[s-cars] Dragstrip day
Djdawson2@aol.com
Djdawson2 at aol.com
Mon Sep 26 20:54:02 EDT 2005
Well...
Finally got the car to the dragstrip. I had my newly installed 928 MAF.
Temps were 81-85 degrees by my dash display, and the dragstrip is at 2700ft.
The runs were made with pump Chevron 91 octane gas.
The results were less than pleasing... but I have to pass them along as data
points, or I'd be a cheater.
4 runs... 13.13 @ 106.48, 13.23 @ 100.85, 13.19 @ 103.10 and 13.20 @ 100.81.
I don't believe I can draw many useful conclusions yet, as the 928 MAF isn't
adjusted properly. The car refused to pull hard in 3rd gear, and somehow,
the early run times (60ft, 330ft, and 1/8 mile) had NO effect on the overall
time.
My best 60ft time was 1.805 sec. My worst launch resulted in a 2.244 sec
60ft. Ironically, the run with the 2.244 60ft was my quickest and fastest run,
when it took me nearly .5 seconds longer to complete the first 60ft. What?
Why?
I discovered A/F ratios were pushing into the mid 13s in 3rd gear. As soon
as this would happen, the timing would back off. I never had a run where the
engine would pull hard in all gears. Very frustrating, and no way to adjust
at the track. From my dyno experience, I know the engine tends to make its
best power when the A/Fs are in the high 10s when under full boost and WOT.
Improvement is certainly available here.
Next, the clutch. The Centerforce isn't up to the task. You can't launch
aggressively, or it will go into an uncontrolled slip. Gotta do something
about this if I'm going to see good dragstrip results. Other cars that were
making it to 106mph were recording mid 12s on the ET.
Finally, the gear ratios. Quandry here... 3rd gear at 8500rpm still won't
get you to the end of the track. However, shifting into 4th is done so late
that it becomes a penalty. As a result, my best time and speed (13.13 @
106.48) was achieved by running 3rd gear to 8500rpm, pushing in the clutch and
coasting through the trap.
So, back to the dyno. Need to get that MAF dialed in. I will dyno and tune
the engine this weekend to get it running right. And then I'll be back to
the strip on Oct 8th for another try.
All wasn't lost, however. When you can run next to a new Z06 (I think was
the designation) at still beat him by 4 or 5 carlengths in a heavy 4 door
sedan... you still feel pretty good, and generate a lot of curiosity in the pits.
Stay tuned.
Dave
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