A600 Cadillac CTS-V (2004) Damper and ARB Learning.

[Fit4aking]

Build:
Twin turbo aspiration swap
Race: Brakes, Dampers, Front Sway Bar, Rear Sway Bar, Chassis Stiffening and Roll Cage, Weight Reduction, Clutch, Transmission, Driveline, Differential.
Race Tire Compond (Slicks)
265/35R19 (Front and Rear)
Hamann Edition Race
Forza Front Bumper and Rear Spoiler


Tune:

Tire Pressure:
Front: 28
Rear: 29


Gearing:
Final Drive: 4.10
1st: 2.89
2nd: 2.02
3rd: 1.47
4th: 1.14
5th: 0.94
6th: 0.80


Alignment:
Front Camber: -1.0
Rear Camber: -0.8
Front Toe: 0.0
Rear Toe: -0.2
Caster: 5.2


Sway Bars:
Front: 22.10
Rear: 19.90


Springs:
Front: 635.5
Rear: 622.5


Ride Height:
Front: 7.0
Rear:7.0

Rebound:
Front: 7.8
Rear: 7.9


Bump:
Front: 4.0
Rear: 4.0


Aero:
Front: 92
Rear: 180

Brakes:
Bias: 47%
Pressure: 105%


Differential:
Front:
Accel: -
Decel: -



Rear:
Accel: 50%
Decel: 45%


Torque Split:
Center: -

This car is loose on cold tires but will come around when they heat up.  Smooth throttle input is an absolute MUST.  The lag of the turbo's help keep the rear end from snapping around but it will get squirrely if you jab the throttle.  I'm not saying its an expert only car but if your not used to a heavier sedan with more than enough power I'd be careful before jumping into any open hoppers.  If you take a few laps to sit and learn how and when to push it you'll be surprised at how quickly the lap times drop.  Not a top 100 car by any means but a RWD alternative none the less.  It was created for PikeJerky's Inaugural Shootout and was tested extensively at Mugello Full.  I would feel confident taking it to just about any flowing mid to long track, not Tsukuba, Amalfi, or tight technical tracks similar to those.


This is the car I was working on during the tail end of the Damping discussion and I think I have a lot of the bugs worked out for my driving style.  Feuer has a copy of the tune and I look forward to what his calc outputs would change.  Feel free to build one out, give it a spin, and let me know what you think.  Just keep in mind that a 3100lb car with 480hp isn't always going to be the most forgiving car, specially when I traded in full 275 width slicks for a few extra pounds off.  It didn't affect tire temps or lap times much so I don't think it was a bad move.  

[Blooze]

What is the Curb Weight on the thing? 

$

[feuerdog]

By only looking at the numbers themselves, the car looks like its pretty stable.
Without driving it my observations are thus -

- I might try stiffening the rear ARB and softening the front,...in addition to softening the rear springs and stiffening the front, but only very slightly. The intention being to maintain neutral state balance while improving turn entry and exit mechanical grip. Essentially the springs and ARB stiffness just exchange a little of the work around.
The reason for this exchange relates to the lower rear camber. I suspect that it was lowered not for aerodynamic camber, but for uneven heating in the corners and a "loose" feeling under acceleration.
A stiffer rear ARB will keep the rear tires flatter and planted.
The slight bias in spring bias will retain the cars "squat" traction.
The softer front ARB will retain front steering grip and allow the caster to work more effectively.

- Turn-exit push? Turn-entry lag? - Again probably in an effort to keep the rear end behind the front, the rear rebound looks a touch high. Good for control, but poor for rapid chassis response. These rebound values may get shifted by about 1 from front to rear.

- Compliance, again, only based on observation, bump looks low and springs look stiff,....but only slightly. The relationship is right for feel, but the rebound damping indicates that the car feels twitchy for its weight. That hints to me that spring strength can be dropped a little, and bump damping can be increased to retain feel. That will also bring the rebound damping closer to a ratio that I trust,...around 1:1.4 or 1:1.5
Softer springs tend to enhance weight transfer grip too, and RWDs tend to accentuate thier own oversteer or understeer characteristics so a little weight transfer can help load the working end of the car.

- The tires are plenty wide for the weight. I'd even consider a smaller front tire.

- The car has gobs of power, so i'll be looking at gearing to keep my auto-shifting power application in check.

- Slicks. After driving my new BTCC inspired Citroen C4 on Fujimi extensively last night, i've come to the conclusion that slicks are a wolf in sheeps clothing when combined with sub-R-class aero. They have great grip up until the point of traction loss, but , very realistically to real world, when they do break traction they literally feel like they lose all traction, and quick.
Your comment about being smooth simply reinforces my thoughts on this.
If one end of the car does lose grip you have to expend alot of momentuum regaining it,...again proving the smooth is fast rule. The other tire compounds have only slightly less grip, but give you much more time to respond and control thier loss of traction.

Again, this is just an observation based on your post here, and the differences i'm sharing are going to be VERY slight.

I'll get this car thoroughly test driven and retuned tonight to see what you think.

