So I was very uncompetitive at the last autocross despite going to bigger tires. The time has now come for me to stop throwing shiny parts on it and start doing actual suspension setup to get the thing sorted.
What happens is the car responds very well to steering inputs, but the rear of the car likes to come around and go into full on drift mode if I throw it in a corner too hard. My corner entry speeds are leaving a lot to be desired.
After doing a lot of research, it seems as if the it's a combination of factory suspension design issues combined with lowering the car further compounding those issues. The front center of gravity is too high above the front roll center. As the car is lowered, teh front roll center gets closer and closer to the ground much faster than the center of gravity does. The rear roll center drops much slower, so my roll center for the car goes from in the dirt in the front of the car to the hatch glass in the rear (not quite that pronounced, but thats the basic idea). As I pitch the car into a corner it will roll over on the front tire and lift a lot on the inside rear tire, leaving only one rear tire for any significant amount of traction. This is compounded further by my very large rear sway bar and slightly smaller than ideal front sway bar.
You can actually see how the car dives onto the front tire hard during any sort of lateral cornering. This is halfway through this corner, not under hard braking. Note how much weight the car is throwing on the front tire, and how much the car is trying to lift the inside rear tire.
So the solution is to get a panhard bar relocation kit that lowers the axle side panhard bar mount an adjustable amount. This will lower the rear roll center. It will keep the front of the car from rolling over and lifting the rear inside tire so much. This requires much stiffer rear springs and a stiffer rear sway bar than normal. I can, for now cut the factory rear springs and stiffen them up and lower the rear of the car. Since I can keep the roll center low lowering the rear of the car doesnt matter. This is somewhat counterintuitive, but by increasing the difference between the center of gravity and the roll center, I can tune the behavior of the car going into a corner. At least that's the idea. I already have the biggest available rear sway bar and a good set of shocks to control the higher spring rates so Im covered in that regard. Now lowering the rear of the car a lot will leave the car lower in the back than the front...
But theres more. The other half of the solution is extended ball joints.
http://daymotorsports.com/proddisp.php?ln=25437
These will basically act as drop spindles and restore factory front suspension geometry while simultaneously lowering the car by .5" . This will result in bump steer (toe in under compression) but there's nothing I can really do about it. A bump steer kit isnt going to fit inside my wheel hub. But Im thinking it will be worth it. It will bring the front roll center up towards the front CG further balancing the car.
There is no "goal" here, except to help the car balance traction on all four tires better, and right now it's pitching over onto the outside front tire badly, so if I can address the roll center issue it should be a LOT better about it. This will lower the car by .5 inches in the front and ideally .5-.75 inches in the rear. As a side effect, decreasing the distance between the front roll center and center of gravity will give the cg less leverage on the front suspension which will allow me to run slightly softer springs and maybe a softer sway bar, which compensates for my factory front sway bar which is large at 34mm, but the largest factory bar is 36mm so it's technically less than ideal in this case. raising the roll center back up will actually compensate for this and should help the car get better mechanical grip on the front since large sway bars are inherently compromises. You give up grip for trying to stabilize the car.
Anyway, for those that read that far and have any comments/corrections, I'm glad to hear it. This is stuff I've only recently learned about, and Im still figuring it all out.
And as far as cosmetic stuff, I plastidipped the wheels anthracite but I got tired of people thinking they were black, so I decided to experiment. I got some plastidip "pearlizer". It's a glossifier with white plastidip mixed in (opaque) with a pearl additive. This stuff out of a can is a bit tricky to apply allegedly, but I think it turned out FANTASTIC. It's not an exact copy of corvette competition gray which is what I was after the whole time, but it's even cooler than that color to me.
And a memorial picture of my muffler. It decided to depart the vehicle while in transit from this photoshoot never to be found again. I can only presume some good samaritan snagged it before I could get back to it again. It sounded amazing, but was insanely loud. I've got a Hooker Aerochamber on the way that should tame it down quite a bit.