GT4 – Japanese Championship

I reached a point in Gran Turismo 4 where the need for tuning knowledge is absolutely necessary. The Gran Turismo World Championship became to be a wall after many attempts in trying to tune an AMG Mercedez CLK-GTR Race Car. I found it impossible to beat the competition with the stock setup on any tires. Therefore, I decided to give it a break and start the Japanese Championship with any odd car that I find in the UCD. I purchased a Subaru Legacy B4 Blitzen ’00 and took it to the first race. Surely enough, I fell behing the leader by more than a minute in five laps. What I found surprising is that the stock suspension is incredibly soft and won’t help much when braking in the turns (even though the brakes seem to be great). Without any doubt, I installed an adjustable suspension so I can stiffen the springs, harden the shocks, and lower the ride height. With this initial tune, my time has drop about 3 seconds per lap but I am still about 44 seconds behind the leader, who looks to be driving an Acura NS-X. No fucking wonder.

20110920-011059.jpg

Fastest lap with stock settings:
Fuji Speedway ’90s – 1:52.375 (TCS 5)

400 meters [0:14.418 (0)]
0:15.935 TCS 10
0:14.524 TCS 5
0:14.418 TCS 0

It seems like the TCS gets in the way of sending the power to the wheels. Fortunately, the Legacy is a 4WD and the distribution of power is optimum to all four of them. As a result, the using the TCS doesn’t have very much effect.

Fully Customizable Suspension (*represent settings that were not changed throughout the testing):

Spring Rate 5.6/4.6
Ride Height *137/137
Shock Absorbers *-/-
Shocks (bound) *8/8
Shocks (rebound) *8/8
Camber Angle *2/1.0
Toe Angle *0/0
Stabilizers *4/4

400 meters
0:15.069 (10)
0:14.457 (5)
0:14.527 (0)

Fuji Speedway ’90 Time Trial [1:47.630 (0)]

These time trials represent the evolving process of tuning the Legacy in preparation of the first race of the Japanese Championship at Fuji Speedway ’90.

1:49.750 (TCS 0, over 0, under 0)

1. ADJUSTING THE SPRING RATE:

Soft 2.8/2.3
1:49.445 [oversteer]
Stiff 15.0/15.0
1:49.966 [understeer]

8.9/8.9 (mid)
1:48.750

5.8/5.8 (softer)
1:47.713

5.8/8.9 (softer front)
1:47.630

8.9/5.8 (softer rear)
1:48.336

Final Settings for springs (settings is bold letters are to remain final until a better setting is found):

Spring Rate *5.8/8.9
Ride Height 137/137
Shock Absorbers *-/-
Shocks (bound) *8/8
Shocks (rebound) *8/8
Camber Angle *2/1.0
Toe Angle *0/0
Stabilizers *4/4

2. ADJUSTING THE RIDE HEIGHT:

102/102 (lowest)
1:48.686 (0)

400 meters
0:14.521 (0)
0:14.652 (5)
0:15.112 (10)

184/184 (highest)
1:48.982 (5)

A higher ride height setting will increase wind resistance and therefore cause slower times (approx. +0.453). It will also cause the car to become somewhat unbalanced. Other settings may need to be adjusted at a later time to overcome this.

143/143 (mid)
1:49.193 (5)

120/137 (lower front)
1:48.858 (5)

Japanese Championship usual suspects:
-Honda NS-X Type S Zero ’97
-Subaru Impreza Sedan WRX STI Ver. VI ’99
-Nissan Skyline GT-R V-Spec II ’00
-Mazda RX-7 Spirit R Type A (FD) ’02
-Mazda RX-8 Type S (J) ’03

Best: Lap 3 1:51.056 (5)
Gap +47.175

After more testing of the different elements of the suspension, I came to the temoorary conclusion that there is little else I can do to reduce my lap time. I tried different settings and all of them give about the same results (around 1:48….).

5.8/8.9
120/120
1/1
1/1
2/1
0/0
4/4
Time 1:48.544

8.9/8.9
140/145
8/10
8/10
1.0/1.5
0/0
5/6
Time 1:48.705

I think I will stick to a lower stiff setting since a higher soft ride showed some instability when taking a sharp turn from high speed and plus the change in elevation at Fuji is not very noticeable. At least not at 140mph. I didn’t have a chance to try camber and toe angles but at the speeds I’m running, it will not matter much or at all. It’s about time to get into tire selection and maybe even getting sports breaks. Both to reduce my total braking distance, which will result in improved lap times.

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