V8 Series XI - Tuning Talk

G'day,

Figure this thread could be useful for newbies to tuning like myself. So to start off:

At the end of qual, my right rear tire had significant wear as compared to the left rear. As far as tuning goes, what are potential issues to look for/change to help address this?  Note I am in Pro-Am with TCS.

Lots of other tuning things I wish I understood. Feel like the car is always on the limit but I really am unsure with what to adjust first. At least trial and error is easy. lol

Cheers,
ozmadair

With one particular "drive" wheel wearing more than the other, it would be probable that the "diff accel" setting is too low and wheel spin under acceleration is the likely cause of that. Need to increase that setting....somewhere between 30-40% MAY be the magic number however thre wear differences when TCS is on or off is something I dont know.....

Mitch,

Thanks, I'll have a look although I think I'm at 60% or so. *shrug*

Tuning is a bit overwhelming for someone just venturing out and it's difficult to know where to start. Do you or anyone else know of a good guide to follow?

Examples being: When I get into a car and get sorted with gears, where do I start? If the car is understeering, do you adjust front ARB, rebound, spring rate, tire pressure or what first? I swear with so many options for everything it's difficult to know "Start ".

-ozmadair

Hmmmm, what was the wear difference between the two rear tyres? COULD be "too tight", and the inside rear tyre is twisting on itself on the slow/sharp turns..?

Yes it is, and Forza is a mixed bag when it comes to tuning too. There are a few ideologies BUT i'll brief you on the "standard" issue tuning guide.

Firstly, only tune the end of the car that you have an issue with. If it oversteers, work on the rear. If it understeers, work on the front. My own rule with starting a new tune is work on the "driven end first". So on a RWD I tune the rear first before the front.

SUSPENSION: The tuning ideologies for suspension is hard and low as possible. The lesser the body movement is most ideal, and makes for a car that reacts quicker to steering input BUT this isn't always ideal as there are various surface irregularities to contend with (so your car need to ride well) and there are characteristics of every turn that suits both a softer and stiffer setup. A STIFFER setup is ideal to tackle corners and switchbacks/chicanes that are short and sharp. But long sweepers demand something that is on the softer side of things. Softer springs also means that there is more chance of bottoming out. (To see if your car bottoms out, when in a race next, select "d-pad up" which will bring up your telemetry. Scroll right using the d-pad until you see "four bars" that moves with your suspension movement. If at any stage of a corner does those white bars MAX out, that you need to increase your ride height.)

As a starter, the balance of your suspension works around your cars weight distribution. Front engined cars will generally be heavier on the front axle, therefore it needs to be stiffer than the rear. For circuits that have more sweeping corners, start with suspension stiffness about 35-40% stiffness, with the rear being about 5% softer than the front. For circuits that are more "point and shoot" with shorter, sharper corners, start at about 50-55% stiffness. Tune the suspension by SOFTENING.

REBOUND DAMPING: Tunes your cars corner ENTRY and EXIT balance. Best starting at "11.0" for your rebound and work your way down the scale (aka "soften") to tune it.
IF your car UNDERSTEERS going into or out of corners, SOFTEN your front rebound.
If your car OVERSTEERS going into or out of corners, SOFTEN your rear rebound. (IF you are searching for better "powerdown" grip then softening rear rebound won't assist much. Soften rear rebound for when there is a natural/inherited "oversteer" balance on corner entry or exit that you want to tune out. To assist with powerdown grip, soften rear suspension if you haven't already made adjustments to your diff).

BUMP DAMPING: in conjunction with suspension, adjust bump your car's mid-corner balance. Best starting at "6.0" for your bump and work your way down the scale (soften) to tune it.
IF your car UNDERSTEERS mid-corner, soften the front bump (or front suspension).
IF your car OVERSTEERS mid corner, soften the rear bump (or rear suspension).

ROLL BARS: Roll bars I find are a funny thing. They assist with a little bit of everything. How I tune the roll bars is by this: once I have a "baseline" tune worked out, I set my suspension and damping, do some laps, adjust the roll bars here and there depending on what end of the car is doing what. IF I don't find what I am looking for in that setup, I reset the roll bars back to the 60ish% position, make adjustments to the suspension and damping again, and repeat the roll bar process.

DIFF: On the "accel" setting, a lower number means it will spin the inside wheel under acceleration, a higher number with see both wheels spin. If the Accel % is too LOW, on corner exit when attempting to apply more throttle may result in excessive wheelspin from the inside (and unweighted) tyre. Too HIGH of a % in a powerful car and it will overwhelm both driven tyres, causing "powerdown oversteer" OR in a lesser-powered car will cause understeer (as there isn't enough grunt to overwhelm the tyres) Ideally you want that "accel" number to be as low as possible, but not too low. Usually start around the 17-18% and increase until you notice that power is better distributed through both driven tyres, and not leaving "single-peggers" on corner exit.
The "DECEL" setting is operates exactly the same as accel, but when the car is slowing down. On a RWD or AWD car, this % needs to be low, around 9-15%. Start or leave at 9% and increase only if you find the rear moving around under braking.

