So last Saturday I did another open track day at COTA with Edge Adicts. I ran all 5 sessions and really didn't have any big issues. I had hoped to post another video but operator error seems to have struck and the memory was blank. Sorry.............
On another issue, I have figured out the vibration under braking thing. Since the last time at the track, I had the front rotors turned. I lathe operator was asked to only remove a minimum of material so as to expose the virgin surface. I think the max amount he took off was a bit less than 2 thou. In any case, the vibration is COMPLETELY gone. Not a hint.
I used the first session to gently bed in the pads (Wilwood B see chart below) on the new rotor surfaces and then began to add pace throughout the day in later sessions. The sessions are 30 mins so you get about 6-7 hard laps per session. I will tell you that at 150mph I was able to just about stand on the brakes and as the downforce bleed off begin to modulate the brakes to prevent lock-up. This was a hard technique to commit to and a big change from the sort of tentative adding leg as the car began to slow and to confirm complete control over a longer brake zone.
The best times of the day were around 2:38, a fairly brisk pace, with brake zone entry speeds above 140MPH and seeing 150 a few times on the back straight. I believe that there are 20s in this car but maybe not in the driver. These are "no bench racing" numbers.
I can say that times really come down when you take 50 and then a 100 feet out of the high-speed brake zones. In any case, the brakes really work well now.
The other big setup changes for this event were the spring rate changes. The front got the rears 800s an increase from the 650s on it before and the rear got new 900s. It was necessary to add two clicks to both compression and rebound on all four shocks. I think the shocks are getting near their adjustability envelope. There may be a shock valve tune in the future. I'm guessing but I think any more spring rate and the QA-1 are not going to work, at least in their stock configuration.
I left the anti-roll bars alone and didn't change their settings. I did feel that at the end of the SSes I was getting a bit of understeer but I will need to think about that at a later date. I am also very pleased with the ability to do my own alinements and being sure about what is on the car as far as settings.
Toe : F = in 1/16 both sides. Toe R = nearly straight ahead, biased towards in approx 1/32
Camber : F = -1.5. R = -1.25
Caster: both +5-6 best guess but the same on both sides. I want to really get this nailed down and calculate or measure where I am. I don't think that I want to change it but I would like to have the data in hand.
The steering ratio could be better (faster) at slow speeds and in turns of more than 70 degrees or so. I would also make the car easier to catch in an oversteer situation. As it is, once the car gets its tail out the car is much faster than the steering rack/ my hands. I work very hard not to slide the car around as a result. High-speed straight-line and 3rd - 4th gear fast corner feel is very good as is.
The car feels a lot better at high speed especially at the beginning of the brake zones. Before the spring changes, I was thinking that the rear of the car was being aero compressed and then destabilizing the front as the speed/downforce came down and the front responded to added loading resulting from the rear lifting. It just felt weird and now the car feels like it is much more balanced and stable from beginning to end under hard braking from 145-150mph down to 50 or so. A good change I think.
Lastly, It was a very hot day. Air temps were in the very high 90s and very little wind, full sun. I did get a vapor lock stall in the pit lane at one point and needed to open up the back of the car to cool it off for a couple of mins. Maybe cut some holes in the rear clam this winter. I still need to repaint the nose so maybe do it then and repaint the two clams at the same time. Water temps were good all day. 180-200F Engine Oil 200-220F Grbx 170-190F (no cooler)
So I hope this continuing saga of a "behind the curtain" look at a completely amateur attempt to build and develop what is really a homemade prototype is useful. The one thing I do know for sure is the car is never done. BUT you can learn stuff and do most of the work yourself if you just give it a try.
The journey continues........................................... I want to run the car at a much slower track with more slow corners next time.............and see what I see.