When to shift

[loosecannon]

I auto-x my 2004 Boxster (non-S) and was curious about what is the best RPM to launch and shift at. I experimented with launching at 3000, 4000 and 5000 rpm, and with shifting at 6000, 6500 and 7000 rpm. I used a MaxQdata system and did it on a runway we use for auto-x, always starting in the same area, going in the same direction and letting the tires cool between runs. The tires were Bridgestone RE-01R and the only mod to the car is a home made cat back exhaust. I re-tested the different launch RPM at the end of the test to ensure that the conditions were the same. Sorry for not listing the other shift data but I deleted all the data except for the launch at 5000, shift at 7000 rpm ones because that was easily the quickest. Launching at 5000 rpm, shifting at 6000 rpm resulted in 6.1 seconds, shifting at 6500 was 5.7 seconds. Here's the data to 60 mph when shifting at 7000 rpm(before it hits the rev limiter at 7200 rpm) but I have the whole chart to 1/4 mile-note that 0-60 mph is 5.5 seconds:
Time------g--- MPH-- ft
0.000 +0.65 4.04 0.0
0.050 +0.58 5.27 0.4
0.100 +0.54 6.28 0.9
0.150 +0.53 7.06 1.4
0.200 +0.54 7.69 1.9
0.250 +0.55 8.28 2.6
0.300 +0.55 8.86 3.2
0.350 +0.55 9.40 3.9
0.400 +0.57 9.89 4.6
0.450 +0.58 10.37 5.4
0.500 +0.58 10.90 6.2
0.550 +0.58 11.50 7.0
0.600 +0.59 12.14 7.9
0.650 +0.60 12.79 8.9
0.700 +0.62 13.44 9.8
0.750 +0.60 14.47 10.9
0.800 +0.60 15.91 12.1
0.850 +0.63 17.54 13.4
0.900 +0.67 18.79 14.7
0.950 +0.69 19.83 16.2
1.000 +0.69 20.90 17.7
1.050 +0.65 22.09 19.4
1.100 +0.57 23.11 21.0
1.150 +0.51 23.95 22.8
1.200 +0.45 24.69 24.6
1.250 +0.42 25.36 26.5
1.300 +0.43 25.94 28.4
1.350 +0.47 26.45 30.3
1.400 +0.49 26.91 32.3
1.450 +0.49 27.38 34.3
1.500 +0.48 27.87 36.4
1.550 +0.46 28.38 38.4
1.600 +0.45 28.89 40.6
1.650 +0.48 29.38 42.7
1.700 +0.51 29.87 44.9
1.750 +0.54 30.35 47.1
1.800 +0.56 30.82 49.4
1.850 +0.54 31.32 51.7
1.900 +0.52 31.86 54.0
1.950 +0.49 32.52 56.4
2.000 +0.48 33.24 58.9
2.050 +0.46 33.98 61.4
2.100 +0.46 34.62 63.9
2.150 +0.46 35.17 66.5
2.200 +0.47 35.68 69.1
2.250 +0.48 36.18 71.8
2.300 +0.48 36.69 74.4
2.350 +0.48 37.19 77.2
2.400 +0.47 37.68 79.9
2.450 +0.49 38.16 82.7
2.500 +0.50 38.66 85.6
2.550 +0.51 39.11 88.4
2.600 +0.54 39.52 91.3
2.650 +0.53 39.93 94.3
2.700 +0.53 40.40 97.2
2.750 +0.50 40.89 100.2
2.800 +0.47 41.32 103.2
2.850 +0.44 41.71 106.3
2.900 +0.44 42.14 109.4
2.950 +0.44 42.55 112.5
3.000 +0.43 42.90 115.7
3.050 +0.41 43.22 118.9
3.100 +0.39 43.59 122.0
3.150 +0.36 44.02 125.3
3.200 +0.29 44.35 128.5
3.250 +0.23 44.58 131.8
3.300 +0.17 44.76 135.1
3.350 +0.08 44.95 138.4
3.400 +0.10 45.10 141.7
3.450 +0.18 45.16 145.0
3.500 +0.28 45.23 148.3
3.550 +0.42 45.41 151.7
3.600 +0.54 45.75 155.0
3.650 +0.58 46.22 158.4
3.700 +0.58 46.77 161.8
3.750 +0.52 47.35 165.3
3.800 +0.45 47.93 168.8
3.850 +0.38 48.50 172.4
3.900 +0.35 49.03 176.0
3.950 +0.35 49.43 179.6
4.000 +0.36 49.71 183.3
4.050 +0.36 49.93 186.9
4.100 +0.36 50.21 190.6
4.150 +0.38 50.52 194.3
4.200 +0.38 50.83 198.1
4.250 +0.38 51.12 201.8
4.300 +0.37 51.46 205.6
4.350 +0.37 51.82 209.4
4.400 +0.37 52.18 213.2
4.450 +0.37 52.52 217.1
4.500 +0.35 52.88 221.0
4.550 +0.34 53.25 224.9
4.600 +0.34 53.60 228.8
4.650 +0.35 53.93 232.7
4.700 +0.37 54.27 236.7
4.750 +0.38 54.62 240.7
4.800 +0.38 54.96 244.8
4.850 +0.38 55.31 248.9
4.900 +0.38 55.69 252.9
4.950 +0.36 56.08 257.1
5.000 +0.34 56.44 261.2
5.050 +0.34 56.77 265.4
5.100 +0.33 57.12 269.5
5.150 +0.32 57.47 273.8
5.200 +0.33 57.82 278.0
5.250 +0.34 58.15 282.3
5.300 +0.35 58.50 286.5
5.350 +0.38 58.86 290.9
5.400 +0.37 59.23 295.2
5.450 +0.38 59.62 299.6
5.500 +0.38 60.01 304.0

[Viper5]

Thats pretty good considering it's rated at 6.2sec

[blinkwatt]

Doesn't the PST record any rev in the redline?

[loosecannon]

Originally Posted by Viper5

Thats pretty good considering it's rated at 6.2sec

Yeh, Porsche definitely underrates it's stuff. On street tires the car pulls .69 G on the launch, which is outstanding but yesterday when running Hoosier A6's, it pulled .8 G.

[blue2000s]

We've covered this in detail before and it always brings out many opinions. In actuality, the shift point for best acceleration is dictated by which gear/RPM provides the most torque to the wheels at a given road speed. It's a bit more complicated than looking at the power or torque curves (sorry Randal ) You have to look at the torque curve, the gear ratios, and the road speed.

For most high performance cars, the manufacturer will choose gear ratios that take full advantage of the rev range. So almost always, high performance cars will give the best acceleration if the car is run to redline. The numbers prove this out on the Boxster and also agree with what loosecannon has found.

I wouldn't worry much about stage 1 over-revs by hitting the fuel cut-off at redline, that's not damaging to the engine. It's the miss-shift that runs the engine beyond red line that you should and Porsche does care about.