Pescarolo power understeer

[nomis3613]

Hi Folks,

Any ideas for getting rid of the power understeer in the Pescarolo Playstation car?

I have got it to a nice handling balance generally, except as soon as I hit the gas, the nose lifts and she doesn't wanna know about holding the line to the corner exit. Stiffening the shocks has helped me get rid of pitching in other cars, but doesn't seem to help in this one and the car is already scared of bumps so I don't wanna go any stiffer.

I've also added -2 front toe which did little (unlike any other car I've tuned).

It's interesting that the front ride height is the minimum by default. Do you think ground effect for the front wing is modelled for this car? Anyway, when I raised the car slightly the understeer was even worse.

Any ideas?

Thanks,
Simon

 

[sukerkin]

Hi Simon

I think it'd help garner you some detailed answers if you could let us know what state of tune you're running the car in (hardware and settings).

It could just be something as simple as this car requires you to wait a little before jumping on the loud pedal out of a corner i.e. get as straight a line as you can from the apex to the exit. PD hasn't modelled high-torque, FR, European/American cars all that well in GT and changing the style of driving is often the easiest course for getting around their torque=overwhelming the tyre grip=understeer miscalculation.

 

[Dotini]

http://www.gtvault.com/gt4/setup-view/s_sid::7385/Pescarolo-PlayStation-C60-Judd-Race-Car/

Simon, as sukerkin said, from your description of the problem it's hard to know what you are working with and what you are trying to do with it. But it's possible the above setup may be of help to you.

 

[nomis3613]

Hi guys,
Sorry for not replying sooner, I didn't have the email notifications set up properly.

Anyway, here is my setup:
Racing Exhaust
No computer
No NA tuning
Super Hard racing tyres F + R (I'd like to find a setup using these tyres cos I'm up to the endurance races)
no turbine, intercooler, supercharger
Normal brakes
Brake controller: 3/3 f/r

Racing Suspension:
springs 13.5 / 16,5
ride height 50 / 85
damper bound 5 / 9
damper rebound 5 / 7
camber 2.0 / 1.0
toe -2
stabiliser 3 / 5

full gearbox: 4.52 / 2.97 / 2.26 / 1.48 / 1.20 , final 2.00
standard clutch, flywheel, prop shaft
driving aids all off
downforce 63 / 70
full lsd: 5 / 10 / 5
no weight ballast

Cheers,
Simon

 

[Vince247]

To me, the LSD accel is a bit too low. Try raising that, and see if it helps.

And I also have my doubts about the dampers, they seem a bit high, even for a racecar.

Try this:
Bound: 4/4
Rebound: 3/3

And apply changes to your needs, the values I give here are a good starting point.

 

[Parnelli Bone]

Hi guys,
Sorry for not replying sooner, I didn't have the email notifications set up properly.

Anyway, here is my setup:
Racing Exhaust
No computer
No NA tuning
Super Hard racing tyres F + R (I'd like to find a setup using these tyres cos I'm up to the endurance races)
no turbine, intercooler, supercharger
Normal brakes
Brake controller: 3/3 f/r

Racing Suspension:
springs 13.5 / 16,5
ride height 50 / 85
damper bound 5 / 9
damper rebound 5 / 7
camber 2.0 / 1.0
toe -2
stabiliser 3 / 5

full gearbox: 4.52 / 2.97 / 2.26 / 1.48 / 1.20 , final 2.00
standard clutch, flywheel, prop shaft
driving aids all off
downforce 63 / 70
full lsd: 5 / 10 / 5
no weight ballast

Cheers,
Simon

Looks like you're doing everything you can. I was gonna say put a softer grade of tire up front so it looks like: (R2/R1). And then have a look at the GTVault settings Dotin posted earlier--whoever put those up has the same idea, but with softer tires.

I would also shift ballast just a tad forward if i really got desperate (no more than -10). This is tricky, though...obviously the more you shift, the more the rear gets a chance to loosen, which can be more dangerous than your original understeer/problem.

If the rear starts getting loose (and you haven't shifted balance but have swapped those front tires) you can then try lowering the rear...you've currently got it way jacked up, i see.

