CSX3170 autox prep

[Cobra #3170]

I thought it was time for an update on Scott and my effort to get into the Goodguys shootout this year in Scottsdale. We have made a number of changes to improve the car. I replaced the Penske 3-ways with JRI 2-way shocks which was a major improvement. Evaluated 3.54 and 3.73 rear gears in place of the 3.31 and Torsen T2R, Salisbury and Tracloc differentials. We also tried some different caster camber combinations and toe settings. The car gets so low in the rpm band at Goodguys we loose intake velocity followed by an explosion of torque so driving is pretty difficult. Scott did qualify for Scottsdale by winning the Pleasanton Goodguys autox so that is out of the way early this year and did it with the 3.54 ratio. We have changed to smaller master cylinders because the brakes were too difficult to modulate. ended up with .75 front and .625 rear.
We tried two different brake pads and decided on Porterfield R4-1. We have tried Rival S, Falken 615k and Bridgestone RE71 tires. Still have not identified the best brand however, more testing is needed. I have raised the front roll center to reduce RC migration and reduced camber which helped handling and also improved braking.
The car is now at 2.8 D front camber with 5D of caster. Rear is 2.2 D. of camber, front and rear toe varies depending on the course from 0 to 1/8" total in.
The car is really beginning to work well now, I like the 3.73 with Tracloc the best because it does not under steer as you bring up the power. Brake changes are positive too, much better modulation and higher G stopping.
I still have some knock back so may float the rotors to address that.
We ran it this weekend at Crows Landing in California and it was pulling 1.1 G
acceleration at 70 mph and a solid .9 acceleration at 91 mph and 5500 in 3rd. I am still losing belts at high revs so will be installing an idler pulley on the belt this week.
All in all the car is really improved over last year but so is everyone elses car.
I like the JRI shocks, when you change a setting things happen unlike the Penskes and they have a huge range of adjustment. I will write an update on tire testing and alignment settings when we complete the sorting.
The good news is that the car is competitive on a tiny asphalt lot or a big wide open airport. The AAS series allows modern Corvettes in our class (Cam-S) even though SCCA does not and the Cobra has beat new 2015 Z06's so it is no slouch in an autox even on 200 TW street tires and no electronic nanies.