OS entry vs. OS exit - need tuning advice

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1

Aston Martin V12 Vantage - class A.

I had already applied a baseline tune that was pretty good. I built in a decent amount of OS for help in corner entry, since I was initially getting slow response (US) to turns and even hairpins at slow speeds were not turning in as well as I liked. I adjusted the Springs by lowering the F and raising the R. I then noticed a bit of bobbing and ‘floatiness’ in addition to getting a good deal of OS on corner exit. It’s not sudden OS, and the rear doesn’t slip much, if at all, this just happens during acceleration out of the corner and starts the car a little sideways. When I start to counter, I get into a bad state where I am then fighting to keep the car on the track. The OS usually occurs about 1/3 - 2/3 through my acceleration in the gear I’m exiting with (typically 2nd).

In response;

I raised the F & R rebound about 2.0 each to eliminate the ‘floatiness’. ← this worked
I then lowered the F rebound 0.3 and raised the R rebound 0.3 for the corner exit oversteer. ← didn’t work and resulted in corner entry issue again
I lowered the F bump 0.2 and raised the R bump 0.2 for the corner exit oversteer. ← didn’t work and resulted in corner entry issue again

Yes, I realized I broke a cardinal rule by adjust for two problems at the same time, but it was late and I was going OCD about getting it straightened out before going to bed. So, then I was caught fighting the corner entry US by adjusting the Springs (F - down, R - up) and then trying to dial out the corner exit OS subsequently with the Dampers (rebound/bump F - down, R - up).

But, things just got worse. I was up really late last night, so perhaps I’m missing something, but can anyone give me a bit of advice on how to get out of this quandry (OS to aid corner entry, remove exit OS for smooth acceleration away)?

In case you need to know, I have it built to SHALB values of 8.0 / 6.5 / 7.8 / 8.0 / 6.4 - (no option on upgrading brakes)

Springs: Race
F-ARB: Race
R-ARB: Race
Diff: Race
Compound: Race
F-Tire: 245 (default)
R-Tire: 315
Rims: Lexani LTC-704
F-Aero: Forza
R-Aero: Forza
Tranny: default
Wgt. : ~3740 lbs
F-wgt: 51%
Power: 518 hp
Torque: 425 lb-ft
Lat. G’s: 1.118

I don’t remember my Spring or Damper values (and I don’t have my notebook with me), but I remember my Diff is A/D: 48% / 20%

Help?

2

It weighs WAY too much

3

:slight_smile:

Yes, it is part of a challenge, it needs to be over 3500 lbs. to compete. The Vantage is quite close to the PI cap for class A, so I can’t afford the PI and still give it the power and grip needed. I’ve tried taking it down in weight, did a whole spreadsheet of combinations of builds using various weight saving methods (I have a knack for the whole min/maxing of building to a particular class) and I consistently get better results with leaving the weight alone and addressing the grip (and acceleration) was a higher priority. Believe me, it preys on my mind, but the numbers don’t lie, there wasn’t enough PI to take that 200+ pounds out and still get decent accel/grip.

4

Try sport or street tires, with less width on the rear and maybe some on the front. Try to get some weight out as well. Adjust your diff. Up the decc.

5

Things I would try (one at a time):

  • Lower Accel diff
  • Softer rear springs
  • Softer rear ARB

Also possibly softer bump for both.

6

/facepalm

Jeez, this is as embarrassing as admitting I wore parachute pants back in the '80s…

I just re-read my post and realized that I was lowering my Front rebound and bump while raising my Rear rebound and bump, thereby increasing my OS problems on corner exit. No wonder I kept having more problems with the handling, LOL!

Duh Gemini!
Duh Gemini!750×600 62.8 KB

I blame sleep deprivation. That will teach me to start getting to bed before 4am…

7

Yea, I’d agree that softening the front while stiffing the rear shocks would give you more handling issues with over steer lol. I’d agree and say sleep is much needed

8

Now, I have to re-do everything I did last night because I stopped taking notes after I had my initial tune, so it is back to there tonight and then at least I’ll know to avoid sleep-walking through the adjustments :slight_smile:

BTW, the Vantage is a beautiful car to drive, it has everything right in it, the right pitch in the motor for the rpms, the weight distribution makes the car feel more settled than something equally heavy like a Mercedes-Benz, the way it sets and turns into a corner, and even the default gearbox is setup properly. I hate when I see a default gearbox that alternates short and long gears…ugh. Aston Martin and Maserati are probably my two favorite manufacturers right now in FM4 & FM5.