Off-original-topic, but your springs are very stiff. This might be fine at a track like Fuji (which is mirror smooth) but i'd imagine some problems at bumpier tracks.

 

[sukerkin]

At first glance it didn't look too bad but more careful examination suggests a couple of things to try.

First, flatten the car out. Wedging via ride height works well with MR cars to play with the fore and aft roll centres but with FR's (which I think this is (I've never driven it )) it can give odd results such as entry oversteer and exit understeer.

Second, go up a grade on the tyres. R2's might not last as long but the grip difference can be dramatic.

Third, the damper settings are an interesting experiment and I have used a 'reversed' version before now on a car. I would suggest tho' trying resetting them to Bound 4/4 and Rebound 8/8 and then altering the rebound at one end a click at a time until testing shows you how the car reacts to altering the speed of roll.

Fourth, try reducing the rear springs a kg at a time and seeing if that frees the rear end up a little. Too much roll stiffness at the rear can, counter-intuitively, cause understeer.

Fifth, try reorganising the gears to utilise a higher final drive - it's amazing how much the gearing can alter the character of a cars handling, especially when there's an LSD fitted.

 

[Rotary Junkie]

The pesky is MR

 

[sukerkin]

Ah, cheers RJ 👍.

Then the question becomes what are it's handling characteristics like under most circumstances? If it's pretty stable then a wedged ride height might not be the way to go. If it's hard to turn and then suddenly slides then a wedged approach is a good bet, or maybe a flat but higher ride.

 

[nomis3613]

Hi guys,
Thanks f0r all your tips. Much appreciated.

I had another drive, let me try to describe the problem a bit better. Turns out it is not just when accelerating coming out of a corner, but also the rearward weight transfer on corner entry when I stop braking. Seems like transient pitching motions are upsetting the car. Also it isn't able to hold a steady 4 wheel drift, it seems each braking or accelerating input causes a different cornering stance with a harsh transition between them.

For example, where I would normally lift off when the car understeers exiting a corner, a car should gently tuck in the nose and get back to the desired line. The Pescarolo would give a harsh but small rear slide then wait for aaaaaages before finally the tyres bite and it gets back on line. Hopefully that description makes sense!

So here's what I tried:
@Vince: I tried both tightening the diff on accel and using the shocks you suggested, but they didn't really help. Thanks anyway.

@Parnelli: 10 ballast on front helped a bit with corner exit, but didn't help with the pre-apex problems which I didn't describe before. I also noticed less speed on the straight (which is surprising given it's only 10kg out of 800ish!)

Tried out lowering the rear ride height...and...RIGHT ON!!!! That was the magic cure. A bit of experimenting and I settled on 55 / 60. The reason I was running such a wedge before was because that was the default settings (very strange!) and I thought maybe Polyphony were doing some funky ground effect stuff for this car. Appears not. Just really strange default settings.

You're right about the very stiff springs (dampers, too). I prefer softer setups, so I usually start with tuning with all dampers and stabilisers at 4, but I had worked my way stiffer trying to fix this problem. So I soffened the car again, but this brought some of the problem back. After testing springs and dampers seperately, I actually found that the original settings I posted were the best. Normally these would be too stiff for my liking, but worth the compromise in this case to avoid the nasty transient roly-poly.

@sukerkin: Yup, it was the wedge ride height. Good call!

Thanks All,

Simon

 

[Parnelli Bone]

@sukerkin: Yup, it was the wedge ride height. Good call!

Thanks All,

Simon

Hey i said it before sukerin! Just used different wording.

If the rear starts getting loose (and you haven't shifted balance but have swapped those front tires) you can then try lowering the rear...you've currently got it way jacked up, i see.

anyways, glad we could help.

 

[nomis3613]

True, true. You both picked it.

Actually all the paragraphs I wrote before sukerkins thanks were "at" you Parnelli, including the ecstatic "right on!!! etc etc" and ummm the thanks that I forgot to say cos of the excitement.

So the Pescarolo beast is tamed thanks to all your help. Good thing, too, cos it cost a pretty penny to buy!

Cheers,
Simon

 

[Parnelli Bone]

Isn't it interesting that these cars that seem as though they'll so easy to drive fast are the ones the usually require the most tuning knowledge?