SETUP / 2005
One step of anti-roll bar, six seconds
At my first session at Fuji Speedway I moved the front anti-roll bar from 2/5 to 5/5. The time came down by three seconds, and after that I got it wrong. The record of that day.
In September 2005 I drove the rebuilt Fuji Speedway for the first time. I knew the old circuit, but on driving it the impression was of a completely different circuit. The second half is closer to Motegi.
How the day went
Air temperature 17–18℃, ADVAN A048 MH, tyre pressure 2.3. I arrived three hours before the session and attended the drivers’ meeting.
| Time of day | Anti-roll bar | Time | What was happening |
|---|---|---|---|
| Early (around lap 4) | F2/5 R2/3 | 2:07–2:08 | Same settings as SUGO. Oversteer arrived at once in the second half, I could not use the throttle, and everything after the chicane was in 2nd |
| 10 minutes later | F4/5 R2/3 | 2:02s | 3rd became usable in the second half. About 3 seconds quicker |
| Time attack | F5/5 R2/3 | 2:01.7 | Understeer at the hairpin → force it through → oversteer on exit |
Faster, but wrong
F5/5 produced the best time of the day, but at the time I rated it a failure. Swing it all the way towards understeer and you end up forcing the car through what it will not turn, and the reaction comes back as oversteer on exit. The time came because the circuit has long straights. As a way of driving it was a dead end.
My conclusion was that the middle ground — F4/5 — is the right one.
The range of effect is too large
Stiffen the anti-roll bar = towards understeer, soften it = better turn-in. That is textbook, but on the 964 RS the range of effect was larger than I imagined. At Fuji Speedway, F2/5 to F5/5 moved about 6 seconds.
Raising the rear ride height, on the other hand, was clearly counter-productive (1:38.531 → 1:39.388).
The conclusions I hold now
| Item | SUGO | Fuji Speedway (new circuit) |
|---|---|---|
| Front anti-roll bar | F2/5 | F4/5 |
| Rear anti-roll bar | R2/3–R3/3 | R2/3 |
| Tyre pressure (PS Cup) | F/R 2.3 | — |
| Tyre pressure (A048 MH) | F 2.0 / R 2.2 | 2.3 |
| Ride height | Lowest possible on stock | Same |
| Best | 1:36.997 | 2:01.7 |
The day I worked on the A048 at SUGO
19 October 2005. With 225s on the front I expected big oversteer at the final corner, but it went the other way, towards not turning. The mechanic’s reading was that the A048 has far higher lateral stiffness than the PS Cup, and because it does not flex it does not turn.
| Step | Anti-roll bar | Tyre pressure | Ride height | Best |
|---|---|---|---|---|
| Start | F3/5 R2/3 | F/R 2.3 | Stock lowest | 1:40.381 |
| Change 1 | F4/5 R2/3 | F/R 2.3 | Stock lowest | 1:41.130 |
| Change 2 | F2/5 R2/3 | F/R 2.3 | Stock lowest | no time recorded |
| Change 3 | F2/5 R2/3 | F 2.0 / R 2.2 | Stock lowest | 1:38.531 |
| Change 4 | F2/5 R2/3 | F 2.0 / R 2.2 | Rear up 3 turns | 1:39.388 |
What worked most was lowering the tyre pressure. Not the anti-roll bar, not the ride height.
Notes on gearing
SUGO’s final corner is 3rd in the 964 RS. In the six-speed 993 GT2 and 993 RSCS it becomes 4th. Turns 1 and 2 are 3rd, and the SP corner is 3rd as well (2nd is possible, but signs of oversteer appear).
This — 3rd or 4th at the final corner — is the key to the time difference between the 964 RS and the 993 GT2 on the same day.
Source： Session logs No.10–12 / 16 / 17 / 18 / 19 / 21 / 23 / 24 / 26 / 34 / 35 / 36 / 38 / 41 / 42 / 46 / 49 / 73 / 75
Written in Japanese and translated. The video descriptions themselves are left in the original Japanese.