[Fit4aking]

Lots to ponder Feuer.  I didn't even think to reduce the tire compound when I took the width away.  Call it a safety net.  I've only got this and one other car on slicks in my entire garage, save the R-classes, so it makes sense to try and remove a bit of compound for the sake of extending the friction loss from a cliff dive to a sliding board.  However I'm not sure what the trade off in PI would be.  The weight is already as low as it can go and it has gobs of power.  Maybe the power upgrades that also reduce the weight further could enhance more than acceleration and help with braking and transfer.

IIRC the weight is just over 3100, like in the 3160's but I'm not positive.
-Spring rate is 40%
-Bias is likely in the 50.5% to 51.5% range but I lost those values when I toasted my hard drive.
-ARB are at 52.5% so reducing that bias to match the spring bias may just bring it to your observed spec.
-I lowered the rear camber for tire temp, not aero, and only slightly increased spring to balance the added effect of spoilers and wings.
-Caster was lowered 1 click due to dynamic camber being too high in steady state cornering causing a push.  The first and last sweeper on Mugello were my nemesis until I adjusted that value.
-Rebound rates are simply by feel for the transistion section but I never could get the downhill transition to occur how I like so it is still a compromise but the best I figured up until now.
-Bump rates are default for me and I didn't move them at all in an effor to keep the "curb effect" in check by running things soft. 

While this car is "done" as far as the entry into the competition I'm not completely finished with it.  The Caddy has become quite the learning platform for me and my tuning ability so I decided to enlist the help of some "pros" (read: Forza-Tuning!!) before I simply settled on it.

[Blooze]

Okay, what I am going to lay on ya is based on the weight.  I'll go with 3160.  However, it only affects the springs and it is only significant if your recollection is way off.  Everything else stays the same, just like in Forza.

I'll list just the things that are different that what you listed.

Rear Toe: -.1

Sway Bars:
Front: 16.3
Rear: 16.3

Springs:
Front: 734.5
Rear: 734.5

Rebound:
Front: 8.4
Rear: 7.9

Bump:
Front: 4.2
Rear: 4.2

Accel: 32
Decel: 26

I know it looks sort of hoaky with the ARB and Springs being set to identical values and all but trust me, it works.  I have an A Class 09 CTS-V set up similarly (different weight/springs) and I can drive it around MVS as hard as one of my AWD cars.  Try it!

$

[feuerdog]

btw Fit, you posted the rear toe as .2(positive/toe out) is that a typo?

[Fit4aking]

It is in fact -0.2.  I had the wife double check to be sure.  She loves having to fire up the ole laptop and look up Forza things. (hehe)

Your setup does look like it would accomplish many of the same things I was after only in different ways.  I'll be sure to check it out and then also see that the weight is close to how I remember it.

[feuerdog]

OK, just checkin'.  The tune you sent me has +.2 rear toe as well,.....which definitely didn't help oversteer issues.

I got your tune, built the car, and used -.2 rear toe and went for a few test laps on a few tracks.

- Initial thoughts.....Drift setup? Tons of tire spin. Really stiff.

- 3 laps later......Stable, and predictable turn-in and mid-corner, but curbs are bad joojoo. The only time I had a problem with car control was anytime I wasn't absolutely and totally passive with the throttle. It felt like driving the Top secret drift car in FM2 at times. It did hook up well, but I found myself getting slower to avoid any kind of throttle without being pointed straight down the road. Point and shoot car for sure.
Those slicks break fast, and that monster power didn't help.


My tune - Much of what I mentioned in my earlier post. Camber and caster were dead on, springs slightly softer, and an inversion of ARB values.
Damping saw some big changes, and I think established a slightly better feel. Toe settings changed slightly, but nothing of note. I dropped the aero to 100f 150r to keep within my 2:3 ratio. Diff reset to 40/40, brakes to 48@100, tires at 29/29. I sent you a copy of my tune.
The biggest changes I made were in the gear box. I booted your 4.10FD in favor of a 3.50FD, and slightly reworked the gears so that the car would at least do 170mph, something I think most A-missiles should be capable of.

Test drive - Same number of laps, same tracks. Same times. I couldn't actually make any improvements in lap times, easily attributable to the amount of time you spent tuning the car originally. To me, my tune felt easier to drive, but many of the observations I made about your tune were still there. The car still felt stiff, and still broke out into oversteer quickly. The taller gearing made the car easier to drive but also didn't slow the car down as much as I thought. The biggest difference was that I could more readily clip the curbs without unsettling the chassis as much,....as long as I wasn't on the throttle.


Build changes - If you bump the rears to 275, and drop the fronts to 255, the PI stays at A600. Using this combo and my tune I managed a clean Amalfi test lap of 1:00.624 on the third lap.
I'd also try the supercharger, with a sport cams, and sport pistons, instead of the twin turbos.


In summary - The cars a beast, no doubt. Big, heavy, powerful, but not as fast as i'd like. It compares very closely in stats to my B500 BMW M5 E60, the only real difference being slicks and the grip stats.
You've got my tune now, so lemme know if it makes any difference to you.