This past weekend I entered a ProSolo competition which features a drag start for 125 ft. followed by an autox course.
I run a stock 2004 Z06 with Hoosier A6s. I share the car with a co-driver who drives the exact same car.
My issue is that I was consistantly beating my co-driver in RT and 60 ft times, but he was beating me to the end of the 125 ft mark with higher speeds of 4 to 8 mph. We were both shifting to second at the same spot on the course, about 35 feet from the end of the strip and before the autox course.
I launched between 2000 and 2300 rpms with a little tire spin and good grip. He said he was launching at 2500 rpms with significant wheel spin. Both of us were foot to the floor in first when the wheels hooked.
What's the physics as to why he was faster??? Some one explain it to me please. I would have thought that since I was hooking up sooner than him I should have been faster to the end of the strip.
With 500 passes in two C5Zs, I've done a lot of experimentation.
You are focusing on the launch. I would focus instead on the 1-2 shift.
(1) rpm for clutch-in; optimal is right before the limiter. Say clutch-in at 6500. There can be a two-three tenth variance made by shift point correctness.
(2) speed of the shift, amount of time the clutch is in and the car is not accelerating. There can easily be a two tenth difference in shift speed.
Ranger
__________________ '06 Z06 red 300 passes
Bone Stock Stock Tires……11.02 127.25 1.70 video
Bone Stock DRs......….…….10.71 130.32 1.60 video '02 Z06 350 passes
Bone Stock Stock Tires……11.81 117.26 1.78
w/ CAI & DRs………...........11.52 120.21 1.64 video My PRsBurnoutLaunchShiftingClutch Care
The biggest impact of shift-point misses is on the 1-2, where acceleration (G-force) is highest. An early shift sacrifices an increment of the strong acceleration the car produces. Same is true on clipping or banging the limiter at the top of first, where momentum is lost as the nose of the car drops.
Location: 2007 Nat'l Corvette Challenge 11.50 index Champ. New Jersey
His excessive wheelspin could also be giving him a falsely higher MPH...
Ron
__________________
09Z06Bone stock on DR's
10.750@128.19,1.563 60'@MIR,MD 3/25/11 Timeslip,10.79Video
06Z06 M.S. Bone Stock
11.242@122.38, 1.688 60' @ Atco,NJ 11/17/06 Bone Stock on DR's
10.912@126.32,1.62 60' 12/5/08@Atco,NJ
Black 03ZO6
RPS clutch,Hurst,160* tstat, headers,Vararam, LS1 edit tuned, RPM trans & DTE brace all @ECS. Best Pass: 11.21@122.30,1.58 60' 11/18/05 @ Atco,NJ. Slip Best Street tire Pass: 11.67@119.3,1.711 60' 10/17/03@ Atco,NJ w/ a Vararam & Tune only
Location: 2007 Nat'l Corvette Challenge 11.50 index Champ. New Jersey
Not what I meant.
Usually, wheelspin can yield MPH's that are higher then on non-wheel spun runs (so to speak). If he has more wheelspin then you, his MPH can be higher.....
If not, then his shiftpoints were better, & possibly faster shifts then yours.....
With greater wheel spin he is keeping the engine RPMs up, higher into the horsepower range, while at the same point you are closer to bogging. Kind of like a stall speed converter on an automatic. As long as the tires don't go completely up in smoke, he is getting more power to the track, an the average, over the 125' than you are.
Remember, too, if the timers are set up like a drag strip, RT is not a component of ET. ET starts at the point RT ends.
With greater wheel spin he is keeping the engine RPMs up, higher into the horsepower range, while at the same point you are closer to bogging. Kind of like a stall speed converter on an automatic. As long as the tires don't go completely up in smoke, he is getting more power to the track, an the average, over the 125' than you are.
Remember, too, if the timers are set up like a drag strip, RT is not a component of ET. ET starts at the point RT ends.
RACE ON!!!
That's the explaination he gave me. Spinning the tires more allowed him to keep the RPMs up and as it started to hook he would add throttle until he was fully hooked and at full throttle, way up into the powerband and, as the GPS showed he obtained a higher 125ft speed than me, which he carried throughout the first autox section.
It just seemed to me that if I was hooked and full to the throttle before him, I should have been faster than him to the shift point, which it seems I wasn't.
^^^ If every aspect of two runs to 145 feet are the same except for the amount of wheel spin on the launch, it's still stretches the mind to make that difference "4-8" mph, which is a huge variance in a short distance.
Another variable is the timing method. Were the reading you are comparing captured automatically by the equipment? Was the starting line electronically defined?
In that regard, keep in mind that a 12-inch rollout (initial movement) takes about .40 seconds to traverse by a stock Z06. I'd imagine the starting line at that course is less precise than a drag strip. A one foot difference in starting point can significantly skew timing and mph calculations, especially over your short distance.
Ranger
__________________ '06 Z06 red 300 passes
Bone Stock Stock Tires……11.02 127.25 1.70 video
Bone Stock DRs......….…….10.71 130.32 1.60 video '02 Z06 350 passes
Bone Stock Stock Tires……11.81 117.26 1.78
w/ CAI & DRs………...........11.52 120.21 1.64 video My PRsBurnoutLaunchShiftingClutch Care
^^^ If every aspect of two runs to 145 feet are the same except for the amount of wheel spin on the launch, it's still stretches the mind to make that difference "4-8" mph, which is a huge variance in a short distance.
Another variable is the timing method. Were the reading you are comparing captured automatically by the equipment? Was the starting line electronically defined?
In that regard, keep in mind that a 12-inch rollout (initial movement) takes about .40 seconds to traverse by a stock Z06. I'd imagine the starting line at that course is less precise than a drag strip. A one foot difference in starting point can significantly skew timing and mph calculations, especially over your short distance.
Ranger
They use a professional starting system. You can see the staging and starting line trip-light system in this picture. The grey box is part of the system. They do raise it to eliminate air dam, light tripping, issues.
Corvette Store
Launching a Stock Z06...Help!
