Best 1/4 Mile E.T.
My best 1/4 mile ET occurred the last time I accelerated down the 1,320ft stretch in 1999. It was October 30th, the day was cool (mid 60's) at Lapeer Dragway as I made my passes with Torco 104 octane in the tank and 17psi dialed in on the boost controller.
1.770 second 60ft
7.932 second 1/8 mile @ 92.17 mph
12.236 second 1/4 mile @ 113.31 mph
Starting with the launch, I released the clutch (not quite a dump) when the engine hit 5,000 rpm. I reached WOT in about 0.7 seconds and it took the clutch ~ 1.5 seconds to stop slipping (nearly to the 60ft mark). Note that it takes a finite amount of time for any clutch to stop slipping. If it grabbed immediately, the engine speed would approach 0 rpm and die. On this run, it slipped enough to allow the engine speed to stay above 4,125 rpm.
Overall, the shifts were decent. I always lift off the throttle until the shift is complete. The longest shift, 2-3, kept me off the gas for 0.5 seconds. What should jump out from the datalog is the fact that I shifted into 4th gear well before finishing the 1/4. Not because I was approaching red line, heck I didn't even hit 6,000 rpm. Instead, I shifted to stop the hesitation I was feeling (see the fluctuating O2). By shifting into 4th early, I dropped the rpms and eliminated the hesitation (I knew this would eliminate the hesitation from previous experience). Both the hesitation and the early shift diminished what was an otherwise excellent run (hurting the trap speed more so than E.T.).
Why the hesitation? Well I didn't have time to fix the problem before retiring the car for the winter but I suspect either a wide plug gap (blowing out the spark) or a fuel delivery problem. I replaced the fuel filter, pressure regulator, and tested the fuel pump relays without finding the problem.
I credit the cool ambient, rich fuel settings on the VPC/GCC, and the 104 octane fuel for keeping the knock sum at zero. The 550cc injectors did not exceed 77% IDC yet kept the O2 voltage at or above .86 volts (ignoring the hesitation). Had I not been experiencing the hesitation problem, I would have increased the boost and made more runs. Now I won't be able to attempt 11's until the new engine is completed, can't wait.
since August 7th, 2002
Last Updated: 08/08/02 07:50 PM