modification will be asked of from you.
.2 * weight = hp/per ton (.2 multiply by vehicle weight)
NOTE: This is an example of HP limits via vehicle weight.
Lbs. - Hp Limit
2000 - 400
2050 - 410
2100 - 420
2150 - 430
2200 - 440
2250 - 450
2300 - 460
2350 - 470
2400 - 480
2450 - 490
2500 - 500
2550 - 510
2600 - 520
2650 - 530
2700 - 540
2750 - 550
2800 - 560
2850 - 570
2900 - 580
2950 - 590
3000 - 600
3050 - 610
3100 - 620
3150 - 630
3200 - 640
3250 - 650
3300 - 660
3350 - 670
3400 - 680
3450 - 690
3500 - 700
Modifications
NOTE " * " means it is a required modification.
Brakes:
Any
Drivetrain:
Any
Others:
Weight Reduction
NOTE: You have either choice of weight reduction stages. You can choose either stage 1 or go all the way to stage 3.
Stage 1
Stage 2
Stage 3 Racing Modification
For Professionals
To be discussed
Suspension:
* Full Customization
* Super Soft Slick Tires
Tires
* Super Soft Slick Tires
GT: All vehicles are at or below 250 hp per ton
Vehicles in this class are able to be equipped with most modifications but not all. Power mods are free to go but hp must not exceed the hp per ton limit of 250hp/per ton. A list of modification will be asked of from you.
.125 * weight = hp/per ton (.2 multiply by vehicle weight)
NOTE: This is an example of HP limits via vehicle weight.
Lbs. HP Limit
2000 - 250
2050 - 256
2100 - 262
2150 - 268
2200 - 275
2250 - 281
2300 - 287
2350 - 293
2400 - 300
2450 - 306
2500 - 312
2550 - 318
2600 - 325
2650 - 331
2700 - 337
2750 - 343
2800 - 350
2850 - 356
2900 - 362
2950 - 368
3000 - 375
3050 - 381
3100 - 387
3150 - 393
3200 - 400
3250 - 406
3300 - 412
3350 - 418
3400 - 425
3450 - 431
3500 - 437
Modifications
NOTE " * " means it is a required modification.
Brakes:
Any
Drivetrain:
NOTE: You have a choice of staying with the normal transmission, or choosing either Sports or Semi-Racing Transmissions.
Normal
Sports
Semi-Racing
Clutch
Any
For Professionals
NOTE: RWD and FWD vehicles may choose either 2 way, 1.5 way, or 1 way LSD differentials. AWD/4WD vehicles must use stock differentials.
Normal
2 Way Limited-Slip
1.5 Way Limited-Slip
1 Way Limited-Slip
Flywheel
Any
Driveshaft
NA
Others:
Weight Reduction
NOTE: You have either choice of weight reduction stages. You can choose either stage 1 or go all the way to stage 3.
Stage 1
Stage 2
Stage 3
For Professionals
NA
Suspension:
* Full Customization
Tires
* Super Soft Slick Tires