Mitch,

Absolutely awesome post. Thank you.

One quick question. On the SPRINGS, you said that if one of the 4 bars fill up, it means you're bottoming out. Now I always thought those 4 bars represented spring travel. e.g. if it hit 100, that means your spring fully compressed and  you need to stiffen it up. Is that not right? As I read it as you wrote, if the bar fills up, increase ride height.

Thanks for the clarification. Can't wait to try this out.

Cheers,
ozmadair

ozmadair wrote:Mitch,

Absolutely awesome post. Thank you.

One quick question. On the SPRINGS, you said that if one of the 4 bars fill up, it means you're bottoming out. Now I always thought those 4 bars represented spring travel. e.g. if it hit 100, that means your spring fully compressed and  you need to stiffen it up. Is that not right? As I read it as you wrote, if the bar fills up, increase ride height.

Thanks for the clarification. Can't wait to try this out.

Cheers,
ozmadair

No problem at all!

Okay ride height: yes what you say is true BUT there needs to be a compromise between ride and balance, and bottoming out.

For example, lets start with the tuning dilemma with Sonoma in a V8SC.
The first sector: the first 4 corners contains both fast and slower-speed long sweeping corners, with large dips and rises mid-corner, with both positive and negative camber characteristics. Naturally this calls for a setup on the softish side with longer suspension travel to properly attack those curves and dips, and a higher diff accel setting to prevent wheel spin as the inside tyre is unloaded for a longer period of time. Turn 5 however is a sharp, straightforward turn that naturally suits something stiffer in the springs, and a "looser" diff, to allow the rear end to twist better on itself. Try and stay off the kerbing in sector one, although you will need to use some of it the crest of turn 4, but dont apply the poerr until you are properly straight and off the kerb.

Sector 2 contains two long sweepers (turns 6 and 7) where a lot of time can be lost from inferior powerdown. Again, softer would better here BUT come the "double apex" of turn 8 and 9 sees something that needs to bit hard and sharp, but as mid corner speed is approximate 80kmh, getting 600hp to the road is tricky as well, so a bit of rear end "squat" to assist with powerdown help heres. Like sector one, time can be lost from attacking kerbing, especially in turns 8 and 9.

Sector 3 sees turns 10 - 14 is where how well the car rides is critical, as you find yourself really attacking and riding those kerbs through these "high speed esses". Through here you as these turns are long BUT flatter (compared to others on the circuit) so you dont want too much body roll, so softer on the springs BUT stiffer rollbars. Turn 15 is slow and flat, where low speed powerdown is critical (again, rear end squat helps with powerdown) and is easy to induce wheelspin, affecting your laptime for the next lap.

As you can see, its a mixed bag where several compromises need to be made. Myself, I cant attack the first sector, and I lose time chasing and ideal setup for sector one as it does not suit the rest of the circuit. Im naturally quicker through sector two and three, so I focus there and just ensure I dont balls S1 up too much.

Invaluable advice, thank you for your time in writing this Mitch. I can see more tweaking over the next few days. In an effort to contribute I will share my tuning story.

I have spent about a week 'tweaking' the Volvo to try and find a forgiving enough tune to deal with Sonoma due to all the camber changes and peaks with the biggest challenge being the high speed entry into turn 1 for me. In a slower, less powered car you have a more straight entry to the corner so you can come at it in a more aggressive approach but I am finding in the V8SC that the lead up to the corner is basically a long sweep into a sharp switchback with changing camber and a peak, basically the perfect off point. It is very hard to apply the brakes and if you miss this corner you will have trouble with the turns 2, 3 and 4 due to being off line. The other challenging sector for me is the second to last turn (sweeping right hander) where I find under steer to be a big issue.

I find setting these cars up to be forgiving means check the ride height as Mitch said, jack it up. Soften the rear springs substantially to help power down out of the corners and keep the fronts pretty stiff to help avoid body roll, I have all but taken my rear ARB off (but may change that after reading Mitch's advice) to help with over steer. Stand the rear tires up a bit to help avoid wheel spin on power down, but not to much or you will begin to reintroduce over steer on corner exit.

The loud pedal and a very gentle foot (or finger) is the most important tuning instrument you have at your disposal. Knowing when and how to put the power down will fill you with confidence and then in the next turn demoralize you, a trick I have found is to not lift all the way off when you start to lose control, these cars like to have some drive under them.

Yes, a poor turn one ruins entry into turn 2, by then there is a higher chance of the car being unsettled and out of rhythm into turn 3, 4 and crossed up going into turn 5. There is just a certain way to manhandle the first sector.

If anyone wants a nice stable benz tune for controller I got one. Let me know I'll give ya all the numbers.

Won't win rounds but might help with frustration